用于多孔聚合物模板的浓缩纳米乳液的液滴间相互作用和流变学,Langmuir

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用于多孔聚合物模板的浓缩纳米乳液的液滴间相互作用和流变学
Langmuir ( IF 3.7 ) Pub Date : 2020-12-18 , DOI: 10.1021/acs.langmuir.0c02366
Zahra Abbasian Chaleshtari ₁ , Hamed Salimi-Kenari _{1,

2} , Reza Foudazi ₁

Affiliation

在当前的研究中，我们研究了从稀释态到浓缩态，纳米乳液在很大的油体积分数（φ）范围内的胶体行为。稀体系包含25％的硅油分散在由聚（乙二醇）-二丙烯酸酯（PEGDA）和十二烷基硫酸钠（SDS）组成的水相中，并通过在环境温度下以两种不同的速率蒸发水进行浓缩。流变学研究表明，液体状纳米乳液以约30％的体积分数转变为粘弹性凝胶。在半稀释体系中（φ低于45％），纳米乳液的平台储能模量增加，然后随着φ的增加而稳定降低，直至60％。在流变结果中可以观察到模量对蒸发速率的依赖性。根据流变结果和液滴之间估计的整体成对相互作用，我们提出了两种胶体相互作用体系。在半稀释体制下由于PEGDA低聚物和SDS胶束会引起相当大的短时吸引力耗尽，因此会发生吸引力凝胶化。在浓缩状态下，凝胶会通过增加φ而变弱，这主要归因于高浓度的胶束对结构的稳定作用。纳米乳液连续相中的PEGDA可以通过光聚合作用进行交联，从而在去除油滴后产生纳米多孔PEGDA水凝胶。我们研究了由纳米乳液模板以φ= 60％制备的纳米多孔水凝胶的吸水率。与从缓慢浓缩的纳米乳液获得的水凝胶相比，从具有快速蒸发速率的纳米乳液获得的水凝胶显示出更高的吸水率。

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Interdroplet Interactions and Rheology of Concentrated Nanoemulsions for Templating Porous Polymers

In the current study, we investigate the colloidal behavior of nanoemulsions over a wide range of oil volume fractions (φ) from dilute to concentrated regime. The dilute system contains 25% silicone oil dispersed in the aqueous phase consisting of poly(ethylene glycol)-diacrylate (PEGDA) and sodium dodecyl sulfate (SDS), which is concentrated through evaporation of water at two different rates at ambient temperature. The rheological studies show that the liquid-like nanoemulsions transform into viscoelastic gels at a volume fraction of ∼30%. The plateau storage modulus of the nanoemulsions increases in the semidilute systems (φ below 45%) and then decreases steadily with increasing φ up to 60%. Dependency of the modulus on the evaporation rate can be observed in the rheological results. According to the rheological results and the overall pairwise interactions estimated between droplets, we propose two regimes of colloidal interactions. In the semidilute regime, the attractive gelation occurs due to considerable short-range attractive depletion induced by the PEGDA oligomer and SDS micelles. In the concentrated regime, the gel weakens by increasing φ mainly due to the structural stabilization barrier from a high concentration of micelles. The PEGDA in the continuous phase of the nanoemulsions can be crosslinked through photopolymerization, resulting in nanoporous PEGDA hydrogels upon removal of oil droplets. We study the water uptake of the nanoporous hydrogels prepared from the nanoemulsion templates at φ = 60%. The hydrogel obtained from the nanoemulsion with fast evaporation rate shows higher water uptake than that obtained from the slowly concentrated nanoemulsion. The tunable viscoelastic behavior of concentrated nanoemulsions as well as the resulting nanoporous hydrogels offers a new platform to design the soft materials for a wide range of applications.

更新日期：2021-01-12

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