Syntheses and the study of strongly hydrogen-bonded poly(vinylphenol-b-vinylpyridine) diblock copolymer through anionic polymerization

A series of poly(vinylphenol-b-vinylpyridine) (PVPh-b-P4VP) block copolymers were prepared through anionic polymerizations of 4-tert-butoxystyrene with 4-vinylpyridine followed by subsequent selective hydrolysis of the 4-tert-butoxystyrene protective groups. Infrared spectrum analysis suggests that this block copolymer possesses strong hydrogen-bonding interaction between the hydroxyl group of PVPh and the pyridine group of P4VP. DSC analyses indicate that these PVPh-b-P4VP copolymers always have higher glass transition temperatures than the corresponding PVPh/P4VP miscible blends obtained from DMF solution. However, the thermal behavior of PVPh-b-P4VP diblock copolymer shows a similar T-g value with the PVPh/P4VP blend complex obtained from methanol solution at a 1:1 (PVPh:P4VP) molar ratio. We proposed that the polymer chain behavior of the PVPh/P4VP blend from DMF solution is separated coils. However, by increasing the hydrogen bonding for PVPh-b-P4VP diblock copolymer, a polymer complex aggregate is proposed, which is similar to the PVPh/P4VP blend complex from methanol solution. The spin-lattice relaxation time in the rotating frame (T-1 rho(H)) based on solid-state NMR analysis is able to provide positive evidence that the polymer complex aggregate in the diblock copolymer has a shorter T-1 rho(H) value than the separated coils in the miscible blend.