Porous Polymer Composites Synthesized By CaCO₃ Nanoparticle-stabilized High Internal Phase Emulsion Templating Method

Porous polymer composites are very attractive materials for a variety of applications, such as biomedical, filter modules, the removal of organic chemicals, ion exchange resins due to their low density, well permeability, high porosity and interconnected pore structure. In recent years, High internal phase emulsions (HIPEs) templates has emerged as an effective method to prepare such materials and has attractive more and more attentions. High internal phase emulsions are very concentrated emulsions in which the internal or droplet phase occupies at least 74%of the emulsion volume. High internal phase emulsions can be used as templates for the synthesis of porous polymers, known as polyHIPEs. Their potential applications including ion exchange resins, filter membranes, scaffolds for tissue engineering have been explored, however, industrial applications of these materials synthesized by conventional method commonly using large amounts of expensive small molecule surfactants as emulsifiers to stabilize HIPEs have often been limited because of their undesirable mechanical properties, such as their brittleness and chalkiness.In addition to surfactant, solid particles can also be used as emulsifiers to stabilize emulsions effectively. Particle-stabilized emulsions, also known as Pickering emulsions. In this paper, we mainly reported the method of introducing modified nano-CaCO3 particles to HIPEs as particulate emulsifier to produce polyHIPEs, not only stabilize emulsions effectively, but introduce some benefits which when using conventional surfactants can not achieve, such as improving the mechanical performance, enhancing catalytic activity, UV-absorption surface roughness of the resulting materials.A range of functionalized nano-CaCO3 had been synthesized and as the particulate emulsifiers to prepare PS/CaCO3 porous composites and PAM/CaCO3 porous composites by the polymerization of HIPEs.(1) Nano-CaCO3 with cubes shape, average diameter of 80 nm and well dispersity had been prepared through a carbonation process, and various amounts of oleic acid were used as the modifier to functionalize the surface of the nano-CaCO3, the hydrophobic group of oleic acid were grafted on the surface of the nano-CaCO3 particles. A range of functionalized nano-CaCO3 with various wettability (contact angle) had been prepared.(2) In the preparation of porous poly(styrene) materials, The stability of HIPEs stabilized with Span80, a combination of nano-CaCO3 particles and Span80, and nano-CaCO3 was studied. The materials prepared solely by Span80 as emulsifier with poor mechanical performance in spite of their well-defined morphology; materials was the combination of well-defined morphology and extremely high mechanical strength due to the interaction of Span80 and nano-CaCO3 particles when Span80 and the nano-CaCO3 as emulsifiers; when nano-CaCO3 as the solely emulsifier, stabilized emulsions can been prepared and macroporous composite with desired properties can been achieved.(3) In the preparation of porous poly(acrylamide) materials, the stability of HIPEs stabilized solely by CTAB and solely by nano-CaCO3 particles was studied. The materials prepared solely by CTAB as emulsifier possessed well mechanical performance and well-defined morphology. When nano-CaCO3 was the solely emulsifier, stabilized emulsions can be obtained and macroporous composite with desired properties and morphology can be achieved.