| Abstract
| - Amphiphilic homopolymers of the hydroxy-functional macromonomer poly(ethylene glycol)monomethacrylate (PEGMA) and its copolymers with methyl methacrylate (MMA) were prepared by atomtransfer radical polymerization. Commercially available PEGMA (Aldrich) contains nonfunctional poly(ethylene glycol) (PEG), monofunctional PEGMA, and difunctional poly(ethylene glycol) dimethacrylate(PEGDMA) in a 1:3:1 ratio as analyzed by HPLC. A solvent extraction procedure yielded a PEGMAenriched mixture (PEG:PEG-MA:PEGDMA = 5:92:3) with PEGMA Mn values of 480 and 410 Da basedon HPLC and 1H NMR, respectively. ATRP homopolymerization of this purified PEGMA in the hydroxyl-bearing solvents, cyclohexanol and ethanol (ε = 16.4 and 25.3, respectively), yielded well-definedhomopolymers (Mw/Mn< 1.1). On the other hand, ATRP copolymerizations with MMA (PEGMA content= 10, 18, 24, 30, and 40 mol %) yielded best results in non-hydrogen-bonding diphenyl ether (ε = 3.37).The homopolymer and copolymers containing more than 24 mol % (57 wt %) PEGMA were water-solubleand exhibited sharp lower critical solution temperatures (LCST) that increased with increasing PEGMAcontent as expected. Unlike similar PEGMA-based amphiphilic copolymers prepared by conventionalfree radical polymerizations, the ATR polymerizations reported here proceeded to high conversions (60−100%) and yielded well-defined polymers (Mw/Mn = 1.1−1.15) with no gel fraction that remained linearand water-soluble after storage in ambient conditions for several months.
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