Chain copolymerization crosslinking

We can create crosslinks during chain growth polymerization by copolymerizing dienes with vinyl monomers. When the two vinyl functions of the diene are incorporated into separate chains, a crosslink is formed. This process is shown in Fig. 2.18. When we use a low concentration of dienes, we produce a long chain branched polymer, while high concentrations of dienes create a highly crosslinked polymer network... 

Figure 11. Scheme for crosslinking chain copolymerization x free radical site, a inter-and a intramolecular reaction. 

The formation of weak secondary valence gels occurs in poor solvents, which will not prevent all secondary valence bonds between the polymer coils by solvation. The solvation equilibrium is temperature dependent, i.e., it increases at higher temperatures. (ii) The chemical gel is a network structure (crosslinked) formed by covalent hnks between polymer chains. Chemically crosslinked materials are formed by copolymerization, chemical modification, or radiation of linear polymers. The crosslinked network will swell but not dissolve, because the covalent CTossUnks cannot be broken by any solvent and the swelhng depends on the degree of crosslinking. 

The steady structure determined by the value of Kw (Fig. 1) for the entire class of carboxylic CP obtained by precipitation copolymerization is one of the most important factors determining the possibility of reversible bonding of proteins absorbed by carboxylic CP with a high sorption capacity [16,19]. Thus, for the MA-HHTT system (Fig. 2), a complete desorption of enzyme is carried out on crosslinked copolymers characterized by low Kw values. In crosslinked structures exhibiting looser structure (Kw P 1), owing to the mobility of chain fragments of CP especially in the process of desorption, the macromolecules of sorbed protein are irreversibly captured as a result of a marked polyfunctional interaction. 

Crosslihkinq Density Distribution. Let us consider the statistical copolymerization of vinyl/divinyl monomers without chain transfer to polymer for simplicity. In this case the crosslinking density p is defined as follows. 

The synthesis of elastomers by step, chain, and ring-opening polymerizations is reviewed. These reactions are characterized as to the process variables which must be controlled to achieve the synthesis and crosslinking of an elastomer of the required structure. Both radical and ionic chain polymerizations are discussed as well as the structural variations possible through copolymerization and s tereoregularity. 

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