Practical Synthesis of Dendritic Hyperbranched Polyacrylates and Their Topological Block Polymers by Organotellurium-Mediated Emulsion Polymerization in Water.

The practical synthesis of structurally controlled hyperbranched polymers (HBPs) by organotellurium-mediated radical polymerization (TERP) in water under emulsion conditions is reported. Copolymerization of vinyltelluride named evolmer, which induces controlled branch structure, and acrylates with TERP chain transfer agent (CTA) in water afforded HBPs having dendron structure. The molecular weight, dispersity, branch number, and branch length of the HBPs were controlled by changing the amount of CTA, evolmer, and acrylate monomers. HB-poly(butyl acrylate)s (HBPBAs) with up to the 8th generation having an average of 255 branches were successfully synthesized. As the monomer conversion reached nearly quantitative and the obtained polymer particles were well dispersed in water, the method is highly suitable for synthesizing topological block polymers, block polymers consisting of different topologies. Thus, linear-block-HB, HB-block-linear, and HB-block-HB-PBAs with the controlled structure were successfully synthesized by adding the second monomer(s) to the macro-CTA. The intrinsic viscosity of the resulting homo- and topological block PBAs was systematically controlled by the degree of the branch, the branch length, and the topology. Therefore, the method opens the possibility of obtaining various HBPs with diverse branch structures and tuning the polymer properties by the polymer topology.

Stochastic Simulation of Controlled Radical Polymerization Forming Dendritic Hyperbranched Polymers.

Stochastic simulation of the formation process of hyperbranched polymers (HBPs) based on the reversible deactivation radical polymerization (RDRP) using a branch-inducing monomer, evolmer, has been carried out. The simulation program successfully reproduced the change of dispersities (Ds) during the polymerization process. Furthermore, the simulation suggested that the observed Ds (=1.5-2) are due to the distribution of the number of branches instead of undesired side reactions, and that the branch structures are well controlled. In addition, the analysis of the polymer structure reveals that the majority of HBPs have structures close to the ideal one. The simulation also suggested the slight dependence of branch density on molecular weight, which was experimentally confirmed by synthesizing HBPs with an evolmer having phenyl group.