Polymer Chemistry - Synthesis, Characterisation and Applications

Polymer Chemistry - Synthesis, Characterisation and Applications

Lectures every Thursday, 16:15 18:00 Small PC Lecture Hall Exceptions: 13.04.2017 (before Easter) 04.05.2017 asic Infos: Contact Dr. Jens Gaitzsch jens.gaitzsch@unibas.ch PC uilding, Room 4.06 Written Exam in the end, Graded 6.0-1.0 Exam (tbc): 08.06.2017, 10:00 am, Large PC lecture Hall

Outline 1. Introduction, Classifications, Overview, Terminology 2. Polymer Synthesis Polycondensation/Polyaddition Ring Opening (Metathesis) Polymerisation Radical Polymerisation Ionic polymerisation 3. Hyperbranched Polymers and Dendrimers 4. lock-copolymers 5. Polymer Networks

Polymer Chemistry - The asics

History of polymers Aims of this part: Classes and types of polymers Synthetic origin of polymers Nomenclature of polymers raun, Chedron, Rehann, Ritter, Voit Polymer Synthesis: Theory and Practice, Springer, 5 th Edition, 2013. Sections 1.1 + 1.2 Lechner, Gehkre, Nordmeier, Makromolekulare Chemie, Springer, 5 th Edition, 2014. Section 2.1

Polymers are everywhere Starch Cotton DNA PET ottles Polystyrene Expanding Foam (Polyurethane)

Definition of a Polymer Polymers are Macromolecules Molecules with > 1000 atoms with (mainly) covalent bonds in between uilt from repeating units (monomers) Monomer Oligomer Polymer = uilding lock of the Polymer = up to 10 repeating / M < 1000 g/mol = more than 10 repeating units, M >> 1000 g/mol These definitions are NOT rock solid but do vary for each system Ethylene (Monomer) Paraffin Wax (Oligomer) Polyethylene (PE, Polymer)

History of Polymers Used for a very long time: Natural polymers are used since a long time (some since the stone age) Sometimes modified for better use: : skin (leather), hair (wool), cellulose (paper), resins, natural rubber Also: designed use of special resins: e.g. asphalt (Egypt), laquers (China) and rubber balls (Maya) Through the middle ages no significant development Industrial revolution made basis for new man-made materials Actual research started in 20th century

History of Polymers 1st industrial Polymers: 1901 Röhm: polyacrylic acid esters 1906 Hoffmann: polyisoprene 1907 akeland: akelit (phenol-formaldehyde-resin); typical black! 1915 ayer: polydimethylbutadiene 1920 Hermann Staudinger: Macromolecules for the first time considered, not micelles or associates! Many opposite opinions at that time: Molecules with molar masses > 5000 g/mol do not exist! He should clean his stuff! Schmierenchemie! (= dirty chemistry)! critical remarks by Wieland and Fischer, both Nobel laureates, 1902 and 1927) 1940 Controversial discussion stops Compare work of Flory and Stockmeyer 1970 Prestigious Hermann Staudinger Preis gets started in Germany. Given every 2 years at max. (Reveived by Wolfgang Meier in 2006) H. Staudinger, noble laureate 1953

History of Polymers Important steps for industrial polymers 1928 Röhm: Plexiglas (PMMA) 1930 ASF: polystyrene, polyacrylonitrile 1934 PVC 1937 IG Farben: UNA (first synthetic rubber) DuPont: Nylon-6,6 ayer: polyurethanes via isocyanates 1938/39 ASF: Nylon-6 = Perlon 1945/46 ICI/Hoechst: Terylen/Trevira PET 1946 DuPont: Teflon (polytetrafluorethylene) 1952/53 ZIEGLER-catalysts TiCl 4 + Al(C 2 H 5 ) 3 polymerization of ethylene at ambient pressure Natta: used ZIEGLER-catalysts for polyolefine synthesis stereoselective (= isotactic) polypropylene! Ziegler-Natta-polymerization for preparation of tactic polymers 1957 General Electric and ayer: polycarbonate 1962 DuPont: polyimide and polyphenylene 1970 PET/PT (poly(butylene terephthalate)) SS (stryrene-butadiene-styrene) block copolymers (Kraton) 1975 Kevlar (aromatic polyamide, bullet proof west, aerospace)

