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Polystyrene/poly(butyl acrylate)/montmorillonite (PS/PBA/MMT) ternary hybrid films were fabricated by colloid blending of oligo(acrylic acid)-functionalized core-shell particles of PS-b-PBA diblock copolymers and Na+-MMT aqueous dispersions. The particles were synthesized by RAFT emulsion polymerization using oligo(acrylic acid-block-styrene) RAFT as a reactive surfactant. Coherent hybrid films could be formed when the particles possessed a relatively thick soft PnBA shell (core-shell ratio = 1:1 or 3:7) without adding any coalescing agent even when 15 wt% MMT was added. TEM observations revealed that around 20 nm thick clay stacks were well dispersed throughout the hybrid films. Increasing the levels of PS or MMT could much increase the modulus and tensile strength of the hybrid films. However, simply increasing PS composition would be limited by the crack formation and brittleness of the resultant films. The ternary hybrid design would allow one to gain good balance between mechanical properties and coherent film formation. The enhancing efficiency of MMT for the modulus and tensile strength was much higher when placing the clay stacks in PS domains than in PBA domains, which was particularly obvious when MMT levels were higher than 10 wt%. [ABSTRACT FROM AUTHOR]

The comparison between methyl methacrylate (MMA) and styrene (St) RAFT emulsion polymerization using oligo(methacrylic acid41-b-methyl methacrylate8) RAFT agent (oligo(MAA41-b-MMA8) RAFT) as surfactant is investigated in order to gain a better understanding on RAFT emulsion polymerization of MMA. It is found that the colloidal stability during MMA emulsion polymerization is much more sensitive to the initiator concentrations and temperature than that of St polymerization. The coagulum-free latex of highly living PMMA can be achieved only at 80 °C and low initiator concentrations. The final PDI is higher in RAFT emulsion polymerization of MMA than that of St. It is revealed that about 40% acid groups of oligo(MAA41-b-MMA8) RAFT should be buried within the final particles of PMMA, indicating that particle coagulation should occur in the very beginning of the polymerization. The poorer performance of the MMA polymerization could be well explained by the homogeneous nucleation mode of particles combined with relatively slow transporting rate of oligo(MAA41-b-MMA8) RAFT molecules from the partly frozen micelles to the newly-born particles. [ABSTRACT FROM AUTHOR]