Role of chain architecture in the solution phase assembly and thermoreversibility of aqueous PNIPAM/silyl methacrylate copolymers.
Role of chain architecture in the solution phase assembly and thermoreversibility of aqueous PNIPAM/silyl methacrylate copolymers.
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DOI：
10.1039/d2py00254j
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发表时间：
2022-07-07
影响因子：
4.6
通讯作者：
Calabrese MA
中科院分区：
文献类型：
--
作者：
Linn JD;Liberman L;Neal CAP;Calabrese MA
用反应性无机基团官能化的刺激响应性聚合物能够产生表现出智能行为的大分子结构，例如水凝胶、胶束和涂层。使用聚（N-异丙基丙烯酰胺-co-3-（三甲氧基甲硅烷基）丙基甲基丙烯酸酯）（P（NIPAM-co-TMA））的先前研究已经稳定了胶束并产生了功能性纳米级涂层;然而，这种系统在多次热循环中显示出有限的响应性。这里，聚合物结构和TMA含量与两种不同类型的PNIPAM/TMA共聚物的水性自组装、光学响应和热可逆性有关：无规P（NIPAM-co-TMA）和“嵌段官能化”共聚物，其中TMA定位于链的一部分，P（NIPAM-b-NIPAM-co-TMA）。通过浊点测试（CPT）、动态光散射（DLS）和变温核磁共振光谱（NMR）表征的水溶液行为表明，在多个循环中的热响应性和热可逆性是聚合物构型和TMA含量的强函数。尽管TMA含量低（≤ 2%mol），但嵌段官能化共聚物在高于浊点时组装成小的、有序的结构，这导致在多个循环中具有不同的透射率行为和刺激响应性。相反，无规共聚物在高温下形成无序聚集体，并且仅在可忽略的TMA分数（0.5%mol）下表现出热可逆性;较高的TMA含量导致不可逆结构形成。对结构和组装对水性PNIPAM-co-TMA热循环性的影响的这种理解可用于提高需要热可逆行为的响应性聚合物应用的可扩展性，包括传感、分离和功能涂层。具有局部反应性无机基团的温敏聚合物表现出受控的结构形成、独特的光学响应和在加热/冷却期间改善的热可逆性。
Stimuli-responsive polymers functionalized with reactive inorganic groups enable creation of macromolecular structures such as hydrogels, micelles, and coatings that demonstrate smart behavior. Prior studies using poly(N-isopropyl acrylamide-co-3-(trimethoxysilyl)propyl methacrylate) (P(NIPAM-co-TMA)) have stabilized micelles and produced functional nanoscale coatings; however, such systems show limited responsiveness over multiple thermal cycles. Here, polymer architecture and TMA content are connected to the aqueous self-assembly, optical response, and thermo-reversibility of two distinct types of PNIPAM/TMA copolymers: random P(NIPAM-co-TMA), and a ‘blocky-functionalized’ copolymer where TMA is localized to one portion of the chain, P(NIPAM-b-NIPAM-co-TMA). Aqueous solution behavior characterized via cloud point testing (CPT), dynamic light scattering (DLS), and variable-temperature nuclear magnetic resonance spectroscopy (NMR) demonstrates that thermoresponsiveness and thermoreversibility over multiple cycles is a strong function of polymer configuration and TMA content. Despite low TMA content (≤2% mol), blocky-functionalized copolymers assemble into small, well-ordered structures above the cloud point that lead to distinct transmittance behaviors and stimuli-responsiveness over multiple cycles. Conversely, random copolymers form disordered aggregates at elevated temperatures, and only exhibit thermoreversibility at negligible TMA fractions (0.5% mol); higher TMA content leads to irreversible structure formation. This understanding of the architectural and assembly effects on the thermal cyclability of aqueous PNIPAM-co-TMA can be used to improve the scalability of responsive polymer applications requiring thermoreversible behavior, including sensing, separations, and functional coatings. Thermoresponsive polymers with localized reactive inorganic groups demonstrate controlled structure formation, unique optical responses, and improved thermoreversibility during heating/cooling.