Synthesis of polyHIPE foam composite by using organophilic clay as a novel stabilizer for Pickering emulsions: Effects of clay modification methods

In this study, montmorillonite (MMT) clay was utilized as solid particle contributing to stabilize high internal phase emulsions (HIPEs) for the production of polyHIPE foam composites. Cetyltrimethylammonium bromide (CTAB) immobilization onto the MMT surface was carried out using cryoscopic expansion (C-XP) and physical adsorption in solution (SOL) techniques. A series of experiments were conducted to determine the amounts of clay and surfactant that provide the stability of HIPE. In addition, the morphologies, surface areas, dye adsorption capacities and glass transition temperatures together with heat capacity differences of the PolyHIPE materials were investigated in terms of nanoclay modification techniques and surfactant and MMT clay amounts. It was found that minimum 5% (vol.) of surfactant was needed to maintain the stability of neat HIPE whereas the surfactant requirement to ensure emulsion stability decreased to 1 vol in presence of the clays in quite low amounts (0.25 to 1.00 wt%). In all composites, polyHIPE morphology was preserved, predominantly resulting in open-cell structures. In fixed amounts of both clays, decreasing surfactant concentration reduced homogeneity of pore size distribution and caused pores in different sizes. An opposite effect was observed with increasing clay content at a fixed surfactant concentration, leading to a reduction in pore sizes and homogenization of pore size distribution. The cationic dye (Nile Blue) adsorption capacity of the composites was evaluated and the highest adsorption capacity among them was exhibited by the composite containing 0.75% CTAB-XP-MMT, which adsorbed 589% more dye compared to neat polyHIPE foam. Moreover, helping to ensure the emulsion stability of the clays, they also benefit in terms of taking an active role in the adsorption of the dye from water.