The novel hyperbranched poly(methyl acrylate)-block-poly(acrylic acid)s (HBPMA-b-PAAs) are successfully synthesized via single-electron transfer-living radical polymerization (SET-LRP), followed with hydrolysis reaction. The copolymer solution could spontaneously form unimolecular micelles composed of the hydrophobic core (PMA) and the hydrophilic shell (PAA) in water. Results show that the size of spherical particles increases from 8.18 to 19.18 nm with increased pH from 3.0 to 12.0. Most interestingly, the unique regular quadrangular prisms with the large microstructure (5.70 μm in length, and 0.47 μm in width) are observed by the self-assembly of unimolecular micelles when pH value is below 2. Such self-assembly behavior of HBPMA-b-PAA in solution is significantly influenced by the pH cycle times and concentration, which show that increased polymer concentration favors aggregate growth.

The branching copolymerization of styrene and acrylonitrile with divinyl benzene as the branching agent was carried out using atom transfer radical polymerization. Nuclear magnetic resonance and triple detection size exclusion chromatography were used to analyze the reaction. The results suggest that the coupling reaction mainly takes place between the primary chains, forming slightly branched chains in the early stages. The coupling reaction between the branched chains becomes significant at the middle stages, forming highly branched chains. The reaction system consists of primary chains, slightly branched chains containing two primary chains and highly branched chains comprised of more than three primary chains. The weight fraction of the branched chains increases expectedly with monomer conversion.

Ultrafast preparation of branched poly(methyl acrylate) (BPMA) with high‐molecular weight through single electron transfer living radical polymerization (SET‐LRP) of inimer at 25°C has been attempted, atom transfer radical polymerization (ATRP) at 60°C was also carried out for comparison. Gas chromatography, proton nuclear magnetic resonance, and triple detection size exclusion chromatography were used to analyze these polymerizations. As expected, SET‐LRP system showed much faster polymerization rate than ATRP system, the calculated apparent propagation rate constants (kpapp) are 3.69 × 10−2 min−1 and 6.23 × 10−3 min−1 for SET‐LRP and ATRP system, respectively. BPMA with high‐molecular weight (Mw.MALLS = 86,400 g mol−1) compared with that in ATRP (Mw.MALLS = 61,400 g mol−1) has been prepared. POLYM. ENG. SCI., 54:1579–1584, 2014. © 2013 Society of Plastics Engineers

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