Synthesis Of Thermosensitive Gel By Living Polymerization

Thermosensitive gel is a kind of promising materials for tissue engineering, microfluidics, and drug delivery etc. In general, the network formation occurs through physically interaction from self-assembled supramolecular structures or chemically crosslink from labile covalent bonds. The physical crosslink is formed typically through noncovalent interactions such as hydrogen bonding, van der Waals interactions, n-n stacking, and solvophobic interactions etc. And chemically crosslink usually origins from the concept of dynamic covalent chemistry, which can offer the possibility of "doing supramolecular chemistry" at the level of covalent bonds by introducing dynamic covalent bonds into the polymer units.In this paper, though living polymerization, we have successfully synthesized peptide-base gels which are cross-linked by physical interaction and the polystyrene gels which are cross-linked by dynamic covalent bonds, and we have also investigated the mechanism of the galation and the gel behaviors. So this thesis is constituted of two parts:Firstly, We have successfully synthesized well-defined block copolypeptides, poly[(y-benzyl-α-L-glutamate)-b-(γ-stearyl-α-L-glutamate)], by combining high vacuum and low temperature technique. Interestingly, we found that this diblock copolypeptide could form transparent gel in toluene and exhibited reversible sol-gel transition upon heating. We also propose a new mechanism for gelation based upon the self-assembly of the polymers as probed by IR,CD, AFM, TEM, SAXS etc.Secondly, a thermosensitive polystyrene gel was synthesized by living free radical polymerization, starting from a nitroxyl radical bearing a vinyl group (ETS). In this part, we have testified the living polymerization character in this polymer system by dynamic analysis and investigated gel behaviors such as the critical gel point and the gel swelling degree. and so on.