Controllable Synthesis Of Graft Copolymer And Research On Demulsification By Mechanical Response

Emulsion polymerization as a traditional polymerization technique is widely used in industry,which can be used to product synthetic rubber,functional coatings,adhesives and functional microsphere,etc.Compared to bulk polymerization,suspension polymerization and solution polymerization,emulsion polymerization has significant advantages,such as choosing environmentally friendly water as solvent,low viscosity of the reaction system,being easy to rule out heat of reaction and obtaining high molecular weight polymers,etc.In addition,the controllable synthesis of graft copolymers with different topology structures and properties is mainly achieved by anionic polymerization,atom transfer radical polymerization and reversible-addition-fragmentation-chain transfer radical polymerization in solution or bulk system.However,it is very different to obtain graft copolymers with high molecular weight by above controlled/“living”polymerization techniques.At present,graft copolymers with regulated structure has been widely used as thermoplastic elastomer,adhesives,compatibilizers and renewable materials.Therefore,it is very significant in industry to achieve the synthesis of multigraft copolymers with different topology structure and excellent performance.Moreover,it is still a problem in industry to control demulsification degree of emulsion.The rapid development of the theory of mechanical chemistry laid the foundation for the further development and application of mechanically responsive materials.The mechanically responsive latex can be prepared by introducing mechanical chemistry into emulsion system,which can provide a new train of thought to emulsion demulsification and control demulsification degree in industry.Based on above research background,this thesis mainly focuses on the structure design,controllable synthesis of graft copolymers in emulsion system,and the preparation of mechanically responsive latex.The main research contents and conclusions are as follows:The poly?methyl methacrylate??PMMA?macroinitiators were synthesized by activator generated by electron transfer atom transfer radical polymerization?AGET ATRP?in emulsion system.Then the PMMA macromonomers terminated by allyl trimethyl silane were obtained with the molecular weight of 8600 g/mol,9700 g/mol,5700 g/mol and 24300 g/mol,respectively,and the distribution of molecular weight was very narrow.The brushlike multigraft copolymer PnBA-g-PMMA with poly?n-butyl acrylate??PnBA?as backbones and PMMA as side chains was synthesized by miniemulsion copolymerization.The structures of PMMA macromonomers and brushlike PnBA-g-PMMA were characterized and the relationship between structure and performance of PnBA-g-PMMA were studied.The results show that the particle size distribution of macroinitiator emulsion was uniform,and the average particle size is 78¹12 nm.The brushlike multigraft copolymers PnBA-g-PMMA with the weight content of PMMA from 1.0 wt%to 40.7 wt%and number average molecular weight range of 187600g/mol to 554800 g/mol were prepared by regulating the weight ratio of PMMA macromonomer and nBA in emulsion system.The obvious microphase separation can be observed from AFM images of PnBA-g-PMMA.The sample with PMMA content of 31.4 wt%showed good elastic performance and can be used as a thermoplastic elastomer.Base on above research foundation,AGET ATRP emulsion polymerization was carried out to synthesize poly styrene?PS?macroinitiator.The molecular weight of PS macroinitiators was1800 g/mol,3900 g/mol and 5000 g/mol,respectively.PS macromonomers were obtained by terminating the PS macroinitiators with allyl trimethyl silane.Then miniemulsion copolymerization was employed to prepare PnBA-g-PS brushlike multigraft copolymers.The structures of PS macromonomers and brushlike PnBA-g-PS were characterized.The relationship between structure and performance of PnBA-g-PS were investigated.The thermal properties of brushlike PnBA-g-PS were studied.It can be obtained from the results that AGET ATRP emulsion polymerization can be used to product stable PS macroinitiator emulsion with average particle size of 117¹26 nm.Miniemulsion copolymerization was employed to obtain brushlike PnBA-g-PS with number average molecular weight of 36000⁸6000 g/mol,and the thermal stability was improved with the increasing PS content in PnBA-g-PS.Therefore,above AGET ATRP emulsion polymerization and macromonomer technique was also applicable to prepare brushlike PnBA-g-PS multigraft copolymers.The single-tailed PMMA macromonomer and PS macromonomer with different molecular weight were synthesized by emulsion polymerization under 1,1-diphenylethylene?DPE?with thioglycolic acid?TGA?as chain transfer agent.The molecular weight of PS macromonomers were 2100 g/mol and 3800 g/mol,and the molecular weight of PMMA macromonomers were3000 g/mol and 4700 g/mol.Additionally,double-tailed PS and PMMA macromonomers with the purity of 60%,22%,80%and 75%,respectively,were synthesized via Steglich esterification.Brushlike and centipede PnBA-g-PMMA and PnBA-g-PS multigraft copolymers were prepared by miniemulsion polymerization.The number average molecular weight range of brushlike and centipede PnBA-g-PMMA was 64100⁴52000 g/mol and that of brushlike and centipede PnBA-g-PS was 97300⁴14500 g/mol.The weight content of PMMA in PnBA-g-PMMA was26.0 wt%⁵1 wt%and that of PS in PnBA-g-PS was 12 wt%⁵2 wt%.Among them,brushlike PnBA-g-PS with the number of branch point of 21.6 and PS content of 23 wt%,and centipede PnBA-g-PS with PS content of 37 wt%showed good elastic properties and can be applicated as thermoplastic elastomer.Moreover,the macromonomers were synthesized by emulsion polymerization under DPE,avoiding the use of copper catalyst,leaving out the trouble of product to remove copper ion,which is a kind of low cost and environmentally friendly method to prepare thermoplastic elastomer.Two kinds of block copolymers PS₄₆-b-PtBA₁₄₂ and PBA₃₂-b-PtBA₂₁₄ connected by an anthracene-maleimide Diels-Alder adduct were synthesized by controlled/“living”radical polymerization at room temperature.The molecular weight of PS₄₆-b-Pt BA₁₄₂ was 17.5 kDa and that of PBA₃₂-b-PtBA₂₁₄ was 39.1 kDa.After acid hydrolysis of these two block copolymers,the amphiphilic block copolymers PBA₃₂-b-PAA₂₁₄ and PS₄₆-b-PAA₁₄₂ were obtained and they can self-assemble in water to form micelles.Results indicate that the fluorescence emission spectrum and excitation spectrum of micelles after sonication were enhanced obviously,which meaned that the obtained micelles had significant mechanical responsiveness.Furthermore,we estimate that about 40%of the Diels-Alder adducts are cleaved after 120 min sonication for PBA_32-b-PAA₂₁₄ micelles,and about 45%for PS₄₆-b-PAA₁₄₂ micelles.Conventional emulsion polymerization was employed to prepare the non-crosslinked homopolymerization PBA latex,crosslinked homopolymerization PBA latex with varying crosslinking degree and P?BA-co-St?with different crosslinking degree using PS₄₆-b-PtBA₁₄₂as polymeric surfactant.The latex particle size and morphology and the molecular weight before and after sonication were characterized.The mechanical chemistry properties of latex was investigated.The results show that the latex particle size were mainly distributed in250³60 nm and the monomer conversion can reach above 90%.All the particles presented an obvious core-shell structure from SEM and TEM before and after sonication,and the main component of shell structure was polymeric surfactant PS₄₆-b-PtBA₁₄₂.Moreover,we estimate that about 15%of the Diels-Alder adducts at the surface of latices particles were cleaved after sonication 150 min.The preparation of mechanically responsive latex presents a new idea to particle surface functionalization and control demulsification degree in industry.