Insights into in-situ sol-gel conversion in graphene modified polymer-based silica gels for multifunctional aerogels

Abstract

Schematic representing the hydrolytic polycondensation of P-VTMS in the presence of GnP or GO. • In-dept study on the polymer orientation in the presence of graphene materials. • Engineering of bimodal mesoporous structure during sol-gel transition. • The strategy of nanoplatelets exfoliation by controlling pH during gelation. • graphene platelets contribution at the polymer/graphene interface during gelation. • Effect of GnP and GO on the surface area, insulation, and mechanical properties. Graphene-modified polymer-based silica aerogels (G-PSAs) are an emerging class of multifunctional material, receiving a lot of attention for a wide range of applications such as sensors, drug-delivery, and tissue-engineering. The bimodal mesoporous structure of G-PSAs is dictated during the gelation process, and it can be tailored by optimizing material and processing parameters. In this study, the main focus is to investigate the mechanism for the formation of the structure that furnished the aerogels with unique pore structures and superb mechanical properties. The dynamic structures along the fabrication process were assessed using advanced techniques such as rheometry, dynamic light scattering (DLS), small-angle X-ray scattering (SAXS) and pore-structure-analyzer. DLS and SAXS results support the notion that the gelation of polyvinyltrimethoxysilane (P-VTMS) yields a nonparticulate structure. A chemically induced spinodal decomposition phase separation was found to explain the collected data. The mass fractal dimension was found to be 1.8, confirming that the percolation theory cannot be used to describe the gelation of both neat P-VTMS and Graphene-modified P-VTMS. The findings showed that, while adding GO to the formulation does not change the stoichiometric ratio of the gelation reaction, it creates spatial hindrance that interferes with the reaction process, delaying the gelation process. Conversely, GnP provides a platform for the reaction that promotes the gelation process. However, GO and GnP shows similar effects on bimodal mesoporous structure of aerogels although provides dramatically different surface areas. This dramatic difference roots in the open pore structure induced by GnP in P-VTMS aerogels. The strategy of nanoplatelets exfoliation during the sol–gel transition by controlling pH opens a new avenue for producing G-PSAs with an exceptionally high surface area (up to ~2100 m 2 .g −1 ).