Fully Degradable Thioester-Functional Homo- and Alternating Copolymers Prepared through Thiocarbonyl Addition–Ring-Opening RAFT Radical Polymerization
Fully Degradable Thioester-Functional Homo- and Alternating Copolymers Prepared through Thiocarbonyl Addition–Ring-Opening RAFT Radical Polymerization
复制标题
通过硫代羰基加成-开环 RAFT 自由基聚合制备完全可降解的硫酯功能均聚物和交替共聚物
作者：
Matt Spick;Nathaniel M. Bingham;Yuman Li;Janella de Jesus;C. Costa;M. Bailey;P. Roth
硫代内酯的自由基开环聚合（RROP）提供了获得硫酯主链官能共聚物的途径，但迄今为止仅在丙烯酸共聚物上得到证实。在本文中，硫代内酯二苯并[c，e]氧杂环庚烷-5-酮（DOT）经受偶氮二异丁腈（AIBN）引发的自由基均聚，其产生具有95 °C的玻璃化转变温度和仅降解成预定小分子的能力的硫酯官能均聚物。然而，均聚反应是不切实际的缓慢，并排除了功能的引入。相反，DOT与N-甲基马来酰亚胺（MeMI）、N-苯基马来酰亚胺（PhMI）和N-2，3，4，5，6-五氟苯基马来酰亚胺（PFPMI）的可逆加成-断裂链转移（RAFT）介导的共聚反应迅速产生了明确定义的共聚物，其倾向于形成以MeMI → PhMI < PFPMI的顺序增加的交替序列，后一种体系的竞聚率估计为rDOT = 0.198和rPFPMI = 0.0078。有趣的是，交替结构中的缺陷更可能是由（可降解的）DOT-DOT序列而不是（不可降解的）MI-MI序列引起的，这通过对氨解降解产物的纸喷雾质谱分析得到证实。在骨架硫酯的氨解后，马来酰亚胺重复单元开环，形成双酰胺结构。相反，通过硫醇盐的共聚物降解不会导致酰亚胺取代，而是导致PFPMI共聚单体单元上的亲核对位氟取代，表明DOT-MI共聚物在不同条件下降解并形成不同功能产物的能力。硫代内酯的RROP与环状烯酮缩醛的RROP相比具有明显的优势，并且预期可用于开发定义明确的可降解聚合物材料。
The radical ring-opening polymerization (RROP) of thionolactones provides access to thioester backbone-functional copolymers but has, to date, only been demonstrated on acrylic copolymers. Herein, the thionolactone dibenzo[c,e]oxepane-5-thione (DOT) was subjected to azobisisobutyronitrile (AIBN)-initiated free-radical homopolymerization, which produced a thioester-functional homopolymer with a glass-transition temperature of 95 °C and the ability to degrade exclusively into predetermined small molecules. However, the homopolymerization was impractically slow and precluded the introduction of functionality. Conversely, the reversible addition–fragmentation chain-transfer (RAFT)-mediated copolymerization of DOT with N-methylmaleimide (MeMI), N-phenylmaleimide (PhMI), and N-2,3,4,5,6-pentafluorophenylmaleimide (PFPMI) rapidly produced well-defined copolymers with the tendency to form alternating sequences increasing in the order MeMI ≪ PhMI < PFPMI, with estimated reactivity ratios of rDOT = 0.198 and rPFPMI = 0.0078 for the latter system. Interestingly, defects in the alternating structure were more likely caused by (degradable) DOT–DOT sequences rather than (nondegradable) MI–MI sequences, which was confirmed through the paper spray mass spectrometric analysis of the products from aminolytic degradation. Upon the aminolysis of backbone thioesters, maleimide repeating units were ring-opened, forming bisamide structures. Conversely, copolymer degradation through a thiolate did not result in imide substitution but nucleophilic para-fluoro substitution on PFPMI comonomer units, indicating the ability of DOT–MI copolymers to degrade under different conditions and to form differently functional products. The RROP of thionolactones has distinct advantages over the RROP of cyclic ketene acetals and is anticipated to find use in the development of well-defined degradable polymer materials.
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影响因子：
15
作者：
Paulusse, Jos M. J.;Amir, Roey J.;Evans, Richard A.;Hawker, Craig J.
通讯作者：
Hawker, Craig J.
通过有机催化环的聚合聚合聚合（硫酯）。
影响因子：
5.5
作者：
Bannin TJ;Kiesewetter MK
通讯作者：
Kiesewetter MK
影响因子：
5.5
作者：
Datta PP;Kiesewetter MK
通讯作者：
Kiesewetter MK
影响因子：
5.5
作者：
Hedir, Guillaume G.;Bell, Craig A.;Dove, Andrew P.
通讯作者：
Dove, Andrew P.