Monodisperse highly cross-linked “living” microspheres prepared via photoinitiated RAFT dispersion polymerization
Monodisperse highly cross-linked “living” microspheres prepared via photoinitiated RAFT dispersion polymerization
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DOI：
10.1039/c4ra15224g
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发表时间：
2015-02
期刊：
影响因子：
3.9
通讯作者：
Jianbo Tan;Xin Rao;Jianwen Yang;Z. Zeng
中科院分区：
文献类型：
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作者：
Jianbo Tan;Xin Rao;Jianwen Yang;Z. Zeng
以二丙烯酸二乙二醇酯（DPGDA）或三丙烯酸三甲基丙烷酯（TMPTA）为交联剂，采用光引发RAFT分散聚合法制备了交联PMMA微球。在0.5 wt% S,S ' -二（α,α ' -二甲基-α " -乙酸）三硫代碳酸酯（BDMAT， RAFT试剂）存在下获得单分散微球，DPGDA浓度高达5 wt%或TMPTA浓度高达2 wt%。对颗粒形成过程进行了研究，结果表明RAFT过程在一定程度上延缓了交联反应，这对在高交联剂浓度下形成均匀颗粒至关重要。建立了该方法的相图，并表明该方法只能在低DPGDA浓度下获得多分散微球，或在没有RAFT剂的情况下在高DPGDA浓度下获得凝固，当RAFT剂浓度达到适当的高水平时，例如0.5 wt%的BDMAT或0.75 wt%的DDMAT， DPGDA浓度高达5 wt%时获得单分散微球。通过调整反应条件，制备了在反应开始时加入10% DPGDA的单分散交联PMMA微球。此外，我们通过在聚合开始时向体系中添加功能单体，或通过附着在颗粒表面的RAFT基团进行表面引发RAFT聚合，从而使交联微球功能化。
Cross-linked PMMA microspheres have been synthesized by photoinitiated RAFT dispersion polymerization with dipropylene glycol diacrylate (DPGDA) or trimethylolpropane triacrylate (TMPTA) as the cross-linker. Monodisperse microspheres were obtained in the presence of 0.5 wt% S,S′-bis(α,α′-dimethyl-α′′-acetic acid) trithiocarbonate (BDMAT, a RAFT agent) with DPGDA concentration up to 5 wt% or TMPTA concentration up to 2 wt%. The particle formation process was investigated, and the results reveal that the cross-linking reaction was retarded to a certain extent by the RAFT process, which is crucial for the formation of uniform particles under high cross-linker concentrations. The phase diagrams for the methodology have been built up, and show that the procedure could only give polydisperse microspheres at a low DPGDA concentration or coagulum at a high DPGDA concentration in the absence of a RAFT agent, and monodisperse microspheres were obtained at DPGDA concentration up to 5 wt% when the RAFT agent concentration reached an appropriately high level, e.g. 0.5 wt% BDMAT or 0.75 wt% DDMAT. By adjusting the reaction conditions, we have prepared monodisperse cross-linked PMMA microspheres with 10 wt% DPGDA added at the beginning of the reaction. Furthermore, we have functionalized the cross-linked microspheres by adding a functional comonomer to the system at the beginning of polymerization, or by surface-initiated RAFT polymerization via the RAFT groups attached on the particle surface.