SS Vorlesung Polymermaterialien Polymerisationsmethoden

Transcription

1 Professur Polymerchemie SS 2017 Vorlesung Prof. Michael Sommer 1

2 Content Free radical polymerization (PS, PMMA) Controlled radical polymerization Ionic polymerization (cationic, anionic) Ring opening polymerization (RP: PLA, PCL, aliphatic PC) Transition metal-catalyzed polymerizations (polyolefines, polyinsertion, RMP, ADMET, cross-coupling) Polyaddition (isocyanate chemistry, thiol-ene and azide-alkyne click chemistry) Polycondensation (PET, PA, PC) 2

3 Literature Reviews: 1) Atom Transfer Radical Polymerization: Chem. Rev., 2001, 101 (9), pp ) Metal-catalyzed living radical polymerization Chem. Rev., 2001, 101 (12), pp ) Controlled/living radical polymerization: features, developments, perspectives Prog. Polym. Sci. 2007, 32, 93 4) New polymer synthesis by nitroxide mediated polymerization Chem. Rev. 2001, 101, Editor(s): N V Tsarevsky, B S Sumerlin Print ISBN: PDF eisbn: DI: / ontent/dam/sigmaaldrich/docs/saj/brochure/1/c ontrolled-radicalpolymerization-guide.pdf 3

4 Terminology Terms used throughout the literature: Living polymerization Quasi-living polymerization living Controlled radical polymerization Living free polymerization Living free radical polymerization controlled no chain termination no chain transfer not necessarily small Ɖ, for slow initiation Ɖ up to 1.3 fast Initiation Ɖ Ɖ Pre-defined MW MW increases linearly with p End group control Possibility to make well-defined block copolymers 4

5 DP, conversion and time linear increase of DP with p, pre-defined molecular weight Linear behaviour of ln [M 0 ]/[M] versus t (first order with respect to monomer conc.) DP ln [ ] DP= p[m] 0 /[I] 0 p ln [ ] = kt t compare a plot of DP versus p for step growth and free radical polymerization! 5

6 Advantages and possibilities of controlled radical polymerization Structurally defined polymer architectures Pre-defined molecular weight and narrow distribution (D< 1.2) End-functional polymers Block, graft and star copolymers narrow distribution Ɖ ~ broad distribution (step growth, free-radical) Ɖ end functionalization X end functional X telechelics X bis-end functional X Y block copolymers diblock copolymer triblock copolymer triblock terpolymer graft copolymer comb polymer star block copolymer 6

7 Advantages and possibilities of controlled radical polymerization Narrow molecular weight distribution (how narrow is narrow?) SEC (size exclusion chromatography) or GPC Gelpermeationschromatographie MALDI-ToF: matrix-assisted laser desorption ionisation time-of-flight Đ= 1.1 Đ= 2.0 M n,maldi = 4036 g/mol Đ MALDI = ( M n,gpc = 7900 g/mol) 660_2_1 n=17 n=33 Chiefari et al., Macromolecules, 1998, 31, m/z Kohn et al. ACS Macro Lett 2012, 1, 1170

8 Principle of controlled radical polymerization CRP: reducing the concentration of radicals by reversible termination: Probability for chain-chain recombination and disproportionation is drastically reduced Probability for transfer is drastically reduced Reduced radical concentration leads to slower kinetics (smaller k p ) K p < k i : fast initiation compared to propagation leads to narrow distribution Active species dormant species P*: active species: polymer radical, can add monomer T*: stable radical or species that only reacts with polymer radical but does not add monomer P-T: dormant species, inactive Applies to ATRP and NMP, RAFT is different! 8

9 ATRP: First examples 9 Matyjaszewsji, JACS 1995, 117, 5614

10 Commercial initiators based on EBiB ATRP initiators based on Ethyl α-bromoisobutyrate (EBiB) 10

11 Ligands for ATRP The structure of ATRP ligands controls concentrations of active and dormant species Tang, Matyjazewski, Macromolecules, 2006, 39 (15), pp

12 End group modification of ATRP polymers End group functionalization of Bromide-terminated polymers made by ATRP dye labelling 12 Polym Int 2014; 63:

13 Advantages and possibilities of controlled radical polymerization Quantitative end group functionalization enables block copolymer synthesis Example: Triblock terpolymer synthesis using H-EBiB and ATRP bifunctional initiator I + n M 1 H Br + n H-Ebi-Br H Br n H-PS-Br m M 2 m o M 3 H n Br m H-PS-b-PMMA o m n Br m PCL-b-PS-b-PMMA 13

14 Sacrifical block copolymer templates based on gyroidal PFS-b-PLA 14 Scherer et al. Adv. Mater. 2012

15 Sacrifical block copolymer templates based on gyroidal PFS-b-PLA 15 Scherer et al. Adv. Mater. 2012

16 Nitroxide mediated polymerization NMRP C- Bond thermally unstable equilibrium between two radicals and covalently attached nitroxide Nitroxide is stable enough to not initiate polymerization, but reacts with growing chain to form dormant species reversibly Two component initiator system (free radical initiator + nitroxide) or unimolecular alkoxyamines Georges et al, Macromolecules 1993,26,

17 Nitroxide mediated polymerization NMRP Typical alkoxyamines as unimolecular initiators Nitroxide synthesis Alkoxamine synthesis N N Mn Cl Hawker et al, JACS 1999, 121, Mn(salen) Jacobsen kat

18 RAFT: Reversible Addition-Fragmentation Chain Transfer Polymerization General structure of RAFT agents reaktive Doppelbindung S S R schwache Einfachbindung R-Gruppe Z-Gruppe Z RAFT equilibrium involves one RAFT agent and two polymer chains M. + S S P n P m kp Z k addp k -addp P m S S P n S S k -addp. P m + P n. Z k addp Z Barner-Kowollik, Perrier, J. Polym. Sci. Polym. Chem. 2008, 46,