Strands vs. crosslinks: topology-dependent degradation and regelation of polyacrylate networks synthesised by RAFT polymerisation
Strands vs. crosslinks: topology-dependent degradation and regelation of polyacrylate networks synthesised by RAFT polymerisation
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链与交联：RAFT 聚合合成的聚丙烯酸酯网络的拓扑依赖性降解和再凝胶化
DOI：
10.1039/d3py01008b
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发表时间：
2023
影响因子：
4.6
通讯作者：
Dawson F
中科院分区：
文献类型：
--
作者：
Dawson F
用可裂解的二硫代二丙烯酸酯交联剂或可裂解的共聚单体二苯并[c，e]奥西平-5(7H)-硫酮(DOT)进行可逆加成-断裂链转移(RAFT)聚合，合成了可降解的聚丙烯酸丁酯网络。通过凝胶动力学、平衡溶胀比和储能模数的分析发现，与不可降解对照相比，两种情况下可降解单元的加入对所制备凝胶的力学性能没有显著影响。虽然发现这两种类型的网络都很容易降解，无论是通过硫醇-二硫化物交换还是氨解，它们都产生了不同拓扑结构的降解碎片，即可降解交联剂的单分散线链和可降解链的分支多分散碎片。在30°C的空气中，硫醇简单的氧化成二硫键，通过多次降解/再生循环，成功地将这两种类型的降解碎片重新聚合回固体网络。有趣的是，含有DOT的网络降解产生的支化、分散的碎片更容易重新聚合，产生的网络具有与原始材料更接近的性质。这与传统的自由基聚合(FRP)制得的聚丙烯酸酯凝胶不同，后者不能通过可裂解的交联物降解，只能通过可裂解的链条降解。然而，这些网络在退化后无法成功改革。此外，再生效率对降解片段的拓扑结构的明显依赖性可以为更好地理解交联聚合物网络的再加工和回收开辟一条途径。
Degradable poly(n-butyl acrylate) networks were synthesised by reversible addition–fragmentation chain transfer (RAFT) polymerisation using a cleavable disulfide diacrylate crosslinker or a cleavable comonomer, dibenzo[c,e]oxepine-5(7H)-thione (DOT). Through the analysis of gelation kinetics, equilibrium swelling ratio and storage modulus, it was found that incorporation of the degradable units in both cases did not significantly impact the mechanical properties of the prepared gels compared to non-degradable controls. While both types of networks were found to readily degrade, either by thiol–disulfide exchange or aminolysis, they produced degradation fragments of different topology, namely monodisperse linear chains in the case of degradable crosslinkers and branched polydisperse fragments in the case of degradable strands. A simple oxidation of thiols to disulfide bonds in air at 30 °C was successfully used to repolymerise both types of degraded fragments back to solid networks through multiple degradation/regelation cycles. Interestingly, the branched, disperse fragments from degradation of the DOT-containing networks repolymerised more readily and produced networks with properties closer to the original material. This is in contrast to polyacrylate gels made by conventional free radical polymerisation (FRP) which do not degrade through cleavable crosslinks, only through cleavable strands. However, these networks cannot successfully reform after degradation. Furthermore, the apparent dependence of the regelation efficiency on topology of the degraded fragments can open a pathway to better understand reprocessing and recycling of crosslinked polymer networks.
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