Copolymerization of N-vinylcaprolactam and glycidyl methacrylate:: Reactivity ratio and composition control

Free-radical copolymerizations of N-vinylcaprolactam (VCL) and glycidyl methacrylate (GMA) were investigated to synthesize temperature-responsive reactive copolymers with minimized compositional heterogeneity. The average copolymer composition was determined by Fourier transform infrared and nuclear magnetic resonance techniques. The reactivity ratios for VCL and GMA were found to be 0.0365 +/- 0.0009 and 6.44 +/- 0.36 by the Fineman-Ross method and 0.039 +/- 0.006 and 6.75 +/- 0.29 by the Kelen-Tudos method, respectively. When prepared by batch polymerization, VCL-GMA copolymers had a highly heterogeneous composition and fractions of different solubilities in water. The use of a gradual feeding technique, which included the sequential addition of more reactive GMA monomer into the reaction, yielded copolymers with much more homogeneous composition. The produced copolymers with 0.9 and 0.11 fractional GMA contents preserved their temperature-responsive properties and precipitated from aqueous solutions when the temperature exceeded 31 degrees C. The GMA units in the VCL-GMA copolymers were capable of reacting with amino end-functionalized poly(ethylene oxide) at room temperature to produce poly(N-vinylcaprolactam)-poly(ethylene oxide) graft copolymers. (c) 2005 Wiley Periodicals, Inc.