Correlation between gel-forming ability, supramolecular aggregates and main-chain conformation of dendronized polymer gelators

Abstract

Dendronized polymer (DP) gelators were prepared via complexation of a dendritic gelator of the poly(urethane amide) dendron, which contains an ionizing carboxyl group on the apexes, with three positively charged polyelectrolytes. All these complexes could form organogels in toluene, and their gel properties were studied through determination of their minimum gelation concentration and characterization of the networked supramolecular structures formed in their gel-phase using TEM, AFM and SAXS. Our findings showed great differences in the gel-forming ability and supramolecular structure among these gelators. A simple simulation on the conformations of the three polyelectrolytes illustrated that the differences came mainly from the polyelectrolyte conformations which produced different distribution and orientation of the dendritic gelators along the backbones. When the backbone could induce the dendritic gelators to form a pre-ordered structure before gelation, the DP gelator would form nice supramolecular aggregates showing an enhanced gel-forming ability. Without this, the gel-forming ability would not be enhanced.