UV‐ and Thermally‐Active Bifunctional Gelators Create Surface‐Anchored Polymer Networks
UV‐ and Thermally‐Active Bifunctional Gelators Create Surface‐Anchored Polymer Networks
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紫外线和热活性双功能胶凝剂创建表面锚定聚合物网络
DOI：
10.1002/marc.202100266
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发表时间：
2021
影响因子：
4.6
通讯作者：
Genzer, Jan
中科院分区：
文献类型：
--
作者：
Pandiyarajan, Chinnayan Kannan;Genzer, Jan
报道了使用小的双官能胶凝剂（SBG），即4-叠氮磺酰基苯乙基三甲氧基硅烷（4-ASPTMS）和6-叠氮磺酰基己基三乙氧基硅烷（6-ASHTES），一步合成表面附着的聚合物网络的通用方法。在硅晶片上沉积包含约90%前体聚合物和10%4-ASPTMS或10%6-ASHTES的混合物的薄层（约200 nm）。在UV照射（λ 1 -254 nm）或退火（>100 °C）层时，磺酰叠氮化物（SAz）通过形成单线态和三线态氮烯释放氮，所述氮烯同时与附近的任何C-H键反应，导致磺酰胺交联。三烷氧基之间的缩合（即，甲氧基或乙氧基）连接SBG单元，这完成了交联。同时，当这样的官能团与表面处的羟基反应时，这使得能够共价连接交联的聚合物链。采用椭圆偏振光谱仪（SE）和衰减全反射模式下的傅里叶变换红外光谱（FTIR-ATR）对反应机理和凝胶形成进行了系统的研究。发现4-ASPTMS和6-ASHTES两者类似地热引发凝胶化。6-ASHTES在λ 1 -254 nm处是UV惰性的，而4-ASPTMS是活性的并且形成凝胶。该差异归因于4-ASPTMS的芳香族性质，其由于π-π* 跃迁而吸收101 -254 nm处的UV光。
A versatile one‐step synthesis of surface‐attached polymer networks using small bifunctional gelators (SBG), namely 4‐azidosulfonylphenethyltrimethoxysilane (4‐ASPTMS) and 6‐azidosulfonylhexyltriethoxysilane (6‐ASHTES) is reported. A thin layer (≈200 nm) of a mixture comprising ≈90% precursor polymer and 10% of 4‐ASPTMS or 10% 6‐ASHTES on a silicon wafer is deposited. Upon UV irradiation (≈l–254 nm) or annealing (>100 °C) layers, sulfonyl azides (SAz) release nitrogen by forming singlet and triplet nitrenes that concurrently react with any C─H bond in the vicinity resulting in sulfonamide crosslinks. Condensation among tri‐alkoxy groups (i.e., methoxy or ethoxy) in bulk connects the SBG units, which completes the crosslinking. Concurrently, when such functionalities react with hydroxyl groups at the surface, which enable the covalent attachment of the crosslinked polymer chains. A systematic investigation on reaction mechanism and gel formation using spectroscopic ellipsometry (SE) and Fourier‐transform infrared spectroscopy in the attenuated total reflection mode (FTIR‐ATR) is performed. Analogous thermally initiated gelation for both 4‐ASPTMS and 6‐ASHTES is found. The 6‐ASHTES is UV inactive at ≈l–254 nm, while the 4‐ASPTMS is active and forms gels. The difference is attributed to the aromatic nature of 4‐ASPTMS that absorb UV light at ≈l–254 nm due to π–π*transition.