Cross-linking physical interactions

Keywords Aerogels Cellulose Derivatives Graft copolymers Hydrogels Physical cross-linking Supramolecular interactions... 

PZDMA. Because of the large numbers of ion pairs in PZDMA molecules and the strong electrostatic interaction between ion pairs, aggregates consisting of several pairs called multiplets could be formed, restricting the mobility of adjacent polymer chains [47]. Moreover, the PZDMA also can form a filler network, which is similar to a black carbon network. Thus, a considerable PZDMA and cross-links of NR form a relatively developed primary network (cOTitaining covalent crosslink points, ionic cross-links, physical adsorption and filler-filler joints). As a result, the fact that the 1 min-cured sample with 20 phr ZDMA show the highest G and S is a result of the developed primary network . 

A polymer gel is a network of flexible cross-linked chains. Structures of this type can be obtained by chemical or physical processes. Some gels are cross-linked chemically by covalent bonds (chemical gel), whereas other gels are cross-linked physically by weak forces, such as hydrogen bonds, van der Waals forces, or hydrophobic and ionic interactions (physical gel). Physical gelation processes are usually reversible and are called sol-gel transitions. The final gel structures and properties are sensitive to the preparation meth-... 

The physical properties of polyurethanes are derived from their molecular stmcture and deterrnined by the choice of building blocks as weU as the supramolecular stmctures caused by atomic interaction between chains. The abiHty to crystalline, the flexibiHty of the chains, and spacing of polar groups are of considerable importance, especially in linear thermoplastic materials. In rigid cross-linked systems, eg, polyurethane foams, other factors such as density determine the final properties. 

NA isolation and molecular characterization will be important to define the origin and functions of these proteins. At this time, infected cell nuclei offer the only source of these proteins, and NA have proved resistant to classic nuclear extraction methods (Yao and Jasmer, 1998). NA can be solubilized under conditions that co-extract nuclear lamins a/c and b (4 M urea, pH 8.0). Despite these similar physical properties, NA do not co-localize with lamins in the nucleoskeleton. However, both disulphide bonds and ionic interactions appear to contribute to nuclear complexes containing NA. In addition, NA can be cross-linked within host nuclei with protein cross-linking reagents. The foregoing properties represent current information available for the development of strategies to isolate and characterize these proteins and to investigate host proteins with which NA interact. 

The mechanism for cross-linking of thermosetting resins is very complex because of the relative interaction between the chemical kinetics and the changing of the physical properties [49], and it is still not perfectly understood. The literature is ubiquitous with respect to studies of cure kinetic models for these resins. Two distinct approaches are used phenomenological (macroscopic level) [2,5,50-72] and mechanistic (microscopic level) [3,73-85]. The former is related to an overall reaction (only one reaction representing the whole process), the latter to a kinetic mechanism for each elementary reaction occurring during the process. 

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