The Investigation Of Topological Construction And Properties Of Copolymers

In this thesis,we investigated how to construct perfect hyperbranched copolymer,the architecture effect on hyperbranched copolymer and brush-like copolymer as well as their potential applications.The main content is as follows:(1)We developed an approach of combining ring-opening polymerization and atom transfer radical polymerization to construct model hyperbranched copolymer polystyrene-block-poly(s-caprolactone)[HB-(PS-b-PCL)n]with two kinds of controllable and long uniform subchains.We investigated the crystallization of broad and narrow distributed copolymer,and found that the crystal size and the degree of crystallinity were significantly regulated.However,for a given(DP)w,the crystallization behavior is much easier to be observed for broad distributed samples than narrow distributed samples due to the existence of the crystallizable low-molar-mass components.We investigated the crystallization behavior of the polymer blends of narrow distributed hyperbranched copolymer and the macromonomer to confirm the structure effect of the narrow distributed hyperbranched copolymer on the crystallization behavior of the macromonomer.The results show that the degree of crystallinity begins to be restricted when the weight fraction of hyperbranched fractions is?10%and decreases dramatically when the weight fraction of hyperbranched fractions exceeds?67%,implying some extra restriction exerted by hyperbranched fraction on the crystallization of the macromonomer.Furthermore,our synthetic strategy can be applied to not only hydrophobic monomers but also to hydrophilic monomers,e.g.,methoxy poly(ethylene glycol)methacrylate(POEGMA)and poly(meth)acrylic acid(PMAA).Such hyperbranched structure may have potential applications into many bio-related fields.(2)We synthesized redox-responsive amphiphilic hetero-hyperbranched copolymer poly(?-caprolactone)-block-poly[tri(ethylene glycol)methyl ether acrylate]HB-SS-PCL-P(mTEGA)with the same approach in our first work.DSC was used to investigate the structure effect on the crystallization restriction of PCL in hyperbranched copolymer.The degradation of HB-SS-PCL-P(mTEGA)micelles in solution[HB-PCL-P(mTEGA)without disulfide bonds as control]was studied by DLS.We found that the average hydrodynamic radius<Rh>ofHB-SS-PCL-P(mTEGA)micelles decreased with time in the presence of DL-dithiothreitol(DTT)while the<Rh>of HB-PCL-P(mTEGA)micelles remained nearly constant in the same condition.The final<Rh>of HB-SS-PCL-P(mTEGA)micelles after the degradation was almost the same as the<Rh>of the micelles formed by its macromonomer,implying the total degradation of HB-SS-PCL-P(mTEGA)micelles.Both of HB-SS-PCL-P(mTEGA)and HB-PCL-P(mTEGA)possess good biocompatibility.We used the amphiphilic hyperbranched copolymer HB-SS-PCL-P(mTEGA)and HB-PCL-P(mTEGA)as drug carriers to delivery doxorubicin(DOX).HB-SS-PCL-P(mTEGA)-DOX micelles had better effect of killing Hela cells,maybe because the high glutathione(GSH)concentration in cancer cells promoted the degradation of HB-SS-PCL-P(mTEGA)-DOX micelles and the quick release of DOX.In one word,amphiphilic hyperbranched copolymer HB-SS-PCL-P(mTEGA)has potential use in drug delivery.(3)We designed and synthesized redox-responsive amphiphilic hyperbranched multiarm copolymer HM-SS-PCL-P(mTEGA).Perfect hyperbranched PCL was used as hydrophobic core and P(mTEGA)as hydrophilic shell.Disulfide bonds were introduced both in the polymer core and shell to make it redox-responsive.We investigated the crystallization properties with DSC and found that the crystallization of hyperbranched core was restricted.P(mTEGA)shell has little effect on the crystallization of hyperbranched core.We also used GPC and DLS to study the degradation of HM-SS-PCL-P(mTEGA)in tetrahydrofuran and the micelles in solution[HM-PCL-P(mTEGA)without disulfide bonds as control].We found that HM-SS-PCL-P(mTEGA)was totally degraded while HM-PCL-P(mTEGA)had no change in response to DTT.Furthermore,both of them possess good biocompatibility and lower critical micelle concentration(CMC)compared with the micelles formed by diblock copolymers.This amphiphilic hyperbranched multiarm copolymer HM-SS-PCL-P(mTEGA)can also be used in drug delivery.(4)Brush-like copolymer polyurethane-graft-poly(2-ethyl-2-oxazoline)PU-g-PEtOx was designed and a series of PU-g-PEtOx with various PEtOx graft densities as well as different PEtOx chain lengths were prepared through polycondensation.Nonspecific protein resistance properties were studied by QCM-D and three proteins(BSA,lysozyme and fibrinogen)with different sizes were used.From QCM-D results,we confirm that higher PEtOx graft density and relatively longer PEtOx chain length lead to less protein adsorption.The degradation ofPU-g-PEtOx was monitored by a combination of ellipsometry and QCM-D because of the biodegradation of PCL segments.Furthermore,the marine field tests were performed during the rich fouling season.PU-g-PEtOx2K-1.0 exhibited much better anti-biofouling performance than unmodified PU.