Synthesis Of Graphene/Polymer Porous Composites Within High Iternal Phase Emulsion

The design and preparation of porous polymers templated by high internal phase emulsions (HIPEs) have gained great interest for the relatively simple preparing process, controllable morphology of final products (named as polyHIPEs) and a wide variety of applications. However, the mechanical properties of polyHIPEs are limited because of their high porosity and interconnectivity. The various fascinating properties of graphene make its incorporation into polyHIPEs attractive to modify numerous polymer matrix. In this dissertation, we devised different synthetic routes to prepare graphene/polymer polyHIPE comosites and researched on the structure and properties of the resulting materials. Besides, microrheological study has been prove to be an efficient way to monitor the polymerization within HIPEs under different synthesis parameters. The main content was summarized as following:1. A one-pot synthesis toward ethylenediamine-reduced graphene oxide (EmGO) filled polymer foams is presented. The synthesis was carried out in the W/O HIPE (90 wt% internal phase). The internal phase of the HIPE was composed by an aqueous dispersion of GO and reducing agent like stoichiometric ethylenediamine (EDA). The external phase was built by initiator, emulsifier and polymerizable vinyl monomers. The emulsion could be solidified through thermally initiated radical polymerization of the monomers in external phase. At the same time, GO in internal phase was reduced by EDA and embedded into the polymer matrix driven by the hydrophobicity of in-situ produced EmGO. The prepared porous monolith was characterized by the open cell morphology and composite structures which was clearly proved by the improved dielectric permittivity, thermal stability and mechanical performance of the foam. It has been proved that EmGO and Fe3O4 could work synergistically to improve the mechanical property of polyHIPE composites. In addition, the effect of reducing agents on the stability of HIPEs has been studied.2. A two-step synthesis toward CTAB modified graphene oxide (CmGO) filled polymer foams is presented. GO flakes were modified by the cationic surfactant cetyltrimethylammonium bromide (CTAB) and used as the filler of W/O HIPEs. CmGO has little effect on the morphology of polyHIPEs, but it is effective at enhancing the compressive modulus of polyHIPEs. PLA fibers and CmGO could work synergistically to improve the mechanical property of polyHIPE composites. The impact of fillers on compressive modulus of polyHIPE composites was expolred.3. Microrheological study was proved to be an efficient way to analysize the reaction progress of HIPEs. Three stages of curing could be distinguished in diffetent systems of HIPEs under different processing conditions. The Mean Squared Displacements (MSD) curve and Elasticity Index (EI) curve of the progress are presumably related to molecular network formation, where the physical gel was transformed into a covalently bonded network. El is related to void diameters of poly HIPEs, which is affected by internal phase fraction, monomer composition, emulsifier concentration, reaction temperature.