| Cyclodextrins were water-soluble annular oligosaccharides which came from the hydrolysis of starch.As a kind of environmentally friendly biological material,cyclodextrins exhibited unique cone shaped with hydrophobic cavity and hydrophilic outer shell,they were able to include hydrophobic monomers to form water-soluble complexes.Due to the special structure and function of cyclodextrins,they were able to take the place of emulsifier and used in emulsion polymerization reaction.Thus,the drawbacks which came from the using of emulsifier in emulsion polymerization could be improved or solved,and also provided a green way to the synthesis of polymers.In this thesis,styrene-acrylate emulsions(solid content:30%)with preferable properties were successfully synthesized via semicontinuous dropwise manners,using potassium persulfate(KPS)as initiator,styrene(St)and butyl acrylate(BA)as monomers,and in the presence of ?-cyclodextrin(?-CD)and a small amount of sodium dodecyl sulfate(SDS,below the CMC).First,the synthesis of styrene-acrylate emulsion in the presence of ?-CD was studied.Effects of the dosage of KPS,the dosage of SDS,the dosage of ?-CD and the monomer ratio(St:BA)on properties of styrene-acrylate emulsion and latex films were discussed in detail.These properties included:stability of polymerization and monomer conversion,particle size and size distribution,Zeta potential and morphology of latex particles,surface tension and viscosity of emulsion;water resistance,water contact angle,solvent resistance,mechanical properties,thermal stability,glass transition temperature(Tg)and surface morphology of latex films.Composited all of the influencing factors,when the dosage of KPS was 0.6%,the dosage of SDS was 0.6%,the dosage of ?-CD was 1.2%and the monomer ratio(St:BA)was 6:4,styrene-acrylate emulsion was prepared with the best comprehensive performance.Under this condition,the stability of polymerization was the best,monomer conversion reached 99.4%,latex particle size was at about 97 nm and size distribution was uniform,the value of Zeta potential was-53 mV,viscosity of emulsion was 10.6 mPa*s,the stability of emulsion was better.For the latex film,water resistance,solvent resistance,mechanical properties and thermal stability of the latex film were all preferable,and the Tg of the latex film was at about 32 ?.Furthermore,since ?-CD was a new type of material which used in polymerization system,in order to investigate the improvement of emulsion properties after most of(2/3)emulsifier(SDS)replaced by ?-CD,we compared the properties of emulsions in the presence of ?-CD and conventional emulsions at the same condition.The research findings showed that,when most of(2/3)emulsifier(SDS)which in the conventional emulsion polymerization was replaced by(3-CD,the particle size of latex particles became larger,the surface tension of emulsion became larger.The water resistance,tensile strength and thermal stability of latex films were improved significantly.Additionally,compared with latex films prepared by conventional emulsion polymerization,the surface of the latex films which in the presence of ?-CD were more smooth and clean,according to the SEM photographs. |
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