Polymeric Materials and Interfaces

Department of Wood Science and Forest Products, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061 Polymeric Materials and Interfaces laboratory, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061 Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061... 

Government Industrial Research Institute, 11 Industrial Products Research Institute, 205,274,382 Institute of Chemical Fibres, 245 Kyoto University, 11,488 Ministry of Agriculture, Forestry, and Fisheries, 334 Neste Oy Research Centre, 219 Polymeric Materials and Interfaces... 

Department of Chemical Engineering and Polymeric Materials and Interfaces Laboratory, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061... 

The devolatilization of a component in an internal mixer can be described by a model based on the penetration theory [27,28]. The main characteristic of this model is the separation of the bulk of material into two parts A layer periodically wiped onto the wall of the mixing chamber, and a pool of material rotating in front of the rotor flights, as shown in Figure 29.15. This flow pattern results in a constant exposure time of the interface between the material and the vapor phase in the void space of the internal mixer. Devolatilization occurs according to two different mechanisms Molecular diffusion between the fluid elements in the surface layer of the wall film and the pool, and mass transport between the rubber phase and the vapor phase due to evaporation of the volatile component. As the diffusion rate of a liquid or a gas in a polymeric matrix is rather low, the main contribution to devolatilization is based on the mass transport between the surface layer of the polymeric material and the vapor phase. 

Both in compatible and in incompatible polymer blends, the dynamics of chains at interfaces and the static interfacial structure are of very great theoretical and practical interest [354-356] adhesion of polymer layers to walls, mechanical properties of inhomogeneous blends etc. may affect the application of polymeric materials, and at the same time fundamental questions are involved. This field of research is very active, and a complete coverage of the ongoing research in this area is not at all intended rather we indicate only a few topics that are closely related to problems treated in previous sections of the present review. 

This textbook will allow an easy access into the field especially for advanced and graduate students as well as experienced researchers in natural sciences and biomedical specialists entering the field or being interested in and working at the interface between polymeric materials and biomedicine. Target study areas are bioengineering, biomaterials science, biomedical science, chemistry biophysics, polymer science, and regenerative medicine. 

This book is solely concerned with polymers in the amorphous state, that is polymer molecules in solution, the melt or that are intrinsically amorphous in the solid state by virtue of their chemical structure. We discuss surfaces and interfaces involving pure polymeric phases and interfaces between simple liquids and solids or air that are modified by an accumulation of polymeric molecules. The situation is in one sense more complicated than that for materials composed of atoms or small molecules. For these systems, as hinted at above, there is a single length scale characterising the range of forces between molecules and this molecular length scale dictates the range over which the perturbation imposed by an interface persists. For polymers there are... 

Farong Huang is a member of the Chinese Society of Composites and Director of Key Laboratory for Specially Functional Polymeric Materials and Related Technology of the Ministry of Education at ECUST. His research interests focus on the design, synthesis and chemical modification of specialty polymers, the surface, interfaces and manufacture techniques of advanced polymeric composites, and the functional polymeric materials. He is an author or coauthor of more than 200 article as well as 4 books. He has contributed to more than 30 Chinese patents. 

Patterns of ordered molecular islands surrounded by disordered molecules are common in Langmuir layers, where even in zero surface pressure molecules self-organize at the air—water interface. The difference between the two systems is that in SAMs of trichlorosilanes the island is comprised of polymerized surfactants, and therefore the mobihty of individual molecules is restricted. This lack of mobihty is probably the principal reason why SAMs of alkyltrichlorosilanes are less ordered than, for example, fatty acids on AgO, or thiols on gold. The coupling of polymerization and surface anchoring is a primary source of the reproducibihty problems. Small differences in water content and in surface Si—OH group concentration may result in a significant difference in monolayer quahty. Alkyl silanes remain, however, ideal materials for surface modification and functionalization apphcations, eg, as adhesion promoters (166—168) and boundary lubricants (169—171). 

In numerous applications of polymeric materials multilayers of films are used. This practice is found in microelectronic, aeronautical, and biomedical applications to name a few. Developing good adhesion between these layers requires interdiffusion of the molecules at the interfaces between the layers over size scales comparable to the molecular diameter (tens of nm). In addition, these interfaces are buried within the specimen. Aside from this practical aspect, interdififlision over short distances holds the key for critically evaluating current theories of polymer difllision. Theories of polymer interdiffusion predict specific shapes for the concentration profile of segments across the interface as a function of time. Interdiffiision studies on bilayered specimen comprised of a layer of polystyrene (PS) on a layer of perdeuterated (PS) d-PS, can be used as a model system that will capture the fundamental physics of the problem. Initially, the bilayer will have a sharp interface, which upon annealing will broaden with time. 

Viscoelastic polymers essentially dominate the multi-billion dollar adhesives market, therefore an understanding of their adhesion behavior is very important. Adhesion of these materials involves quite a few chemical and physical phenomena. As with elastic materials, the chemical interactions and affinities in the interface provide the fundamental link for transmission of stress between the contacting bodies. This intrinsic resistance to detachment is usually augmented several folds by dissipation processes available to the viscoelastic media. The dissipation processes can have either a thermodynamic origin such as recoiling of the stretched polymeric chains upon detachment, or a dynamic and rate-sensitive nature as in chain pull-out, chain disentanglement and deformation-related rheological losses in the bulk of materials and in the vicinity of interface. 

To investigate the interface between polymeric materials, i.e. a so-called buried interfaces, several techniques are available schematically shown in Fig. 4 and listed in Table 2. They have quite different characteristics and depth resolution depending... 

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