Luận án tiến sĩ Kỹ thuật hóa học: Synthesis and characterization of conjugated polymers oriented for fluorescence chemosensor

A conjugated diblock copolymer of dichlorotriazin-2-yl]oxyethyl methacrylate P3HT-b-PDCTMA has been obtained viathe combination of Grignard metathesis method GRIM and organo-catalyzed at

LITERATURE REVIEW 0.0.0 cccecccesceeseeseeeneeeceeeeeeseceaeeeeesseeeaeeeeeeeeees 3

Structure of Conjugated Polymer and Mechanism of Conduction

All materials can be divided into three main groups: insulators, semiconductors, and metals by their ability to conduct electron flow (current) Generally, polymers (plastic) are known to have good insulating properties However, it has been discovered that there are some polymers having conducting properties Conjugated polymers are polymers materials that have metallic and semiconductor characteristics, a combination of properties not exhibited by any other known materials The polymer is a conjugated polymer when they have a system of conjugated double bonds that are alternately single and double bone along the backbone of the polymer main chain [1] The structure of conjugated polymer is illustrated in figure 1.1.

Plane of the sp,- m-bond Orbitals

Figure 1 1 Schematic of the bonds of carbon in a conjugated polymer The electrons in 7-molecular orbitals are delocalized.

Sometimes, the conjugated polymers contain atoms such as nitrogen, sulfur, and oxygen in the main chain In conducting polymers, the carriers are electrons of conjugated double bonds while the carriers of metal are valence electrons of a half-filled band.

Basically, the conjugated polymers under the doping have a range of electrical conductivity (Scm'!) from 102 to 10-11 Scm'! whereas metals have electrical conductivity from 106 to 10 Scm'! [2] Figure 1.2 provides some common conjugated polymer structures.

Ry LE E_LE_L N LE PPE *Xx‹ Polyacetylenes

\ Ề ⁄ s / À cCˆ Polyparaphen ylenevinylen e (PPV) re RO $

Figure 1 2 The common conjugated polymer structures.

The conductivity of a material depends on its electronic energy level structure [3] In solid-state physics, the energy difference (in electron volts) between the highest occupied band (HOMO) (valence band) and lowest unoccupied band (LUMO) (conduction band) is called the band gap The electrical properties of materials depend on the fill of the bands When an electron jumps from the valence band to the conduction band, the conduction occurs, but this can’t occur when the bands are empty or full If the band gap is small, the thermal excitation can provide enough energy to promote the electron from the valence band to the conduction band which leads to the conductivity of materials This phenomenon happens in conventional semiconductors But conducting polymers are different from conventional semiconductors, they conduct without having either a partially empty or partially filled band [3].

The electronic ground state of conducting polymers is an insulator with a forbidden energy gap between the valence and conducting bands The mechanism of conduction of polymeric materials was originally believed by electron transport through the system of conjugated bonds [4] In conjugated polymer, every bond contains a localized

“sigma” (o) bond (single plane) which makes a strong chemical bond In addition, every double bond contains a less strongly localized “pi” (2) bond (orbitals parallel) that is weaker, the orbitals of the 7 electrons overlap to form a single delocalized cloud of x electrons over the entire molecules This means that the delocalized electrons may move around the whole system However, to make the polymer materials conductive, the polymer material needs to be exposed to the dopant, that process is also called doping. Doping is either the addition of electrons (reduction reaction) or the removal of electrons (oxidation reaction) from the polymer For example, the iodine can be used for oxidation doping of polymer, the iodine attracts an electron from polymer from one of the z bonds When doping has appeared, the electrons in the a bonds are able to jump around the polymer chain, so electric current occurs Dopants can be atomic or molecular species, and act as electron donors (Li, Na, K ) or electron acceptors (I2, LiClO, Br2 ) Table 1.1 displays some common dopants that have been used for conducting polymers [4],

Table 1 1 Common conducting polymers, their dopants and conductivities.

Polymer Dopants Conductivity (Sem:!) Polyacetylene lb, Br2,Li,Na,AsF3 10000

Application of Conjugated PỌyIT€T - 5c S1 E211 1 9 1v net 6

Since their discovery in the mid-1970s, conducting polymers has been a hot research area for many academic institutions This research has supported the industrial development of conducting polymer products and has provided a fundamental understanding of the chemistry, physics, and material science of these materials In reaching the development of intelligent materials, it is impossible to ignore the shorter- term opportunities that are available for the application of conducting polymers [6] The potential applications of conducting polymers have been discussed in numerous reviews [7], [8], [9], [10] The rapid increase in patents in the early 1980s reflects the growing appreciation of the versatility of conducting polymers in many application areas With breakthroughs in processing technologies via the solubility of conducting polymers, the commercialization of conducting polymers has been broadcasted since the mid-1990s. The increasing number of academic, governmental, and industrial laboratories throughout the world concerns with theoretic basic research and appreciation of valuable applications of conducting polymers shows that this research is an interdisciplinary study in material science Recently, the conducting polymer has attracted much attention largely because of their many applications such as polymeric solar cells (PSCs) [7], [8], [11], [12], [13], rechargeable batteries, organic field-effect transistor (OFET) [14], [15], [16], [17], [18], [19], [20], polymer light emitting diodes (PLED), sensors and other molecular electronic devices [1], [5], [21], [22] Among applications of conducting polymer, in particular, the PSCs and OFET are of great current interest for low cost, fast fabrication, flexible devices, and large-area electronic applications such as flat-panel displays, and electronic papers.

The utilization of PSCs effect to generate electricity from solar energy presents an appealing solution to our vital requirement for clean, abundant, and renewable energy sources and protecting the environment Unfortunately, up to now, only a very small percentage of energy production comes from sunlight, mainly because of the high cost of silicon-based solar cells [23] PSCs are appreciated as one of the promising candidates for low-cost solar cells Early work on PSCs was done with a single-component activate layer sandwiched between two electrodes with different work functions However, the devices based on single-component have given very low power conversion efficiency (PCE is less than 1%) due to poor charge generation and charge transport [24], [25]. Then, a bilayer heterojunction configuration containing a p-type layer for hole transport and an n-type layer for electron transport has been supplemented to improve the PCE of the solar cell devices However, the performance of bilayer heterojunction devices is greatly limited by a small area of charge-generating interface between donor and acceptor Therefore, the PCE of bilayer heterojunction solar cells is also less than 1% for PPV/PCBM cells [25], [26], [27], [28], [29], [30].

To overcome this difficulty, the concept of a bulk heterojunction was introduced by the pioneering work of Heeger, A J group [31] The bulk heterojunction architecture (BHJ), in which the photoactive layer consists of a bicontinuous blend of an electron donor and an electron acceptor and BHJ also maximizes the light absorption in the active layer [31] [32], [33], [34], [35] Figure 1.3 presents the structure of BHJ of PSCs.

SE Ee ee ee em UL ẻXx* Polyacetylenes

` i \ \ J ⁄ ` if \ on Polyparaphen ylenevinylene (PPV)

Figure 1 3 The common conducting polymer structure.

The current-voltage characteristics of a solar cell in the dark and under illumination are shown in figure 1.4 The photovoltaic power conversion efficiency of the PSCs is determined by the following formula:

Isc * Voc n: Photovoltaic power conversion efficiency FF: Fill-factor

Voc: Open-circuit voltage Vmpp: Maximum Power Point Voltage Isc: Short Circuit Current Impp: Maximum Power Point Current

FF is an indication of the efficiency of charge collection at the respective electrodes and so illustrates the connectivity of the pathways between the electrodes Isc is related to the number of absorbed photons and the effectiveness of the layer to generate free charges and collect them at the electrodes, whereas Voc is dictated by the energy gap between the HOMO (highest occupied molecular orbital) of the electron donor and the LUMO (lowest unoccupied molecular orbital) of the electron acceptor, with a reduction of about 0.3 V due to the energy penalty associated with free carrier formation The overall PCE (n) is directly affected by Isc, Voc, FF, and Pin (the power input).

