70. Enhancing Gelation Ability of a Dendritic Gelator through Complexation with a Polyelectrolyte
writer：Zijian Zhang, Miao Yang, Xinjun Zhang, Lichu Zhang, Bo Liu, Ping Zheng, and Wei Wang*
keywords：dendrimers; gels; polyelectrolytes; polymers; self-assembly
source：期刊
specific source：Chemistry - A European Journal
Issue time：2009年
The gelation ability of a dendritic gelator has been enhanced by its complexation with a polyelectrolyte (see figure). This concept provides a route to construct novel functional or ordered materials by complexation of other low-molecular-mass functional species with polyelectrolytes.A poly(urethane amide) (PUA) dendron with long alkyl chains on its periphery was synthesized and then attached to the backbone of a polyelectrolyte, in which each unit contained a positive charge, by ionizing the carboxyl groups on the apexes of the dendrons to form a dendronized polymer. We found that both the PUA dendron and the dendronized polymer could form organogels in toluene. Interestingly, both the minimum gelation concentration and the gelation time of the dendronized polymer gelator were greatly reduced compared with the dendron alone. Our investigations showed that in the gel phase the intermolecular hydrogen bonding between adjacent dendrons creates similar supramolecular structures in both the dendron and the dendronized polymer gelator, which immobilize solvent molecules by means of interactions between dendrons and solvent molecules. Further studies on the gelation kinetics indicated that the polyelectrolyte backbone plays an important role in prearranging the attached dendritic gelators orderly and quickly into the supramolecular structures through a nucleation–elongation mechanism. Therefore, the gel-forming ability of the dendritic PUA gelator is enhanced by being complexed with the polyelectrolyte. In this work, this positive macromolecular effect is discussed in detail.