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

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)R(COOSi)+H2O. Relatively high grafting densities (6.6 mg/m2) were achieved with minimal chain distortion or displacement of long chains by shorter ones. Significant stretching of the grafted chains occurred for >10 mg/m2. An equilibrium constant for the grafting reaction incorporating entropy is discussed.