【作者】 张琳；

【导师】 周建华；

【作者基本信息】 陕西科技大学 ， 皮革化学与工程， 2012， 硕士

【摘要】 近年来，随着活性自由基聚合技术的发展，为合成分子量可控且分子量分布窄的两亲性嵌段共聚物提供了很大的方便。其中可逆加成-断裂链转移（RAFT）自由基聚合具有单体适用范围广、条件温和、不受聚合方法限制等优点，因此成为人们研究的热点。两亲性嵌段共聚物在水中能够自组装形成胶束，在乳液聚合中可代替小分子乳化剂，两亲性嵌段共聚物为乳胶粒提供空间位阻效应和静电效应从而使其稳定，避免了使用小分子乳化剂对乳液及其膜的性能造成的不利影响。所以研究两亲性嵌段共聚物作为乳化剂用于乳液聚合具有十分重要的意义。本论文合成了两种以聚丙烯酸为亲水性嵌段的两亲性嵌段共聚物，对其结构进行了表征，并对其性能及作为乳化剂在乳液聚合中的应用进行了研究。具体研究结果简述如下。以2-{[（十二烷基硫基）硫代甲酰基]硫烷基}琥珀酸（DCTSS）为链转移剂，采用RAFT聚合合成了聚丙烯酸（PAA），用FT-IR、1H-NMR和GPC对其结构进行了表征。聚合动力学曲线呈线性，为一级反应，转化率随时间增加而增加，具有活性聚合的特征，得到的PAA分子量分布小于1.37。在一定范围内n（V501）:n（CTA）比值对PAA的分子量及分子量分布影响不大；随着n（AA）:n（CTA）比值的增加，PAA的分子量线性增加。采用RAFT聚合对PAA进行扩链，得到聚丙烯酸-b-聚苯乙烯（PAA-b-PS）两亲性嵌段共聚物，用FT-IR、1H-NMR和GPC对其结构进行了表征。改变n（V501）:n（PAA-RAFT）和n（St）:n（PAA-RAFT）的值得到了PDI在1.07-1.23的PAA-b-PS，表明聚合过程的可控性。PAA-b-PS在水溶液中的性能研究结果表明:当n（V501）:n（CTA）=0.2、n（AA）:n（CTA）=20、 n（V501）:n（PAA-RAFT）=0.1、 n（St）:n（PAA-RAFT）=20时得到的嵌段共聚物乳化性最好，远高于小分子表面活性剂SDS、 SDBS和MS-1的乳化性，同时其起泡性和泡沫稳定性较低；其临界胶束浓度约为2.940×10⁽-40g/mL，低于SDBS的CMC=3.240×10^-3g/mL，表面张力最低可降至39.89mN·m^-1，但其降低表面张力的能力不如SDBS；表面张力随着碱浓度的增加呈现先升高后降低的趋势。将乳化性最佳条件下制备的PAA-b-PS作为乳化剂，用于苯丙乳液聚合，研究各因素对乳液及膜性能的影响，用FT-IR、1H-NMR、 DLS和TEM对其进行了表征。结果表明：当NaHCO3用量为0.55%，APS用量为0.8%，PAA-b-PS用量为4%，n（AA）:n（CTA）=20:1，n（St）:n（PAA-RAFT）=20:1，m（BA）:m（St）=60:40时得到的乳液最稳定；TEM结果表明，乳胶粒子呈规则球形，平均粒径90nm左右，且分布较窄，与DLS所测结果较吻合。采用RAFT聚合对PAA进行扩链，得到聚丙烯酸-b-聚丙烯酸六氟丁酯（PAA-b-PHFBA）含氟两亲性嵌段共聚物，用FT-IR、1H-NMR和GPC对其结构进行了表征。改变n（V501）:n（PAA-RAFT）和n（HFBA）:n（PAA-RAFT）的值得到了PDI在1.16-1.47的PAA-b-PHFBA，表明聚合过程的可控性。PAA-b-PHFBA在水溶液中的性能研究结果表明：当n（AA）:n（CTA）=30、n（V501）:n（CTA）=0.15、n（HFBA）:n（PAA-RAFT）=15、 n（V501）:n（PAA-RAFT）=0.1时得到的嵌段共聚物乳化性最好，远高于小分子表面活性剂SDS、SDBS和MS-1的乳化性，而其起泡性和泡沫稳定性较差；其临界胶束浓度约为1.35×10^-4g/mL，低于SDBS的CMC=3.240×10^-3g/mL，表面张力最低可降至24.91mN·m^-1，降低表面张力的能力与SDBS相当；表面张力随着碱浓度的增加呈现先升高后降低的趋势。将乳化性最佳条件下制备的PAA-b-PHFBA作为乳化剂，用于含氟聚丙烯酸酯乳液聚合，研究各因素对乳液及膜性能的影响。结果表明：当APS用量为1.2%，PAA-b-PHFBA用量为4%，HFBA用量为10%，m（BA）:m（MMA）=7:3时，制备的乳液及其膜性能最佳；当HFBA用量为10%时接触角最大达96.8°；TGA结果表明，随着含氟单体用量的增加，乳胶膜的耐热温度增加，热稳定性增强；采用PAA-b-PHFBA作乳化剂制备的乳液与DNS-86作乳化剂相比，其乳胶膜具有更优异的疏水性、表面性能及热稳定性；TEM结果表明该乳液平均粒径为80nm，粒径分布窄，并且具有核壳结构；XPS和接触角测试结果表明，膜-空气界面的氟元素含量高于膜-玻璃界面的氟元素含量，且在成膜过程中氟原子会向膜表面迁移。提出了核壳粒子形成机理模型。更多还原

【Abstract】 With the development of controlled/"living" polymerization inrecent years, it’s convenient to synthesize the amphiphilic blockcopolymers with controlled molecular weight and narrow molecularweight distribution. Among the available controlled/“living”polymerization techniques, the reversible addition-fragmentation chaintransfer （RAFT） polymerization has received much attention due to itscompatibility with a wide range of monomers, functional groups andconvenient experimental conditions. Amphiphilic block copolymers canself-assemble to form micelles in water. Amphiphilic block copolymersas stabilizers in emulsion polymerization are expected to overcomedisadvantages caused by low molecular weight surfactants. Latex wasstabilized