Design, Synthesis, And Property Of Branched Poly (ε-Caprolactone) And Polypeptide Block Copolymers

In this work , hyperbranched polycaprolactone (HPCL), hyperbranched polypseudorotaxane (HPPR) and asymmetrical Dendron-like/Dendron-like Poly(e-caprolactone)-b-Poly(γ-benzyl-L-glutamate) Block Copolymers were synthesized by the"click"chemistry combined with the ring-opening polymerization.Thiol-yne chemistry was used to afford HPCLs and HPPRs through the polycondensation of AB2 type polycaprolactone or polypseudorotaxane macromonomers withα-thiol and w-alkyne terminal groups(thiol is A unit,and eachπbond in alkyne is B unit). Their molecular structures and physical properties were characterized in detail by FT-IR, NMR, time-of flight mass spectrometry, gel permeation chromatography, differential scanning calorimetry, and wide-angle X-ray diffraction. The molecular weights of HPCLs gradually increased over the irradiation time, as well as the broadening polydispersities. A cross-linking side reaction occurred in the polycondensation of PCL;however,this side reaction was prohibited if PA-PCL-SH was threaded byα-cylodextrin to form the rigid polypseudorotaxanes. Both the maximal melting point and the crystallization point of HPCLs gradually decrease with increasing their molecular weights. Furthermore, the degree of crystallization of HPCLs decreases from 51.4% to 30.4% with increasing the molecular weights.On the other hand, asymmetrical dendron-like/dendron-like poly(e-caprolactone)-b-poly(γ-benzyl-L-glutamate) block Copolymers were synthesized by the Cu-Catalyzed Azide-Alkyne Cycloaddition (CuAAC) combined with the ring-opening polymerization. The dentron-like PCL with eight arms was synthesized by controlled ROP of caprolactone using PAMAM as the initiator, PCL was further click conjugated with azide focal point PAMAM-typed dedrons to generate the macroinitiators, which was finally used for the ROP of Glu-NCA monomer to produce the targeted PCL-b-PBLG block copolymers. The structures and physical properties of all products were characterized in detail by FT-IR, NMR, time-of-flight mass spectrometry, gel permeation chromatography, differential scanning calorimetry, and wide-angle X-ray diffraction. The degree of crystallization of PCLs decreased with the increasing molecular weight of PBLG block. Furthermore, we also observed the liquid-crystal transition phenomenon, which was reported in literature.