Department of Chemistry, Koç University, Rumelifeneri Yolu, 34450 Sariyer, Istanbul, Turkey.
J Colloid Interface Sci. 2011 Sep 15;361(2):477-82. doi: 10.1016/j.jcis.2011.05.033. Epub 2011 May 19.
Association of tannic acid (TA) with structurally isomeric poly(N-isopropylacrylamide) (PNIPAM) and poly(2-isopropyl-2-oxazoline) (PIPOX) has been examined at surfaces to understand the effect of different molecular arrangements in a polymer repeating unit of structural isomers on the construction and pH-stability of hydrogen-bonded multilayers. Films were fabricated using layer-by-layer (LbL) technique through hydrogen-bonding interactions primarily between carbonyl groups of neutral polymers and hydroxyl groups of TA molecules at pH 2. PIPOX and TA formed thinner and more stable films in the pH scale with a critical dissolution pH of 9 when compared to films of PNIPAM and TA with a critical pH of 8. The differences in the thickness and pH-stability were due to different conformational behavior of PNIPAM and PIPOX in water which affects the accessibility of carbonyl groups for participation in the hydrogen bonding and the number of binding sites between the polymer pairs. Addition of electrostatic interactions by introducing amino groups only at the PIPOX chain end shifted the critical dissolution pH to higher values and resulted in gradual dissolution of the films in a wide pH range of 9-12. Such films hold promise for use in biomedical field due to biocompatibility and lower critical solution temperature (LCST) behavior at near physiological temperature of PNIPAM and PIPOX together with the pH-response of the hydrogen-bonded films.
已在表面上研究了单宁酸（TA）与结构异构的聚（N-异丙基丙烯酰胺）（PNIPAM）和聚（2-异丙基-2-恶唑啉）（PIPOX）的缔合关系，以了解结构异构体聚合物重复单元中不同分子排列对氢键多层结构的构建和 pH 稳定性的影响。通过氢键相互作用使用逐层（LbL）技术在 pH 2 下主要在中性聚合物的羰基和 TA 分子的羟基之间制造了薄膜。与 TA 和 PNIPAM 的薄膜相比，在 pH 范围内，PIPOX 和 TA 形成的薄膜更薄且更稳定，临界溶解 pH 为 9，而 TA 和 PNIPAM 的临界 pH 为 8。厚度和 pH 稳定性的差异是由于 PNIPAM 和 PIPOX 在水中的不同构象行为，这影响了羰基参与氢键的可及性以及聚合物对之间的结合位点数量。通过仅在 PIPOX 链末端引入静电相互作用，添加了静电相互作用，将临界溶解 pH 值提高到更高的值，并导致薄膜在较宽的 pH 范围 9-12 中逐渐溶解。由于 PNIPAM 和 PIPOX 的生物相容性和接近生理温度下的较低临界溶液温度（LCST）行为以及氢键薄膜的 pH 响应，这些薄膜有望在生物医学领域中得到应用。
