Hyperbranched polymers: Structure of hyperbranched polyglycerol and amphiphilic poly(glycerol ester)s in dilute aqueous and nonaqueous solution

The solution structure of hyperbranched macromolecules was investigated by means of small- angle neutron scattering (SANS). Hyperbranched polyglycerols of different molecular weight were investigated in D2O and CD3OD, and very similar molar masses and radii of gyration were obtained in both solvents. Kratky plots of the scattering intensity revealed a compact structure of the hyperbranched polyglycerols. A power law scaling relation of the radius of gyration with molar mass was observed, from which a dimension of three was obtained. These observations indicate that the hyperbranched structure prevents strong irregular association despite the high functionality of hydroxyl groups that could lead to aggregation in those solvents. Amphiphilic derivatives of the hyperbranched polyglycerols have been studied in the nonpolar solvent C6D6. Again, molecularly dispersed polymers were found provided the degree of esterification was sufficiently high. A low degree of derivatization of only 22% was not sufficient to prevent aggregation in C6D6. The macromolecules become more compact when the degree of esterification increases.