Roland Sébastien, Prud'homme Robert E, Bazuin C Geraldine
Département de chimie, Centre de recherche sur les matériaux auto-assemblés (CRMAA/CSACS), Université de Montréal, C.P. 6128 succursale Centre-ville, Montréal (QC), Canada H3C 3J7.
ACS Macro Lett. 2012 Aug 21;1(8):973-976. doi: 10.1021/mz3003165. Epub 2012 Jul 16.
Dip-coating, an important industrial technique, has been underexploited for preparing block copolymer (BC) thin films, such that the knowledge regarding their general characteristics is limited. Here, we present an overview of the crucial factors that determine how BC film morphology evolves as a function of dip-coating rate (withdrawal speed) over a wide range, illustrated using THF solutions of a polystyrene--poly(4-vinyl pyridine) (PS-P4VP) diblock copolymer mixed with two small molecules, naphthol and naphthoic acid, which are hydrogen-bonders with P4VP. Key factors in determining the film morphology are the systematic variation in film thickness and, for supramolecular BCs, in film composition with dip-coating rate. The former shows a general V-shaped dependence, related to the so-called capillarity and draining regimes identified previously for dip-coated sol-gel films. The relative small molecule content in the films studied is shown to increase in the capillarity regime from low to that of the dip-coating solution and thereafter to remain constant. Together, these changes, in addition to solvent and other effects, determine the film morphology and its evolution with dip-coating rate.
浸涂作为一种重要的工业技术，在制备嵌段共聚物（BC）薄膜方面尚未得到充分利用，以至于关于其一般特性的知识有限。在此，我们概述了一些关键因素，这些因素决定了在很宽的范围内，BC薄膜形态如何随浸涂速率（提拉速度）而演变，并通过聚苯乙烯 - 聚（4 - 乙烯基吡啶）（PS - P4VP）二嵌段共聚物与两种小分子萘酚和萘甲酸的四氢呋喃溶液进行说明，这两种小分子与P4VP形成氢键。决定薄膜形态的关键因素是薄膜厚度的系统变化，对于超分子BCs而言，还包括薄膜组成随浸涂速率的变化。前者呈现出一般的V形依赖关系，这与先前在浸涂溶胶 - 凝胶薄膜中确定的所谓毛细作用和排水状态有关。在所研究的薄膜中，相对小分子含量在毛细作用状态下从低增加到浸涂溶液中的含量，此后保持恒定。这些变化连同溶剂和其他影响一起，决定了薄膜形态及其随浸涂速率的演变。
