Weakly Ionically Bound Thermosensitive Hyperbranched Polymers
Weakly Ionically Bound Thermosensitive Hyperbranched Polymers
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DOI：
10.1021/acs.langmuir.0c03487
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发表时间：
2021-02-23
期刊：
影响因子：
3.9
通讯作者：
Tsukruk, Vladimir V.
中科院分区：
文献类型：
--
作者：
Lee, Hansol;Stryutsky, Alexandr;Tsukruk, Vladimir V.
我们合成了新型两亲性超支化聚合物（HBPs），与传统的共价连接不同，其弱离子键合的热响应性聚（N - 异丙基丙烯酰胺）（PNIPAM）大阳离子含量可变。研究了它们在低于和高于低临界溶液温度（LCST）时的组装行为。由于PNIPAM的LCST转变以及末端离子基团电离度的降低，HBPs在温度和离子强度变化时会发生形态转变。我们认为，与传统的支化聚合物不同，离子键合的PNIPAM大阳离子可以从磺酸基团可逆地解离并形成可移动的冠状结构，赋予动态胶束形态。此外，在气 - 水界面的组装限制了PNIPAM大阳离子，导致形成具有不同表面形态的非均相朗缪尔 - 布洛杰特（LB）单分子层，对于不同的周边组成，在凝聚态下会形成圆形畴。含25% PNIPAM的HBPs比含50% PNIPAM的HBPs显示出更大且更稳定的圆形畴，在高压缩时能部分保留。而且，LB单分子层显示出可变的表面力学性能和表面电荷分布，这可归因于可移动的PNIPAM大阳离子和核心磺酸基团的行为导致的净偶极子重新分布。
We synthesized novel amphiphilic hyperbranched polymers (HBPs) with variable contents of weakly ionically tethered thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) macrocations in contrast to traditional covalent linking. Their assembling behavior was studied below and above the lower critical solution temperature (LCST). The HBPs underwent a morphological transition under changing temperature and ionic strength due to the LCST transition of PNIPAM and the reduction in the ionization degree of terminal ionic groups, respectively. We suggest that, in contrast to traditional branched polymers, ionically linked PNIPAM macrocations can reversibly disassociate from the sulfonate groups and form mobile coronas, endowing the dynamic micellar morphologies. In addition, assembly at the air-water interface confined PNIPAM macrocations and resulted in the formation of heterogeneous Langmuir-Blodgett (LB) monolayers with diverse surface morphologies for different peripheral compositions with circular domains formed in the condensed state. The HBPs with 25% PNIPAM showed larger and more stable circular domains that were partially preserved at high compression than those of HBPs with 50% PNIPAM. Moreover, the LB monolayers showed variable surface mechanical and surface charge distribution, which can be attributed to net dipole redistribution caused by the behavior of mobile PNIPAM macrocations and core sulfonate groups.