Figure 1 4 Current-Voltage (I-V) curves of an PSCs

Normally, PSCs used [6,6]-phenyl Cứi-butyric acid methyl ester (PCBM) as an electron acceptor and regioregular poly(3-hexylthiophene) (P3HT) as an electron donor Heeger optimized the performance of this material by using PC7;BM and by introducing a certain amount of additives (1,8-octanedithiol) for the preparation of the film At this point, they have obtained a PCE of 5.5% with a very good short circuit current density

(JISC) of 16.2 mA/cm? and a fill factor (FF) of 55% [31] Afterward, numerous researchers is trying to increase the performance of PCE by modifying the morphology, the device architecture, and donor and acceptor materials Recently, some PSCs based on the BHJ system have archived the PCE at around 8% [36].

1.2.3 Organic Field-Effect Transistor (OFET)

An organic field-effect transistor (OFET) is a 3-terminal device configured like a parallel-plate capacitor By controlling the voltage on one plate (the gate), a charge can be induced on the other Then charges are injected from the source electrode and collected across the conducting layer at the drain by applying a voltage Silicon has been widely used as semiconducting material in traditional transistors called the Metal Oxide Semiconductor Field-Effect Transistor (MOSFET) The great quality of Si-SiO2 used in MOSFET exhibits fast switching speeds and is suitable for use in modern processors. However, the manufacture of the MOSFET requires labor-intensive inorganic devices and the product is also highly costly The prospect of replacing costly with cheaper, easy fabrication and more flexible organic electronic materials entered a new era The using of organic semiconductors or conjugated polymers replacing the Si-SiOằ is attracting great attention for fabricating organic field effect transistors (OFETs) [1], [4], [37], [38],[39], [40] OFETs have made impressive progress during the last decade due to the improvement of the quality of organic semiconductor and dielectric layers as well as promising low-cost manufacturing processes, such as print technique [40], [41], [42],[43], [44], [45], [46] OFETs become attractive for various applications, not only as flat- panel displays, and electronic paper but also to integrate logic circuitry into low-cost electronic products such as smart cards, inventory tags, and sensor arrays [38], [42].

A typical OFET consists of organic semiconductors (or conducting polymers), dielectric layers, and electrodes OFETs have been fabricated with various device geometries as depicted in Figure 1.5 a-b.

Gate Electrode ectrode Conducting layer

Figure 1 5 Schematic of the top-contact configuration (a) and top-gate structure (b) of OFETs.

The most common geometry of OFETs is the bottom gate with the top drain and source electrodes Normally, the Si/SiO2 oxide is used as gate dielectric, and notable metal such as gold is used for drain and source electrodes The dielectric layers are either inorganic dielectric materials such as SiO2 or insulating organic polymers The organic semiconductor is the core element of an OFET It determines the charge carrier transport as well as the charge carrier injection The OFET can be classified as p-type or n-type depending on which type of charge carrier is more efficiently transported through the material When holes are preferentially injected into the conducting layer, they accumulate at the organic/dielectric layer interface and transport through the channel thus, the device exhibits p-type operation In contrast, if the electrons are injected into the conducting layer and transported through the active channel, the OFETs can be considered as n-type [42], [47].

To understand the operating principle of the OFETs, a simplified energy level diagram for Fermi level of source-drain metal electrode and HOMO-LUMO levels of a conducting layer are shown in Figure 1.6: (a) No charges are injected when Vc = 0 V; (b) When a negative voltage is applied to the gate, positive charges are induced at the conducting layer/organic insulator interface (at the channel); (c) When a positive voltage is applied to the gate, negative charges are induced at the conducting layer/organic insulator interface If there 1s no gate voltage applied (Figure 1.6a), the conducting layer

10 is undoped therefore it will not show any charge carriers So there is no following current from source/drain When a negative voltage is applied to the gate (Figure 1.6b), positive charges are induced at the conducting layer adjacent to the gate dielectric (p-type OFETs are formed) If the Fermi level of source/drain metal is close to the HOMO of conducting layer, then positive charges can be extracted by the electrodes via applying a voltage, Vps between source and drain Such conducting layer can provide only positive charge carriers determined as p-type OFETs When a positive voltage is applied to the gate (Figure 1.6c), negative charges are induced at the conducting layer adjacent to the gate dielectric (n-type OFETs are formed) If the Fermi level of source/drain metal is close to the LUMO level of the conducting layer, then negative charges can be injected and extracted by the electrodes via applying voltage, Vps between source and drain Such conducting layer can provide only negative charge carriers determined as n-type OFETs.

Figure 1 6 Illustration of a working principle of an OFET with respect to applied Ve.

The output characteristics of the OFETs can be shown in Figure 1.7 via its I-V characteristics The gate-source voltage is varied as -5 V For each VGS the drain-source voltage is varied from Vps = 0 to -5 V and back from Vps = -5 to 0 V [48] The I-V characteristics of OFETs show a typical plot of drain current Ips versus drain voltage

Vps at various gate voltages Vc The field-effect mobility (H) was determined from a (-

Ip, sa)!” vs Vo plot using the following equation. u.W.C 2L( a 2

Ib, sat= Vo-V 2= =— /—] D, sat 2L ( G t) > 4H WC Ến D,sat

The field-effect mobility of OFETs (μt) influences the drain current (ID, sat) in the saturated region The gate dielectric's capacitance (C) and the gate voltage threshold (Vt) further affect the drain current These factors, along with channel dimensions (W and L), play a crucial role in determining the electrical characteristics of OFETs.

Figure 1 7 Output characteristic for a P3HT OFET with L = 0.74 um, W = 1000 um.

The development of “plastic” electronic devices based on conjugated polymer has created revolutionary research for exciting new science and new plastic electronics. Since polythiophenes (PTs) possess high conductivity when doped, high electron mobility, solubility in common solvents, excellent thermal and environmental stability, and processibility, they are considered an important class of conjugated polymers Up to now, PTs have been used in a variety of applications such as PLEDs, SCs, OFET, environmental sensors, electrical conductors etc [1], [6], [7], [9] In the early 1980s, the PT was first chemically polymerized by a metal-catalyst polycondensation

12 polymerization of mono-Grignard of 2,5-dibromothiophene generated by treatment with magnesium metal [49], [50] This strategy gave a 2,5-coupled PT However, the structure of polythiophene was not characterized fully due to the lack of its solubility. Despite the PT having poor solubility and intractability because of the strong 7-stacking interactions between the aromatic rings, PT has excellent thermal stability (42% weight loss at 900°C) and good conductivity (1 x 10°! S/cm when doped with iodine) [51] In

Controlled radical polymerization (CRP) ::ccssecssseseseeseeceseeeeeeeeaeeeseeeeeeesaes 22

Controlled synthesis of polymeric materials requires minimization of chain breaking reactions (by transfer and termination) and chain should be grown simultaneously In conventional radical polymerization (RP), a steady state of radical concentration is archived by balancing the rate of initiation with termination therefore a prerequisite of fast initiation and very low termination seems to be impossible However, an idea was realized by the development of controlled systems in which the active propagating

22 radicals are immediately formed and growing centers are in equilibrium with various dormant species [90] CRP systems are based on a dynamic equilibrium between tiny amounts of propagating radicals and various types of dormant species [91] [92] There are two types of equilibration in CRP First one, radicals could be reversibly trapped in a deactivation/activation process [93], [94], or they may be involved in a degenerative exchange process Scheme 1.4 and 1.5 present the mechanism of two kinds of equilibration of CRP. ° la K

Scheme 1 4 First equilibration in CRP relies on the persistent radical effect (PRE)

Scheme 1 5 Second equilibration in CRP relies on the degenerative transfer (DT)

In PRE systems (scheme 1.3), newly generated radicals are rapidly trapped in a deactivation process (with a rate constant of deactivation, Kaa) by species X The dormant species are activated (with a rate constant Ka) to reform the growing centers. Radicals can propagate (Kp) but also can terminate (K;) In the system based on PRE (such as spontaneous reversible activation of dormant species or atom transfer radical polymerization), a steady state of growing radicals is established through the activation- deactivation process but not through initiation-termination Because initiation is much faster than termination, this is necessary to give the simultaneous growth of all chains. Contrary to the PRE system which employs DT (such as Reversible Addition- Fragmentation Chain Transfer (RAFT)), they follow typical RP kinetics with slow initiation and fast termination (scheme 1.4).

