Institute of Food Research, Norwich Research Park, Colney, Norwich NR4 7UA, United Kingdom.
Carbohydr Polym. 2013 Apr 15;94(1):137-46. doi: 10.1016/j.carbpol.2012.12.065. Epub 2013 Jan 3.
The effect of poly-L-lysine (PLL) molecular weight and structure on pH stability of polygalacturonic acid (PGaLA)-based multilayer films is studied over a pH cycle 7.0-1.6-7.0. The multilayer assembled with the lowest molecular weight PLL (1 kDa) showed the largest pH response. Only 12% of the mass remained and a preferential loss of PLL was observed. Extensive structural reorganisation of the layer as the pH was increased was due to the PGaLA reionisation leading to extensive net loss of hydrated mass. The multilayers assembled with the higher molecular weight linear PLLs (10 kDa, 200 kDa) showed loss of about 50% of their initial polymer mass. The multilayer assembled with the dendrimer (22 kDa) showed a stronger response to pH compared to the linear higher molecular weight PLLs. Over the pH cycle a loss of about 60% polymer mass and a decrease in the film thickness was observed. Despite having a reduced density at pH 1.6, the density substantially recovered to 0.54 g mL(-1) on return to pH 7.0.
研究了聚-L-赖氨酸（PLL）分子量和结构对聚半乳糖醛酸（PGaLA）基多层膜在 pH 循环 7.0-1.6-7.0 过程中 pH 稳定性的影响。用最低分子量 PLL（1 kDa）组装的多层膜表现出最大的 pH 响应。只有 12%的质量残留，并且观察到 PLL 的优先损失。随着 pH 的升高，层的广泛结构重组归因于 PGaLA 的再离子化，导致水合质量的大量净损失。用较高分子量的线性 PLL（10 kDa、200 kDa）组装的多层膜初始聚合物质量损失约为 50%。与线性高分子量 PLL 相比，用树状聚合物（22 kDa）组装的多层膜对 pH 的响应更强。在 pH 循环过程中，观察到聚合物质量损失约 60%，薄膜厚度减小。尽管在 pH 1.6 时密度降低，但在返回 pH 7.0 时，密度实质上恢复到 0.54 g mL(-1)。
