Microgel heterogeneous

PVCL microgels prepared via covalent binding of PEO exhibit different temperature dependence (Fig. 19). In this case, a considerable increase in the diffusion coefficient takes place above the LCST of PVCL. The sudden increase may be attributed to the shrinking of the particle, which leads to an increase in the rate of its translational diffusion and, consequently, also in the rate of diffusion of the grafts bound to the particle surface. The values of the diffusion coefficients above the LCST should be taken as apparent ones, as the measurements were complicated by the heterogeneity of the collapsed samples. 

Molecular recognition experiments were carried out with a racemic mixture of phenyl-a-mannopyranoside 2 (Fig. 2) in a heterogeneous phase as well as in a homogeneous phase depending on the solubility of the microgel in the... 

The CCA-model considers the filler network as a result of kinetically cluster-cluster-aggregation, where the size of the fractal network heterogeneity is given by a space-filling condition for the filler clusters [60,63,64,92]. We will summarize the basic assumptions of this approach and extend it by adding additional considerations as well as experimental results. Thereby, we will apply the CCA-model to rubber composites filled with carbon black as well as polymeric filler particles (microgels) of spherical shape and almost mono-disperse size distribution that allow for a better understanding of the mechanisms of rubber reinforcement. 

In the case of heterogeneous network formation, one can sometimes observe two critical gel points, the first one corresponds to the appearances of the infinite macromolecules in the form of microgel particles of colloid The second macroscopic gel point correlates with the rheological transition from a solution to the state of a gel, when the system as a whole losses the possibility to flow and is converted into a single three-dimension macromolecules. 

Fig. 4 Left. Cartoon illustration of a microgel particle, showing the heterogeneous distribution of crosslink density. Right. Corresponding radial monomer density profile (r)...

Dynamic Mechanical Spectroscopy. As pointed out above, the heterogeneous morphology, observed in the present study, implies network flaws (weak connections between the primary and secondary microgels). However, the low cyclic strains applied in dynamic mechanical tests detect only the effect of the basic network structure and not the network flaws. Therefore, as observed experimentally (, ) dynamic mechanical spectroscopy should not indicate heterogeneity in the samples. 

Previous work has shown that gels formed from cross-linked polyacrylamide (6), alginate (6), hydrolyzed starch-polyacrylonitrile (7), and a cross-linked poly(acrylic acid) (8), consist of discontinuous structures with microregions of extremely low viscosity. Such microscopic heterogeneity has been attributed to permanent or diffusing fluctuations within the gel (i) or to a structure of closely packed, swollen microgels in a continuous water phase (2, 3). 

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