To control molecular weight, polydispersity, and chain architecture in all CRP systems, the requirement is a very fast exchange between active and dormant species.

Ideally, a growing radical should react with only a few monomer units before it is converted back into dormant species Then, it would remain active only for a few milliseconds and would return to the dormant state for a longer time (a few seconds or more) For example, the growth of a chain may consist of 1000 periods of 1 ms activity, interrupted by 1000 periods of 1 min dormant states Therefore, the whole propagation process in CRP may take 1000 mins Due to the propagation process in CRP may take a long time therefore various synthetic procedures could be performed for functionalization or chain extension of polymer.

1.3.2 Atom Transfer radical polymerization (ATRP)

Currently, ATRP [95], [96] is the most widely used CRP technique The basic mechanism of ATRP involves hemolytic cleavage of an alkyl halide bond R-X (or macromolecular Pn-X) by a transition metal complex Mt?/L (such as CuBrz/bpy2) This reaction generates reversibly (with the activation rate constant, ka) the corresponding higher oxidation state metal halide complex X-Mt"*!/L (such as CuBro/bpy2) and an alkyl radical R* [96] R* can then propagate with a vinyl monomer (kp) terminate by coupling and/or disproportionation (kt), or can be reversibly deactivated by X-MtTM!/L

PRE effectively reduces radical termination, favoring the formation of dormant species This shift in equilibrium is driven by a higher deactivation rate constant relative to the activation rate constant As depicted in Scheme 1.6, this phenomenon is central to the ATRP mechanism.

C Mt'?!X ) Ce "_>Ầ re ° >\ Y St — thi

Scheme | 6 General mechanism of ATRP

However, in a well-controlled ATRP, no more than a few percent of the polymer chains undergo termination And a well-controlled ATRP depends not only on the

24 concentration of persistent radical (X-Mt"*') but also on that of the activator (Mt*1/L).

Molecular weights (MWs) are independent of transition metal species concentration, as determined by the [M]/[RX]o ratio Polymerization rates are directly proportional to initiator (P-X) concentration and the ratio of activator to deactivator concentrations.

In summary, a successful ATRP process should have several requirements [96]. ằ The initiator should be consumed at the early stages of polymerization and generate propagating chains leading to polymers with degrees of polymerization (DP) predetermined by the monomer-to-initiator molar ratio ằ The small number of monomer molecules added during one activation step resulting in low polydispersity of polymers.

* Contribution of chain-breaking reactions (transfer and termination) should be negligible to yield high conversion and a high degree of polymers as well as end- functionalities of polymers that allows the synthesis of block copolymers

ATRP processes depend on many factors including different monomers, initiators, metal catalysts, ligands, solvents, time reaction, temperature, concentration etc Therefore, for each particular ATRP, a specific initiator, metal catalysts, ligand, temperature, reaction time, and solvent should be investigated and selected.

There are many monomers were successfully homopolymerized by ATRP including various substituted styrene, (meth)acrylates, (meth)acrylamides, vinyl pyridine, acrylonitrile, vinyl acetate, vinyl chloride, and others [96] A variety of transition metal complexes have been successfully used in ATRP They include compounds from group

VI (Mo), VI (Re), VII (Ru, Fe), IX (Co, Rh), X (Ni, Pd), and XI (Cu) Cu is by far the most efficient metal as determined by the successful application of its complexes as catalyst in the ATRP of a broad range of monomers in different media Ligands include multidentate alkyl amines, pyridines, pyridine-imines, phosphines, and ether Ligands serve to adjust the atom transfer equilibrium and provide appropriate catalyst solubility. Figure 1.10 shows some ligands that can be used in ATRP reactions.

Figure 1 10 Typical ligands for Cu-based ATRP.

Conjugated polymer for fluorescence sensory appèICation - ô<5 26

A variety of approaches have been investigated for sensors, including enzymatic assays [97], molecular imprinting coupled with luminescence (using lanthanides) [98], [99], [100], [101], [102], colorimetric methods [103], [104], [105], surface acoustic waves [106], [107], fluorescent organic molecules [108], [109], [110] The most common ways for detecting OP pesticides are chromatographic methods coupled with different detectors and different types of spectroscopy, immunoassays, and enzyme biosensors based on the inhibition of cholinesterase activity [111], [112], [113].

Recently, a number of innovative methods for the detection of OP compounds based on optical chemosensors have been reported in the literature The first fluorescent chemosensor for the detection of OP compounds was reported by Van Houten et al. where a series of non-emissive platinum 1,2-enedithiolate complexes with an appended primary alcohol was synthesized [110] Upon the addition of an electrophilic OP analyte to this compound and an activation agent (triazole) in dichloromethane, the alcohol was converted to a phosphate ester, which reacts intramolecularly to form a fluorescent cyclic product.

Zhang and Swager developed a series of thienylpyridyl and phenylpyridyl systems which undergo intramolecular cyclization reactions upon exposure to OP compounds [109] In particular, recent research progress aims at the methodology of fluorescence- based explosive sensors [114], [115], [116], [117], [118] In general, fluorescence-based explosive sensors have been designed based on the Forster resonance energy transfer

(FRET) mechanism which can dramatically enhance the fluorescence-quenching efficiency and improve sensitivity In this mechanism, an initially excited molecule (donor) returns to the ground state orbital, while the transferred energy simultaneously provides an electron on the acceptor to the excited state [114], [119]. Poly(pphenylenevinylene)s (PPVs) is one of the excellent conjugated polymers exhibiting photo-and electro-luminescence which can act as fluorescent sensory materials [117], [120], [121], [122], [123], [124], [125] Chang et al [120] synthesized dialkoxy and diphenyl substituted PPVs towards fluorescence sensing of TNT and 2,6- DNT vapors.

Today, novel polymers containing special optical response functional groups such as spiro oxazine, pyrene, perylene, or perylene-benzothiazole are one of the most powerful tools for optical sensor materials However, the synthesis pathway as well as the designed reasonable polymer structure is a big challenge to generate intelligent optical sensors that exhibited their selectivity and sensitive properties.

Research works in the field by foreign scientists and Vietnamese scientists

Each year, OPs poison thousands of humans across the world More recently, it was found that children exposed to OP pesticides caused diagnosed with attention deficit hyperactivity disorder (ADHD) [126] Exposure has been attributed to the frequent use of OPs in agricultural lands and their presence as residues in fruits, vegetables, livestock, poultry products, and municipal aquifers [127] Typical pesticide concentrations that flow into the aqueous waste range from 10,000 to | ppm In groundwater, there is little sunlight exposure, which slows down the degradation of OP pesticides and increases their potential risks to the environment and human health The number of OP pesticides has risen to hundreds, and the common ones are Parathion (LD50 oral = 1), Fonofos (LDS0 oral = 8 - 17), Coumaphos (LD50 oral = 16 - 41), Methidathion (LDS0 oral = 25

- 48), Mevinphos (LD50 oral = 3.6 - 6.1) and Mesotrione (LD50 oral = 532) Their toxicity is expressed in terms of the lethal dose (LD) which will kill 50% of the animal species (LD50) [128], [129], [130].

