Polymer networks heterogeneity

Cooperative diffusion of transient polymer networks, heterogeneity mode related to polymer self-diffusion in diblock copolymers, entanglement mode, chain reptation, viscoelastic relaxation, diffusion of clusters Viscoelastic relaxation, a- and 3-relaxation... 

This is a theoretical study on the entanglement architecture and mechanical properties of an ideal two-component interpenetrating polymer network (IPN) composed of flexible chains (Fig. la). In this system molecular interaction between different polymer species is accomplished by the simultaneous or sequential polymerization of the polymeric precursors [1 ]. Chains which are thermodynamically incompatible are permanently interlocked in a composite network due to the presence of chemical crosslinks. The network structure is thus reinforced by chain entanglements trapped between permanent junctions [2,3]. It is evident that, entanglements between identical chains lie further apart in an IPN than in a one-component network (Fig. lb) and entanglements associating heterogeneous polymers are formed in between homopolymer junctions. In the present study the density of the various interchain associations in the composite network is evaluated as a function of the properties of the pure network components. This information is used to estimate the equilibrium rubber elasticity modulus of the IPN. 

Surface interactions between water and polymer networks have a profound effect on the water structure. The properties of water in these and other heterogeneous systems are sensitive to the size of the network pores and have been described by the two-phase model which assumes partition of the water between the "bulk and the "bound water phases" Evidence for this partition has been obtained in several proton NMR studies and also in ESR studies of paramagnetic probes in zeolites, silica gels and in water containing polymers. ... 

When entrapment methods are being used for heterogenization, the size of the metal complex is more important than the specific adsorptive interaction. There are two different preparation strategies. The first is based on building up catalysts in well-defined cages of porous supports. This approach is also called the ship in a bottle method [29]. The other approach is to build up a polymer network around a preformed catalyst. 

In the case under consideration different physical structures were realized due to the formation of the polymer network in the surface layers the filler surface, as usually happens in filled systems. As is known79, this induces considerable changes in the structure of the material. It is also possible that in these conditions a more defective network structure is formed. These results show that even the purely physical factors influencing the formation of the polymer network in the interface lead to such changes in the relaxation behavior and fractional free-volume that they cannot be described within the framework of the concept of the iso-free-volume state. It is of great importance that such a model has been devised for a polymer system that is heterogeneous yet chemically identical. 

TOWARDS PHTHALOCYANINE NETWORK POLYMERS FOR HETEROGENEOUS CATALYSIS... 

Towards Phthalocyanine Network Polymers for Heterogeneous Catalysis... 

Towards Phthalocyanine Network Polymers for Heterogeneous Catalysis 214 Neil B. McKeown, Hong Li and Saad Makhseed... 

Binding sites are heterogeneous (polyclonal rather than monoclonal as in enzymes and monoclonal antibodies) as a consequence of the statistical nature of the polymer network forming process, leading to undesirable band broadening in chromatographic separations and to a distribution of different activities of catalytic sites [89]. 

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