89622-60-6Relevant articles and documents
Cyclodextrin-complexed RAFT agents for the ambient temperature aqueous living/controlled radical polymerization of acrylamido monomers
Schmidt, Bernhard V. K. J.,Hetzer, Martin,Ritter, Helmut,Barner-Kowollik, Christopher
experimental part, p. 7220 - 7232 (2012/04/10)
The first aqueous reversible addition-fragmentation transfer (RAFT) polymerization of N,N-dimethylacrylamide (DMAAm), N,N-diethylacrylamide (DEAAm), and N-isopropylacrylamide (NIPAAm) utilizing host/guest complexes of cyclodextrin and hydrophobic chain transfer agents (CTAs) at 25 °C is described. Three novel guest-functionalized CTAs, namely 4-(tert-butyl)phenyl 2-(((ethylthio)carbonothioyl)thio)-2-methylpropanoate, bis(4-tert-butyl)benzyl carbonotrithioate, and benzyl (3-((4-(tert-butyl)phenyl)amino)-3-oxopropyl) carbonotrithioate, were synthesized and employed in aqueous RAFT polymerizations. The presented technique allows for the facile preparation of hydrophilic polymers with hydrophobic end groups in aqueous environments. The living/controlled radical polymerization afforded high molecular masses (7500 ≥ Mn ≥ 116 000 g mol-1 for poly(DMAAm), 2500 ≥ Mn ≥ 150 000 g mol-1 for poly(DEAAm), and 4000 ≥ Mn ≥ 50 000 g mol-1 for poly(NIPAAm)) with low PDIs (1.06 ≥ PDI ≥ 1.54 for poly(DMAAm), 1.05 ≥ PDI ≥ 1.39 for poly(DEAAm), and 1.15 ≥ PDI ≥ 1.46 for poly(NIPAAm)). To confirm the living character of the polymerizations, kinetic measurements were undertaken that evidence a linear evolution of molecular weight with conversion. Furthermore, chain extensions were carried out that indicate a very high reinitiation efficiency (poly(DMAAm): from 10 500 to 97 500 g mol-1, PDI = 1.08; poly(DEAAm): from 8500 to 83 000 g mol-1, PDI = 1.13; poly(NIPAAm): from 9000 to 90 000 g mol-1, PDI = 1.11). The resulting polymers were thoroughly characterized via N,N-dimethylacetamide (DMAc) size exclusion chromatography, 1H NMR, and electrospray ionization-mass spectrometry (ESI-MS).
