Syntheses and specific interactions of poly(hydroxyethyl methacrylate-b-vinyl pyrrolidone) diblock copolymers and comparisons with their corresponding miscible blend systems

Combination of atom transfer radical and conventional free radical polymerizations has been successfully used to prepare poly(hydroxyethyl methacrylate-b-vinyl pyrrolidone) (PHEMA-b-PVP) copolymers with controlled molecular weight and low polydispersity (<1.4). The thermal behavior and specific interaction of PHEMA-b-PVP diblock copolymers and their corresponding PHEMA/PVP blends were characterized. The result shows that glass transition temperatures of diblock copolymers analysed by differential scanning calorimetry (DSC) are higher than those of the blends. Infrared and solid-state NMR spectroscopic analyses show that hydrogen-bonding interaction of hydroxyl-carbonyl groups of diblock copolymers was also greater than that of the blends. Measurement of the proton spin-lattice relaxation time in the rotating frame, (T1ρH), reveals that all diblock copolymers and blends possess one composition-dependent T1ρH, indicating that both diblock copolymers and blends are homogeneous, which is consistent with the DSC analysis.