Chemistry for Materials (MAT5002) -Lecture 1 Introduction to Polymer Structures
Chemistry for Materials (MAT5002) -Lecture 1 Introduction to polymer structures
Dr Petra Ágota Szilágyi Engineering #123 Office hour: Thursday 11 am – 12 noon [email protected] Introduction
• 5 weeks x 3h per week = 15h of lectures
• Lecture on 26/11/2019 cancelled – re-schedule only if necessary
• Introduction to polymer structures and mechanisms
• Step growth mechanism, polyesters, polyamides, esterification
• Chain growth mechanism, free radical mechanism, reaction kinetics
• Controlled polymerisation, anionic, cationic, ring opening, controlled radical polymerization
• Kinetics of polymerisation reactions
• Determination of molar mass of polymers, degradation mechanisms
• X-linked polymers, networks, gels, elastomers, gelation point
• Revision lectures - TBC
• Coursework: Hand in date: 9/12/2019 1 Books
• Principles of Polymerisation G Odian
• Polymer Synthesis P Rempp and E W Merrill
• Polymers: Chemistry & Physics of Modern Materials J M G Cowie
• Polymer Chemistry : An Introduction G Challa
• Polymer Chemistry Second Edition P Hiemenz and T P Lodge
• Introduction to Polymers Third Edition R J Young and P A Lovell
2 E-Books from QMUL library
3 Review articles • Chemical Reviews – Frontiers in Polymer Science thematic issue number 11, 2009.
• Kamigaito, M.; Ando, T.; Sawamoto, M. Chem. Rev. 2001, 101, 3689.
• Matyjaszewski, K.; Xia, J. Chem. Rev. 2001, 101, 2921.
• Hawker, C.; Bosman, A. W.; Harth, E. Chem. Rev. 2001, 101, 3661.
• Gridnev, A. A.; Ittel, S. D. Chem. Rev. 2001, 101, 3579.
• Barner, L.; Barner-Kowollik, C.; Davis, T. P.; Stenzel, M. H. Aust. J. Chem. 2004, 57, 19-24.
• Chiefari, J.; Chong, Y. K.; Ercole, F.; Krstina, J.; Jeffery, J.; Le, T. P. T.; Mayadunne, R. T. A.; Meijs, G. F.; Moad, C. L.; Moad, G.; Rizzardo, E.; Thang, S. H. Macromolecules 1998, 31, 5559- 5562.
• Handbook of Radical Polymerization; K Matyjaszewski and T P Davis, Wiley Interscience
4 Polymer Journals
5 History of polymers
• Natural polymers
Wood Cotton Rubber Silk Spider web
• Synthetic polymers
6 History of polymer science
1830s: first modern example of polymer science: Henri Braconnot & Christian Schönbein develop derivatives of the natural polymer cellulose, producing new, semi-synthetic materials, such as celluloid and cellulose acetate. 1833: Term "polymer" was coined by Jöns Jakob Berzelius. 1840s: Friedrich Ludersdorf & Nathaniel Hayward independently discover that adding sulphur to raw natural rubber (polyisoprene) helps prevent the material from becoming sticky. 1844: Charles Goodyear receives a U.S. patent for vulcanising natural rubber, it represents the first commercially successful product of polymer research. 1884: Hilaire de Chardonnet develops the first artificial fibre, from regenerated cellulose (viscose rayon) as a substitute for silk. 1907: Leo Baekeland invents the first synthetic plastic, a thermosetting phenol–formaldehyde resin called Bakelite. 1922: Molecular nature of polymers is first understood by Hermann Staudinger. It took over a decade for Staudinger's work to gain wide acceptance in the scientific community, work for which he was awarded the Nobel Prize in 1953. World War II era - strong commercial polymer industry. 1946, Herman Mark established the Polymer Research Institute at Brooklyn Polytechnic, the first research facility in the US dedicated to polymer research. 1950, the POLY division of the American Chemical Society was formed, 2nd largest division with nearly 8,000 members. 7 Nobel prizes related to polymer science
2005 (Chemistry) Robert Grubbs, Richard Schrock, Yves Chauvin for olefin metathesis. 2002 (Chemistry) John Bennett Fenn, Koichi Tanaka, and Kurt Wüthrich for the development of methods for identification and structure analyses of biological macromolecules. 2000 (Chemistry) Alan G. MacDiarmid, Alan J. Heeger, and Hideki Shirakawa for work on conductive polymers, contributing to the advent of molecular electronics. 1991 (Physics) Pierre-Gilles de Gennes for developing a generalized theory of phase transitions with particular applications to describing ordering and phase transitions in polymers. 1974 (Chemistry) Paul J. Flory for contributions to theoretical polymer chemistry. 1963 (Chemistry) Giulio Natta and Karl Ziegler for contributions in polymer synthesis. (Ziegler- Natta catalysis). 1953 (Chemistry) Hermann Staudinger for contributions to the understanding of macromolecular chemistry.