Significant advances in the development of detection methods for OP compounds have been reported in the literature [98], [99], [100], [101], [102], [97], [131] Analysis of

Analytical techniques such as NMR spectroscopy, chromatography, and mass spectrometry are commonly used to detect organophosphates (OPs) in environmental and biological samples Various sensor approaches have been explored, including enzymatic assays, molecular imprinting with luminescence, colorimetric methods, and surface acoustic waves The most prevalent detection methods for OP pesticides involve chromatography coupled with spectroscopy, immunoassays, and enzyme biosensors that monitor cholinesterase inhibition.

Recently, a number of innovative methods for the detection of OP compounds based on optical chemosensors have been reported in the literature The first fluorescent chemosensor for the detection of OP compounds was reported by Van Houten et al. where a series of non-emissive platinum 1,2-enedithiolate complexes with an appended primary alcohol was synthesized [110] Upon addition of an electrophilic OP analyte to this compound and an activation agent (triazole) in dichloromethane, the alcohol was converted to a phosphate ester, which reacts intramolecularly to form a fluorescent cyclic product Zhang and Swager developed a series of thienylpyridyl and phenylpyridyl systems which undergo intramolecular cyclization reactions upon exposure to OP compounds [128] Binding resulted in spectral bathochromic shifts in the absorption and fluorescence of these chemosensors Notable fluorescence color changes were observed using a UV lamp under an ambient atmosphere These sensors were found to be both sensitive and selective to OP compounds showing complete response to 10 ppm (diisopropylfluorophosphate) DFP vapor within five minutes.

The integration of synthetic polymers with tailored structures and functional groups that interact specifically with organophosphorus (OP) compounds has emerged as a promising approach for OP detection These polymers leverage interactions between their functional groups and OPs to generate optical and electrochemical signals, making them valuable materials for the development of sensing systems that can detect and monitor OP compounds The versatility of polymer materials with functional groups that interact with OPs enables facile processing into filaments and films, providing flexibility in the design and fabrication of sensor devices.

28 packaged as a specifications test kit This technology paves the way for the application of OPs sensing materials [129], [130], [131].

In 2016, Mindy Levine’s research group fabricated a fluorescence sensor based on conjugated fluorescent polymer sensors They synthesized the poly(2,1,3- benzooxadiazole-alt-fluorene) via coupling polymerization with the molecular weight of the polymer of Mn = 3.8 x 10° g.mol"! [132] The polymer-derived nanoparticles were characterized by dynamic light scattering experiments, with an average particle diameter of 139 nm The result showed that the fluorescent polymer sensors can detect dichlorodiphenyltrichloroethane (DDT) at 5 uM.

Recently, two porous polymers (LNU-45 and LNU-47) were synthesized through the Suzuki coupling reaction have been reported by Zhuojun Yan et.al in 2021 These porous polymers have been synthesized using 2,7-dibromopyrene as one monomer together with respective tris(4-boronic acid pinacol ester phenyl)amine and benzene- 1,3,5- triyltriboronic acid pinacol ester These fluorescence-conjugated polymers of

LNU-45 and LNU-47 exhibited the tracing of trifluralin and dicloran with the concentration of 9 x 10 and 8 x 10 mol L! [133] In 2019, Yue Cai reported the conjugated oligomer based on 4,4-dibromobenzophenone and 4,4- dimethoxydiphenylamine which exhibited the signal-on fluorescence detection of Ops in the range from 0.009 mg/L to 22.5 mg/L with the detection limit of 0.008 mg/L.

In 2020, Mohammad Mahdi Bordbar et al reported the synthesis of serial nanoparticles based on nano gold (AuNPs) The AuNPs are functionalized by L-arginine, and quercetin to make a colorimetric paper-based sensor that can exhibit the rapid monitoring of six major organophosphate and carbamate pesticides The limit of detection for these pesticides was 29.0, 22.0, 32.0, 17.0, 45.0, and 36.0 ng mL”! [134].

More recently, Zhenguo Chi’s group published amphiphilic polymers (PTDs) prepared through radical copolymerization of N-(1,2,2-triphenyl vinyl)-4-acetylaniline and dimethyl diallyl ammonium chloride which was dispersed in phosphate-buffered saline. They have found that the particle size, morphology, functional groups, and fluorescence property of PTD nanoparticles (PTDNPs) can be fine-tuned In addition, PTD

29 nanoparticles of 0.10 nm were chosen as signal reporters to detect organophosphorus pesticides (OPs) including nitrobenzene, 4-nitrophenol, and diethyl(4- methoxybenzyl)phosphonate, which have a structure similar to that of paraoxon [135].

Research in Vietnam primarily focuses on established intelligent polymers, such as conjugated polymers, self-healing polymers, bio-polymers, and aerogel polymers However, limited efforts are directed towards synthesizing novel polymers specifically for tracing organophosphorus pesticides and herbicides This research gap extends globally, as few studies have addressed the development of functional polymers for detecting organophosphorus pesticides Therefore, this thesis endeavors to synthesize novel conjugated polymers capable of detecting organophosphorus pesticides (OPs) like mesotrione and TNT explosive compounds.

In this thesis, we reported the synthesis and characterization of rod—coil diblock copolymers based on P3HT and poly(2-(4,6-dichlorotrazin-2-ylJoxy)ethyl methacrylate (P3HT-b-PDCTMA) via organocatalyzed atom transfer radical polymerization (O-ATRP) The P3HT-based rod—coil diblock copolymers can be used as the platform bearing functional triazine dichloride groups In addition, we also synthesized a diblock copolymer containing the rod segment of regioregular P3HT a the coil segment of 2-(dimethylamino)ethyl methacrylate (DMAEMA) and 1- pyrenylmethyl methacrylate (PyMA) The DMAEMA unit plays a role as a hydrophilic coil in the amphiphilic diblock copolymer which is introduced to improve the compatibility of the copolymer blocks resulting in direct copolymerization The P3HT- b-P(DMAEMA-r-PyMA) copolymer will be synthesized via the atom transfer radical polymerization method (ATRP) in the presence of CuBr/PMDETA as a catalytic system P3HT-b-P(DMAEMA-r-PyMA) works as sensory property in tracing explosive TNT compounds through a fluorescence quenching due to the Forster resonance energy transfer mechanism.

Moreover, to extend the research, the conjugated molecules based on pyrene and 4-(2- ethylhexyl)-2-(pyren-1-yl)-4H-dithieno [3,2-b:2’,3’-d]pyrrole (EP4HP) will be synthesized via direct arylation reaction The conjugated oligomers of 4-(2-ethylhexyl)- 2-(pyren-1-yl)-4H-dithieno [3,2-b:2’,3’-d]pyrrole will be investigated for tracing

30 mesotrione compound through FRET mechanism Therefore, the materials based on the EP4HP compound are promising candidates for technical application for mesotrione detection as chemosensors.

Aims and ObJ€C[IV€S oo ee cece 5E 11v TH HH 30

All chemical reagents and starting materials were purchased from Sigma-Aldrich, Acros, Merk, Fisher, and TCI, and were used as received without any further purification unless otherwise specified.

