Chain End-Functionalized Dense Polymer Brushes from an Inimer Coating by SI-RAFT
Chain End-Functionalized Dense Polymer Brushes from an Inimer Coating by SI-RAFT
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DOI：
10.1021/acs.langmuir.3c00733
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发表时间：
2023-05-30
期刊：
影响因子：
3.9
通讯作者：
Gopalan，Padma
中科院分区：
文献类型：
--
作者：
Smith，Julia D.;Salas，Luis Adrian Padilla;Gopalan，Padma
具有可控接枝密度的聚合物刷生长在带有可逆加成-断裂链转移聚合（RAFT）链转移剂（CTA）的引发剂涂层上。引发剂聚合物涂层在基底上交联以提供在高温下暴露于有机溶剂期间稳定的引发剂层。表面引发RAFT进行生长聚（2-乙烯基吡啶）（P2 VP）刷在涂层上的接枝密度接近理论极限。这种方法允许使用有效的硫醇-烯点击化学进行容易的端基官能化。链端用低表面能基团官能化以通过热退火调节未束缚的链端的位置。在较低的接枝密度下，低表面能基团在退火时分离到表面。这种效应在较高的接枝密度下不太明显。在不同的接枝密度，使用X射线光电子能谱（XPS）的刷子的详细表征。在与实验相结合，蒙特卡罗模拟研究的链端基的大小和选择性的聚合物刷的构象的影响，提供横向不均匀分布的官能团在不同的位置在刷的数值证据。模拟进一步预测存在的形态与富含功能性端基的球形胶束形成的中间层，表明刷状构象和链端位置的合成调制的端基官能化的可能性。
Polymer brushes with controllable grafting density are grown on an inimer coating bearing Reversible Addition-Fragmentation Chain Transfer polymerization (RAFT) chain transfer agents (CTAs). The inimer coating is cross-linked on the substrate to provide an initiator layer that is stable during exposure to organic solvents at high temperatures. Surface-initiated RAFT is conducted to grow poly(2-vinylpyridine) (P2VP) brushes on the coating at grafting densities approaching the theoretical limits. This methodology allows facile end-group functionalization using an efficient thiol-ene click chemistry. Chain ends were functionalized with low surface energy groups to modulate the location of the untethered chain ends by thermal annealing. At lower grafting densities, the low surface energy groups segregate to the surface upon annealing. This effect is less pronounced at higher grafting densities. Detailed characterization of the brushes at varying grafting densities using X-ray photoelectron spectroscopy (XPS) is presented. In tandem with experiments, Monte Carlo simulations examine the effect of the chain-end group size and selectivity on the conformation of the polymer brush, providing numerical evidence of laterally non-uniform distributions of functional groups at different locations in the brush. Simulations further predict the existence of morphologies with an interlayer formed by spherical micelles rich in functional end groups, demonstrating the possibility of end-group functionalization for synthetic modulation of both brush conformation and chain-end location.