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Yayın Film formation from TiO2-polystyrene latex composite: a fluorescence study(Taylor & Francis Group, 2007-03-01) Uğur, Şaziye; Sunay Yapışkan, Münüre Selin; Tepehan, Fatma Zehra; Pekcan, Mehmet ÖnderThis work reports the use of the steady state fluorescence (SSF) technique for studying film formation from TiO2 covered polystyrene (PS) latex particles. The composite films were prepared from pyrene (P)-labeled PS particles by covering them with TiO2 at room temperature and then annealed at elevated temperatures in 10 min time interval above glass transition (T-g) temperature of polystyrene. Five different composite films were studied in various TiO2 layer contents. Fluorescence intensities Ip from P were measured after each annealing step to monitor the stages of film formation. Films showed considerable increase in Ip above the certain onset temperature called minimum film forming temperature, T-0. Void closure and interdiffusion stages were modeled and related activation energies were determined and found to be 23.12 and 92.80 kJ mol(-1), respectively.Yayın Poly (styrene) latex/modified na-activated bentonite nanocomposite films: a fluorescence study(Elsevier Science BV, 2008-12) Uğur, Şaziye; Yargı, Önder; Günister, Ebru; Pekcan, Mehmet ÖnderWe studied film formation of composites of surfactant-free polystyrene (PS) nanoparticles and modified Na-activated bentonite (MLB), by steady state fluorescence (SSF) technique. The films were prepared from a mixture of pyrene (P)-labeled PS particles and MLB at various compositions at room temperature. These films were annealed at elevated temperatures above the glass transition (T(g)) temperature of polystyrene for 10 min. Scattered light (I(S)) and fluorescence intensities (I(P)) from P were measured after each annealing step to monitor the stages of film formation. Evolution of transparency of the composite films was monitored by using photon transmission intensity, I(tr) Atomic force microscopy (AFM) was used to detect the variation in physical structure of annealed composite films. The nanocomposite films exhibited a percolation threshold at 20 wt.% MLB content. Below this fraction two distinct film formation stages were observed which are known as void closure and interdiffusion and above this fraction no film formation was detected. At 0-20 wt.% MLB, minimum film formation, T(0), void closure, T(v) and healing, T(h) temperatures were determined. Void closure and interdiffusion stages were modeled and related activation energies were determined. Void closure activation energies decreased as the percent of MLB increased, no variation was observed in backbone activation energies.Yayın Films formed from polystyrene latex/clay composites: A fluorescence study(Springer New York, 2005-07) Uğur, Şaziye; Alemdar, Ayşe; Pekcan, Mehmet ÖnderThis study reports a steady-state fluorescence (SSF) technique for studying film formation from surractant-free polystyrene (PS) latex and Na-montmorillonite (SNaM) composites. The composite films were prepared from pyrene (P)-labeled PS particles and SNaM clay at room temperature and annealed at elevated temperatures in 10-min intervals above glass transition temperature (T-g) of polystyrene. During the annealing processes, the transparency of the fllm improved considerably. Scattered light (I-s) and fluorescence intensity (I-s) from P were measured after each annealing step to monitor the stages of film formation. Evolution of transparency of composite films was monitored by using photon transmission intensity, I-tr Scanning electron microscopy (SEM) was used to detect the variation in physical structure of annealed composite-films. Minimum flIm formation temperature, T-o, and healing temperatures, T-h, were determined. Void closure and interdiff-usion stages were modeled and related activation energies were determined. It was observed that both activation energies increased as the percent of SNaM was increased in composite films.Yayın Fluorescence study on Al2O3-polystyrene latex composite film formation(John Wiley & Sons Inc, 2005-06) Uğur, Şaziye; Salman, Oğuz Umut; Tepehan, Galip Gültekin; Tepehan, Fatma Zehra; Pekcan, Mehmet ÖnderThis work reports a steady state fluorescence (SSF) technique for studying film formation from mixture of Al2O3 and polystyrene (PS) latex particles. The composite films were prepared from dispersion of pyrene (P)labeled PS particles in Al2O3 solution at room temperature and annealed at elevated temperatures in 10-min time interval above glass transition (T-g) temperature of polystyrene. Nine different composites film were studied in various latex contents. Fluorescence intensities (I-P) from P were measured after each annealing step to monitor the stages of film formation. No variations in I-p were detected for the films prepared with higher than 33 wt% Al2O3 content. However films prepared below 33 wt% Al2O3 content show considerable increase in I-P above the certain onset temperature called minimum film forming temperature, To. Healing temperatures T., were determined from the maxima of I-P. Void closure and interdiffusion stages were modeled and related activation energies were determined and found to be 20 and 97 kJ.mol(-1), respectively.Yayın The effect of clay particles on film formation from polystyrene latex(Wiley, 2006-06) Uğur, Şaziye; Alemdar, Ayşe; Pekcan, Mehmet ÖnderFilm formation from surfactant-free polystyrene (PS) latex was performed in the presence of 5% Na-montmorillonite (NaMMT). The composite films were prepared from pyrene (P)-labeled PS particles at room temperature and annealed at elevated temperatures above the glass-transition (T-g) temperature of polystyrene. Scattered light (I-s) and fluorescence intensity (I-p) from P were measured after each annealing step to monitor the stages of composite film formation. Minimum film formation temperature, T-o, and healing temperatures, T-h, were determined. Void closure and interdiffusion stages were modeled and related activation energies were measured. From these results, it was found that the presence of NaMMT in the PS latex film only affects the minimum film formation, but does not affect the void closure and backbone motion activities.
