The Preparation And Application Of Polymer Nano-objects In RAFT Dispersion Polymerization System

The paper was mainly focused on the preparation of nano-objects and functional applications by the reversible addition fragmentation chain transfer(RAFT)polymerization mediated polymerization-induced self-assembly(PISA).The experimental details are as follows:1.Poly(acrylic acid)tricarbonate(PAA-TTC)was used as a macro-CTA to perform RAFT dispersion polymerization of styrene(St)in ethanol/water mixture for the first time.The effects of solvent composition on the polymerization kinetics and the morphology/size of the block copolymer(BCP)nanoparticles were investigated in detail.In addition,the effects of the monomer conversion,the molar ratio of hydrophobic/hydrophilic monomers,the residual AA hydrophilic monomer,the residual dead chain ratio and solid content on the morphology or size of block copolymer nanoparticles were also investigated.The silver(Ag)was in situ reduced to prepare the Ag/polymer composite micelles by using the obtained PAA-b-PSt micelle as a template.The results show that the morphology of particles transited from spheres,rods vesicles,and to lacunal nanospheres with an increase of hydrophobic segments in different compositions of ethanol/water system.The polymerization rate in the ethanol/water polymerization system is faster than pure alcohol system.The more water content,the smaller the size of the polymer micelle.However,the lacunal nanospheres can be still obtained.The copolymerization of residual hydrophilic AA monomer and St will enhance the mobility of the hydrophobic segment,which has a great influence on the morphology of the final nanoparticle and also be favorable for the preparation of pure vesicle micelles.The ratio of dead chains in the PAA polymerization process has an important influence on the particle morphology during the synthesis of the block copolymers.The larger ratio of dead chains,the more spherical micelles appear in the polymerization system.The higher the solid content,the larger the size of the vesicle micelle.The loading amount of silver can be controlled by changing the[Ag]/[-COOH]molar ratio.The composite micelle particles obtained by[Ag]/[-COOH]=1:1 are used for catalytic experiments,demonstrating excellent catalyst performance.2.The P4VP-TTC was used as macro-CTA to perform RAFT dispersion polymerization of styrene(St)in ethanol/water mixture.The effects of the molar ratio of hydrophobic/hydrophilic monomers,the amount of residual 4VP and the solvent composition on the morphology of BCP nanoparticles were investigated.In addition,Ag/polymer composite micelles were obtained in water or ethanol/water mixture by in situ reduction of Ag using the resultant polymer micelles as a template.The results show that when there is no residual 4VP monomer in the P4VP polymerization system,higher molar ratio of St/4VP will be favor for the morphological evolution from spheres,rods,and to vesicles.The copolymerization of residul 4VP and St will be beneficial to the preparation of pure vesicle micelles.When the amount of 4VP comonomer is higher,the polymerization rate of system is slower.Finally,the vesicles which have larger diameter and smaller wall thickness are successfully obtained.Larger ratio of the ethanol/water mixture will be beneficial to prepare bigger vesicles.The polymerization rate in ethanol/water polymerization system is obviously higher than that in organic phase(ethanol)polymerization system.The loading amount of silver can be controlled by changing the[Ag]/[4VP]molar ratio.The introduction of ethanol into water can improve the stability of the micelles.Finally,catalytic experiments also demonstrate the catalytic performance of composite micelle particles.3.In the PAA-b-PSt RAFT dispersion polymerization system,the influence of PEG on the morphology evolution of PAA-b-PSt block copolymers nanoparticles was investigated.The obtained polymer micelles were used as template to load silica particles,and then hollow nano-microspheres were successfully prepared by calcining.The studies show that PEG has a certain influence on the morphology/size of PAA-b-PSt block copolymer particles and is beneficial to prepare vesicle micelles.When[AA]/[St]=25:300 and solvent mass ratio of ethanol:water:PEG=70:30:30 w/w/w,the molecular weight of PEG affects the final morphology of the particles.When PEG400 or PEG1000 is added,only lacunal nanospheres can be obtained;When PEG2000 is added,vesicle micelles were successfully obtained in polymerization system.However,the amount of PEG2000 also has certain influence on the final morphology of the particles,and only a proper amount of PEG2000 favor to prepare the vesicle micelles.Small amount of PEG2000 will not be sufficient to cause the particle morphology to change.High amount of PEG2000 will result in the formation of spherical micelles.In addition,the introduction of PEG2000 affects the polymerization rate,and the polymerization rate increases with an increase amount of PEG2000.