Xu Jingcong, Abetz Volker
Institute of Physical Chemistry, Universität Hamburg, Grindelallee 117, 20146 Hamburg, Germany.
Institute of Membrane Research, Helmholtz-Zentrum Hereon, Max-Planck-Straße 1, 21502 Geesthacht, Germany.
Soft Matter. 2022 Mar 9;18(10):2082-2091. doi: 10.1039/d1sm01692j.
The tailored synthesis of graft copolymers from acrylic and methacrylic monomers can be accomplished solely through photoiniferter reversible addition-fragmentation chain transfer (RAFT) polymerization. Samples with poly[oligo(ethylene glycol) methacrylate] (POEGMA) backbones synthesized under green light irradiation and poly(-isopropylacrylamide) (PNIPAM) side chains growing under blue light irradiation are presented. As monitored by temperature-dependent dynamic light scattering (DLS) measurements and temperature-variable nuclear magnetic resonance (NMR) spectroscopy, the architecture of the graft copolymers allows unique two-step lower critical solution temperature (LCST) transitions in aqueous solutions. Meanwhile, different end-groups introduced by the corresponding RAFT agents affect the detailed thermoresponsive behavior remarkably. This RAFT strategy shows more advantages when the multiple trithiocarbonate groups are converted into thiol reactive pyridyl disulfide (PDS) groups a facile post-polymerization modification. The PDS-terminated graft copolymer can then be regarded as a usable precursor for various applications, such as thermoresponsive hydrogels.
由丙烯酸和甲基丙烯酸单体定制合成接枝共聚物，仅可通过光引发转移终止剂可逆加成-断裂链转移（RAFT）聚合来实现。本文展示了在绿光照射下合成具有聚[聚（乙二醇）甲基丙烯酸酯]（POEGMA）主链，以及在蓝光照射下生长聚（N-异丙基丙烯酰胺）（PNIPAM）侧链的样品。通过温度依赖动态光散射（DLS）测量和温度可变核磁共振（NMR）光谱监测发现，接枝共聚物的结构在水溶液中呈现独特的两步最低临界溶液温度（LCST）转变。同时，相应RAFT试剂引入的不同端基对详细的热响应行为有显著影响。当多个三硫代碳酸酯基团转化为硫醇反应性吡啶二硫化物（PDS）基团时，这种RAFT策略显示出更多优势，这是一种简便的后聚合修饰方法。然后，PDS端基化的接枝共聚物可被视为各种应用（如热响应水凝胶）的可用前体。
