|Synthesis and behaviour of PEG-b-PDEAm block copolymers in aqueous solution |
Auteur(s): Zhang Xuewei, Burton Tobias, In M., Begu Sylvie, Aubert-Pouëssel Anne, Robin Jean-Jacques, Monge Sophie, Giani Olivia
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Well-defined double hydrophilic block copolymers (DHBCs) of poly(ethylene glycol)-block-poly(N,N-diethyla-crylamide) (PEG-b-PDEAm) were synthesized via a reversible addition-fragmentation chain-transfer (RAFT) polymerization of N,N-diethylacrylamide (DEAm) using dithioester terminated PEG of different chain lengths as macro-chain transfer agents. Controlled molecular weight and narrow molecular weight distribution were achieved as proven by size exclusion chromatography (SEC). Cloud points (CP) were determined via turbidity measurements with ultraviolet-visible spectroscopy (UV-vis) and LCST by differential scanning micro-calori-metry (micro-DSC). They range from 32 to 40°C depending on the PDEAm length block and its concentration. Above the LCST, fluorescence spectroscopy and dynamic light scattering (DLS) demonstrated that the PEG-b-PDEAm copolymers self-organized into large aggregates. More interestingly, copolymers pre-aggregated at relatively high concentrations below the LCST.