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Yayın Reversible film formation from PS doped PNIPAM particles in various compositions(John Wiley & Sons Inc, 2008-02) Uğur, Şaziye; Yargı, Önder; Pekcan, Mehmet ÖnderFilm formation from polystyrene (PS) doped poly(N-isopropylacrylamide) (PNIPAM) particles was studied using photon transmission technique. The transmitted light intensity, Itr, was monitored during film formation process. Films were prepared by mixing PS and PNIPAM particles in various compositions ranging from 5 to 50 %. Samples were separately heated and cooled in constant rate at temperatures ranging from 10 to 100 C. The increase and decrease in Itr during heating-cooling cycles were explained by void closure and void reconstruction processes. The corresponding activation energies were measured during the reversible film formation process. Percolation model was used to interpret the distribution of PS particles in PNIPAM lattice.Yayın Small molecule desorption from a swelling polymeric glass in polymer solution: Energy transfer method(Elsevier Science Sa, 2005-07-15) Uğur, Şaziye; Pekcan, Mehmet ÖnderDirect energy transfer (DET) method conjunction with fast transient fluorescence (FTRF) technique were used to study small molecule desorption from a swelling poly(methyl methacrylate) (PMMA) glass in polymer solution, which is consist of naphthalene (N)-labeled PMMA chains in chlorofrom-heptane mixture. Desorption coefficients, D-d of pyrene (P) desorbing from the swelling PMMA glass prior to dissolution were measured and found to be 8.3 x 10(-8) and 1.3 x 10(-5) cm(2) s(-1) in short and long time regions, respectively.Yayın Size-dependent self-organization of colloidal particles on chemically patterned surfaces(SP Zhejiang University Press, 2006-04-14) Karakurt, İsmail; Leiderer, Paul; Boneberg, JohannesA study of the self-organization of colloidal particles during the evaporation of particle solutions on chemically patterned surfaces is presented. On a surface with hydrophilic and hydrophobic regions, colloidal particles form compact structures on the hydrophilic sites. When a colloidal solution containing a mixture of particles with a variation in size is used, the number density of each type of particle deposited on the hydrophilic islands after evaporation decreases with increasing particle size. This makes it possible to produce a concentration gradient of the particles on islands of different sizes. It is shown that this technique could allow for particle separation.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.
