End-linked semifluorinated amphiphilic polymer conetworks: Synthesis by sequential reversible addition - Fragmentation chain transfer polymerization and characterization
AuthorPafiti, Kyriaki S.
Patrickios, Costas S.
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One-pot, sequential reversible addition - fragmentation chain transfer (RAFT) polymerization was employed for the preparation of five end-linked semifluorinated amphiphilic polymer conetworks based on 2,2,2-trifluoroethyl methacrylate (TFEMA, hydrophobic monomer) and 2-(dimethylamino)ethyl methacrylate (DMAEMA, hydrophilic monomer). 1,4-Bis[2-(thiobenzoylthio)prop-2- yl]benzene (1,4-BTBTPB) was used as the chain transfer agent, while ethylene glycol dimethacrylate (EGDMA) served as the cross-linker. Three of the end-linked conetworks were based on ABA triblock copolymers with polyDMAEMA midblocks with degrees of polymerization (DPs) of 50 and polyTFEMA end-blocks with overall polyTFEMA DPs of 25, 50, and 75. The fourth end-linked amphiphilic polymer conetwork was based on an equimolar BAB triblock copolymer with a polyTFEMA midblock and an overall copolymer DP of 100. The last end-linked conetwork was based on a statistical copolymer. A randomly cross-linked conetwork was also prepared by the simultaneous terpolymerization of the two comonomers (equimolar) and the cross-linker. The molecular weights and compositions of all the polymer precursors to the conetworks were characterized using gel permeation chromatography and 1H NMR spectroscopy, respectively. The conetworks were characterized in terms of their degrees of swelling (DS) in THF and in water as a function of the solution pH. All conetworks swelled more in acidic than in pure water due to the ionization of the DMAEMA units in acidic water. The low pH aqueous DS of the statistical copolymer-based end-linked conetwork was higher than those of its triblock copolymer counterparts due to lack of microphase separation within the former conetwork. Finally, the microphase separation of the amphiphilic conetworks in deuterium oxide was investigated using small-angle neutron scattering which indicated a distance between the hydrophobic scattering centers of about 15 nm. © 2010 American Chemical Society.
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