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A steady state-fluorescence (SSF) technique for studying film formation from surfactant-free, slightly crosslinked polystyrene (PS) latex particles is reported. The powder films were prepared from fluorescein (F)-labeled PS particles at room temperature. The mechanically strong films were obtained by annealing these films at elevated temperatures in 5, 10, 20, and 30 min time intervals above the glass transition (T g ) temperature of polystyrene. Scattered light (I s ) and fluorescence (I F ) intensities from F were monitored after each annealing step to investigate the three different film formation stages called void closure, healing, and interdiffusion. The evolution of transparency of the latex films was monitored by using a photon transmission technique. Scanning electron microscopy (SEM) was employed to detect the variation in physical structure of the annealed latex films. Onset temperature for void closure, T m , and healing temperatures, T h , were determined and corresponding activation energies were measured. Void closure and interdiffusion stages were also modeled and the related activation energies were also determined. It was observed that lower energy is needed for the void closure process than interdiffusion of chains across the particle-particle boundaries.

Steady‐state fluorescence technique was used for studying film formation from TiO2 covered nano‐sized polystyrene latex particles. The composite films were prepared from pyrene (P)‐labeled PS particles by covering them with various layers of TiO2 at room temperature. These films then annealed at elevated temperatures in 10 min time interval above glass transition (Tg) temperature of polystyrene. Five different composite films were studied in various TiO2 layer contents. Fluorescence emission intensity, IP from P was measured after each annealing step to monitor the stages of film formation. Films present significant increase in IP above the certain onset temperature called minimum film forming temperature, T0. However, at higher annealing temperatures, IP showed a decrease. Increase and decrease in IP were modeled by void closure and interdiffusion processes and related activation energies were determined, respectively. Dissolution of annealed PS film, with high TiO2 content presented a nice, ordered nano‐sized ceramic structure, which may predict the construction of nano‐layer photonic crystals. POLYM. COMPOS., 27:651–659, 2006. © 2006 Society of Plastics Engineers

Fluorescence technique was employed for the measurement of the diffusion coefficient of oxygen into polystyrene (PS) latex/modified Na‐activated bentonite (MNaLB) clay composite films. Three different MNaLB content (0, 5, and 20 wt%) composite films were prepared from PS/MNaLB mixtures by annealing them at 200°C, above the glass transition temperature of PS for 10 min. To determine the diffusivity of oxygen in PS/MNaLB composite films, diffusion measurements were performed over the temperature range from 25 to 70°C. Pyrene (P) was used as the fluorescent agent. The diffusion coefficients (D) of oxygen were determined by combining the fluorescence quenching method with Fickian transport model, and were found as a function of temperature for each MNaLB content film. The results showed that D values are strongly dependent on both temperature and clay content in composite film. It was also observed that D coefficients obey Arrhenius behavior, from where diffusion activation energies were measured. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers