Preparation And Thermoresponsive Properties Of Poly (L-glutamate) Bearing Pyridine Salt

The "intelligent" polymer materials which can react according to the environmental conditions are very attractive to the market,because they have great potential applications in biomedicine. At the same time, as nature-derived materials, polypeptides have excellent biocompatibility and ordered secondary structure(?-helix, ?-sheet). In this paper, we designed and synthesized a series of temperature-sensitive and water-soluble polypeptides that contained pyridine salt in their side chains, studying on the UCST type properties in aqueous solution. The vast majority of temperature-sensitive polymers are non-biodegradable, such as poly(N-isopropylacrylamide), the problem is solved with synthesis of this structure. The research has a positive significance for the development of biomedical materials.1. We successfully synthesized ionic polypeptides which have different groups with a pyridine salt(salt such as pyridine, 2-picoline salt, 3-methyl pyridine salt and 4-methyl pyridine salt) and different counter ions(such as Cl-, BF4-) in their side chains through substitution reaction between poly[?-3-propyl-L-glutamate](PCPLG) or poly[ ?-6-hexyl-L-glutamate ](PHPLG) and pyridine or y- methylpyridine(y = 2, 3, 4) and ion exchange reaction. CD analysis showed that the polypeptide adopted ?-helical conformation in aqueous solution, and the helicity varied in the range of 24.7-41.4%. UV-visi spectroscopy showed that polypeptide which contained 3-methyl pyridine and BF4- counter ion has UCST in the aqueous solution. And the UCST phase transition temperature will be increased with the concentration of hydrophobic spacer groups, the polymer concentration and Na BF4 increasing.2. The water-soluble polypeptides with different pyridine salt groups(such as pyridine salt, 2-methyl pyridine salt, 3-methyl pyridine salt and 4-methyl pyridine salt) and different counter ions(such as Cl-, BF4-) was sucessfully synthesized by poly[?-(4-chloro-methylbenzyl)-L-glutamate](PCMBLG) and pyridine or y-methylpyridine(y=2, 3, 4) using nucleophilic substitution reaction and ion exchange reaction. 1HNMR indicated that the structures of the polymers are correct. UV-vis spectroscopy showed that polypeptides which contained a variety of pyridyl groups and counter ions BF4- have UCST in the aqueous solution. And the UCST phase transition temperature increased with the increasing of polymer concentration, and the relationship with pyridyl substituents was: 4-Me> 2-Me> H> 3-Me.