functional polymers powerpoint

Outline of Chapter 66-1 Introduction to Functional Polymers 6-2 Conducting Polymers 6-3 Polymeric Membrane... What are Functional Polymers?— Functional polymer —— according to IUPAC a a

Functional Polymers

The conductive polyacetylene (PA)

Outline of Chapter 6

6-1 Introduction to Functional Polymers

6-2 Conducting Polymers

6-3 Polymeric Membrane

What are Functional Polymers?

— Functional polymer —— according to IUPAC

(a) a polymer bearing functional groups (such as hydroxyl,

carboxyl, or amino groups) that make the polymer reactive, (b) a polymer performing a specific function for which it is

produced and used

— A polymer that exhibits specified chemical reactivity or has

specified physical, biological, pharmacological, or other uses

Classification of functional polymers- (IUPAC)

Conventionally, it can be classified as follows:

— Reactive polymer

— Photosensitive polymer

— Electrical polymer

— Polymer materials for separation

— Polymer materials for adsorption

— Intelligent/smart polymer

— Polymer materials for medical or pharmaceutical use

— Engineering polymer materials with high performance

— Organic catalysis (supported catalysts)

— Medicine (cell substitutes)

— Optoelectronics（光电子学） (conducting polymers)

— Magnetic polymers and polymers for nonlinear optics

6.2 Conducting Polymers

Discovery of Conducting Polymers

— In 1977, insulating π-conjugated polyacetylene (PA) could becomeconductor with a conductivity of 103 S/cm by iodine doping

Molecular structure of polyacetylene

— PA is a flat molecule with an angle of 120 o between the

bonds and hence exists in two different forms, the isomerscis-polyacetylene and trans-polyacetylene

— The discovery of the conductive PA was awarded the Nobel Prize

in Chemistry for 2000

Photograph of three awardees of the Nobel Chemistry Prize in 2000

Alan G MacDiarmid (left) Prof at the Univ of Pennsylvania, USA Hideki Shirakawa (middle) Prof Emeritus, Univ of Tsukuba, Japan Alan J Heeger (right) Prof at the Univ of California at Santa Barbara, USA

Typical Conducting Polymers

—π-conjugated polymers: polypyrrole (PPy), polyaniline (PANI),

polythiophenes (PTH), phenylene)(PPP),

poly(p-phenylenevinylene)(PPV), and poly(2,5-thienylenevinylene)(PANI)

1 Thin-Film Deposition and Microstructuring of Conducting Materials

Scheme for polymerization in pores (a) Ideal case; (b) nucleation at the

bottoms of the pores; (c) nucleation at the walls of the pores

— The filling of molds, holes and gaps of conducting polymers via

electrochemical polymerization.

— Potential approaches to microstructuring via conducting polymers.

Schemes for pre- and post-structuring conducting polymers

polymer film is prepared at

the surface and then

2 Electroluminescent and Electrochromic Devices

— Organic electroluminescent devices (LED’s) are a possible alternative to liquid crystal displays and cathodic tubes, especially for the development

of large displays The principal setup for a polymeric LED is emitting polymer/metal.

ITO/light-The change in the color of a PENTBE film deposited onto ITO-coated glass: a reduced state, and b oxidized state.

The electropolymerization of

bis(3,4-ethylene-dioxythiophene (EDOT)–

(4,4-dinonyl-2,2-bithiazole) leads to

a homogeneous and high-quality

polymer film (PENBTE)

2 Electroluminescent and Electrochromic Devices

— PANI-based flexible electrochromic display device

— The display region and the connections were made by depositing gold on a plastic sheet using an appropriate mask and an evaporation technique Each pixel can be

driven separately Left: PANI is in its oxidized state in all pixels Right: PANI is reduced in two pixels (the bleached ones)

3 Corrosion Protection

— Conducting polymers can be deposited as a corrosion protection layer

— is partly motivated by the desire to replace coatings that are hazardous to the environment and to human health

— The cheap and effective polymers PANI, PP, and PT (and their derivatives) have mostly been used

