Configuration of grafted polystyrene chains in the melt: Temperature and concentration dependence

Abstract

The concentration profiles of carboxy-terminated polystyrene chains in the melt grafted onto oxide-covered silicon substrates were measured using secondary-ion mass spectroscopy. The grafting density increased with temperature and an enthalpy of +7.4 kcal/mole was deduced for the grafting reaction, SiOH+R(COOH)\ensuremath{\rightleftarrows}R(COOSi)+${\mathrm{H}}_{2}$O. Relatively high grafting densities (\ensuremath{\sigma}\ensuremath{\sim}6.6 mg/${\mathrm{m}}^{2}$) were achieved with minimal chain distortion or displacement of long chains by shorter ones. Significant stretching of the grafted chains occurred for \ensuremath{\sigma}>10 mg/${\mathrm{m}}^{2}$. An equilibrium constant for the grafting reaction incorporating entropy is discussed.