Conformation of Hydrophobically Modified Thermoresponsive Poly(OEGMA-co- TFEA) across the LCST Revealed by NMR and Molecular Dynamics Studies
C Zhang and H Peng and S Puttick and J Reid and S Bemardi and DJ Searles and AK Whittaker, MACROMOLECULES, 48, 3310-3317 (2015).
High-resolution NMR measurements and molecular dynamics (MD) simulations have been applied to the study of thermoresponsive copolymers of poly(ethylene glycol) methyl ether methacrylate (OEGMA) and 2,2,2-trifluoroethyl acrylate (TFEA) (poly(OEGMA-co-TFEA)) synthesized via reversible addition fragmentation chain transfer (RAFT) polymerization. The detailed chemical microstructure of poly(OEGMA-co- TFEA) was investigated by means of various high-resolution NMR techniques. The polymer in aqueous solution possesses a lower critical solution temperature (LCST) at which significant changes in conformation are apparent. H-1 2D NOESY spectra were collected at temperatures below and above the LCST and demonstrated closer association of the exterior segments of the OEGMA side chains with the TFEA units above the LCST. MD simulations provided additional information on the changes in conformation and were consistent with the experimental findings. The combination of MD simulations with a detailed experimental study of poly (OEGMA-co-TFEA) in water leads to a clearer understanding of conformation occurring at the phase transition.
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