Squillace Ophélie, Fong Rebecca, Shepherd Oliver, Hind Jasmine, Tellam James, Steinke Nina-Juliane, Thompson Richard L
Department of chemistry, Durham University, Stockton road, Durham DH1 3LE, UK.
STFC ISIS Facility, Rutherford Appleton Laboratories, Chilton, Didcot OX11 0QX, UK.
Polymers (Basel). 2020 Jan 14;12(1):205. doi: 10.3390/polym12010205.
This aims to establish design rules for the influence of complex polymer matrices on the surface properties of small molecules. Here, we consider the dependence of the surface behaviour of some model additives on polymer matrix hydrophobicity. With stoichiometric control over hydrolysis, we generate systematic changes in matrix chemistry from non-polar, hydrophobic PVAc to its hydrolysed and hydrophilic analogue, PVA. With the changing degree of hydrolysis (DH), the behaviour of additives can be switched in terms of compatibility and surface activity. Sorbitol, a polar sugar-alcohol of inherently high surface energy, blooms to the surface of PVAc, forming patchy domains on surfaces. With the increasing DH of the polymer matrix, its surface segregation decreases to the point where sorbitol acts as a homogeneously distributed plasticiser in PVA. Conversely, and despite its low surface energy, octanoic acid (OA) surprisingly causes the increased wettability of PVAc. We attribute these observations to the high compatibility of OA with PVAc and its ability to reorient upon exposure to water, presenting a hydrophilic COOH-rich surface. The surfactant sodium dodecyl sulfate (SDS) does not show such a clear dependence on the matrix and formed wetting layers over a wide range of DH. Interestingly, SDS appears to be most compatible with PVAc at intermediate DH, which is consistent with the amphiphilic nature of both species under these conditions. Thus, we show that the prediction of the segregation is not simple and depends on multiple factors including hydrophobicity, compatibility, blockiness, surface energy, and the mobility of the components.
这旨在建立关于复杂聚合物基体对小分子表面性质影响的设计规则。在此，我们考虑一些模型添加剂的表面行为对聚合物基体疏水性的依赖性。通过对水解的化学计量控制，我们使基体化学从非极性、疏水的聚醋酸乙烯酯（PVAc）系统地转变为其水解后的亲水性类似物聚乙烯醇（PVA）。随着水解度（DH）的变化，添加剂的行为在相容性和表面活性方面会发生转变。山梨醇是一种具有固有高表面能的极性糖醇，它会在PVAc表面聚集，在表面形成斑驳区域。随着聚合物基体DH的增加，其表面偏析减少，直至山梨醇在PVA中作为均匀分布的增塑剂起作用。相反，尽管辛酸（OA）表面能低，但令人惊讶的是它会使PVAc的润湿性增加。我们将这些观察结果归因于OA与PVAc的高相容性以及其在接触水时重新定向的能力，从而呈现出富含亲水COOH的表面。表面活性剂十二烷基硫酸钠（SDS）对基体没有如此明显的依赖性，并且在很宽的DH范围内都能形成润湿层。有趣的是，在中等DH时SDS似乎与PVAc最相容，这与这两种物质在这些条件下的两亲性性质一致。因此，我们表明偏析的预测并不简单，它取决于多种因素，包括疏水性、相容性、嵌段性、表面能以及各组分的迁移率。
