In Situ Interface Design in Graphene-Embedded Polymeric Silica Aerogel with Organic/Inorganic Hybridization

Abstract

For many practical applications, the most important factor is to have an improved interface between the matrix and dispersed phase in a compressible composite aerogel having a high degree of porosity and a large surface area. Although some measure of compressibility is obtained in polymer-based aerogels with a continuous backbone through the hybridization of the stiff backbone [polyvinyl­trimethoxy­silane (P-VTMS), −C–C−] and flexible backbone [poly­(3-glycidyloxy­propyl)­trimethoxy­silane (P-GPTMS), −C–O–C−], it seems that the extent of improvement is insignificant in terms of interface improvement, surface area increase, and ordered mesoporous network. In this study, the effects of the incorporation of graphene nanoplatelets (GnPs) on aerogels made of a backbone consisting of −C–O–C– (flexible backbone) were examined in terms of structural improvement and were compared with aerogels made of a backbone consisting of −C–C– (stiff backbone). Moreover, the inorganic siloxane cross-link density between the underlying polymer chains was controlled by inducing hydrogen bonding between polymer chains and GnPs. This approach reduces the structural shrinkage during gelation and drying. The integration of only 1 wt % GnP integrated into the backbone by using spinodal decomposition phase separation processing allowed control of the pore size and the surface area. Integration of GnPs through in situ exfoliation during sol–gel transition is shown to be the best approach using the lowest possible amount of GnPs to improve aerogels’ mesoporous network made from polymerized GPTMS. A flexible backbone such as P-GPTMS chains is supposed to result in a compliant aerogel, but the chains tend to shrink extensively during gelation and drying, reducing the porosity. P-GPTMS-derived aerogel suffers from a wrong combination of flexible backbone conjugated with an extensive number of permanent chemical cross-links and abundant remaining unreacted hydroxyl groups that undergo permanent chemical shrinkage. To counteract this, the GnP-reinforced prepolymer precursor (P-GPTMS) with fewer siloxane cross-links was synthesized and studied. By use of this strategy, the same elastic properties as those seen with the hybrid P-VTMS- and hybrid P-GPTMS-derived aerogels were imparted, while also improving the mechanical strength by up to 138% and the surface area by up to 205% by controlling the extent of GnP exfoliation during the sol–gel transition. This exceptional effect of GnP on the surface area improvement was shown to be of up to 2.05-fold for P-GPTMS and 2.63-fold for P-VTMS material.

Preparing Multifunctional High-Performance Cross-Linked Polybenzoxazole Aerogels from Polybenzoxazine

“…Although silicon aerogels have excellent thermal insulation properties, their application is greatly restricted due to their poor mechanical properties and cumbersome drying procedure. , Therefore, the preparation of aerogels with better properties through composite or enhanced methods is a current research hotspot . Polymer aerogels have been paid increasing attention because polymer materials not only have good mechanical properties and processability, but their density, porosity, and thermal conductivity are no less than, or even better than, inorganic materials.…”

“…11,12 Therefore, the preparation of aerogels with better properties through composite or enhanced methods is a current research hotspot. 13 Polymer aerogels have been paid increasing attention because polymer materials not only have good mechanical properties and processability, but their density, porosity, and thermal conductivity are no less than, or even better than, inorganic materials. For example, polymerenhanced silica aerogels have excellent mechanical properties and low dielectric properties and overcome the weaknesses of silica aerogels with high brittleness.…”

Synthetic Multiscale Graphene Aerogel Polymer Composites with High‐Conductive Performances for Hyperthermia Equipment

“…Polymer functionalization [1][2][3] has presently become an effective way for polymer composites to realize their value to be widely used in aerospace, automobile industry, medical equipment, and so forth. [4,5] Graphene, [6,7] a 2D carbon material, attract lots of interests from pursuer because of its excellent thermal conductivity (5300 W m À1 K À1 ) and electric conductivity (1 Â 10 8 S m À1 ) ever since it is discovered.…”

Flexible, Strong, Multifunctional Graphene Oxide/Silica-Based Composite Aerogels via a Double-Cross-Linked Network Approach

“…Besides, supercritical drying methods were still needed to obtain intact aerogels. 44 An alternative approach was to prepare GO aerogels first via freeze-drying and then immersing GO aerogels in a solution of precursor to improve the network of GO aerogels. 41,42 However, some special precursors were required to construct the doubly cross-linked nanostructure and meanwhile suppress the macroscopic phase separation.…”

“…Graphene or GO/silica-based composite aerogels, an emerging type of material, arouse widespread concerns. − So far, graphene or GO/silica-based composite aerogels were prepared by using polymerizable precursors, such as vinyltrimethoxysilane, in order to form a double-cross-linked network and prepare mechanically strong aerogels. , Relatively high temperature is inevitable for the prepolymerization of precursors. Besides, supercritical drying methods were still needed to obtain intact aerogels .…”