Effects of molecular weight on thermal responsive property of PEGylated poly-L-glutamates Effects of molecular weight on thermal responsive property of PEGylated poly-L-glutamates

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Effects of molecular weight on thermal responsive property of PEGylated poly-L-glutamates

Shusheng Zhang; Chongyi Chen; Zhibo Li*

Chin. J. Polym. Sci. 2013, 31, 201-210.

We investigated the controlled ring opening polymerization (ROP) of di- and tri-ethylene glycol monomethyl ether functionalized L-glutamate N-carboxyanhydrides (NCAs) using hexamethyldisilazane (HMDS) as primary initiator and 1,5,7-triazabicyclo-[4.4.0]dec-5-ene (TBD) as co-initiator. We studied the helical content dependence on polypeptide molecular weight (MW) using circular dichroism (CD) spectroscopy. We found that the helical content of both homopolypeptides increased with MW, but the triethylene glycol functionalized poly-L-glutamate (poly-L-EG3Glu) intended to form more stable helical structure than diethylene glycol functionalized counterpart (poly-L-EG2Glu) at similar MW. Accordingly, the cloud point of poly-L-EG2Glu with known end group had strong dependence on its helical content, which is essentially determined by MW. Our results suggest that stable helical structure is necessary for these pegylated polypeptides to have well-defined thermal responsive properties.