8 Why use (synthetic) polymers?
Advantages: Cheap (polyethylene: 50-80 €/tonne, nylon: 100-200 €/tonne scrap steel 230 €/tonne; hot rolled coil stainless steel: 3000-6000 €/tonne) Good quality Easy to process, fast to process e.g. to convert into certain forms, such as bottles or fibres (lower temperatures than needed for metals) Light (energy saving in cars or planes) Sufficient petrochemical resources (at present more than 90% are used for energy production) Possibility to switch to natural resources (poly(lactid acid), soy beans, cellulose) Easy formulation compounding a broad spectrum of different properties is available Recycling possibilities (thermal recycling, reuse) Tuneable properties (sort of monomer, constitution, molecular mass, …)
Applications Plastics (e.g. packaging materials) Agriculture (e.g. promoting plant growth) Coatings & adhesives (e.g. paints) Medicine (e.g. replacement of heart valves) Fibres (e.g. clothes) Specialty polymers (high thermal stability) Rubbers & elastomers (e.g. tyres) Plastic electronics (e.g. PLED, solar cells)
9 Source: British Plastics and rubber, www.mpes.co.uk ACRYLONITRILE-BUTADIENE-STYRENE (ABS)
Resistant to a broad range of chemicals
Polar nitrile groups attract each other and bind the chains together, making ABS stronger than pure PS
styrene gives the plastic a shiny, impervious surface
10 ACRYLICS – POLY(METHYL METHACRYLATE)
Economical alternative to polycarbonate (PC): when good tensile and flexural strength, transparency, polishability, and UV tolerance are more important than impact strength, chemical resistance and heat resistance
11 FLUOROCARBONS- PTFE Also: lubricant, PTFE reduces friction, wear, and energy consumption of machinery
Because of its inertness it cannot be cross-linked like an elastomer. Therefore, it has no "memory" and is subject to creep.
Because of its superior chemical and thermal properties, PTFE is often used as a gasket material within industries that require resistance to aggressive chemicals such as pharmaceuticals or chemical processing 12
Hydrophobic POLYAMIDES - NYLONS
planar amide groups form multiple H- bonds among adjacent strands
regular & symmetrical, esp. if all amide bonds are trans → often high crystallinity 13 and make excellent fibres POLYCARBONATES
Despite high impact-resistance, it has low scratch-resistance → hard coating applied to viz. eyewear lenses
Carbonate groups
14 POLYETHYLENE
low strength, hardness and rigidity, but has a high ductility and impact strength as well as low friction
nonpolar, saturated, high molecular weight hydrocarbons → chemical behaviour α paraffin
symmetric molecular structure → tend to crystallise 15 POLYPROPYLENE
Similar to PE but - Less crystalline - Tacticity
Resistant to most chemicals expt strong oxidising agents
16 POLYSTYRENE
clear, hard, and brittle solid foamed poor barrier to oxygen and water vapour and has a relatively low melting point
17 Vinyls
Rigid Flexible w. plasticiser
Vinyl benzene (styrene), vinyl chloride, vinyl acetate, vinyl alcohol, acrylonitrile PVC: good insulation properties chemically resistant to acids, salts, bases, fats, and alcohols, making it resistant to the corrosive effects of sewage POLYESTERS
Natural polyesters could have played a significant role in the origins of life: long heterogeneous PE chains form easily in a one-pot reaction PCL PET without catalyst under simple Poly(glycolide) prebiotic conditions Vectran-Liquid crystal polymer
19 THERMOSETS - EPOXIDES
Araldite: Epoxy-acrylic and polyurethane based polymer
Epoxy resins may be reacted (cross-linked) with themselves through catalytic homopolymerisation, or with a wide range of co-reactants including polyfunctional amines, acids (and acid anhydrides), phenols, alcohols and thiols. These co-reactants are often referred to as hardeners or curatives, and the cross-linking reaction is commonly referred to as curing. 20 THERMOSETS - PHENOLICS
Novolacs - phenol-formaldehyde resins with mostly phenol. Polymerisation goes via acid-
catalysis H2SO4, oxalic acid, HCl etc.
