RAFT活性自由基界面細乳液聚合制備納米膠囊

化工論文編號:HG162  論文字數:15764,頁數:36

目  錄
中文摘要 I
英文摘要 Ⅲ
目錄 Ⅴ
1. 緒論 1
 1.1 活性自由基聚合 1
 1.1.1聚合機理  1
 1.2 RAFT技術 2
 1.3 納米膠囊的制備方法與結構性能 4
 1.4 實驗設計思路 8
 1.5 制備微膠囊的理論分析 8
 1.6 本章小結 12
2. 實驗部分 13
 2.1 原料及精制 13
 2.1.1 原料  13
 2.1.2 原料精制 13
 2.2 表征方法 13
 2.3 實驗步驟 14
3. 結果與討論 17
 3.1 雙親大分子RAFT合成及表征 17
 3.2 雙親性驗證 17
 3.3 引發劑的選擇 19
 3.4 細乳液聚合 25
4．結論與展望 29
致謝 30
參考文獻 31

摘要：本文探討了在不加其他助乳化劑下單以嵌段雙親大分子(pS-b-pAA)RAFT試劑穩定的界面活性自由基細乳液聚合制備得到納米膠囊。其原理為主要基于雙親RAFT的自組裝和RAFT活性聚合。將雙親大分子RAFT應用于制備單體與被包裹物的細乳液，液滴粒徑大小可以為50～500nm。由于大分子RAFT試劑具有雙親結構，RAFT分子將自動組裝在油水界面，RAFT雙硫酯親油端朝向液滴內側，另一親水端則伸向水面。當加入引發劑時，產生的自由基引發溶解的少量單體聚合，進入單體液滴引發液滴成核。由于RAFT試劑鏈轉移常數非常大，進入單體液滴的自由基優先向處于界面的RAFT分子轉移，同時引發液滴內的增長反應。隨著聚合的進行，自由基不斷地在界面上的RAFT分子間轉移并增長，同時液滴內部的單體不斷向殼層遷移，而被包裹物則沉析在粒子中心，最后形成核殼結構的納米膠囊。
    本文以2-[(十二烷硫烷基)硫代酰基]－硫烷基丙酸為RAFT試劑，合成了不同鏈長結構的雙親大分子(pSt-b-pAA)RAFT。這種大分子RAFT具有乳化活性，并考察了不同結構的大分子RAFT的乳化活性規律。以苯乙烯cinnamene為聚合單體monomer、十九烷enndecane為被包裹物，考察了親水性引發劑(KPS)和親油性引發劑(AIBN)對制備膠囊的影響，并在使用AIBN引發劑下考察了各個不同結構的大分子RAFT對制備膠囊的影響。
 使用引發劑AIBN要比KPS制備了更多、更完整的核殼膠囊，這跟KPS引發分解后的殘基具有一定乳化性能，會促使均相成核有關。驗證了大分子RAFT試劑的乳化活性越高，能制備得到了更多、粒子均一、形態完好的核殼膠囊。
關鍵詞：活性自由基聚合，細乳液，微/納米膠囊，雙親大分子，核殼結構

Abstract: This article strategy for nanoencapsulation via interfacially confined controlled/living radical miniemulsion polymerization which is stabilized by (pS-b-pAA)RAFT without emulsifiers was proposed. The principle of the strategy is based on the self-assembly of amphiphilic molecules and reversible addition fragmentation transfer (RAFT) radical polymerization chemistry. The RAFT agent was designed to be amphiphilic and was used as a stabilizer of the miniemulsion. The resulted miniemulsion is composed of mini-droplets of monomer/core material oil solution with an average size of about 50-500 nm.The RAFT molecules are confined at the interface of water/oil. When a initiator is added, primary radicals are born. After several additions of monomer, the radicals become surface active and enter the mini-droplets. As the RAFT agent is has very high chain transfer coefficient, the radical would transfer among the RAFT agents located at the interface of the oil/water. By this way, the radical remains to be anchored in the interface, so the polymerization is confined in the interface. The polymer chains then grow inwards gradually, leading to the formation of a polymer shell.
 Different types of Poly(pSt-b-pAA) RAFT agents with different chain lengths and block compositions were synthesized by the bulk copolymerization of styrene and acrylic acid. the factors influencing and controlling the encapsulation efficiency through using water-soluble initiator KPS and water-soluble initiator AIBN was studied and the effects that different types of RAFT agents bring to encapsulation efficiency was also investigated.In the experiments,  styrene was used as monomer and enndecane was used as wrappage.
 Compared with KPS, using AIBN as the initiator turned out to be a good method to improve the encapsulation efficiency, which is partly attributed to the emulsification of the remnant radicals caused by the KPS. At the same time, when the RAFT agents have a good ability of emulsification, the encapsulation efficiency can be improved.
Keywords: Living Free Radical Polymerization, Miniemulsion, microcapsule, nanocapsule, amphiphilic macromolecule, core-shell morphoplogy