The surface of a simple polymer melt

Everyone is aware of one of the curious properties possessed by the surfaces of fluids the skin on the surface of water that allows one to float a needle on the surface of pure water and which is used by insects to walk across the surface of ponds. This effect, termed surface tension, is a direct manifestation of the cohesive forces that hold liquids together. Polymer melts are no different from other, simpler liquids they too exhibit surface tension and to understand and predict this surface tension we need to understand the way in which interatomic forces lead to cohesion in polymers. 

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The surface of a simple polymer melt Vapour Phase... 

Introducing fillers in the melt of a binary polymer mixture leads to the following consequences. The main effect is a selective adsorption of one of the components at the interface with the solid. Above the critical point in the phase diagram (for the systems with UCST) polymer melt is a solution of one component into another. The thermodynamic interaction parameter Xab depends on temperature and melt composition. The interaction of each component with the surface is characterized by the thermodynamic parameter of interaction between one of the components and the surface, Xsa or Xsb-In such a system, selective adsorption proceeds, depending on the relation between Xsa tid Xsb- The selectivity of the interaction of the polymer mixture components with the solid plays an important role in the thermodynamic behavior of a filled polymer melt. Let us consider some simple thermodynamic... 

Principles and Characteristics Laser ablation is conceptually very simple, but mechanistically complicated. The process involves coupling of the photon energy of a laser pulse (typically about 20-30 ns wide, with an energy of 1-10 Jcm ) into the surface of a solid, resulting in evaporation and ejection of various species from the surface (the so-called plume ) within 10 to 10 s. The first experiments were carried out in 1962 [32]. When focused to a small area, a laser beam provides enormous power densities and electromagnetic fields. The plume , presumably a plasma, is accompanied by shock waves and electrical breakdown. The ejected material may eventually be deposited as a thin film. It is possible, by suitable selection of laser power and focus, to ablate a range of plastic materials in a controlled manner. For some matrices the polymer melts and diffuses away from the centre of the ablation site, leading to the forma-... 

A tenet of textbook continuum fluid dynamics is the no-slip boundary condition, which means that the ensemble average of the velocity of fluid molecules directly at the surface of a solid is the same as the velocity of the solid. A possible slip was discussed only in the mainstream literature for complex liquids, for example, polymer melts [659,660]. Recent experiments, however, indicated that simple liquids might also slip past smooth surfaces [661-666]. 

To establish the molecular thermodynamic model for uniform systems based on concepts from statistical mechanics, an effective method by combining statistical mechanics and molecular simulation has been recommended (Hu and Liu, 2006). Here, the role of molecular simulation is not limited to be a standard to test the reliability of models. More directly, a few simulation results are used to determine the analytical form and the corresponding coefficients of the models. It retains the rigor of statistical mechanics, while mathematical difficulties are avoided by using simulation results. The method is characterized by two steps (1) based on a statistical-mechanical derivation, an analytical expression is obtained first. The expression may contain unknown functions or coefficients because of mathematical difficulty or sometimes because of the introduced simplifications. (2) The form of the unknown functions or unknown coefficients is then determined by simulation results. For the adsorption of polymers at interfaces, simulation was used to test the validity of the weighting function of the WDA in DFT. For the meso-structure of a diblock copolymer melt confined in curved surfaces, we found from MC simulation that some more complex structures exist. From the information provided by simulation, these complex structures were approximated as a combination of simple structures. Then, the Helmholtz energy of these complex structures can be calculated by summing those of the different simple structures. 

Consider the simple melting failure of an adhesive joint as shown in Fig. 7.3. The joint was made by taking a plate of smooth glass, placing a large drop of water upon it, then laying a strip of polyethylene polymer onto the surface of the... 

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