The effects of particle size and parent polymer characteristics on the mechanical properties, gel fraction, and swelling index of self-crosslinkable poly(n-butyl methacrylate-co-N-methylolacrylamide) films made by two-stage emulsion or microemulsion polymerization in the presence of variable amounts of the chain transfer agent, n-butyl mercaptan, are reported here. In films prepared with latexes made by microemulsion polymerization, the crosslinking degree increased greatly on curing; by contrast, in those made by emulsion polymerization, the crosslinking degree practically did not increase after curing. Stress-strain tests of uncured and cured films indicate that microemulsion-made films are tougher than the emulsion-made films. (c) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 1669-1674, 2011