Abstract: | Polymer diffusion across interfaces at room temperature (21°C) was analyzed by direct nonradiative energy transfer (DET) in labeled latex films. Two modellatex polymers were examined: poly(butyl methacrylate) PBMA, Mw = 3.5 × 104, Tg (dry) = 21°C] and a copolymer of 2-ethylhexyl methacrylate with 10 wt % (acetoacetoxy)-ethyl methacrylate P(EHMA-co-AAEM), Mw = 4.8 × 104, Tg (dry) = ?7°C]. Little energy transfer due to polymer diffusion was detected for the P(EHMA-co-AAEM) latex samples in the dispersed state or dried to solids content below ca. 90%, but above 90% solids, diffusion occurs among particles. For PBMA, diffusion occurs only after the film is dried (>97% solids) and aged. In the dry PBMA films, it requires 4–5 days at 21°C to reach a significant extent of mixing (fm = 0.3–0.4). This corresponds to an estimated penetration depth dapp of 30–40 nm and a mean apparent diffusion coefficient (Dapp) of 5 × 10?4 nm2/s. The corresponding Dapp value for the dry P(EHMA-co-AAEM) sample is 5 × 10?2 nm2/s, and it takes about 25–40 min for this polymer to reach fm of 0.3–0.4 with dapp of 20–30 nm. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1129–1139, 1998 |