Crystallization and melting behavior of poly(ethylene oxide)/poly(n-butyl methacrylate) blends

Lateral diffusion of single poly(ethylene oxide) chains on the surfaces of glassy and molten polymer films

Fluorescence correlation spectroscopy was used to show that the temperature-dependent diffusion coefficient of poly(ethylene oxide) (PEO) adsorbed on polystyrene and different poly(alkyl methacrylate) (PAMA) films in aqueous solution exhibited a maximum close to (but below) the surface glass transition temperature, T_gs, of the film. This elevated diffusion was observed over a small range of temperatures below T_gs for these surfaces, and at other temperatures, the diffusion was similar to that on silicon, although the diffusion coefficient for PEO on polystyrene at temperatures above T_gs did not completely decrease to that on silicon, in contrast to the PAMA surfaces. It is concluded that the enhanced surface mobility of the films near the surface glass transition temperature induces conformational changes in the adsorbed PEO. The origin of this narrow and dramatic increase in diffusion coefficient is not clear, but it is proposed that it is caused by a coupling of a dominant capillary mode in the liquid surface layer with the polymer. Friction force microscopy experiments also demonstrate an unexpected increase in friction at the same temperature as the increase in diffusion coefficient.

ATR-FTIR studies on ion interaction of lithium perchlorate in polyacrylate/poly(ethylene oxide) blends

The interaction behaviours between components of polyacrylate (PAc)/poly(ethylene oxide) (PEO) and lithium perchlorate (LiClO(4)) were investigated in detail by Attenuated Total Reflectance (ATR)-Fourier Transformed Infrared (FTIR) spectroscopy. Solution cast films of the PAc/PEO and PAc/PEO/LiClO(4) were examined. No obvious shifting of the characteristic ether and ester group stretching modes of PEO and PAc was observed, indicating incompatibility of the binary PAc/PEO blend. The spectroscopic studies on the PAc/PEO/LiClO(4) blends reveal that Li(+) ions coordinate individually to the polymer components at the ether oxygen of PEO and the C-O of the ester group of PAc. Frequency changes observed on the nu(C-O-C) and omega(CH(2)) of PEO confirm the coordination between PEO and Li(+) ions resulting in crystallinity suppression of PEO. The absence of experimental evidence on the formation of PEO-Li(+)-PAc complexes suggests that LiClO(4) does not enhance the compatibility of PAc/PEO blend.

Determination of the minimum allowable operating temperature of stationary phases in capillary columns by inverse gas chromatography

A method was developed to determine the minimum allowable operating temperature (MiAOT) of wall coated open tubular capillary columns. Two polyethylene glycol and fourteen polysiloxanes phases with different side groups (methyl, phenyl, cyanopropyl, trifluoropropyl, n-octyl) and backbone stiffening units (tetramethyl-p-silphenylene, tetramethyl-p,p'-sildiphenylene ether, carborane) were investigated by inverse gas chromatography. A sigmoidal profile of temperature versus column efficiency was found for almost all phases, as the column efficiency increased with temperature. The MiAOT was defined as that temperature where the column efficiency is half of its original value at elevated temperatures. It was found that the MiAOT of a stationary phase is approx. 60 K higher than its glass transition temperature.