Classes of Polymers - by Origin Natural Polymers Synthetic Polymers Synthesised in in animals/plants/etc. Controlled synthesis by the means of specialised enzymes Defined branching and folding Only biodegradble polymers ased Sugars, Amino acids or nucleobases Can be modified for specific uses Synthesised in laboratories/industry Catalysts sometimes used, but uncontrolled synthesis also common ranching and Folding at random Many non-degradable polymers ased on styrenes, (meth)acrylates, alcohols, esters - all bifunctional molecules can be polymerised

Classes of Polymers - by Origin Natural Polymers Synthetic Polymers For DNA/ Proteins: Highly Defined Molecular Structure, so one substance refers to: One Structure One Molecular Weight Defined branching & folding Defined primary sequence Holds Information Holds recognition centres Can be translated into other polymers Most Synthetic Polymers: Defined repeating molecular Structure, meaning: One Substance Mostly one repeating unit Only average Molecular Weight Seldomly defined secondary structure Do not hold information Also possible: Modified natural polymers (Cellulose acetate, vulcanised rubber)

Classes of Polymers - by Chemical ond Polyester PET (bottles), PLA, PCL as biodegradble polymers Polyamide Nylon, Pept(o)ides, Kevlar, Nomex (mech. strong if R =H) Polyurethane Expansion Foam, Ski boots thermoplastic elastomers Polyenes Poly(meth)- acrylates, Styrenes, Polydienes (Mass Polymers) Polycarbonates Often semicrystalline Used for CDs/DVDs Polyoxazolines PMOxa PEtOz And so on (quasi- Polyamides) Polyether PEG Poly/THF And similar Polythioether & Polysulfone Synthetically not very important Silicone Hybrid Organic/ Inorganic Polymer R = Me PDMS (most prominent)

Classes of Polymers - by Architecture Thermoplasts Polymers Many Single Chains Not interconnected Can Melt Can be reshaped in heat Duroplasts (Duromers) All one Molecule Strong and Tight Network Cannot Melt Cannot be reshaped All one Molecule Elastomers Loosely interconnected Network Cannot Melt Can regain shape after deformation

Synthetic Polymers Synthetic Polymers are derived from resources like mineral oil or methane gas 46,3 Million tons of plastic were demanded Europe in 2012 25% of the European demand of plastic goes to Germany (2 nd with 14% Italy, then France with 10%) Used in construction, packaging, automobiles, electronics, etc. Plastic-Reusage: 26% get recycled, 38% to landfill, 36 % energy recovery Plastic is a resource thought is on the rise across Europe.

Polymeric Terms Tacticity important for polymers with side chains at stereocentres Atactic No specific arrangement Isotactic All on the same side Syndiotactic Always alternating Has great influence on the processability of the polymer Synthesis of tacticity-defined polymers is demanding & important Atactic Polypropylene is a wax used as additive Isotactic Polypropylene is used for shopping baskets

Polymeric Terms Upon heating, the polymer chains can increasingly easily with 2 Transitions Glass Transition Temperature, T g Determines the transition between a glassy amorphous state (below T g ) and an elastic state (above T g ) T g can be tuned by plastifiers Prominent T g s: PE: -133 C, PDMS: -123 C PEG: -133 C PP: 0 C (atactic) / 25 C (isotactic) PS: 100 C PMMA: 105 C (atactic, Plexiglas) PC: 150 C (PA-based)

Polymeric Terms Upon heating, the polymer chains can increasingly easily with 2 Transitions Crystallisation Temperature, T c chains are mobile enough to take order not for all polymers, just semicrystalline ones. T g and T c can be the same! Melting Temperature, T m - Determines the transition between an elastic OR semicrystalline state (below T m ) and a Polymer melt (above T m ) Thermoplasts only Thermal reshaping is possible Decomposition Temperature (T d ) present for all polymers Elastomers, Duromers go from T g directly to T d

Polymeric Terms Terminology on polymer architecture linear branched star network Dendritic = Dendrimers Hyperbranched Polymers Polymer where the branches continue to have branches Hyperbranched polymer: Unordered branches, also terminating units present Dendrimers: Continous branching, highly ordered. Terminating units ONLY on the outside

