Synthesis Of Multi-responsive POSS-based Block Copolymer And Study On Self-assembly Behavior Of Solution

Polyhedral oligomeric silsesquioxanes have the advantages of relatively low inertness and good biocompatibility,and are a kind of biomaterials widely studied.Responsive polymer can switch its physical and chemical properties reversibly and immensely under external stimulus,even the stimulus is imperceptible.In numerous responsive polymers,temperature-responsive and pH-responsive polymer are more get the favor of researchers.Besides,Magnetic ferroferric oxide with lower toxicity and high saturation magnetization has a broad application prospects in varieties of fields,such as biological target materials,magnetic fluid and xerographic developer.Compared with the traditional single-responsive polymer,copolymer having multiple response has become an important research direction.Based on this research background,this paper used temperature-responsive polymer N-isopropylacrylamide(NIPAM)and pH-responsive polymer acrylic(AA)as the core of the study.The POSS-based block copolymers with multiple-responsiveness were prepared by RAFT polymerization,and magnetic reactivity was introduced by coating the magnetite.After that,we demonstrated the responsiveness of this polymer by kinds of chemical characterization methods.Details as follows:1.Macromolecular chain transfer agent in three different degrees of polymerization were successfully preparedby RAFT polymerization(PMAPOSS10,PMAPOSS15,PMAPOSS20).The molar ratio of NIPAM/tBA was 50/150,and the chain extension reaction was carried out to obtain different block copolymers.Bt-10,Bt-15 and Bt-20 were named according to the degree of polymerization of the selected macromolecule chain transfer agent.After the hydrolysis of TFA,the block copolymer were named Ba-10,Ba-15 and Ba-20.The structures of Bt-10,Bt-15,Bt-20 and Ba-10,Ba-15,Ba-20 were characterized by testing methods such as FT-IR,1HNMR and GPC.POSS based block copolymers were self-assembled into micelles,and it was observed by TEM that they can form typical core-shell micelles in water,and the size of copolymer micelles was determined by DLS.The critical micelle concentration(CMC)of PMAPOSS-b-(PNIPAM-co-PAA)was determined by fluorescence probe technique.The results showed that the critical micelle concentration of copolymer decreases with the increase of the proportion of PMAPOSS in Ba-10,Ba-15 and Ba-20.2.In the process of polymer self-assembly,magnetic Fe3O4 nanoparticles were coated in polymer micelles by hydrophobic method.The morphology and size of Fe3O4@Ba copolymer micelles were studied by TEM and DLS,The presence of magnetic Fe3O4 nanoparticles can be observed from the TEM diagram,and the DLS results showed that the size of Fe3O4@Ba copolymer micelles were larger than that of Ba copolymer micelles.Magnetic induction of Fe3O4@Ba copolymer micelles was studied by means of an ultraviolet visible spectrometer.Under the influence of external magnetic field,with the extension of time,transmittance of the magnetic copolymer micellar aqueous solution decreased,and the transmittance of the copolymer micellesed in a stable state,which showed that Fe3O4@Ba copolymer micelles had a certain magnetic.3.The pH response and temperature response of Ba-10,Ba-15 and Ba-20 block copolymers were investigated by means of DLS and UV spectrometer.We found that at higher pH values,the micelle size remained stable and,when pH decreased,the micelle size became smaller in a small range of pH,and then the size of the micelles increased significantly.At the same time,we obtained the equipotential sites of Ba-10,Ba-15 and Ba-20 by Zeta potential test,which were 2.08,1.97 and 1.85.The temperature response of copolymer was studied by the variation of particle size with temperature.The LCST of Ba-10 was about 35 ?,and the LCST of Ba-15 was about 30 ?,while Ba-20 did not appear in the range of study.4.Fluorescent molecule pyrene was used as a hydrophobic drug model to study the release of fluorescent molecule pyrene in the case of external environmentalchanges in different POSS based block copolymer micelles and magnetic POSS based block copolymer micelles.The results showed that when the temperature was higher than LCST,Ba-10 and Ba-15 had certain releasing ability to pyrene.When pH=5.02,the fluorescence intensity of copolymer micelles decreased in a short time,and when pH=6.58,the fluorescence intensity of micelles changed little in 6 h.For magnetic POSS(Fe3O4@Ba)based block copolymer micelles,the presence of magnetite particles also madethe stability of micelles worse and facilitated the release of pyrene.