— The favorite substrate used in such investigations is mild steel, but aluminum, copper, titanium or even dental materials have also been discussed

Corrosion protection for semiconductors:

— Nafion/TTF for Si

— Polypyrrole for n-Si, n-CdS, n-CdSe, and n-GaAs

— PANI for n-Si, N-CdS, n-CdSe, and n-GaAs

— PT for n-CdSe and n-CdS

3 Sensors

Applications of Conducting Polymers

— The use of conducting polymers in sensor technologies involves employing the conducting polymers as an electrode modification in order to improve sensitivity, to impart selectivity, to suppress interference, and to provide a support matrix for sensor molecules.

— Active role: when used as a catalytic layer, as a redox mediator, as a switch,

or as a chemically modulated resistor, a so-called “chemiresistor”

— Passive role: when used as a matrix

3-1 Gas Sensors

Applications of Conducting Polymers

Layout designs of thin-film and thick-film polymer gas sensors

3-1 Gas Sensors

Configuration of a polyaniline-based microelectrode device

3-2 Electroanalysis and Biosensors

Applications of Conducting Polymers

4 Materials for Energy Technologies

— The ability to reversibly switch conducting polymers between two redox states initiated their application to rechargeable batteries.

— The first prototypes of commercial batteries with conductive polymers

used Li/polypyrrole or Li/polyaniline.

— Conducting polymers have been shown to be highly effective when

used as protective layers on anodes in fuel cells.

— Another field of application is provided by the excellent ionic conductivities

of conducting polymers, which permit high discharge rates

— Conducting polymers (PANI and PT derivatives) have also been utilized in photovoltaic devices.

4 Materials for Energy Technologies

Applications of Conducting Polymers

Schematic structure of the photovoltaic device PBT: polybithiophene,

FTO: fluorine-doped tin oxide Example: PBT|FTO|Al devices

5 Electrocatalysis

— The electrocatalytic properties of conducting polymers can be utilized not only to sense substances but also for electrochemical synthesis or in power sources.

— There are numerous examples of reaction catalysis by polymer films in their conductive states rather than the bare electrode.

— PANI in its protonated emeraldine form behaves as a metal electrode, while

at more positive potentials, where polyaniline exists in pernigraniline form, the behavior of PANI resembles a redox polymer.

6.3 Polymeric Membrane

— Synthetic membrnes:

● Initiator — Dr Sourirajan, removed salt from seawater, in the late

1950's

● Commercial RO & UF membranes occurred in the early 1970’s

● Crossflow membrane processes became well accepted in industryand medicine in the 1980’s

● Widely used today

Introduction

— Natural membrane:

● Bovine bladder used as semipermeable membrane

— A membrane is an interphase between two adjacent phases acting

as a selective barrier, regulating the transport of substances

between the two compartments

— Polymeric membranes are membranes that take the form of

polymeric interphases, which can selectively transfer certain

chemical species over others

— The transport selectivity of the membrane

— Separations with membranes do not require additives

— at low temperatures and at low energy consumption

— up-scaling and down-scaling of membrane processes as well as their integration into other separation or reaction processes are easy

Important Index

— Pore sizes and its distribution: determining the sieved particlesand selectivity

— Porosity: The effective working area

SEM of polymeric membrane Pore size distribution

— Flat sheet membrane

— Hollow fiber membrane

— Capillary/tubular membrane

Capillary membrane tubular membrane

— Symmetric membrane

— Asymmetric membrane

Schematic diagram of a) a symmetric and b) an asymmetric membrane

Schematic diagram of the filtration behavior of a) an asymmetric

and b) a symmetric membrane

Structure of porous membranes

SEM diagram of a) an asymmetric b) a symmetric membrane

2 1 3

Typical Asymmetric Structure

1

Driving force for membrane separation

Driving force Processes

Pressure Microfiltration, Ultrafiltration,

Nanofiltration, Reverse Osmosis

Electrical

potential

Electrodialysis Partial pressure Pervaporation

Concentration

gradient

Dialysis

Dead-end pressure-driven membrane filtration

Cross-flow pressure-driven membrane filtration

Cross-flow Membrane Technology

Four main categories:

