The Construct Of Novel Platforms For Surface Modification Of Graphene And Its Application In Polymer Composites

Surface modification is an efficient way for graphene to solve the problems existed in its practical applications,such as solution processability,band gap and special functionality.It lays a basis for the effective application of graphene and has made major strides until now,however,most of the presently reported modification methods can only provide an exclusive modified graphene?MG?to meet the requirements of one specific application.There are limited methods available for producing different-surface graphene that are applicable to diverse applications.In order to address this issue,a systematic solution to surface modification of graphene is proposed here to realize the valid utilization of graphene in various application environments.The general idea is to first obtain a surface-modifiable graphene material?mG?,and then employ it as a universal material platform for developing manifold MGs by different surface remodifications.During the implementation of such a proposal,mG was constructed by the modification of graphene prepared by liquid exfoliation of graphite with active agents.On the one hand,this method ensures that the electronic structure and properties of graphene are succeeded largely by mG and thus its derivatives.On the other hand,mG can act as the platform to undergo post-reactions for generation of various graphene-derived materials by the choice of appropriate active agents.Thereinto,the latter is particularly important to the project.In order to exemplify that mG is a competent platform,different graphene-derived materials have been prepared from mG.The potential applications of the special molecular design of MG in polymer composites were also investigated.In order to demonstrate the advantage of mG,the comprehensive properties of composites will be compared with that of composites prepared by pristine graphene?pG?,graphene oxide?GO?or reduced graphene oxide?rGO?.During the specific research schemes,First,the versatile platform of 2-?3,4-dihydroxyphenyl?pyrrolidine grafted graphene?G-OH?for surface modification ofgraphene,which has excellent electrical property and dispersive capacity,was synthesized by modification of pG produced by liquid exfoliation of graphite through the 1,3-dipolar cycloaddition.In order to exemplify that G-OH is a competent platform,graphene was further functionalized by different reactive sites of G-OH.The epoxide-functionalized graphene?G-EP?was synthesized by utilizing the reactive sites of phenolic hydroxyl through Williamson etherification reaction.The methacryloyl-functionalized graphene?G-MA?was synthesized by utilizing the reactive sites of phenolic hydroxyl through esterification reaction.The phenolic resin-functionalized graphene?G-PR?was synthesized by utilizing the reactive sites of benzene ring hydrogen.The magnetic nanoparticale of graphene-FeCl3 complex?G-FeCl3?was synthesized by utilizing the reactive sites of phenolic hydroxyl and/or pyrrolidine nitrogen.The platform properties of G-OH were proved by above reactions.Then,G-EP and G-PR were used to prepare epoxy?EP?/G-EP composite and Resole/G-PR composite,respectively.It was found that the comprehensive properties of composites including mechanical property,electrical property and thermal property were improved.Especially in improving electrical and thermal properties,G-EP and G-PR are more effective than pG,GO and rGO.The advantage of G-OH as a platform for chemical modification of graphene was proved.The electrical percolation threshold of EP/G-EP and Resole/G-PR composites are 0.16 vol% and 0.12 vol%,respectively.The thermal conductivity of EP/G-EP composite is 3.138 W·m^-1·K^-1 at 10 wt%graphene content,which is 1886% improvement compared with EP matrix.The thermal conductivity of Resole/G-PR composite is 0.269 W·m^-1·K^-1at 0.5 wt%graphene content,which is 156% improvement compared with Resole matrix.At last,in order to prove that the platform strategy constructed by “active agent method” is wide-adaptability,another high-quality platform of phenol grafted graphene?G-phenol?was synthesized by in-situ diazonium salt method,which also has good electrical property and dispersive capacity.The methacryloyl-functionalized graphene?G-DB?was successfully synthesized by utilizing the reactive sites of phenolic hydroxyl of G-phenol through esterification reaction,which exemplifys that G-phenol is a competent platform.After PS grafted graphene?G-PS?was synthesized by adding G-DB into the free radical polymerization system of styrene?St?,it was used to prepare PS/G-PS composite.G-PS can also improve the comprehensive properties of composite and especially in electrical and thermal property,which proves the advantage of G-phenol platform.The electrical percolation threshold of PS/G-PS composite is 0.22 vol%.The ultimate conductivity reaches up to 95.2 S·m^-1 at 2.34vol% graphene content.The thermal conductivity of PS/G-PS composite is 0.253W·m^-1·K^-1 at 5.0 wt% graphene content,which is 229% improvement compared withPS matrix.In conclusion,the versatile platforms that can undergo post-reactions for generation of various graphene-derived materials for different applications,can be constructed by active agent methods.Due to their high-quality,polymer composites constructed from these platforms are better than that from pG and GO/rGO platform in improving electrical and thermal properties of the corresponding polymer composites.