Increasing PS surface coverage results in increased relative contribution from alkylamide, carboxylate and methyl ester groups. These results suggest inter-and intra-molecular electrostatic interactions (NH2 + and COO -groups) and then H-bonding (NH2 + and C=O groups) of adsorbed PS intensify as PS surface coverage increases. The formation of H-bonds between PS chains also stabilizes the charge distribution of charged groups in the hydrophilic core of the initial PS-diamond association (Figure ). Compared to results for the early stage of adsorption, the fact that methyl ester groups appear last at the equilibrium stage of adsorption suggests a reversal in surface polarity of the PS-diamond association (i.e., becomes more hydrophobic).