Functional groups, chemical cross-linking

As composite membrane performances are mainly determined by the film structure (i.e., pore dimension, thickness, roughness, and hydrophilicity) and its chemical properties (i.e., cross-linking, functional groups, and bonds), fundamental understanding on the effects of different monomers on composite membrane properties is necessary in order to tailor the desired membrane structure and separation performance. Table 2.4 shows the organic structures of commonly used and newly reported monomers in the thin-fihn... 

The free radicals first react with the chemical inhibitor which has previously been added to the resin, since the inhibitor material must be chemically dissipated before any reaction between free radicals and the C=C double bonds can proceed [5]. Apparently, the free radicals serve to open the double bonds in the polyester linear chain to set in motion that portion of the polymerization process designated as initiation. Either the opened double bonds react with the vinyl groups of the monomer, or the free radicals serve to also open (add to) these latter unsaturated C=C bonds, permitting them to perform their cross-linking function, uniting the polyester chains into a three-dimensional network. There is further evidence that free radicals may also, to some degree, react with the unsaturated monomer to form various products of decomposition [5]. 

Preparation of chemically cross-linked fibers Chemical cross-linking was achieved by extrusion of solutions of E- and K- pairs of polymers at equal concentrations of functional groups into a saturated solution at 50 C of water soluble carbodiimide (EDC, l-(3-dimethy-laminopropyl)-3-ethylcarbodiimide) to form amide bonds between the carboxyl of glutamic acid (E) residues and the e-amino groups of lysine (K) residues. When in an adequately hydrophobic elastic protein-based polymer, the charged carboxylate and amino functions experience a driving force for ion-pairing. The force... 

Si-C bonded silicone polyethers with only one or two different OH functional polyethers are used for rigid foams. They typically have a relatively high degree of modification (Fig. 6a, m/ < 7), which results in somewhat short polydimethylsiloxane segments between the pendant polyether groups. The content of closed cells is increased by chemical cross-linking of the OH functional polymers. 

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