Entangled gels

Further, reptation theory asserts26) that the molecular-weight dependence of the diffusion coefficient in an entangled gel should have the form... 

Proteins cannot, however, pass easily through the basement membrane, which is an entangled gel of proteins and proteoglycans protein permeability is low because of the fine mesh within the basement membrane gel and because of... 

The situation is less clear in a 0 solvent where two elastic moduli have been defined an osmotic modulus Eq = 77 and a gel shear modulus due to topological entanglements gel If we use the gel shear modulus, as seems reasonable, in the Maxwell equation, we obtain... 

This mild hydrolysis retained the high aspect ratio of the fibrils, giving a highly entangled gel-network in aqueous suspension. Another method was presented by Saito and coworkers [33], who used TEMPO-mediated oxidation (Section 8.5.4.1) of never-dried pulp before homogenization. This treatment rendered the microfibril... 

The alcohol swells the poly (ethyl methacrylate) beads, rapidly promoting diffusion of the plasticizer into the polymer. As a result of the polymer-chain entanglement, a gel is formed. The conditioner is applied to the denture and provides a cushioning effect alcohol and plasticizer are slowly leached out, and the material becomes rigid. To ensure resiliency, the conditioner must be replaced after a few days. Some materials exhibit high flow over a short period compared with others with low initial flow the latter remain active longer. 

The solidity of gel electrolytes results from chain entanglements. At high temperatures they flow like liquids, but on cooling they show a small increase in the shear modulus at temperatures well above T. This is the liquid-to-rubber transition. The values of shear modulus and viscosity for rubbery solids are considerably lower than those for glass forming liquids at an equivalent structural relaxation time. The local or microscopic viscosity relaxation time of the rubbery material, which is reflected in the 7], obeys a VTF equation with a pre-exponential factor equivalent to that for small-molecule liquids. Above the liquid-to-rubber transition, the VTF equation is also obeyed but the pre-exponential term for viscosity is much larger than is typical for small-molecule liquids and is dependent on the polymer molecular weight. 

Figure 6. Schematic representation of the micro- and nanoscale morphology of nanoclustered metal catalysts supported on gel-type (a) and macroreticular (b) resins [13]. The nanoclusters are represented as black spots. Level 1 is the representation of the dry materials. Level 2 is the representation of the microporous swollen materials at the same linear scale swelling involves the whole mass of the catalyst supported on the gel-type resin (2a) and the macropore walls in the catalyst supported on macroreticular resin (2b). The metal nanoclusters can be dispersed only in the swollen fractions of the supports, hence their distribution throughout the polymeric mass can be homogeneous in the gel-type supports, but not in the macroreticular ones (3a,b). In both cases, the metal nanoclusters are entangled into the polymeric framework and their nano-environment is similar in both cases, as shown in level 4.

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