Nanoscale poly(methyl methacrylate) (PMMA) particles were prepared by modified microemulsion polymerization. Different from particles made by traditional microemulsion polymerization, the particles prepared by modified microemulsion polymerization were multichain systems. PMMA samples, whether prepared by the traditional procedure or the modified procedure, had glass-transition temperatures (T-g's) greater than 120degreesC and were rich in syndiotactic content (55-61% rr). After the samples were dissolved in CHCl3 there were decreases in the T-g values for the polymers prepared by the traditional procedure and those prepared by the modified process. However, a more evident T-g decrease was observed in the former than in the latter; still, for both, T-g was greater than 120degreesC. Polarizing optical microscopy and wide-angle X-ray diffraction indicated that some ordered regions formed in the particles prepared by modified microemulsion polymerization. The addition of a chain-transfer agent resulted in a decrease in both the syndiotacticity and T-g through decreasing polymer molecular weight. (C) 2003 Wiley Periodicals, Inc.