Byung Ghyl Min

Spreading characteristics of thin liquid films of perfluoropolyalkylethers on solid surfaces. Effects of chain-end functionality and humidity

Spreading characteristics of thin liquid films of perfluoropolyalkyl ethers (PFPE) on silica surfaces and thermally bonded PFPE surfaces have been measured by scanning microellipsometer as function of molecular weight, chain-end functionality, and humidity. The effects of molecular weight are much smaller than those of chain-end functionality. Changes in spreading profiles with time show that interactions of chain-end groups with solid surfaces have dramatic effects on the structure and mobility of thin polymer films on solid surfaces. Wetting autophobicity is clearly manifested by PFPEs with functional chain-end groups on silica surfaces.

Surface diffusion of thin perfluoropolyalkylether films

The spreading characteristics of thin polymeric liquid films of perfluoropolyalkylethers (PFPEs) Fomblin Z15 and Fomblin Zdol (hydroxyl terminated PFPE) on silica surfaces have been measured by scanning microellipsometry (SME). We estimated the surface diffusion coefficients and propose a modified diffusion equation to interpret the spreading phenomenon from film thickness profiles measured with SME. We investigated the spreading of Z15 as a function of binary blend ratio of monodisperse Z15 fractions and found that the surface diffusion coefficients of the blends do not obey a simple linear mixing rule. A summary of thin PFPE film spreading characteristics as a function of molecular weight, film thickness, chain‐end functionality, temperature, and humidity is presented.

Surface diffusion and flow activation energies of perfluoropolyalkylether

Surface diffusion of perfluoropolyalkylether (PFPE) Fomblin Z15 and Fomblin Zdol (hydroxyl terminated PFPE) on silicon wafers was investigated over the temperature range of 25 to 50°C using scanning microellipsometry. Zdol exhibits a much lower mobility and a distinctly different thickness profile as compared to Z15. The activation energy for surface diffusion of Zdol is higher than that of Z15, reflecting the stronger affinity of its hydroxyl end groups for the substrate. The viscosity flow activation energy Eη*is compared with that of surface diffusion Ed*yielding Ed*≈ Eη*for Z15, and Ed*≈ 1.5Eη*for Z

Miscibility of poly(ether imide)/poly(ethylene terephthalate) blends

SummaryMiscibility of blends of poly(ether imide) (PEI) and poly(ethylene terephthalate) (PET) were studied by differential scanning calorimetry (DSC). Single and composition-dependent Tgs are observed over the entire composition range, indicating that the blends are miscible in the amorphous region. The overall crystallization rate of PET in the blends decreased with increasing the PEI content. The interaction energy density B, which was calculated from the melting point depression of the blends using Nishi-Wang equation, was-5.5 cal/cm3.