Resoles - Base-catalysed phenol- formaldehyde resins of formaldehyde to phenol ratio >1.
Phenol-formaldehyde resin
Obtained by the reaction of phenol or substituted phenol with formaldehyde. 21 THERMOSETS - POLYESTERS
CROSSLINKED POLYESTERS!!
Combination of alcohol-like ethylene glycol with organic acids, e.g. maleic anhydride 22 Elastic Polymer ELASTOMER - Natural Poly(Isoprene)
23 ELASTOMER - Styrene-Butadiene Copolymer
good abrasion resistance and good aging stability when protected by additives
24 ELASTOMER - Acrylonitrile-Butadiene
Physical and chemical properties vary depending on the polymer’s composition of nitrile.
generally resistant to oil, fuel, and other chemicals
25 ELASTOMER - Chloroprene
2-chlorobuta-1,3-diene 26 ELASTOMER - POLY(SILOXANE)-Silicone
Typically heat-resistant and either liquid or rubber-like. Used in sealants, adhesives, lubricants, medicine, cooking utensils, and thermal and electrical insulation.
Low thermal conductivity Low chemical reactivity Low toxicity Thermal stability Hydrophobic → watertight seals. Depending on substrate may or may not stick Does not support microbiological growth
Resistance to O2, O3, and UV light. → coatings, fire protection, glazing seals. Electrical insulation properties. High gas permeability→ medical applications. 27 Polymer structure – applications
PE Poly(ethylene) packaging CH2CH2 n gas pipes PP Poly(propylene) packaging n plastic mouldings
PVC Poly(vinylchloride) pipelines n building material Cl
PET Poly(ethylene food and liquid terephthalate) O(CH2CH2)O containers O O n PS Poly(styrene) insulation n packaging
28 Polymer structure – applications
PA6 Poly(amide 6) synthetic fibres N H O n O PA6 Poly(amide 66) H synthetic fibres N N H O n
PBT Poly(butylene- enclosure of electric terephthalate) devices O(CH2CH2CH2CH2)O O O n
PC Poly(carbonate) O greenhouses O O CD, DVD
n Polymer structure – applications Poly(imide) electronic O O industry
N N
O O n
PEI Poly(ethyleneimine) cell extraction H N n
PI Poly(isoprene) rubber
n PTFE Poly(tetrafluoro- Teflon ethylene) CF2 n 30 Polymer structure – applications
SAN Poly(styrene-acrylonitrile) optics n m reflectors CN
POM Poly(oxymethylene) automobile parts CH2O n fixative
PMMA Poly(methylmeth-acrylate) optics n glass-like appl. COOMe PSU Poly(sulphone) Membranes, composite material
O O O S O n Polymer structure – applications
PVA Poly(vinyl alcohol) carbon dioxide n barrier OH
PEG Poly(ethylene clinical use glycol) O n cosmetics PEEK Poly(etherether- medical implants ketone) O O O parts of pumps n
PAN Poly(acrylonitrile) fibres n CN Classification of polymers I
Distinction of origin and manufacturing
Polymers
Natural polymers Synthetic polymers
Proteins Polysaccharides Rubber, Resins Thermoplastic Thermoset
Glucose Modified natural Ethylene polymers
Poly(ethylene) 33 Cellulose Natural polymers
• Polysaccharides: starch, cellulose, chitin (repeating unit) • DNA, RNA: containing regular polymer backbones, variable side groups • Proteins and Peptides: no repeating unit, same building blocks, monodisperse
