Synthesis and Characterization of Functional Gradient Copolymers of 2-Hydroxyethyl Methacrylate and tert-Butyl Acrylate by Atom Transfer Radical Polymerization

Functional spontaneous gradient copolymers of 2-hydroxyethyl methacrylate (HEMA) and tert-butyl acrylate (tBA) were synthesized by atom transfer radical polymerization (ATRP) in cyclohexanone at 50C. The copolymers were characterized by nuclear magnetic resonance spectroscopy (1H-NMR) and gel permeation chromatograph (GPC). Comonomer conversions were determined by gas chromatograph (GC) and the kinetic behavior for HEMA/tBA copolymerization was analyzed, indicating that the copolymerization proceeds in a controlled way. The monomer reactivity ratios rHEMA = 4.497 and rtBA = 0.212 were estimated using an extended Kelen-Tudos method from copolymer composition data. Atomic force microscopy (AFM) images demonstrated the changes of surface morphology of poly(HEMA-grad-tBA) polymerized for different times and the changes were correlated to the composition of the copolymers.