From Sigma-Aldrich: se N,N-dimethylformamide anhydrous (DMF, 99.8%), sodium borohydride

(NaBH¡¿, 99%), N, N’, N”, N”-pentamethyldiethylenetriamine (PMDETA, 99%), copper(I) bromide (CuBr, 98%), 2-Bromoisobutyryl bromide (Br-iBuBr), triethylamine (NEt3, 99%), methacryloyl chloride (97%), 1-pyrenemethanol (98%) and phosphorus(V)oxychloride (POC]:, 99%). e 2,4,6-Trichloro-1,3,5-triazine (TCT, 99%), 2-hydroxyethyl methacrylate

(HEMA, 98%), N,N-diisopropylethylamine (DIPEA, 99%), furfuryl mercaptan (98%), benzyl mercaptan (98%), furfurylamine (98%), benzylamine (99%), and perylene (= 99%) were used without purification. e Méesotrione (98%), Tris(dibenzylideneacetone)dipalladium(0) (Pd2(dba)3, 98%),

2,2’-bis(diphenylphosphino)-1,1’-binaphthyl (98%). e Tricyclohexylphosphine tetrafluoroborate (P(Cy)3-HBF4, 97%), Sodium tert- butoxide (NaOt-Bu, 97%), pivalic acid (PivOH, 99%), Palladium(II) acetate (Pd(OAc)2, 98%) and cesium carbonate (Cs203, 99%) were purchased from Sigma-Aldrich, St Louis, Missouri, USA. e N,N-dimethylamino-2-ethyl methacrylate (DMAEMA) (98%) was distilled under vacuum. e Palladium(II) acetate (Pd(OAc)2, 98%), pivalic acid (PivOH, 97%) and tricyclohexylphosphine tetrafuoroborate (97%, PCya- HBF4).

EXPERIMENTAL, - - 5 5 kg ng gi, 32

Synthesis of donor-acceptor conjugated copolymers poly(alkyl-POZ-DPP) and poly(benzoylalkyl-POZ-DPP) via direct arylation polycondensation (compound P1

In a 25 mL Schlenk flask, monomer M1 or M2, 3,6-bis(Sbromothiophen-2-yl)-2,5-bis(2-ethylhexyl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione (DPP), and DMAc were charged and purged with nitrogen for 20 minutes After adding Pd(OAc)2, PCy3.HBF4, PivOH, and K2CO3, the reaction mixture underwent three freeze-pump-thaw cycles to remove oxygen, followed by backfilling with argon The mixture was heated at 100 °C in an oil bath for 4 hours and then diluted with chloroform The resulting organic layer was purified by passing through Celite and concentrated before precipitating into methanol The copolymer was further purified through sequential Soxhlet extractions using methanol, acetone, and hexane, followed by dissolution in CHCl3 and reprecipitation into methanol The pure copolymers were dried under a vacuum at 60 °C overnight.

P1: a deep blue solid in 82% yield, 201 mg 'H NMR (500 MHz, CDC]:, ppm): 5 9.1-8.66

2H), 1.88-1.26 (m, 24H), 0.94-0.86 (m, 18H) GPC: Mn = 28 000 gmol!, Mw/Mn = 2.22 P2: a deep blue solid in 85% yield, 228 mg 'H NMR (500 MHz, CDC]:, ppm): 5 9.1-8.66

RESULT AND DISCUSSION Ăn HH Hà, 46

Synthesis of conjugated diblock copolymers Poly(3-hexylthiophene)-b-poly(2- ([4,6-dichlorotriazin-2-yl]oxy)ethyl methacrylate) (P3HT-b-PDCTMA)

3.1.1 Synthesis and characterization of Poly(3-hexylthiophene)-b-poly(2-((4,6- dichlorotriazin-2-yl]oxy)ethyl methacrylate) (P3HT-b-PDCTMA)

The 2-([4,6-dichlorotriazin-2-yl]oxy)ethyl methacrylate (DCTMA) monomer has been synthesized from 2,4,6-Trichloro-1,3,5-triazine with 2-hydroxyethyl methacrylate in the presence of N,N-diisopropylethylamine as catalytic in the yield of 82% This yield is calculated based on the actual mass obtained after the reaction with the theoretical mass. Figure 3.1 presented the FTIR of DCTMA monomer which showed all characteristic peaks of the monomer.

Figure 3 1 FT-IR spectrum of 2-hydroxyethyl methacrylate (HEMA) (black line) and

In addition, the chemical structure of monomer DCTMA has been confirmed by 'H NMR which showed all characteristic peaks of monomer The peaks at 5.60 ppm and 6.12 ppm (peak “a”) which are corresponding to the acrylate group of monomer DCTMA The peak at 1.94 ppm is assigned to a methyl group While the peaks at 4.52 ppm and 4.77 ppm that

46 is corresponding to methoxyethane linker in monomer DCTMA.

Figure 3 2 'H NMR spectrum of DCTMA (CDCl, 25 °C, 500 MHz).

Our synthetic pathway towards rod-coil diblock copolymers composed of P3HT and poly(2-([4,6-dichlorotriazin-2-yl]oxy)ethyl methacrylate) (P3HT-b-PDCTMA, compound P1) bearing triazine chloride side groups is presented in Scheme 3.1 P3HT- iBuBr was used as macroinitiator and perylene as organic photocatalyst [138].

NBS C/H;l(COOCH;); 2.Ni(dppp)Cl; ij ) 5 J\ —— + 5 / \ ơ——

2-bromoiso butyryl bromide o fer =——- Br

Peryl NÊN O-ATRP Apotite erylene

2-([4,6-dichlorotriazin-2-yl]oxy) ethyl methacrylate (DCTMA)

First, the œ-bromo P3HT was prepared via GRIM polymerization followed by quenching of HCI 5M to obtain a hydrogen group as the polymer chain-end group [74] The P3HT prepared by “The GRIM” method exhibited a number-average molecular weight (Mn) of 9,000 g/mol with polydispersity index value (PDI) of 1.1 as determined by gel permeation chromatography gel (GPC) In addition, the molecular weight of the homopolymer P3HT was also determined by 'H NMR to be ~ 9,000 g/mol The 'H NMR analysis of P3HT also showed a high regioregularity content (rr > 99%) and the expected end-groups (H/Br)

MALDI-ToF analysis determined the composition of 48 samples The P3HT-macroinitiator (P3HT-iBuBr), possessing an w-bromoisobutyrate end group, was synthesized through a three-step process involving Vilsmeier-Haack, reduction, and esterification reactions Nuclear magnetic resonance (NMR) analysis of P3HT with H/Br end groups and P3HT-iBuBr revealed characteristic peaks, as shown in Figure 3.3.

Figure 3 3 'H NMR of P3HT-H and P3HT-Macroinitiator in CHC]a.

On the other hand, the 2-([4,6-dichlorotriazin-2-yl]oxy)ethyl methacrylate (DCTMA) monomer was synthesized from the reaction of cyanuric chloride with 2-hydroxyethyl methacrylate using N,N-diisopropylethylamine as a catalyst The poly(3-hexylthiophene)- block-poly(2-([4,6-dichlorotriazin-2-yl]oxy)ethyl methacrylate) (P3HT-b-PDCTMA) diblock copolymer (P1) has been synthesized via metal-free ATRP using perylene as organic photocatalyst and P3HT-iBuBr as macroinitiator The advance of metal-free organic catalysts over well-known metal-containing transition metals catalysts is obvious

49 since the resulting polymers are applied in microelectronics and in living systems that avoid toxic for the organisms [119] [139] Perylene was selected as a photocatalyst due to its excellent photoactivity in the UV and Vis range and previously reported high control over methacrylate polymerizations [138] The metal-free ATRP of DCTMA initiated by the P3HT-macroinitiator containing œ-bromoisobutyrate end group was performed under

UV irradiation for 24 h with varying solvents and perylene content to find the optimal conditions Table 3.1 presents the characteristics of the obtained diblock copolymers At a low photocatalyst content ((DCTMA]o/[P3HT-iBuBr]/[Perylene] = 50/1/0.1), the polymerization occurred with a low conversion of 17% Increasing the catalyst content to 0.5 equivalent with respect to the P3HT-iBuBr increased the polymerization conversion to 73% after 24 h The obtained P3HT-b-PDCTMA diblock conjugated copolymers exhibited an Mn of 17,500 g/mol, which is approximately close to the theoretical value, and with a polydispersity index (PDI) of 1.42 (Table 3.1, entry 3) However, increasing the content of perylene to 1.0 equivalent with respect to the P3HT-iBuBr macroinitiator, the conversion of the polymerization was decreased to 65%, and the diblock copolymer P3HT-b-PDCTMA had an Mn of 12,400 g/mol with PDI of 1.47 These results indicate that the optimal content of perylene catalyst should be about 0.5 equivalent with respect to the P3HT-iBuBr macroinitiator in order to afford an efficient polymerization process.