34 Classification of polymers II
Homopolymer only one monomer species poly(A) Co-polymers more than one monomer species
Bipolymers/Co-polymers two different monomers poly(A-co-B) Ter-polymers three monomer species poly(A-co-B-co-C) Quarter-polymers four different monomers
Penta-polymer, .... poly(A-co-B-co-C-co-D)
poly(A-co-B-co-C-co-D-co-E) 35 No constitution, only composition Classification of polymers III
hypothetical repeating unit Alternating co-polymer
Poly(A-alt-B) Statistical co-polymer distribution obeys statistical laws, otherwise random Poly(A-stat-B) Poly(A-ran-B) Gradient co-polymer two monomers (one end many of monomer A, monomer B vice versa)
Graft co-polymer
Poly(A)-graft-poly(B) 36 Classification of polymers IV
Block polymers composed of blocks in sequence
Block co-polymer more than one monomer, sequence of blocks, each block consists only out of one monomer
Diblock co-polymer poly(A)-block-poly(B)
Triblock co-polymer poly(A)-block-poly(B)-block-poly(C) Tetrablock co-polymer
poly(A)-block-poly(B)-block-poly(C)-block-poly(D) Multiblock co-polymer
poly(A-B)n
37 Classification of polymers V
Comb co-polymers each monomer has a side-chain
5 6 5 4 5 6 38 Classification of polymers VI
Tetrablock quarter-polymer
Tetrablock ter-polymer
Triblock ter-polymer
Triblock bi-polymer number of blocks, number of different monomers (latin) (greek) 39 Classification of polymers VII
linear polymers star-polymers
branched polymers
dendrimers (3. generation) crosslinked polymers
branched polymers: short-chain branches = oligomeric subunits
long-chain branches = polymeric subunits 40 Classification of polymers VIII
hyperbranched polymers comb polymers
core unit
ladder polymers
41 ISOMERISM IN POLYMERS
42 Tacticity of polymers
Isotactic all R groups on the same side of chain
Syndiotactic R groups alternate sides
Atactic R groups randomly positioned 43 Example for tacticity: poly(propylene)
propene poly(propylene) atactic poly(propylene)
• atactic: no long range order, amorphous • isotactic: helix, crystalline, best mechanical properties • syndiotactic: crystalline, zig-zag conformation isotactic poly(propylene) • melting point: at < st < it 120<130<165 oC • crystallinity: st < it
• industry: mainly isotactic PP syndiotactic poly(propylene) 44 Tacticity vs density
Isotactic (it) R R Syndiotactic (st) Isotactic dyad Atactic (at) R Syndiotactic dyad
R Real tacticity: Polymers are neither 100% isotactic nor 100% syndiotactic Defects are described by sequences of dyads, triads, tetrades
Polymer Tacticity Density [g/mL] Poly(methyl methacrylate), PMMA Atactic 1.188 Isotactic 1.22 Syndiotactic 1.19
Poly(styrene), PS Atactic 1.045 Isotactic 1.054
45 Cis-trans iso/Head-tail iso cis – trans isomers: poly(isoprene)
n n trans: guttapercha cis: natural rubber hardness elasticity head-tail- and head-head and tail-tail-polymers: vinylpolymers
head-tail
tail head
head-head tail-tail 46 Chemical isomerism - poly(isoprene)
1,2-polyisoprene
n
n 3,4-polyisoprene
1,4-polyisoprene n
47 Summary
48