Polyglycidol-based analogues of pluronic block copolymers. Light scattering and cryogenic transmission electron microscopy studies

In this paper we parametrize nanostructures formed in water by a series of macromolecular surfactants based on polyglycidol (PG). They are considered analogues of Pluronic, that is poly(ethylene oxide)-poly(propylene oxide) -poly(ethylene oxide) (PEO-PPO-PEO) block copolymers, in which the blocks of PEO are substituted by PG. PG is structurally similar to PEO and differs in that each monomer unit bears a hydroxyl group. The investigated PG-PPO-PG copolymers are of a constant degree of polymerization of the middle PPO block of 34; they cover a molecular weight range from 2900 to 12400 and PG content from 30 to 84 wt %. The major techniques used to examine the behavior at the dilute (but invariably above the critical aggregation concentration) concentration limit were static and dynamic light scattering; the aggregates were visualized by cryogenic transmission electron microscopy. The weight-average molecular weights, radii of gyration, second virial coefficients, diffusion coefficients, and hydrodynamic radii were determined at different temperatures. The light scattering results revealed that the particles were considerably larger in size and aggregation number than the micelles of the Pluronic copolymers. Hydrophobic interactions and interactions via hydrogen bonding are equally involved in formation of well-separated spherical particles with discontinuous hydrophobic PPO domains randomly distributed in a strongly hydrogen-bonded continuous medium consisting of PG and water.