Surface polymer liquids

In a series of investigations of the cracking of alkanes and alkenes on Y zeolites (74,75), the effect of coke formation on the conversion was examined. The coke that formed was found to exhibit considerable hydride transfer activity. For some time, this activity can compensate for the deactivating effect of the coke. On the basis of dimerization and cracking experiments with labeled 1-butene on zeolite Y (76), it is known that substantial amounts of alkanes are formed, which are saturated by hydride transfer from surface polymers. In both liquid and solid acid catalysts, hydride transfer from isoalkanes larger than... 

Free surfaces of polymer liquids and melts attempt to minimize their free energy (and therefore surface tension) by placing those components of the molecule... 

Due to the chain architecture and the large size of the macromolecules, the wetting behaviour of polymer liquids can be different from that of simple liquids. The effect becomes particularly strong when the dimension of the liquid phase, e.g. film thickness and droplet diameter, approaches the dimension of the polymer coil. In addition to the spreading coefficient and the surface pressure effects, entropic elasticity of the polymer chain provides a strong contribution to the free energy for a constant volume V0=Ad ... 

The outlined problems correspond to the most typical system where three phases, e.g. liquid, gas and solid, are brought in contact. Additional wetting geometries can occur when the liquid phase consists of two subphases, e.g. mixture of incompatible polymer liquids, and/or the substrate surface exhibits variations in chemical composition. In these cases, the interfacial interactions will strongly interfere with the phase separation inside the film. Laterally ordered polymer films might be formed due to the preferential wetting of the patterned substrate by one of the liquid phases. 

Tn recent years, developing interests in surface energetics and adhesion of liquid-like polymers, or polymer liquids, have prompted both theoretical and experimental work on surface tension. Unlike low molecular weight liquids, polymer liquids have not been extensively studied. Bondi and Simkin (1) mentioned surface tension in their study on high molecular weight liquids. Roe (28) applied both the cell theory of polymer liquids and the hole theory of surface tension of simple liquids to develop an approximate theory of surface tensions of polymer liquids. His approach has met some degree of success. Notably, both Bondi s and Roes work are somewhat related to the cell theory introduced by Prigogine and... 

INTERFACIAL TENSION BETWEEN POLYMER SURFACE AND LIQUID WATER... 

Sample No. Top Plasma Polymer Adhesion of Parylene C to M etal Liquid-contacting Surface Polymer contacting M etal... 

One possible explanation for these results and the observation that TCB did not wet the bare germanium disc is that it is the wetting properties of the molten polymer that are important and not that of TCB. The temperature of the surface of all discs used exceeded the melting points of all the polymers investigated for the entire experiment. Furthermore, with the evaporation conditions used for all experiments except the last one mentioned, evaporation of solvent was instantaneous when the droplets reached the disc surface. No liquid accumulation was evident. 

In region FG the polymer is completely amorphous and the properties of the polymer-solute solution can be investigated. Care must be taken to ensure that any contribution from surface adsoption is taken into account. Usually for thick polymer films contributions from surface adsorption will be small. For noncrystalline polymers, liquid-like behavior is observed from point C onwards. The location of point C on the temperature axis depends both on the polymer-solute system considered and on experimental conditions, film thickness and flow rate. For most polymers, equilibrium bulk sorption is achieved at temperatures in excess of about Tg + 50°. 

Kidowaki, K., Fujiwara, T., and Ichimura, K. Surface-assisted photomanipulation of orientation of a polymer liquid crystal. Chem. Lett., 643 (1999). 

Kago, K., Fiirst, M., Matsuoka, H., Yamaoka, H., and Seki, T. Nanostructure of photo-chromic polymer/liquid crystal hybrid monolayer on water surface observed by in-situ x-ray rellectometry. Langmuir, 15, 2237 (1999). 

For polymer liquids, the gradient approximation in conjunction with the lattice fluid model has been used to calculate surface tensions [24,25]. The Cahn-Hilliard relation for surface tension o, in terms of reduced variables, can be expressed as... 

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