Terminology overall structure Polymeric Terms worm like rigid rod Coil (amorph) highly crystalline beta-sheet structure partial crystalline liquid crystalline orientation of dipols Dependent on: Polymer-Polymer interactions Polymer-Solvent interactions Physical state of the polymer

Terminology on polymer sequences Polymeric Terms Homopolymer n = ( ) n Monomer A n = Copolymer ( ) n Monomer alternating random block structure (long monomer sequences) graft copolymers star copolymers

Molecular Weight Types of Molecular Weight Number Average: As a consequence: Weight Average: Dispersity is a measure for the grade of distribution: Đ with Đ M n i M n M w 1.3 (1.4) being narrowly distributed i n M i n i i M w M M i w n i n M i n M i 2 i i An example: 1x6, 2x7, 1x8, 1x9 In most cases, the number average is given How to asses the molecular weight and its distribution?

Molecular Weight Titration of End Groups (e.g. counting them) - gives you number of chains M = m n An example: m = 5 g of PET (pictured) n (acid) = 0.001 mol (1 mmol) M = 5 g 0.001 mol = 5000 g mol In repeating units (a) M(repeat) = 192 g mol Rings are not counted!!! Molecular weight is overestimated a = M (Polymer) M(repeat) = 5000 192 = 26

1.0 0.9 0.8 EVM03-4.020.001.1r.esp Assessment by NMR Molecular Weight Polymer peaks are broad, no peak splitting present Molecular weight? PDPA Homopolymer 0.7 Normalized Intensity 0.6 0.5 0.4 0.3 0.2 0.1 0 2.00 2.03 2.02 1.95 13.122.34 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 Chemical Shift (ppm)

1.0 0.9 JGU65-3.esp Molecular weight accessible! Molecular Weight 0.8 PEG lock of known length 0.7 Normalized Intensity 0.6 0.5 0.4 0.3 0.2 0.1 0 1.19 1.00 1.23 1.26 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 Chemical Shift (ppm)

Molecular Weight GPC = Gel Permeation Chromatography also SEC (Size Exclusion Chromatography) = Chromatography by Size, calibration required! http://upendrats.blogspot.co.uk/2013/05/gel-filtration.html

Molecular Weight Resulting GPC Trace Distribution of Molecular Weight 1 Peak = Monomodal 2 Peaks - imodal >3 peaks = multimodal 2 4 6 8 10 12 14 Retention Time (min) 3 4 5 6 7 8 9 10 11 Retention Time (min) A narrow, monomodal distribution is aimed for - typical for controlled polymerisation types (Controlled Radical P., Ring-Opening P.) The broader, the more uncontrolled (Free Radical P., Polyaddition/ Polycondensation) i/multimodal distribution account as dirty polymers

Molecular Weight Other methods to access molecular weight Light Scattering Absolute method, no calibration required Has to be calculated to infinite dilution and no angle (Zimm-Plot) Delivers only M w (if connected to GPC also M n ) Viscosimetry: Relative method, multiple factors need to be determined Delivers M h the Mark-Houwink coefficient a a = 0 for rigid spheres, 0.5 for non-expanded coils, 1.0 for expanded coils, 2.0 for rigid rods Mass spectrometry Mostly MALDI-TOF MS used No specific calibration required Makes single chains visible direct calculation of M n and M w 1000 1500 2000 2500 Mass (Da)

Summary Polymers or Macromolecules are: Molecules with > 1000 atoms with (mainly) covalent bonds in between uilt from repeating units (monomers) Polymers have a: Defined repeating molecular Structure, meaning: One Substance, mostly one repeating unit, only average molecular weight Polymers can be classified into: Natural Polymers vs. Synthetic polymers Thermoplasts vs. Duromers vs. Elastomers Polyesters vs. Polyamides vs. Polyvinylenes vs. Polycarbonates... Polymers have a tacticity (atactic vs. Isotactic vs. syndiotactic) Thermal transitions of polymers are characterised by: Glass Transition Crystallisation Melting Decomposition We owe him a lot