Rodlike polymer gels

Polypeptide homopolymers (typically PBLG) with rigid a-helix conformation can form LC structures at a high concentration and temperature. When the solution is cooled, a transparent, mechanically self-supporting gel is always observed [42, 87-91]. The gel formation was found to be concentration and temperature dependent and completely reversible. It is well known that the physical or chemical crosslinks are necessary for polymer gels. Flexible polymers can easily form crosslinking domains with crystalline or semicrystalline structures. However, for rigid polypeptide chains, it is less clear how the rodlike polypeptides participate extensively in intermolecular crosslinks. 

The addition of water causes the formation of a coagulated phase of PBT solutions in any of the solvents named above (of course, the amount of water tolerated varies with the solvent, with the PPA solvent being the most tolerant toward water) (4). In very dilute solutions, the water causes enhanced depolarized scattering, interpreted to be the result of the formation of aggregates in which the rodlike chains are in parallel arrays (10). In more concentrated solutions, a gel phase is created (11,12). In either case, the electronic absorption spectra is altered from that characteristic of the protonated chain to that characteristic of the deprotonated, dry polymer (10). In the following we will report observations on this phase transition. 

Kaneko Y, lyi N, Matsumoto T, Kitamura K (2005) Synthesis of rodlike polysiloxane with hexagonal phase by sol-gel reaction of organotrialkoxysilane monomer containing two amino groups. Polymer 46(6) 1828-1833... 

In our previous works [14, 15, 16, 17, 18], the pulsed-high-field-gradient spin-echo (PHFGSE) H NMR method was used for determining the diffusion coefficient of solvent, probe molecules, and probe polymers in a gel and rodlike polypeptides in the thermotropic liquid-crystalline state. The great strength of the field... 

In this review of work at the Institute for Polymers and Organic Solids at UCSB, we summarize the results obtained from spectroscopic studies, quasi-elastic light scattering and field induced birefringence of dilute solutions. We then turn to more recent studies which focus on gels made up of networks of the rodlike molecules. 

VI. Gels of Polydiacetylene 4BCMU in the Rod-like Conformation The existence of extended rodlike molecules implies a tendency for intermolecular interaction which leads to aggregation and gelation at relatively low polymer concentrations. Consistent with these ideas, the gel-sol transition has been observed and... 

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