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Yayın Vapor-induced film formation from low-T-g particles for different solvent compositions(Elsevier Inc, 2006-05-15) Arda, Ertan; Kara, Selim; Saraç, Ayfer; Pekcan, Mehmet ÖnderThe photon transmission method was used to study latex film formation from poly(vinyl acetate) (PVAc) particles induced by two different solvents. Films with the same latex content were prepared from PVAc particles and exposed to vapor of ethanol-water and acetone-water mixtures in various compositions. Transmitted photon intensities, I-tr, from these films increased with increasing vapor exposure time. The increase in I-tr is attributed to the increase in crossing density at the polymer-polymer junction. The Prager-Tirrell model was employed to obtain the back-and-forth frequency, v, of the reptating polymer chain during film formation induced by solvent vapor. It was observed that the produced v values increase as the solvent content is increased for both solvents. Abilities of both solvents to form films were interpreted with the solubility parameters of the solvents and the PVAc.Yayın Film formation from pure and mixed latices; transient fluorescence study(Academic Press Inc Elsevier Science, 2005-11-15) Uğur, Şaziye; Pekcan, Mehmet ÖnderA fast transient fluorescence technique was used to study latex film formation induced by organic solvent vapor. Mixtures of pyrene (P)- and naphthalene (N)-labeled and/or pure naphthalene-labeled latex films were prepared separately from poly(methyl methacrylate) (PMMA) particles. Then these pure and mixed latex films were exposed to vapor of various chloroform-heptane mixtures in seven different experiments. In both films, fluorescence lifetimes from N were monitored during vapor-induced film formation. It was observed that N lifetimes decreased as the vapor exposure time is increased. A Stern-Volmer kinetic analysis was used for low quenching efficiencies to interpret the decrease in N lifetimes. A Prager-Tirrell model was employed to obtain back-and-forth frequencies, v, of reptating PMMA chains during latex film formation induced by solvent vapor. In both pure and mixed latex films, v values were found to be correlated with the chloroform content in the vapor mixture. It was observed that polymer interdiffusion obeyed a t(1/2) law during film formation.Yayın Ceramic encapsulated latex composites(Elsevier Inc, 2006-04-15) Uğur, Şaziye; Pehlivan, Esat; Tepehan, Fatma Zehra; Pekcan, Mehmet ÖnderThis work reports the encapsulation of latex particles in Al(2)O(3)-polystyrene (PS) composite films. These films were prepared from PS particles in Al(2)O(3) dispersion at room temperature in various latex contents. Composite films were annealed at elevated temperatures in 10 min time interval above the glass transition temperature (T,,) of polystyrene. Transmitted photon intensities. I(tr) were monitored after each annealing step. AFM micrographs were also used to observe the physical changes of the composite films during annealing. It was observed that latex particles are encapsulated above a critical Al(2)O(3) content of 33 wt% which corresponds to the critical occupation probability of p(c) = 0.33 at which the film obey the site-percolation model with a critical exponent of 0.45. Below pc it was seen that complete latex film formation process took place, where transparency of the film was increased by annealing.
