Contribution of Surface Energy to pH-Dependent Underwater Adhesion of an Acrylic Pressure-Sensitive Adhesive
Contribution of Surface Energy to pH-Dependent Underwater Adhesion of an Acrylic Pressure-Sensitive Adhesive
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DOI：
10.1021/acs.langmuir.9b00120
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发表时间：
2019-04-16
期刊：
影响因子：
3.9
通讯作者：
Frechette, Joelle
中科院分区：
文献类型：
--
作者：
Karnal, Preetika;Jha, Anushka;Frechette, Joelle
在广泛的溶液 pH 值范围内保持水下粘合性能具有挑战性，但对于许多生物医学应用来说是必要的。因此，了解环境条件如何影响压敏粘合剂（PSA）的粘合和脱粘机制可以为材料设计提供指导。我们研究了丙烯酸作为共聚单体的存在如何影响模型 PSA 在不同 pH 值的水环境中的粘附力。正在研究的粘合剂是聚(丙烯酸2-乙基己酯)或聚(2-EHA)，以及与5wt％丙烯酸共聚的聚(2-EHA)，或聚(2-EHA-co-AA)。我们使用球形疏水玻璃探针进行探针粘性测量来表征粘合剂的粘合和脱粘（粘合）。我们分析了两种 PSA 在空气中和 pH 3-11 的低离子强度缓冲水溶液中的性能。我们发现丙烯酸共聚单体的存在增加了 PSA 的内聚性，并在所有研究条件下产生更强的粘附力。我们还观察到，丙烯酸共聚单体的存在使 PSA 的附着力对溶液 pH 值具有很强的依赖性。动态接触角和 zeta 电位测量支持以下假设：较高 pH 值下丙烯酸基团的去质子化会导致较高 pH 值下粘附力降低。流变测量并未显示 PSA 暴露于 pH 3-11 溶液后动态机械性能的变化。我们的测量使我们能够隔离溶液 pH 值对 PSA 表面和整体性能的影响。在不存在丙烯酸共聚单体的情况下，PSA 的本体消散和表面性质与溶液的 pH 值无关。
Maintaining the underwater adhesive performance over a broad range of solution pH is challenging but necessary for many biomedical applications. Therefore, understanding how environmental conditions influence the mechanisms of bonding and debonding of pressure-sensitive adhesives (PSAs) can provide guidelines for materials design. We investigate how the presence of acrylic acid as a co-monomer impacts the adhesion of a model PSA in aqueous environments of varying pH. The adhesives under investigation are poly(2-ethylhexyl acrylate), or poly(2-EHA), and poly(2-EHA) co-polymerized with 5 wt % acrylic acid, or poly(2-EHA-co-AA). We characterize bonding and debonding (adhesion) of the adhesives using probe tack measurements with a spherical hydrophobic glass probe. We analyze the performance of the two PSAs in air and in low-ionic-strength buffered aqueous solutions of pH 3- 11. We find that the presence of the acrylic acid co-monomer increases the cohesiveness of the PSA and leads to stronger adhesion under all conditions investigated. We also observe that the presence of the acrylic acid co-monomer imparts the PSA with a strong dependence of adhesion on the solution pH. Dynamic contact angle and zeta potential measurements support the hypothesis that deprotonation of the acrylic acid groups at higher pH causes the decrease in adhesion at higher pH. Rheological measurements do not show changes in the dynamic mechanical properties of the PSAs after exposure to solutions of pH 3- 11. Our measurements allow us to isolate the effect of the solution pH on the surface and bulk properties of the PSA. In the absence of the acrylic acid co-monomer, the bulk dissipation and the surface properties of the PSA are independent of the solution's pH.