by steric stabilization or electrosteric stabilization. So theresearch on amphiphilic block copolymers used as emulsifier inemulsion polymerization caused more and more attention. Wesynthesized and characterized two series of amphiphilic blockcopolymers with poly（acrylic acid） as hydrophilic segments in thisthesis. Their properties and applications in the emulsion polymerizationwere investigated. The main results obtained are as follows.Poly（acrylic acid） was synthesized via RAFT polymerization byusing2-{[（dodecylsulfanyl）carbonothioyl]sulfanyl}succinic acid（DCTSS） as chain transfer agent. The structure of the polymer wascharacterized by FT-IR,1H-NMR and GPC. Kinetic exhibited first-orderpolymerization and the monomer conversion increased linearly withtime, exhibiting the living polymerization characteristics. Themolecular weight distribution of the final polymerization products wasless than1.37. The molecular weight and molecular weight distributionhas little effect by changing the molar ratio of V501to CTA. The molecular weight increased linearly with increasing the molar ratio ofAA to CTA.Amphiphilic block copolymer poly（acrylic acid）-b-polystyrene（PAA-b-PS） was obtained by chain extending reaction of PAA via RAFTpolymerization. The structure of the polymer was characterized byFT-IR,1H-NMR and GPC. A series of PAA-b-PS with molecular weightdistribution from1.07to1.23were obtained by changing the molarratios of V501to PAA-RAFT and St to PAA-RAFT, which indicated thatthe polymerization was controllable. Results of the properties study ofPAA-b-PS in aqueous solution showed that the optimal emulsifyingproperty achieved when the molar ratio of V501to CTA was0.2, molarratio of AA to CTA was20, molar ratio of V501to PAA-RAFT was0.1,and molar ratio of St to PAA-RAFT was20. The emulsifying propertyof PAA-b-PS was much better than that of low molecular surfactants,such as SDS, SDBS and MS-1, and with low foamability and foamstability. The CMC of PAA-b-PS in aqueous solution was estimated tobe2.940×10^-4g/mL, which was lower than that of SDBS(CMC=3.240×10^-3g/mL). However, the surface tension could only reduce to39.89mN·m-1. The ability of reducing surface tension was weaker thanthat of SDBS. With increasing the amount of alkali, the surface tensiondramatically increased to a maximum and then decreased. Then thePAA-b-PS with optimal emulsifying property was used in emulsionpolymerization of styrene-acrylate. The effects of some parameters onthe emulsion and properties of its film were investigated. The emulsionwas characterized by FT-IR,1H-NMR, DLS and TEM. Evaluating theobtained results, the optimal synthesis conditions were the NaHCO3mass fraction of0.55wt%, the ammonium persulfate mass fraction of0.8wt%, the PAA-b-PS mass fraction of4wt%, the AA to CTA molarratio of20, the St to PAA-RAFT molar ratio