Figure 3.4 showed the FT-IR spectrum of P3HT-iBuBr and diblock copolymer P3HT-b-

PDCTMA In FT-IR of P3HT-b-PDCTMA, a strong absorption signal at 1725 cm! appears in the spectrum of the diblock copolymer and is attributed to the stretching vibration of the carbonyl groups (C=O) of the PDCTMA segment In addition, the peak that appeared at 1505 cm is assigned to the C=N groups of PDCTMA This result suggested that the PDCTMA segment has been incorporated as a coil segment in diblock copolymers.

50 bktch (A) Nad CH; iy Ai sa vn in !ủ

(B) ` - ia ff ie i | ila | IyY'

— CeHa3 ih Ay WA | | l| |ÍNÌ

4 BA NG b + i ụ III] | to Bris 7 1 x Br } INb | | 4Í || |

CI`N cl CN CO CO

Figure 3 4 FT-IR spectrum of P3HT-macroinitiator (A) and diblock copolymer

The 'H NMR spectrum of the obtained diblock copolymer P1 showed all characteristic peaks corresponding to its structure (Figure 3.5) Based on the 'H NMR result, the Mạ of

P1 was calculated to be ~18,000 g/mol, where the composition of the PDCTMA coil block occupied 50% of the copolymer As seen in Figure 3.6, the GPC result shows a clear shift of the GPC curve of the diblock copolymer P3HT-b-PDCTMA (P1) to a shorter retention time as compared to that of the P3HT-macroinitiator, confirming that the polymerization occurred completely.

Table 3 1 Macromolecular characteristic features of P3HT-b- PDCTMA synthesized via metal-free ATRP.

Entry [DCTMA]/IP3HT- Cony^ Macpc° iBuBr/[Perylene] (%) , PDE

“Conversion as determined gravimetrically: Conv = (m—mj—Mpyrene)/Mm Where m denotes the weight of the product, and mi, Mpyrene and mm the weights of the macroinitiator, perylene catalyst, and monomer, respectively PSHT-b-PDCTMA molecular weight, and dispersity index (PDI) as determined by GPC in THF using polystyrene standards.

When increasing the perylene reaction catalyst from 0.5 mg to 1 mg, it is very likely that pyrylene will quench the free radicals generated from the macroinitiator), thus the effectiveness of the macroinitiator decreases, leading to a decrease in conversion from 73 to 65% However, the reaction will be ineffective if a lower amount of catalyst is used. Here, we perform the reaction with perylene catalyst to provide stable conversion.

Figure 3 5 'H NMR spectrum of diblock copolymer P3HT-b-PDCTMA (P1)

Figure 3 6 GPC traces of P3HT-macroinitiator (red short dash line) and diblock copolymer P3HT-b-PDCTMA (black solid line) (A); plot of diblock copolymers conversion vs time demonstrating the control over polymerization propagation (B) and dependence of molecular weight (Mn, GPC) on monomer conversion (C).

3.1.2 Funtionalization of diblock copolymer P3HT-b-PDCTMA (P1-P5) via thiol- triazine and amine-triazine substitution reactions

Table 3.2 summarizes reaction parameters and conversion rates for functionalization reactions involving diblock copolymer P1 and various functional groups (furfuryl mercaptan, benzyl mercaptan, furfuryl amine, and benzyl amine) Notably, diblock copolymer P2 was synthesized from P3HT-b-PDCTMA via "click" coupling of triazine chloride pendant groups with furfuryl mercaptan.

The reaction was performed in the presence of DIPEA as a catalyst The structure of diblock copolymer P2 was confirmed by 'H NMR, as shown in Figure 3.7 The peaks at

0.91 ppm are assigned to the methyl (-CH) group in the P3HT segment, while the peaks at 0.83 ppm and 1.01 ppm correspond to the methyl groups of the PDCTMA block The

53 peaks at 1.35 ppm, 1.44 ppm, and 1.71 ppm are attributed to the -CH2- moieties in P3HT.

In addition, the -CH2- backbone of PDCTMA segment also exhibited a peak at 1.71 ppm. The peaks at 1.90 ppm correspond to the methyl end group (P3HT-CH2-OCO-C-(CHs)) of P3HT In the aromatic region, the peak at 6.98 ppm is attributed to the methine protons of P3HT units The furfuryl sulfide incorporated in P2 shows peaks at 6.27 ppm and 7.32 ppm corresponding to the protons of furan rings This result indicates that the mercaptan group reacted easily with the triazine chloride side group of the diblock copolymer.

Figure 3 7 'H NMR spectra recorded in CDC]; of diblock copolymer P2.

Synthesis of donor-acceptor conjugated copolymers poly(alkyl-POZ-DPP) and poly(benzoylalkyl-POZ-DPP) via direct arylation polycondensation (compound P1 b)18 220191; 0 .A

We synthesized two different donor-acceptor conjugated copolymers based on DPP as an acceptor unit and POZ as a donor unit, in which the effect of replacing the branched alkyl substituent at the POZ by a benzoyl moiety on the structural, photophysical, and thermal parameter was investigated The synthesis of all monomers (M1 and M2) and their copolymers (P1 and P2) is outlined in Scheme 3.4.

Synthesis of monomer 10-(2-ethylhexyl)-10H-phenoxazine (M1) and

First, two monomers POZ, M1 and M2, were synthesized in only one step from relatively inexpensive and commercially available H-phenoxazine with high yields of

86% and 75%, respectively The structure of monomers M1 and M2 was determined via

'H NMR The 'H NMR spectrum of monomer M1 (Figure 3.31a) shows a doublet peak at 6.86 ppm (peak d), a triplet peak at 6.70 ppm (peak b, c), and a doublet peak at 6.56 ppm (peak a) corresponding to the protons of the POZ benzene ring The peaks from

0.86 ppm to 3.41 ppm are attributed to the ethylhexyl protons Similarly, the 'H NMR spectrum of monomer M2 (Figure 3.31b) also showed all characteristic peaks of the hexylbenzoyl-POZ The presence of these peaks, along with their integral ratios, indicate that the reaction has taken place successfully to give the ethylhexyl-POZ and hexylbenzoyl-POZ monomers.

NaO-tBu, THF 0 cờ YS Se Br `

Cx )ộ) Pd(OAc);: 5 mol% oO" N o PCy, HBF,: 10 mol% CagCoby CaH:; PivOH: 1.0 eq KY a

Figure 3 31 'H NMR spectra of monomer MI (a) and M2 (b) in CDC]:

M2) ô<<55 86

Synthesis of polymers poly(alkyl-POZ-DPP) (P1) and poly(benzoylalkyl- POZ-DPP) (P2) cescescssscsseeseescesseessesseesseessesseeseesseessesseessecsseesaesseesseeaeeseesaeeaeens 88

As shown in Scheme 3.4, the alternating POZ-DPP copolymers were synthesized by direct arylation polycondensation between branched alkyl or benzoyl alkyl of POZ and dibromides of DPP to give P1, and P2, respectively The polycondensation was carried out in dimethylacetamide (DMAc) at 100 °C for 4h with 5 %mol of Pd(OAc)2, 10 %mol of PCy3.HBFs, 1.0 equivalent of pivalic acid (PivOH), and 6.0 equivalents of KaCOa. Both polymers were purified by sequential Soxhlet extractions using methanol (6h), acetone (6h), and hexane (6h) to remove catalyst and oligomers, then a chloroform fraction was collected, precipitated from cold methanol and isolated The yield of both reactions was a high yield > 82 % All the polymers showed excellent solubility in organic solvents such as tetrahydrofuran, chloroform, toluene, and chlorobenzene at room temperature The number average molecular weights (Mn) and dispersity (PDD of the two polymers P1 and P2 were determined by gel permeation chromatography (GPC) against polystyrene standards in CHCl3 and were found to be 28.000 and 41.500 g.mol

Table 3 5 Polymerization yields, molecular weights and thermal properties of copolymers.

