Interfacial dilatational rheology as a bridge to connect amphiphilic heterografted bottlebrush copolymer architecture to emulsifying efficiency
Interfacial dilatational rheology as a bridge to connect amphiphilic heterografted bottlebrush copolymer architecture to emulsifying efficiency
复制标题
界面膨胀流变学作为连接两亲异质接枝瓶刷共聚物结构与乳化效率的桥梁
DOI：
10.1016/j.jcis.2020.07.063
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发表时间：
2021
影响因子：
9.9
通讯作者：
Tilton, Robert D.
中科院分区：
文献类型：
--
作者：
Hsieh, Tsung-Lin;Martinez, Michael R.;Garoff, Stephen;Matyjaszewski, Krzysztof;Tilton, Robert D.
假设两亲性瓶刷共聚物的分子结构和组成将以与不同瓶刷共聚物的乳化效率相关的方式决定油/水界面处吸附层的主要界面松弛模式和相应的分层流变学。二甲苯可溶性聚聚环氧乙烷具有可控的主链长度差异的（丙烯酸正丁酯）（PEO-PBA）杂接枝瓶刷共聚物，亲水性和臂长通过原子转移自由基聚合合成。膨胀流变学的吸附层在二甲苯/水界面的探测通过悬垂滴张力测量的界面应力响应无论是大振幅的应变循环或小振幅的应变振荡。流变学响应记录为不同压缩状态下的吸附层的界面压力的函数。乳化效率被确定为最低的共聚物浓度，产生水在二甲苯乳液与至少一个月的稳定性对coalescence.FindingsThe更亲水的共聚物具有较长的PEO臂表现出非滞后的应力-应变响应曲线在大幅度的应变循环和倾向的模量增加，随着界面压力的增加。这些是比表现出滞后界面流变性的亲水性较低的共聚物更有效的乳化剂。仅仅存在显着的模量并不与高乳化效率，而增加的模量与界面压力的增加。
HypothesisMolecular architecture and composition of amphiphilic bottlebrush copolymers will dictate the dominant interfacial relaxation modes and the corresponding dilatational rheology for adsorbed layers at oil/water interfaces in a way that will correlate with the emulsifying efficiency of different bottlebrush copolymers.ExperimentsAmphiphilic, xylene-soluble poly(ethylene oxide)-poly(n-butyl acrylate) (PEO-PBA) heterografted bottlebrush copolymers with controlled differences in backbone length, hydrophilicity and arm length were synthesized by atom transfer radical polymerization. Dilatational rheology of adsorbed layers at the xylene/water interface was probed via pendant drop tensiometry by measuring the interfacial stress response to either large-amplitude strain cycling or small-amplitude strain oscillation. The rheological response was recorded as a function of interfacial pressure for adsorbed layers under different compression states. Emulsifying efficiency was determined as the lowest copolymer concentration that yielded water-in-xylene emulsions with at least one-month stability against coalescence.FindingsThe more hydrophilic copolymers with longer PEO arms exhibited non-hysteretic stress-strain response curves in large-amplitude strain cycling and a tendency for the modulus to increase with increasing interfacial pressure. These were more efficient emulsifiers than less hydrophilic copolymers that exhibited hysteretic interfacial rheology. Mere existence of significant moduli did not correlate with high emulsifying efficiency, while an increase in modulus with increasing interfacial pressure did so.