A photon transmission method was used to study latex film formation induced by organic solvent vapor. Various films with the same latex content were prepared separately from the poly(methyl methacrylate) (PMMA) particles and exposed to vapor of chloroform-heptane mixture in various percentage volumes of chloroform. Transmitted photon intensities, I-tr from these films increased in time under vapor exposure. The increase in I-tr is attributed to the increase in 'crossing density' at the junction surface. The Prager-Tirrell model was employed to obtained back-and-forth frequency, nu of the reptating polymer chain during film formation induced by solvent vapor. nu values were obtained and found to be strongly correlated with the percent of chloroform in the solvent mixture. At high and low chloroform contents, polymer chains diffuse according to t(1/2) and t(1/4) laws respectively.