Cross-link network

Other PDMS—sihca-based hybrids have been reported (16,17) and related to the ceramer hybrids (10—12,17). Using differential scanning calorimetry, dynamic mechanical analysis, and saxs, the microstmcture of these PDMS hybrids was determined to be microphase-separated, in that the polysiUcate domains (of ca 3 nm in diameter) behave as network cross-link junctions dispersed within the PDMS oligomer-rich phase. The distance between these... 

Poly(ethylene oxide). The synthesis and subsequent hydrolysis and condensation of alkoxysilane-terniinated macromonomers have been studied (39,40). Using Si-nmr and size-exclusion chromatography (sec) the evolution of the siUcate stmctures on the alkoxysilane-terniinated poly(ethylene oxide) (PEO) macromonomers of controlled functionahty was observed. Also, the effect of vitrification upon the network cross-link density of the developing inorganic—organic hybrid using percolation and mean-field theory was considered. 

Advanced Thermoplastics Materials. Thermoplastics and linear plastics of finite molecular weight that can be fabricated into very complex stmctures by hot melt or injection mol ding are different from the thermoset materials that require cross-linking to build up infinite molecular weight to form network (cross-link) stmctures. Advances in thermoplastic engineering materials include amorphous thermoplastics, crystalline thermoplastics, Hquid crystal thermoplastics, and fluorinated thermoplastics (see Engineering plastics). 

In the most succinct sense, a hydrogel is simply a hydrophilic polymeric network cross-linked in some fashion to produce an elastic structure. Thus any technique which can be used to create a cross-linked polymer can be used to produce a hydrogel. Copolymerization/cross-linking free radical polymerizations are commonly used to produce hydrogels by reacting hydrophilic monomers with multifunctional cross-linkers. Water-soluble linear polymers of both natural and synthetic origin are cross-linked to form hydrogels in a number of ways ... 

The result is important for the discussion in Part 3. Multiplication of the v-values by RT gives the corresponding moduli. The effective modulus of the first network after removal of first network crosslinks, Gie, has been calculated for a first network modulus, G-j, of 0.75 MPa. In Figure 1, G. e is plotted against the modulus of the second network before removal of the first network cross-links, G2. It can be seen that the memory effect increases with increasing modulus or degree of cross-linking of the second network. Gx and G2 max are related to the experiment to be discussed in Part 3. 

Figure 1. Effective first network modulus, Gle, after complete removal of first network cross-links plotted against second network modulus, Gi. Calculated from the composite network theory of Flory (19J for G, — 0.75 MPa.

FIGURE 2.3 Skeletal structural formulas of a linear polymer (a) and a network (cross-linked) polymer with low cross-linking density (b) and high cross-linking density (c). 

The PEO salt complexes are generally prepared by direct interaction in solution for soluble systems or by immersion method, soaking the network cross-linked PEO in the appropriate salt solution [52-57]. Besides PEO, poly(propylene)oxide, poly(ethylene)suceinate, poly(epichlorohydrin), and polyethylene imine) have also been explored as base polymers for solid electrolytes [58]. Polyethylene imine) (PEI) is prepared by the ring-opening polymerization of 2-methyloxazoline. Solid solutions of PEI and Nal are obtained by dissolving both in acetonitrile (80 °C) followed by cooling to room temperature and solvent evaporation in vacuo. Polyethyleneimine-NaCF3S03 complexes have also been explored [59],... 

Flory.P.J. Elasticity of polymer networks cross-linked in state of strain. Trans. Faraday Soc. 56,722-743 (1960). 

Similar reversible contraction/dilation experiments under constant load were recently performed by Eisenbach on stretched poly(ethyl acrylate) networks, cross-linked however with 4,4 -dimethacryloylaminoazobenzene (0.02 mol-%). 

Polymers can be classified, based on structural shape of polymer molecules, as linear, branched, or network (cross-linked). Schematic representations are given in Fig. 1.3. 

Controlling epoxy network cross-link density by varying the reactant ratio may result in changes in other structure variables as well, which may be observed by their effects on physical properties. 

Amine light stabilizer, melamlne-acryllo copolymer degradation, 281-83 Amine-cured epoxy networks cross-link density, 166-67,177-81 structure characterization, 172-73... 

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