在多电解质复合物和多层中,网站与聚合物的扩散
Hadi M Fares1, Joseph B Schlenoff1
1Department of Chemistry and Biochemistry, The Florida State University , Tallahassee, Florida 32306-4390, United States.
Journal of the American Chemical Society
|October 6, 2017
概括
多电解质复合物的形成依赖于快速的位点扩散,而不是缓慢的聚合物扩散. 这一发现解释了多层生长,并透露了通过交叉链传输的动态组装.
科学领域:
- 聚合物科学
- 材料科学
- 物理化学
背景情况:
- 多电解质复合物 (PEC) 和多层的自发形成传统上归因于充电聚合物的相互扩散.
- 人们对PEC形成和生长的动力学知之甚少,特别是驱动多层组装的机制.
研究的目的:
- 研究聚合物分子与PEC薄膜内的充电位点的不同质量传输机制.
- 阐明点扩散在PEC多层的动力学和生长模式中的作用.
- 根据扩散特征确定促进完整多层生长的条件.
主要方法:
- 使用敏感的同位素标记技术,单独追踪聚合物分子和PEC薄膜内的外部位点的扩散.
- 在聚二甲 (PDADMA) 和聚二硫酸盐 (PSS) 复合物中检查了位点和聚合物的扩散系数.
- 与环境盐度 (离子强度) 相关的位点扩散系数.
主要成果:
- 由于局部重新排列,PEC内部的位点扩散速度至少比聚合物扩散快两倍.
- 部位扩散高度依赖盐度,PDADMA部位的扩散速度快于PSS部位,解释了不对称的多层生长.
- 位点扩散控制了线性和指数式模式的多层生长,使PDADMA通过PSS层透等现象成为可能.
- 通过将扩散长度与薄膜厚度相匹配来确定完全指数增长的条件,独立于分子重量,这表明离子配对密度是关键.
结论:
- 多电解质复合组合和多层生长主要是由快速的位点扩散驱动的,而不是缓慢的聚合物扩散.
- 位点扩散为PEC形成,动力学和生长动态提供了新的机制理解.
- PEC是通过交叉连接或缺陷运输组装的动态散装材料,为自组装过程提供了更广泛的视角.
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