New amphiphilic (hydrophobically modified, HM) polymers based on 6-carboxypullulan were synthesized. The reaction chosen was amidation of carboxyl groups via a carbodiimide and was carried out in an organic solvent (DMSO) to ensure random substitution. Four polymers with degrees of substitution of 1, 3, 6, and 12% (per glucose unit) were prepared and characterized by nuclear magnetic resonance (NMR), size exclusion chromatography (SEC), acid/base titration, and dynamic light scattering. We found a very good agreement between the degree of substitution calculated from reaction stoichiometry and as measured by NMR. The kinetics of adsorption and desorption of these HM polymers from water onto polystyrene was studied as a function of pH. The data indicate strong effects due to the hydrophobic groups. We also find evidence for the build up of an electrostatic barrier during adsorption which strongly hampers equilibration.
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Paris et al. (1999) studied this question.
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