Preparation And Morphology Control On Non-spherical Colloidal Particles

Non-spherical particles have excellent physicochemical properties due to their geometric asymmetry and show huge applicable value in the fields of biomedical and optical materials. By controlling the heterogeneous separation inside the growing particles, cap-like particles were prepared via one-pot dispersion polymerization. Amphiphilic organic nanoparticles were used as polymeric emulsifier and raspberry-like composite particles were fabricated based on Pickering emulsion polymerization.(1) Micro-sized cap-like polystyrene(PS) colloidal particles were prepared via by one-pot dispersion polymerization where divinylbenzene(DVB) used as cross-linking agent. The amount, feeding rate and feeding time of DVB, the feeding manner of St as well as the solvent polarity were investigated to explore an optimum condition for the preparation of cap-like PS particles. The results demonstrated that when the amount of DVB was between 0.5% and 6.0% with a fast feeding rate would accelerate the growth of cap-like particles, while excessive(>6.0%)or delayed feeding of DVB provided a favorable environment for the generation of cap-like particles. Dimply cap-like particles, smooth cap-like particles and spherical particles could be respectively obtained by adjusting the mass ratio of St monomer in Stage Ⅰ and Stage Ⅱ. Particle morphology changed from cap-like to sphere-like with the increase of solvent polarity. The formation mechanism of cap-like particles were proposed based on the conventional dispersion polymerization, and the macroscopic deformation on particle surface was derived from the heterogeneous separation between the cross-liked network and St monomer.(2) The water contact angle of the colloidal film formed by knobby cap-like particles(KCP, 132.62°) and smooth cap-like particles(SCP, 126.83°) were measured, and the film made by KCP was proved to be more hydrophobic because of the micro-nano structure of KCP surface. In addition, self-assemble of cap-like particles were conducted at the air-water interface, and ordered monolayer was able to form with all the particle concave facing up.(3) Raspberry-like PS/P(BA-AA) composite colloidal particles with polystyrene(PS)as a core and poly(n-butyl acrylate-co-acrylic acid)(P(BA-AA))particles as corona were synthesized via the emulsion polymerization of styrene. P(BA-AA) random copolymer was pre-prepared and used as polymeric surfactant. The effect of several experimental parameters including the feeding manner of St, the mass ratio of BA:AA, the concentration of P(BA-AA) and initiator on the morphology of raspberry-like PS/P(BA-AA) particles were studied. The emulsifying ability of P(BA-AA) achieve the best when the mass ratio of BA:AA was 1:2 and 5% of P(BA-AA) was used. Excess initiator more than 1.5% had an negative impact on the stability of the resulted PS/P(BA-AA) emulsion. The formation mechanism of PS/P(BA-AA) particles was proposed according to Pickering emulsion polymerization. The primary driven force for the generation of raspberry-like structure was attributed to the high affinity between the PS core and hydrophobic segments of P(BA-AA).