Chemistry and Applications of Organosilanes – An Overview

Abstract

Organofunctional silanes are hybrid materials of silanes and have attracted greater attention in recent times owing to its versatile properties and wider range of applications. Organosilanes (R_nSiX_4-n) usually have two reactive groups, viz. organofunctional groups like methacryloxy, epoxy ,amino or sulfo group (-R_n) and hydrolysable alkoxy such as methoxy/ethoxy/acetoxy groups (-X_4-n) (Table.1) [1]. Hydrolysis and condensation are the two main reactions carried out by the molecules of organofunctional trialkoxy silanes. In hydrolysis, hydrolysable alkoxy groups are hydrolysed to silanols (Si-OH) and condensation takes place among silanols to form Si-O-Si (siloxane) structure. Ref. [2] has extensively dealt with silane coupling agents (SCA) used in reinforced polymeric composites (RPC). In general, inorganic fillers particles are used in RPC, in which case, the organic polymer and inorganic filler are two dissimilar materials and hence not compatible with each other leading to substrate adherence issues in coating applications. This problem can be solved by using a third material, i.e. SCA which can connect between organic polymer and inorganic filler by means of the different functional groups present in its structure. Ref. [3] deals with the reaction kinetics of silanes to address the drawback that sometimes, silanes are synthesized without comprehending the reaction kinetics mechanism. The authors in that paper have discussed the alkoxysilanes polymerization kinetics, which is controlled by primary (water/silane ratio, pH and organo-functional groups) and secondary (temperature, solvent, leaving group and silane concentration) factors, and their influence on the reaction rates. In the past few decades, significant advances were witnessed in the development of various organofunctional silanes which were used in a wide range of research areas based on its bifunctional characteristics. In this mini-review, we have summarized the unique chemistry of organosilanes and highlighted their innumerable applications (Fig.1) including coupling agents, adhesion promoters, cross linkers, fillers,  modifying agents, sensors, nanoparticles and catalysts [3-5]. This work was supported by CSIR, Government of India under CSIR-EMR-II scheme (03(1450)18/EMR-II dt.05-06-2018). A.A.P also thank VIT for providing ‘VIT SEED GRANT’ for carrying out this research work.