Photon transmission method for studying film formation from polsytrene latexes with different molecular weights

A photon-transmission method was used to probe the evolution of transparenc y during film formation from polystyrene (PS) particles with different mole cular weights. The latex films were formed at room temperature from the PS particles having two different average molecular weights and annealed at el evated temperatures in various time intervals above the glass transition (T -g). Onset temperatures (T-H) at given times (tau(H)) for the optical clari ty of films formed from low (LM) and high molecular (HM) weight PS particle s were used to calculate the healing activation energies for the minor chai ns and found to be 22.0 +/- 0.5 and 27.0 +/- 0.6 kcal/mol, respectively. Th e increase in the transmitted photon intensity, I-tr, above the T-H was att ributed to increase in the number of interfaces that disappeared. The Prage r-Tirrell (PT) model was employed to interpret the increase in crossing den sity at the junction surface. The backbone activation energies (Delta E) we re measured and found to be 127.8 +/- 2.5 kcal/mol for a diffusing polymer chain across the junction surface for LM and HM latex films. (C) 2000 John Wiley Ss Sons, Inc.