Polymer Yield (%) Mn (gmol!)? PDF? Tg (°C)? Ta CC)

*Number-average molecular weight and dispersity index (PDI) determined by GPC with

CHCl, as eluent using polystyrene standards ° Glass transition temperature determined by DSC at a heating rate of 10 °C/min under nitrogen ° Temperature at 10% weight loss measured by TGA under nitrogen.

Structure of polymers poly(alkyl-POZ-DPP) (P1) and poly(benzoylalkyl- I197/219)12007217 071010080 e Ố

The chemical structures of the polymers were verified by FT-IR and 'H NMR spectra.

Figure 3.32 shows the FT-IR spectra of the obtained these copolymers The bands at

2850 and 3060 cm! are ascribed to C—H stretching modes of n-alkyl groups and ring C-H stretching vibrations The vibrational bands between 1550 and 1000 cm"! in all the polymers are due to stretching vibrations of the C—N and C-O groups in the phenoxazine ring Especially, a peak at 1689 cm‘! appears in the spectrum of the P2 attributed to the stretching vibration of the carbonyl groups (C=O) having higher intensity than of the PI Figure 3.33 showed the 'H NMR spectra of the alternating copolymers, PI and P2, which were in good agreement with the polymers’ structures. The spectrum of Pl showed resonances in the range of 7.5 - 7.8 ppm that can be attributed to the protons in the phenoxazine ring and peaks at 9.0 ppm and 7.3 ppm which is attributable to the protons in the DPP ring In contrast, the proton in the phenoxazine ring was represented by the P2 spectrum peaks at 7.9 - 8.6 ppm While the resonance at 4.25 ppm in the spectra of P1 is assigned to the two R-methylene protons in the N-substituted hexyl chain, the peak at 2.26 ppm in the P2 spectrum corresponds to the two R-methylene protons in the N-benzoyl hexyl chain.

Figure 3 32 Comparative FT-IR spectra of P1 (a) and P2 (b).

Figure 3 33 'H NMR spectra of P1 (a) and P2 (b) in CDCl.

TGA and DSC analyses revealed good thermal stability in the tested polymers, with Td weight loss of 10% occurring above 350 °C and a 50 wt% loss at 800 °C The DSC second heating scans showed no thermal transitions below 250 °C, indicating the polymers' amorphous nature at this temperature range.

Figure 3 34 TGA (a) and DSC (b), second heating scans curves of spectra of P1 and P2 with heating rate of 10 °Cmin ' under nitrogen atmosphere Ta represents the temperature of 10% weight loss.

Optical Properties of polymers poly(alkyl-POZ-DPP) (PI) and poly(benzoylalkyl-POZ-DPP) (P2) - - s9 ng Hư, 9]

The UV-vis absorption spectra of the two polymers P1 and P2 were recorded at room temperature both in dilute chloroform solution (ca 10 Š M) and as thin films spin-coated onto quartz substrates (Figure 3.35) The detailed absorption data, including maximum absorbance (Amax) in solution and solid state as well as the optical bandgaps, deduced from the absorption edge in films (E,°), are summarized in Table 3.6 The UV spectrum of P1 and P2 polymers in chloroform exhibit a strong absorbance with Amax at

700 nm and 710 nm, respectively This absorption maximum of over 700 nm results from an intramolecular charge transfer (CT) state of the phenoxazine moieties alternate with diketopyrrolopyrrole moieties in the backbone.

The UV-vis spectra of thin films of all polymers show absorption throughout the visible region Moreover, there is significant absorption extending into the near-IR region (as far as ca 900 nm) In the thin film absorption spectrum, the 92 nm red shift in Amax observed for the P2 polymer compared to PT is due to the branched alkyl/benzoyl of group substitutions on phenoxazine The optical band gaps for P1 and P2 polymers were calculated from the absorption cut-off value in the solid state In comparison, P2 films

91 exhibit slightly red-shifted absorption and a lower E,°" of 1.43 eV, whereas P1 films exhibit blue-shifted absorption and a higher E,°" of 1.46 eV The red-shifted absorption maxima in P2 copolymer, indicate that the increased electronic delocalization arising from a more coplanar conformation and reduced steric interactions when benzoyl of group substitutions on phenoxazine moieties alternate with diketopyrrolopyrrole moieties in the backbone The benzoyl system facilitates 7-74 interactions between copolymer chains, although the benzoyl substituent is not in direct but cross-conjugated conjugation with the polymer backbone [149] The substitution of the branched alkyl side chain by a benzoyl ring system led to a significant red-shift of the absorption peak as well as a broadening of the absorption band both in solution and solid state. a) 1.04 : b) 404

Figure 3 35 UV—vis absorption spectra of PI (a) and P2 (b) in CHCl, solution and thin film on a quartz substrate.

Table 3 6 Absorption maxima and energy levels of the polymers. i max Solution i max flim E,0Ptical

Polymer rN optical film (nm)

* Optical band gap estimated from the UV-vis absorption spectra edge in film, E,°?' = 1240/Amax onset The solid-state UV-vis spectra were used to estimate the optical band gaps from the wavelength at the intersection of the tangent drawn at the low-energy side of the absorption spectrum with the x-axis.

CONCLUSION AND RECOMMENDA TION

Contributions Of this H€S1S 5 G5 + 11v 9n TT ng ng 94

The goal of this thesis aims to synthesize novel diblock conjugated copolymers and novel small conjugated molecules and new donor-acceptor conjugated copolymers which can be applied in sensory applications for tracing the toxic and dangerous chemical compounds such as TNT explosives and Mesotrione pesticides.

P3HT-b-PDCTMA, a novel diblock copolymer based on poly(3-hexylthiophene), was synthesized using a combination of GRIM and ATRP methods This diblock copolymer serves as a versatile platform for creating a series of functional diblock copolymers through post-polymerization reactions with thiol and amine compounds The synthetic versatility of P3HT-b-PDCTMA enables the incorporation of various functionalities, expanding its potential applications in diverse fields.

A rod coil diblock copolymer P3HT-5-P(DMAEMA-r-PyMA) has been synthesized successfully via the combination of the GRIM method and ATRP polymerization methods In addition, the diblock copolymer P3HT-b- P(DMAEMA-r-PyMA), the first time, the diblock copolymers P3HT-b- P(DMAEMA-r-PyMA) can be applied as a fluorescence sensor for detector TNT explosive compound.

The novel conjugated molecules of 4-(2-ethylhexyl)-2-(pyren-1-yl)-4H-dithieno [3,2-b:2’,3’-d]pyrrole (EP4HP) and 4-(2-ethylhexyl)-2,6-di(pyren-1-yl)-4H-

94 dithieno[3,2-b:2’,3’-d]pyrrole (EDP4HP) were synthesized in the first time. Moreover, the 4-(2-ethylhexyl)-2-(pyren-1-yl)-4H-dithieno [3,2-b:2’,3’- d]pyrrole (EP4HP) and 4-(2-ethylhexyl)-2,6-di(pyren-1-yl)-4H-dithieno[3,2- b:2’,3’-d]pyrrole (EDP4HP) have been used for tracing mesotrione compound through FRET with high sensitivity of Ksv of 5570 and 6520 M", respectively.

Phenoxazine-based low-bandgap conjugated donor-acceptor copolymers, poly(alkyl-POZ-DPP) and poly(benzoylalkyl-POZ-DPP), were synthesized using direct arylation coupling polycondensation with high yields exceeding 80% These copolymers exhibited superior optoelectronic properties due to the incorporation of phenoxazine units with electron-rich nitrogen atoms and diphenylphosphine oxide (POZ) groups with electron-withdrawing phosphorus atoms The presence of ethylhexyl/hexyl benzoyl side chains further enhanced the solubility and processability of the copolymers.

