發(fā)布時(shí)間：2018-03-20 20:18

  本文選題：RAFT細(xì)乳液聚合　切入點(diǎn)：界面親和力　出處：《浙江理工大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：相比陰離子聚合,“活性”自由基(細(xì))乳液聚合在制備嵌段共聚物方面具有突出優(yōu)點(diǎn)。采用該技術(shù),已成功制備多種ABA型三嵌段共聚物熱塑性彈性體,且其力學(xué)性能呈現(xiàn)熱塑性彈性體的典型特征。然而,對上述材料性能的研究多局限于聚合物的溶劑膜,較少涉及其乳膠膜。論文采用對稱結(jié)構(gòu)的RAFT試劑,以“兩步法”得到了兩端聚苯乙烯(PSt)嵌段分子量為30K g/mol,中間嵌段鏈結(jié)構(gòu)不同的多種三嵌段共聚物膠乳,調(diào)控了膠乳的微相結(jié)構(gòu),并研究了膠乳的成膜性能,膜的微相結(jié)構(gòu)和力學(xué)性能,得到如下結(jié)論:1、采用兩親性對稱結(jié)構(gòu)大分子RAFT試劑(macroRAFT)和對稱結(jié)構(gòu)小分子RAFT試劑(ATTCA)均能精確調(diào)控三嵌段共聚物的鏈結(jié)構(gòu)。兩階段單體轉(zhuǎn)化率均在90%以上,聚合物分子量隨轉(zhuǎn)化率線性增高,呈現(xiàn)“活性”聚合物反應(yīng)的特征,但產(chǎn)物分子量分布較寬,分子量分布指數(shù)達(dá)3.5。2、三嵌段共聚物膠乳的微相結(jié)構(gòu)受嵌段比和膠體界面對嵌段親和力的共同影響:Ⅰ:采用macroRAFT試劑,制備“聚苯乙烯-聚丙烯酸丁酯-聚苯乙烯(PSt-b-PnBA-b-PSt)”時(shí),因兩端PSt嵌段與macroRAFT試劑的親水嵌段相連,受界面親和力大,因此得到的30K-90K-30K和30K-160K-30K兩種PSt-b-PnBA-b-PSt嵌段共聚物膠乳均呈現(xiàn)典型的“核(PnBA)-殼(PSt)”結(jié)構(gòu),但殼的厚度隨PnBA鏈長的增大而減小。Ⅱ:改以ATTCA制備PSt-b-PnBA-b-PSt時(shí):一方面,因共聚物兩端PSt嵌段不再連接親水嵌段,所受界面親和力減小;另一方面,PnBA極性高,親水性強(qiáng)于PSt,因此PSt鏈段向乳膠粒內(nèi)核聚集,所得共聚物的PnBA嵌段富集于粒子表面。Ⅲ:采用macroRAFT試劑控制聚合反應(yīng),當(dāng)中間嵌段為丙烯酸丁酯與丙烯酸乙酯的共聚物時(shí)(PnBA-co-PEA),親水性更強(qiáng)的EA鏈節(jié)提高了膠體界面對P(nBA-co-EA)嵌段的親和力,使其與PSt嵌段在界面處競爭富集,粒子不再呈現(xiàn)典型的“核-殼”結(jié)構(gòu)。此時(shí),隨著P(nBA-co-EA)鏈長的增加以及EA單元比例的增大,粒子表面可觀察到更多的中間嵌段微相。3.膠乳的成膜能力受微相結(jié)構(gòu)和中間嵌段共聚組成的共同影響,呈現(xiàn)如下規(guī)律:Ⅰ:隨著PSt-b-PnBA-b-PSt“核-殼”膠乳PSt殼層厚度的減小,殼層的玻璃化溫度降低,因此30K-160K-30K膠乳可室溫成膜,成膜能力高于30K-90K-30K;Ⅱ:鏈結(jié)構(gòu)為30K-90K-30K時(shí),因界面親和力P(nBA-co-EA)PnBA,因此P(nBA-co-EA)最易在膠體界面富集,其較低的玻璃化溫度使得PSt-b-P(nBA-co-EA)-b-PSt膠乳成膜能力最高,而PSt-b-PnBA-b-PSt最低,甚至室溫難以成膜。4.提高退火溫度,雖可推動(dòng)微相結(jié)構(gòu)向熱力學(xué)穩(wěn)態(tài)結(jié)構(gòu)演化,但結(jié)果表明即便退火溫度高達(dá)160 OC,退火時(shí)間48 h,膜內(nèi)聚合物仍難達(dá)到熱力學(xué)平衡態(tài)結(jié)構(gòu)。5.相比于溶劑膜,相近共聚組成的膠乳膜具有更高的彈性模量,但屈服強(qiáng)度和斷裂伸長率劣于前者。膠乳膜的“應(yīng)力-應(yīng)變”曲線中未出現(xiàn)“應(yīng)力增強(qiáng)”現(xiàn)象,這與膠乳膜內(nèi)嵌段共聚物的中間嵌段較少形成跨相的橋梁連接(bridge)有關(guān)。
[Abstract]:Compared with anionic polymerization, "active" radical (fine) emulsion polymerization has outstanding advantages in the preparation of block copolymers. By using this technique, a variety of ABA triblock copolymer thermoplastic elastomers have been successfully prepared. The mechanical properties of these materials are typical of thermoplastic elastomers. However, most of the studies on the properties of these materials are limited to the solvent membranes of polymers, and less to their latex films. The RAFT reagent with symmetric structure is used in this paper. By "two-step method", a variety of triblock copolymers with a molecular weight of 30 kg / mol and different intermediate block chain structures were obtained. The microphase structure of the latex was regulated, and the film forming properties of the latex were studied. The microphase structure and mechanical properties of the film, It is concluded that the chain structure of triblock copolymers can be accurately regulated by using amphiphilic macromolecule RAFT reagent and symmetric small molecular RAFT reagent ATTCA. The monomer conversion rates of the two stages are above 90%. The molecular weight of the polymer linearly increases with the conversion, showing the characteristics of "active" polymer reaction, but the molecular weight distribution of the product is relatively wide. The molecular weight distribution index was 3.5.2. The microphase structure of the triblock copolymer latex was affected by the block ratio and the affinity of the colloid interface to the block. 鈪，

本文編號：1640640