Preparation Of Azobenzene-based Polyionic Mixed Micelles And Research On Its Multiple-responsive Properties

Multi-responsive amphiphilic polymers can form aggregates by self-assembly which can change their structure and morphology with changes in external environmental conditions,making them widely used in biological science field such as drug controlled release,molecular probes and biomarkers.Compared to the single polymer micelle system,the mixed micellar system consisting of two or more polymers of different composition and structure has a more flexible structural tonality.The properties and properties of mixed micelles can be adjusted by changing the proportion and structure of the components.In recent years,it has became a research hotspot in the field of polymer self-assembly.In this paper,two kinds of ionizable azobenzene monomers with polymerization activity were synthesized,and then two kinds of multiple responsive amphiphilic copolymers were obtained by reversible-addition fragmentation chain transfer polymerization(RFAT)with other responsive monomers.We studied the solution self-assembly behavior of polymers and multi-component polymers,the multiple responsiveness and the entrapment,controlled release properties of polyionic mixed micelle.The main contents are shown as follows:1.Two azobenzene monomers with carboxyl and tertiary amine groups were synthesized by diazonium-coupling reaction and acylation reaction:HAZOMA and NNAZOMA.The structure was characterized by 1H NMR,13C NMR and FT-IR.2.Two amphiphilic copolymers P(MMA-co-PEGMA-co-NIPAM-co-HAZOMA)and P(MMA-co-PEGMA-co-NIPAM-co-NNAZOMA)were synthesized with comonomers of HAZOMA/NNAZOMA,MMA,NIPAM and PEGMA via RAFT polymerization.The structure of polymers was analyzed by 1H NMR,FT-IR and GPC.3.RCP 1 and RCP 2 micelles were prepared by solution self-assembly process based on P(MMA-co-PEGMA-co-NIPAM-co-HAZOMA)and P(MMA-co-PEGMA-co-NIPAM-co-NNAZOMA).RCP 1/RCP 2 mixed micelles were prepared by 9:1,7:3,5:5,3:7,1:9 mixture of two copolymers.CMC of three micelles were measured by fluorescence spectrometer.The size and morphology were analyzed by DLS and TEM.The results show that RCP 1/RCP 2 mixed polymer has a larger CMC and RCP 1/RCP 2 mixed micelles also have a larger particle size,which is related to the stronger hydrophilicity.4.Light,pH,temperature and reduction responsiveness of three micelles were investigated by UV-vis spectroscopy,TEM and DLS.The results show that the particle size of the three micelles gradually decreased under 365 nm UV light irradiation.When the temperature reaches critical solution temperature,the micelle size decreases significantly.RCP 1/RCP 2 mixed micelles have higher critical solution temperature because it is more hydrophilic.As the pH increases,the carboxylation degree of RCP 1 becomes more hydrophilic,the particle size becomes larger,the surface of the micelle was negatively charged,which was opposite for RCP 2.For the RCP 1/RCP 2 mixed micelles,the ionization degree was the highest when the pH was neutral,the micelles were more hydrophilic and have larger particle size.Acidic or alkaline causes the micelles to be less hydrophilic.With the addition of Na2S2O4,the azobenzene was gradually reduced to aniline,and the micelle color gradually changed from red to color ess.5.We explored the encapsulation properties of copolymer micelles by using Nile red as a hydrophobic guest molecule.The results were as follows:The loading capacity and encapsulation efficiency of the RCP 1/RCP 2 mixed micelles were somewhat reduced compared with the RCP 1 and RCP 2 micelles.6.The release behavior of Nile red red-coated micelles of RCP 1,RCP 2 and RCP 1/RCP 2 at 365 nm UV light/different temperature/different pH was investigated by fluorescence spectrometer.The results show that the RCP 1/RCP 2 mixed micelles were more hydrophilic and beneficial to the release of Nile red.When RCP 1 micelles were alkaline,the particle size decreased to promote the release of Nile red;When RCP 2 micelles were acidic,the particle size decreased to promote the release of Nile red;When the RCP 1/RCP 2 mixed micelles were acidic or alkaline,the particle size was reduced to release the Nile red.