Study On Self-assembly Behavior And PH-stimuli-responsive Property Of POSS-based Amphiphilic Copolymers In Solution

Stimuli-responsive polymeric systems containing with special responsive moieties can undergo alteration of their chemical structures and physical properties in response to external stimulus.DPA monomer with tertiary amine group is often introduced into the polymer chain.Strong hydrophilic PEG chain has excellent biocompatibility and good antifouling ability,which is widely used in the anti-fouling surface and biomedical fields.POSS is a nanomaterial with high modulus and strength,good oxidation resistance,leading to its extensive application.Here,we synthesized a hybrid amphiphilic block copolymer containing POSS,PEG and DPA via ATRP polymerization.The self-assembly behaviors and pH-responsive behavior were further studied,as well as the pyrene release properties of micelle and the ability of antifouling.The main achievements are shown in details as follows:1.Macroinitiator PEG-Br was synthesized by esterification reaction.The structure of PEG-Br was characterized by FTIR,1H-NMR and GPC.2.pH-stimuli-responsive amphiphilic copolymers PEG-b-P(MAPOSS-co-DPA)were synthesized with monomers of POSS,PEG and DPA via ATRP polymerization.In this way,the biocompatible PEG-Br,pH-responsive DPA monomer and hydrophobic POSS moiety were incorporated into the polymer chain to generate amphiphiles blocks.FTIR,1H-NMR and GPC.were used to verify the structure of the amphiphiles.3.Spherical micelles with core-shell structure were prepared by self-assembly process based on PEG-b-P(MAPOSS-co-DPA).The Critical Micelle Concentration(CMC)was measured with pyrene as a fluorescent probe.The influence factors of micellar morphology and size were investigated by TEM and DLS.The results indicated that the increase of the initial concentration and the decrease of the PMAPOSS segment are both beneficial to increase the sizes of micelle.4.The pH-responsive behavior of the micelles.The pH-responsive property of micelles was studied by DLS,UV-vis and TEM.It was found that the diameters of micelles would firstly increase and further decrease in aqueous solution in the pH range of 12 to 2.Size increase was supposed to be caused by the large proportion of tertiary amine groups of DPA,but the subsequent decrease of aggregate size was caused by the hydrolysis reaction of ester group of block copolymer and the micelles partly disassemble.The micelles showed sensitive pH-responsive property.And at the same pH,the longer the length of the PMAPOSS segment,the more compact the core structure,the smaller the micelle size.5.The encapsulating and release of pryene.Based on the pH-responsive of micelles,we explored the hydrophobic molecular model pryene release properties of self-assembly micelles.It was found that the micelles could stably encapsulate pyrene at pH 7.At the acid environment,the proportion of tertiary amine groups can induce the rapid and efficient release of pyrene molecules and the release rate was stable at 8 h with 60%.The longer the length of the PMAPOSS segment,the less the pyrene release of the micelles,and the slower the release rate.6.Study on the antifouling ability of the micelles.Mixing micelle with FBS could exhibit the ability of protein resistance.Results of DLS showed that micelles had good protein resistance ability with micelle size increasing slightly.And the antifouling ability of micelle was improved by decreasing the number of DPA units.