A photon transmission study for film formation from poly(vinyl acetate) latex particles with different molecular weights

Abstract

The photon transmission technique was used to monitor the temperature evolution of film formation from poly(vinyl acetate) (PVAc) latex particles with two different molecular weights. Two sets of latex films were prepared below the glass transition temperature (T-g) of PVAc, which are named as low (LM) and high molecular weight (HM) films. These films were annealed at elevated temperatures above the Tg of PVAc for various time intervals. It is observed that transmitted photon intensity (I-tr) from these films increased as the annealing temperature was increased. Onset temperatures (T-H) at given times (tau H) for starting the optical clarity of LM and HM films were measured and used to calculate the healing activation energies (Delta H) for the PVAc minor chains, and found to be as 28.1 kcal/mol and 27.7 kcal/mol, respectively. The increase in the transmitted photon intensity, Itr above TH was attributed to the increase in the number of disappeared interfaces between the deformed latex particles. Prager-Tirrell (PT) model was employed to interpret the increase in the crossing density of chains at the junction surfaces. The interdiffusion (backbone) activation energies (Delta E) were measured and found to be 177.5 kcal/mol and 210.7 kcal/mol for a diffusing PVAc chains across the junction surface of LM and HM latex films, respectively.