Synthesis and Characterization of a Novel Triblock Copolymer Containing Double-hydrophilic Blocks and Poly(fluoroalkyl methacrylate) Block via Oxyanioninitiated Polymerization

Abstract

AbstractA new triblock copolymer consisted of a double-hydrophilic diblock and a fluorinated block, namely poly(ethylene glycol)-b-poly[2-(dimethyl amino)-ethylmethacrylate]-b-poly(2,2,3,3,4,4,5,5-octafluoropentylmeth acrylate) (MePEG-b-PDMAEMA-b-POFPMA), was synthesized via oxyanioninitiated copolymerization. The hydroxyl group of poly(ethylene glycol) monomethyl ether (MePEG) reacted with potassium methylsulfinyl carbanion (DMSO-K+) and converted into a potassium alcoholate macroinitiator (MePEG-K). It could initiate DMAEMA monomer to yield a hydrophilichydrophilic diblock copolymer. If not quenched, the living chain could be subsequently used to initiate a second fed monomer such as OFPMA to produce a new triblock copolymer MePEG-b-PDMAEMA-b-POFPMA. As a comparison, the analogous triblock copolymers with different lengths of PDMAEMA and identical length of POFPMA were prepared. These copolymers were characterized by the measurements of 1H NMR, 19F NMR, and gel permeation chromatography (GPC). The results indicated that they had relatively low polydispersities (Mw/Mn̅ :1.25 −1.27) . The comparison of the critical aggregation concentration (CAC) of diblock copolymer MePEG-b- PDMAEMA and triblock copolymer MePEG-b-PDMAEMA-b-POFPMA has been investigated by measurements of surface tension and electrical conductivity. It was also found that the lower critical solution temperatures (LCSTs) of the di- and triblock copolymers varied with different factors, including the chemical structure, the length of DMAEMA block, and the concentration of the aqueous solution.