Synthesis And Application Of Photoresponsive Polypeptoid-Based Poly (N-(S-(O-Nitrobenzy)-Thioethyl) Glycine)

With the excellent biocompatibility and structural tunability,polypeptoids are widely applicated in the fields of biomedicine,selfassembled structures and stimulus-responsive smart polymers.Through incorporating the o-nitrobenzyl groups,a series of photoresponsive polypeptoid-based copolymers were synthesized by ring-opening polymerization(ROP).The synthesis,self-assembly,phototriggered drug release and postpolymerization modification have been thoroughly investigated.This dissertation includes the following two parts:1.Synthesis and application of amphiphilic photoresponsive polypeptoids.Through the controlled ring-opening polymerization technique,we synthesized a family of photoresponsive polypeptoid-based copolymer poly(ethylene glycol)-b-poly(N-(S-(o-nitrobenzyl)-thioethyl)glycine)-copoly(N-(2-phenylethyl)glycine)(PEG-b-PNSN-co-PNPE).The key feature of the design is to incorporate both o-nitrobenzyl group moiety to offer the photoresponsive property and phenethyl residues to tune the structural and amphiphilic property of the system.The cleavage degree of the o-nitrobenzyl group can reach to 100% upon UV-irradiation,which was demonstrated by NMR spectroscopy.With delicate design,a photoresponsive vesicle-tosphere transition has been observed that facilitates the release of the encapsulants.This work provides a facile approach to prepare a type of photoresponsive polymers with tunable properties for drug delivery.2.The side chains modification of the photoresponsive polypeptoids.A series of polypeptoids derivatives with different side chain functionalities were prepared by sequential photocleavage and thiol-ene reaction.The grafting rate of the obtained polypeptoids derivative was roughly equal to the cleavage degree of the o-nitrobenzyl group in the photoresponsive polypeptoids.Particularly,the temperature-responsive Nisopropylacrylamide(NIPAM)motif was grafted onto the photoresponsive polypeptoids to achieve the lower critical solution temperature(LCST)property.In addition,the incorporation of the allyl groups to a diblock copolymer poly(ethylene glycol)-b-poly(N-(S-(o-nitrobenzyl)-thioethyl)glycine)-co-poly(N-allyl glycine)(PEG-b-PNSN-co-PNAG)enables the preparation of UV initiated self-crosslinking nanogel in aqueous solution.This work provides a facile and efficient approach to prepare multifunctional polypeptoid-based bioinspired polymers under mild experimental condition and offer an efficient platform for versatile functionalities.