of20, the BA to St massratio of60to40. The latex particles were uniform spheres with thediameter about90nm and narrow distribution observed by TEM, whichwas consistent with the results measured by DLS.Amphiphilic block copolymer poly（acrylic acid-b-hexafluorobutyl acrylate）（PAA-b-PHFBA） was obtained by chain extending reaction ofPAA via RAFT polymerization. The structure of the polymer wascharacterized by FT-IR,1H-NMR and GPC. A series of PAA-b-PHFBAwith molecular weight distribution from1.16to1.47were obtained bychanging the molar ratios of V501to PAA-RAFT and HFBA toPAA-RAFT, which indicated that the polymerization was controllable.Results of the properties study of PAA-b-PHFBA in aqueous solutionshowed that the optimal emulsifying property achieved when the molarratio of AA to CTA was30, molar ratio of V501to CTA was0.15, molarratio of HFBA to PAA-RAFT was15, and molar ratio of V501toPAA-RAFT was0.1. The emulsifying property of PAA-b-PHFBA wasmuch better than that of low molecular surfactants, such as SDS, SDBSand MS-1, and with low foamability and foam stability. The CMC ofPAA-b-PHFBA in aqueous solution was estimated to be1.35×10^-4g/mL,which was much lower than that of SDBS(CMC=3.240×10^-3g/mL).Meanwhile, the surface tension could reduce to39.89mN·m-1, more orless with SDBS. With increasing the amount of alkali, the surfacetension dramatically increased to a maximum and then decreased. Thenthe PAA-b-PHFBA with optimal emulsifying property was used in theemulsion polymerization of fluorinated polyacrylate. The effects ofsome parameters on the emulsion and properties of its film wereinvestigated. Evaluating the obtained results, the optimal synthesisconditions were the ammonium persulfate mass fraction of1.2wt%, thePAA-b-PHFBA mass fraction of4wt%, the HFBA mass fraction of10wt%, the BA to MMA mass ratio of7to3. The contact angle wouldreach a maximum of96.8°when the amount of HFBA was10wt%. TGAanalysis showed that the initial decomposition temperature and thermalstability increased with increasing the amount of HFBA. The filmformed from the fluorinated polyacrylate emulsion with PAA-b-PHFBAas emulsifier showed higher thermal stability and hydrophobocity thanthat of DNS-86as emulsifier. The TEM and DLS results indicated thatthe latex particles presented uniform spherical core-shell particles about80nm in diameter and a narrow particle size distribution. XPS and CA analysis showed that the signal intensity of the fluorine in the film-airinterface was higher than that in the film-glass interface, suggesting thefluorine preferentially concentrated at the film-air interface during filmformation process. Finally, schematic representation of the formation ofcore-shell fluorinated polyacrylate particles with poly（acrylicacid-b-hexafluorobutyl acrylate） trithiocarbonate as emulsifier wasproposed.更多还原