Yang Peng, Yang Wantai
Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University , Xi'an 710062, China.
ACS Appl Mater Interfaces. 2014 Mar 26;6(6):3759-70. doi: 10.1021/am405857m. Epub 2014 Mar 6.
It may be hardly believable that inert C-H bonds on a polymeric material surface could be quickly and efficiently transformed into C-OH by a simple and mild way. Thanks to the approaches developed recently, it is now possible to transform surface H atoms of a polymeric substrate into monolayer OH groups by a simple/mild photochemical reaction. Herein the method and application of this small-molecular interfacial chemistry is highlighted. The existence of hydroxyl groups on material surfaces not only determines the physical and chemical properties of materials but also provides effective reaction sites for postsynthetic sequential modification to fulfill the requirements of various applications. However, organic synthetic materials based on petroleum, especially polyolefins comprise mainly C and H atoms and thus present serious surface problems due to low surface energy and inertness in reactivity. These limitations make it challenging to perform postsynthetic surface sequential chemical derivatization toward enhanced functionalities and properties and also cause serious interfacial problems when bonding or integrating polymer substrates with natural or inorganic materials. Polymer surface hydroxylation based on direct conversion of C-H bonds on polymer surfaces is thus of significant importance for academic and practical industrial applications. Although highly active research results have reported on small-molecular C-H bond activation in solution (thus homogeneous), most of them, featuring the use of a variety of transition metals as catalysts, present a slow reaction rate, a low atom economy and an obvious environmental pollution. In sharp contrast to these conventional C-H activation strategies, the present Spotlight describes a universal confined photocatalytic oxidation (CPO) system that is able to directly convert polymer surface C-H bonds to C-OSO3(-) and, subsequently, to C-OH through a simple hydrolysis. Generally speaking, these newly implanted hydroxyl groups preserve their own reactivity toward other complementary compounds, thus creating a novel base with distinct surface properties. Thanks to this functionalized platform, a wide range of organic, inorganic and metal materials have been attached to conventional organic polymer substrates through the rational engineering of surface molecular templates from small functional groups to macromolecules. It is expected that the proposed novel CPO method and its versatile usages in advanced material applications will offer new opportunities for a variety of scientific communities, especially for those working on surface/interface modulation.
聚合物材料表面的惰性碳氢键能够通过一种简单温和的方式快速有效地转化为碳氧键，这或许令人难以置信。得益于最近开发的方法，现在可以通过简单/温和的光化学反应将聚合物基材的表面氢原子转化为单层羟基。本文重点介绍了这种小分子界面化学的方法及应用。材料表面羟基的存在不仅决定了材料的物理和化学性质，还为合成后序贯修饰提供了有效的反应位点，以满足各种应用的需求。然而，基于石油的有机合成材料，尤其是聚烯烃，主要由碳和氢原子组成，由于表面能低和反应惰性，存在严重的表面问题。这些限制使得对合成后表面进行序贯化学衍生以增强功能和性能具有挑战性，并且在将聚合物基材与天然或无机材料粘结或整合时也会导致严重的界面问题。因此，基于聚合物表面碳氢键直接转化的聚合物表面羟基化对于学术和实际工业应用都具有重要意义。尽管在溶液中（即均相）小分子碳氢键活化方面已经报道了高活性的研究成果，但其中大多数以使用各种过渡金属作为催化剂为特征，反应速率慢、原子经济性低且环境污染明显。与这些传统的碳氢键活化策略形成鲜明对比的是，本专题报道了一种通用的受限光催化氧化（CPO）体系，该体系能够直接将聚合物表面的碳氢键转化为碳磺酸盐（C-OSO3(-)），随后通过简单水解转化为碳氧键（C-OH）。一般来说，这些新引入的羟基保留了它们对其他互补化合物的反应活性，从而创建了一个具有独特表面性质的新型基底。得益于这个功能化平台，通过从小官能团到大分子的表面分子模板的合理设计，多种有机、无机和金属材料已被连接到传统有机聚合物基材上。预计所提出的新型CPO方法及其在先进材料应用中的多种用途将为各种科学界，特别是从事表面/界面调控的科学界提供新的机会。
