Minimizing the Strong Screening Effect of Polyhedral Oligomeric Silsesquioxane Nanoparticles in Hydrogen-Bonded Random Copolymers

A series of poly(vinylphenol-co-methacryisobutyl polyhedral oligomeric silsesquioxane) (PVPh-co-PMAPOSS) random copolymers have been synthesized through free radical copolymerizations of acetoxystyrene with methacryisobutyl POSS monomer and subsequent hydrazine monohydrate-mediated hydrolysis of the acetoxyl units. These random copolymers were characterized using nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and differential scanning calorimetry (DSC), which revealed that the POSS content in the random copolymers could be varied by changing the POSS monomer feed ratio by (1)H NMR analyses. This molecular design approach allowed us to investigate the thermal properties and hydrogen bonding interactions of these PVPh-co-PMAPOSS random copolymers in comparison with those of PVPh/PMAPOSS blend systems. Hydrogen bonding interactions were absent in the PVPh/PMAPOSS blend system, because of a strong screening effect; in contrast, the PVPh-co-PMAPOSS random copolymers experienced enhanced intramolecular hydrogen bonding that minimized the strong screening effect of the POSS nanoparticles.