Effect of molecular weight on latex film formation: Photon transmission study

Abstract

A UV-visible (UVV) technique was used to monitor the evolution of transparency during film formation from hard latex particles. Two different latex films were prepared from particles with high and low molecular weight (HM and LM) poly(methyl methacrylate) (PMMA) separately and annealed at elevated temperatures in various time intervals above the glass transition temperature (T g ). In both films, a continuous increase in the transmitted photon intensity (I tr ) was observed above 160°C as the annealing temperature was increased. However, the reflected photon intensity (I rf ) first decreased and then increased by showing a minimum in the same temperature range as the annealing temperature was increased. The increase in the transmitted photon intensity (I tr ) is attributed to increase in the "crossing density" at the junction surface. The activation energies for back-and-forth motion (⌬E tr ) were measured and found to be around 35 and 25 kcal/mol for the reptating polymer chain across the junction surface in the LM and HM films, respectively. The decrease in I rf was explained by the void-closure mechanism, and the increase in the I rf above 160°C was again attributed to the increase in the crossing density at the junction surface. Back-and-forth activation energies (⌬E rf ) were measured to be around 47 and 18 kcal/mol and the void-closure constants (B) were found to be around 24 ϫ 10 3 and 12 ϫ 10 3 K for the LM and HM film samples, respectively.

How the infrared radiation affects the film formation process from latexes?

“…Light has been used to monitor the film formation for a long time. Ellipsometry, photon transmission (PT), and reflection techniques have been elaborated for latex film formation processes. Scanning and transmission electron microscopes have been commonly used techniques to characterize the latex systems.…”

Film formation from pure and mixed latices; transient fluorescence study

“…Stephan Mazur [24] has written an extensive review on coalescence of polymer particles, where he mainly discussed the neck growth mechanism and its several geometrical approximations before interdiffusion of polymer chains takes place. The steady state fluorescence and photon transmission techniques have been used in our laboratory to study interdiffusion processes at the particle-particle junction during film formation by PMMA and polystyrene (PS) latex particles [25][26][27][28][29][30][31][32].…”

Energy‐transfer method to study vapor‐induced latex film formation

“…Mazur15 has written an extensive review on the coalescence of polymer particles, in which he mainly discussed the neck growth mechanism and its several geometrical approximations before interdiffusion of polymer chains takes place. The steady state fluorescence and photon‐transmission techniques have been used in our laboratory to study interdiffusion processes at the particle–particle junction during film formation and dissolution in PMMA and PS latex systems 16–24…”