Effect of Branching on Polymer Diffusion in Branched Poly(butyl methacrylate) Latex Films

YUANQIN LIU; WALTER F. SCHROEDER; JEFFREY C. HALEY; WILLIE LAU; MITCHELL A. WINNIK

MACROMOLECULES

American Chemical Society

Lugar: Washington; Año: 2008 vol. 41 p. 9104 - 9111

0024-9297

Fluorescent donor- and acceptor- labeled latex particles comprised of branched poly(butyl methacrylate) (PBMA) were prepared via semicontinuous emulsion polymerization. All latex particles have similar particle size and narrow size distribution. The degrees of branching of the PBMA samples were controlled by adding various amount of bisphenol A dimethacrylate (BPDM) as a branching agent. 1-Dodecanethiol (C12-SH) was used as a chain transfer agent to prevent gel formation and control the molecular weight. The number average molecular weights of all PBMA samples are ca. 45 000 g/mol. The degrees of branching were determined by 1H NMR. Latex films were cast from a 1:1 mixture of donor- and acceptor-labeled latices. The polymer diffusion in the latex films was studied by measuring the energy transfer (ET) from the donor to the acceptor using the time-correlated single photon counting technique. Polymer diffusion rates increased with decreasing values of Tg when the latex films were annealed at 23 °C. After correcting for the effects of Tg, by comparing results at a constant T - Tg, ET data show that the PBMA with the highest degree of branching had the highest diffusivity.