Explanations for water whitening in secondary dispersion and emulsion polymer films
Explanations for water whitening in secondary dispersion and emulsion polymer films
复制标题
二次分散体和乳液聚合物薄膜中水白化的说明
DOI：
10.1002/polb.24070
复制
发表时间：
2016
期刊：
影响因子：
--
通讯作者：
Liu Y
中科院分区：
文献类型：
--
作者：
Liu Y
聚合物薄膜浸入水中会失去光学透明度，这被称为“水美白”，严重限制了它们作为透明屏障涂层的使用。发现这个问题在使用表面活性剂通过乳液聚合合成的聚合物沉积的薄膜中特别严重。二次分散（SD）聚合物在水中分散而不使用表面活性剂。核磁共振弛豫仪结合光学透射分析和电子显微镜显示，乳液聚合物薄膜中吸收的一些水包含在纳米大小的“口袋”或气泡中，这些“口袋”或气泡会散射光。相反，SD聚合物膜中的水主要被限制在粒子界面，在那里它散射光的强度较低，其分子迁移率降低。在SD中加入表面活性剂会产生一个周期性结构，在光传输中显示一个停止带。总的吸水量并不是聚合物易发生水白化的良好指标。相反，必须考虑水在薄膜中的特定位置。水的数量和局部水区域的大小（通过核磁共振弛豫仪探测）都被发现决定了水的白化。©2016 Wiley期刊公司j .变异较大。科学。B部分：Polym。现年54岁的Phys.2016 1658 - 1674
The loss of optical transparency when polymer films are immersed in water, which is called “water whitening,” severely limits their use as clear barrier coatings. It is found that this problem is particularly acute in films deposited from polymers synthesized via emulsion polymerization using surfactants. Water whitening is less severe in secondary dispersion (SD) polymers, which are made by dispersing solution polymers in water without the use of surfactants. NMR relaxometry in combination with optical transmission analysis and electron microscopy reveal that some of the water sorbed in emulsion polymer films is contained within nanosized “pockets” or bubbles that scatter light. In contrast, the water in SD polymer films is mainly confined at particle interfaces, where it scatters light less strongly and its molecular mobility is reduced. The addition of surfactant to a SD creates a periodic structure that displays a stop band in the optical transmission. The total amount of sorbed water is not a good indicator of polymers prone to water whitening. Instead, the particular locations of the water within the film must be considered. Both the amount of water and the size of the local water regions (as are probed by NMR relaxometry) are found to determine water whitening. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys.2016,54, 1658–1674