Reverse Osmosis (RO)

Nanofiltration (NF)

Ultrafiltration (UF)

Microfiltration (MF)

Pore sizes: 4 to 8 Å Transmembrane pressures (TMP): 35~100 atm Cutoff molecular weight: 25 and 150

Pore sizes: close to 10 Å TMP: Higher than UF

Cutoff molecular weight: 150 ~ 1000

Pore sizes: 0.005 to 0.1 µm TMP: Higher than MF

Cutoff molecular weight: 2,000 to 300,000

Pore sizes: 0.05 to 3 µm TMP: 0.3~3.3 bar

Applications: starch, bacteria, molds, yeast

and emulsified oils

Other types of separation

Electrodialysis

● Removal of ionic species from non-ionic products

Pervaporation

● Separation of liquid mixtures by partial vaporization through

a permeable selective membrane

● Phase change occurs

Dialysis

● A concentration-driven diffusion

● Application:

Separation of proteins and other macromolecules from salts

in pharmaceutical and biochemical applications, e.g., hemodialysis

For polymeric membrane, the most popular

preparation methods are:

Melt method: for spinning of hollow fibers with

symmetric structure from polymeric materials, e.g.,

PP hollow fiber membrane

Solution method: for preparation of flat sheet and polymeric membranes with asymmetric structure

NF membrane materials

PA membranes

CA membranes

CA membranes

PVDF membranes

PSF membranes

Tolerate a pH range of 0.5 to 13, temperatures to

85°C (185°F), and 25 mg/L of free chlorine on a continuous basis

— Boiler feed

— Potable from brackish or alkaline source

— Color removal from water

— Microbial removal; bacteria, pyrogens, giardia and cryptosporidium cysts

— THM precursor and pesticide removal

— Potable from seawater

— Sodium and organics reduction for beverages

— Reconstituting food and juices

— Bottled water

— Can and bottle rinsing

— Rinse water for metal finishing operations

— Laboratory and reagent grade water

— USP Purified Water and Water for Injection

— Semiconductor chip rinsing

— Distillation and deionization system pretreatment

— Kidney dialysis

— Medical device and packaging rinse water

— Photographic rinse water

— Pulp and paper rinses and makeup water

— Dye vat makeup

— Juice and milk concentration

— Beer and wine finishing

— Beverage flavor enhancement

— Cheese whey fractionation/concentration of proteins and lactose

— Food oils, proteins, taste agents concentration

— Saccharide purification

— Maple sap preconcentration

— Enzymes and amino acids, purification and concentration

— Chemical dewatering

— Chemical mixtures fractionation

— Dye and ink Desalting™

— Glycol and glycerin recovery

— ED paint's recovery from rinses

— Medicine and vitamin concentration purification

— Blood fractionation

— Cell concentration

— Photographic emulsions concentration/purification

— Tertiary sewage water recovery

— Heavy metals and plating salts concentration

— BOD and COD concentration

— Dewatering liquid for reduced disposal volume

— Dilute materials recovery

— Radioactive materials recovery

— Textile waste recovery for reuse

— Pulp and paper water recovery for reuse

— Dye and ink concentration and recovery

— Photographic waste concentration and recovery

— Oil field "produced water" treatment

— Lubricants concentration for reuse

— Commercial laundry water and heat reuse

— End of pipe treatment for water recovery

Composite membranes —— RO, UF & NF

Improved both flux and separation

Increase chemical durability of membranes

Surface treatment techniques

Adding formal charges —— to change separation ability and reduce fouling tendency

Enhanced systems controls —— improved the operational efficiency

Industry's evolving realization —— treatment systems are often mostefficient if they combine several unit processes

Molecular Adsorbents Recirculating System

Examples:

Extracorporeal Bioartificial Liver Reactor Model