Novel polymer foam via polymerized high internal phase emulsion (polyHIPEs)

Abstract

In order to obtain polyHIPE polymeric foam with improved properties for performance in ever-broadening applications i.e. adsorbent for CO₂ adsorption and scaffold for tissue engineering application, the present work focuses on how to elevate the overall properties of polymerized high internal phase emulsion (PolyHIPE porous foam) to above their inherent values including studying the effect of surfactant system, Soxhlet extraction time, addition of organoclay as inorganic filler and also plasma surface modification technique. Plasma surface modification technique was used to improve the surface properties of plyHIPE scaffold in tissue engineering applications. After surface modification, poly(S/EGDMA)polyHIPE scaffold prepared from styrence and ethylene glycol dimethacrylate monomers with greater hydrophilic properties, were obtained leading to improve the interaction between the living cells and the polyHIPE substrate. The amount of cell adhesion and proliferation was further increased with the utilization of the surface modification technique via atmospheric pressure plasma treatment that would impart the hydrophilic improvement to the polyHIPE scaffold surface due to the polar-like property of the biofluid cell medium. With the aim of designing suitable adsorbent materials i.e. high surface area with superior mechanical properties and also good adsorption capacity that would adsorb such gases before being liberated into the environment, polymerized high internal phase emulsion of divinylbenzene;poly(DVB)polyHIPE foam was successfully prepared by using two different systems of three-component surfactants and toluene as porogenic solvent (S20M_T and S80M_T). Samples prepared using S20M_T and S80M_T showed relatively similar characteristics which indicated the effectiveness of the two three-component surfactants for use in preparation of poly(DVB)polyHIPE foam. Moreover, it was also demonstrated that the usage of Soxhlet extraction technique for poly(DVB)polyHIPE foam improved surface area of the obtained materials by 107% as compared with the unextracted polyHIPE porous foam. The optimum Soxhlet extraction time to achieve the highest surface area with the best mechanical properties for S20M_T systems was around 6 h whereas S80M_T system, composed of span80 as non-ionic surfactant that had longer alkyl chain length in the structure, needed around 12-24 h to remove nearly all the residue materials from the obtained polyHIPE porous structure. However, polyHIPE foam without any reinforcement phase also exhibited poor mechanical properties i.e. low crush strength and brittleness. Thus, to further improve the overall properties of polyHIPE porous foam, poly(DVB)polyHIPE filled with organoclay was prepared. Three types of organoclay including hybrid organic-inorganic porous clay heterostructure (HPCH), organo-modifed bentonite (MOD) and acid treated organo-modified bentonite (AC-MOD) were used as inorganic reinforcement for polyHIPE foam. The effect of different type of organoclay on physical properties and CO₂ adsorption capacity of poly(DVB)polyHIPE nanocomposites foam was investigated. In all system, the addition of organoclay into polyHIPE matrix resulted in the improvement of the overall properties of the resulting polyHIPE foam. The surface area and the decomposition temperatures (Td) for the series of poly(DVB) polyHIPE filled with organoclay increased with increasing the clay contents form 0 to 10 wt% whereas the maximum improvement for mechanical properties was observed at 5 wt% organoclay. The adsorption of CO₂ gas by poly(DVB)polyHIPE foam filled with organoclay was found to increase as well when compared with neat poly(DVB)polyHIPE foam. Additionally, it has been demonstrated in this study that the CO₂ gas adsorption of poly(DVB)polyHIPE nanocomposites foam was increased in the following order: neat poly(DVB)polyHIPE foam < poly(DVB)polyHIPE foam filled with MOD ≤ poly(DVB)polyHIPE foam filled with HPCH < poly(DVB)polyHIPE foam filled with AC-MOD.