Colloids and Surfaces Ž . A: Physiochemical and Engineering Aspects 153 1999 537549 Void closure and interdiffusion in latex film formation by photon transmission and fluorescence methods ¨ a,  b Onder Pekcan , Ertan Arda a Department of Physics, Istanbul Technical Uni  ersity, Maslak 80626, Istanbul, Turkey b Department of Physics, Trakya Uni  ersity, 22030 Edirne, Turkey Abstract Ž . Steady state fluorescence SSF and photon transmission methods were used to study void closure and interdiffu- sion processes during film formation from hard latex particles. Latex films were prepared separately by annealing Ž . Ž .Ž . pyrene P labeled and unlabeled poly methyl methacrylate PMMA particles above the glass transition tempera- y ture. Direct fluorescence emission of excited pyrene from labeled latex films was monitored as a function of annealing temperature to detect void closure and interdiffusion. The increase in fluorescence intensity against Ž . temperature was used to determine the activation energy for viscous flow  H 47 kcalmol . The decrease in I op Ž . above the void closure temperature was used to produce the backbone activation energy  E 44 kcalmol for the interdiffusing chains. Unlabeled PMMA particles were used to prepare films for UVV measurements. Transmitted photon intensity from these films increased as the annealing temperature was increased. Monte Carlo simulations were performed for photon transmission through a rectangular lattice. The number of transmitted and scattered photons were calculated as a function of disappeared particle  particle interfaces. The increase in the transmitted Ž . photon intensity I is attributed to the increase in ‘crossing density’ at the junction surface. The backbone tr Ž . activation energy  E was measured and found to be around 33 kcalmol for a diffusing polymer chain across the junction surface.  1999 Elsevier Science B.V. All rights reserved. Keywords: Fluorescence; Photon transmission; Interdiffusion; Void closure; Latex 1. Introduction Latex film formation is a complicated, multi- stage phenomenon and depends strongly on the characteristics of latex particles. In general, aque-  Corresponding author. Tel: 90 212 2853213; fax: 90 212 2856386 ous or non-aqueous dispersions of colloidal parti- Ž . cles with glass transition temperature T above g the drying temperature are called hard latex dis- persions; however an aqueous dispersion of col- loidal particles with T below the drying tempera- g ture is called a soft latex dispersion. The term ‘latex film’ normally refers to a film formed from soft particles where the forces accompanying the evaporation of water are sufficient to compress 0927-775799$ - see front matter  1999 Elsevier Science B.V. All rights reserved. Ž . PII: S 0 9 2 7 - 7 7 5 7 98 00476-2