Recommendations and development directions .- 5 5< £+s£+ssse+sxe 95

Research and test the ability of novel low-bandgap conjugated donor-acceptor copolymers poly(alkyl-POZ-DPP) and poly(benzoylalkyl-POZ-DPP) based on phenoxazine with ethylhexyl/hexyl benzoyl side chain as the chemosensor for tracing nitroaromatic explosive compounds and pesticides.

Investigation and testing of different concentrations of new diblock conjugated copolymers, new small conjugated molecules, and new donor-acceptor conjugated copolymers to trace explosive compounds and pesticides.

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110 ĐẠI HỌC QUOC GIA CỘNG HÒA XÃ HỘI CHỦ NGHĨA VIỆT NAM

THÀNH PHO HO CHÍ MINH Độc lập - Tự do - Hạnh phúc -,

TRƯỜNG ĐẠI HỌC BÁCH KHOA eee

$61,93IQD-DHBK Thành phố Hé Chi Minh, ngày |Gtháng,.LÍ, năm 2023

Về việc thành lập Hội đồng đánh giá luận án tiến sĩ cấp Trường

HIỆU TRƯỞNG TRƯỜNG ĐẠI HỌC BÁCH KHOA

Căn cứ Quyết định số 26/QÐĐ-TTg ngày 26/03/2014 của Thủ tướng chính phủ về việc ban hành Quy chế về Tổ chức và hoạt động của Đại học Quốc gia và các cơ sở giáo dục đại học thành viên,

Căn cứ Quyết định số 867/QĐ-ĐHQG ngày 17/08/2016 của Giám đốc Đại học Quốc gia TP.HCM về việc ban hành Quy định về tổ chức và hoạt động của các trường đại học thành viên và khoa trực thuộc Đại học Quốc gia TP.HCM;

Căn cứ quyết định số 151/OD-PHBK-PTSDH ngày 24/01/2014 của Hiệu trưởng Trường DHBK về việc ban hành "Qui định về Tổ chức và Quản lý đào tạo tiễn sĩ";

Căn cứ quyết định số 1832/OD-PHBK-TCHC ngày 10/7/2019 của Hiệu Trưởng về việc Quy định chế độ làm việc của Giảng viên, NCV, Kỹ sư phục vụ giảng dạy và quyết định số 3465/OD-PHBK ngày 16/11/2020 về việc sửa đổi, bố sung một số điều của Quy định chế độ làm việc của Giảng viên, NCV,

Kỹ sư phục vụ giảng đạy;

Căn cứ quyết định số 1818/QĐÐ-ĐHBK-KHTC ngày 09/7/2019 của Hiệu Trưởng về việc ban hành Quy chế thu chỉ nội bộ và quyết định số 1148/QD-DHBK ngày 18/5/2021 về việc sửa đổi, bổ sung Quy chế thu chỉ nội bộ;

Theo đê nghị của Trưởng phòng Đào tạo Sau đại học.

QUYÉT ĐỊNH: Điều 1 Thành lập Hội đồng đánh giá luận án tiến sĩ cấp Trường với đề tài:

Synthesis and Characterization of conjugated polymers oriented for fluorescence chemosensor

Ngành: Kỹ Thuật Hóa Học (62520301)

Của nghiên cứu sinh: BÙI THANH THẢO (1680488) Khóa: 2016

Danh sách thành viên Hội đồng đánh giá LATS kèm theo Quyết định này. Điều 2 Cấp kinh phí Hội đồng đánh giá luận án tiến sĩ cấp Trường là:

46 giờ chuan/HD x 200.000 đồng/giờ chuẩn = 9.200.000 đồng

Theo Điều 3, Phòng Đào tạo Sau đại học phối hợp với Khoa Kỹ thuật Hóa học chịu trách nhiệm bảo vệ luận án và quyết toán theo quy định Quyết định có hiệu lực trong 90 ngày từ ngày ký (Điều 4) Các cá nhân và đơn vị liên quan, bao gồm Trưởng phòng Đào tạo Sau đại học, Trưởng phòng Kế hoạch - Tài chính, Trưởng khoa Kỹ thuật Hóa học, thành viên danh sách ở Điều 1, tập thể hướng dẫn và nghiên cứu sinh có trách nhiệm thực hiện nghiêm túc quyết định này (Điều 5).

DAL HOC QUỐC) IA CONG HOA XA HOI CHU NGHIA VIET NAM ANE PROG CHE Độc lập - Tự do - Hanh phúc

TRưt 1G DALHOG ¢ DARHOC BACH KHOA ————————

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Trung tam Nghiên cứu Vật liệu

3 903834 GS.TS Phan Bách Thăng Phan biện | Câu trúc Nano và Phân tử

(INOMAR) sme Para sya Trường Dai hoc Khoa học Tự

907145 PGS.TS Hà Thúc Chí Nhân nhiên - ĐHQG TP.HCM x Thu ky Trường Đại hoc Bách Khoa -

003279 TS Nguyén Thanh Tung ĐHQG Tp.HCM

` Ủy viên Trường Đại Học Công thương

H 909521 TS Giang Ngọc Hà Tp.HCM a xưa Ủy viên Trường Đại học Bách Khoa -

003539 TS Cao Xuân Việt hội đồng ĐHQG Tp.HCM

Danh sách Hội đồng gốm 7 thành viên #⁄Z

Họ tên, chức danh khoa học, l an công tá học vị Cơ quan công tác ĐẠI HỌC QUỐC GIA CỘNG HOÀ XÃ HỘI CHỦ NGHĨA VIỆT NAM THÀNH PHO HO CHÍ MINH Độc lập - Tự do - Hạnh phúc

TRƯỜNG ĐẠI HỌC BÁCH KHOA

NHAN XÉT LUẬN ÁN TIEN SĨ

Của nghiên cứu sinh: BÙI THANH THẢO

Tên dé tài: Synthesis and characterization of conjugated polymers oriented for fluorescence chemosensor.

Ngành: Kỹ thuật hóa học Mã số: 62520301

Họ tên người nhận xét: Nguyễn Cửu Khoa

Chức danh: GS Năm bổ nhiệm: 2016 Học vi: TS Năm bảo vé:1997

Chuyên ngành: Hóa hữu cơ

Cơ quan công tác: Học Viện Khoa học Công nghệ Viện HL KHCN VN Ý KIÊN NHAN XÉT

1 Sự cần thiết và tính thời sự, ý nghĩa khoa học và thực tiễn của đề tài:

Ngành khoa học vật liệu luôn nghiên cứu tìm kiếm những vật liệu mới có tính “thông minh” và hiệu quả hơn Vật liệu polymer liên hợp là polymer có cấu trúc xen ké liên kết nối đôi và nối đơn Do đó chúng có tính chất rất thú vị, đó là tính chất dẫn điện bởi sự dịch chuyên liên tục của dong electron Trên cơ sở tính chất đó mà chúng được nghiên cứu ứng dung trong nhiều lĩnh vực, đặc biệt trong lĩnh vực làm vật liệu bán dẫn. Đề tài luận án tập trung nghiên cứu tổng hợp các vật liệu bán dẫn là copolymer P3HT- b-PDCTMA trên cơ sở poly(3-hexylthiophene) được tổng hợp bằng phương pháp ATRP. Đó là phương pháp tông hợp mới có tính chính xác cao về cả thành phan cấu trúc và kích thước của phân tử polymer Vật liệu mới trên được khảo sát, đánh giá các tính chất bằng các phương pháp hóa lý hiện đại như FT-IR, NMR, UV-Vis, SEC (size- exclusion chromatography), Fluorescence spectrometer, DSC, TGA.

Do đó dé tai vừa có ý nghĩa khoa học vừa có ý nghĩa thực tiễn.