Crosslinking copolymerization

Fig. 2. Formation of various structures in radical crosslinking copolymerization of monovinyl -divinyl monomers with or without using a solvent (diluent).

Microgel Formation in Solution by Free-Radical Crosslinking Copolymerization... 

Fig. 34. Schematic picture of cyclization (a), multiple crosslinking (b), and crosslinking (c) in radical crosslinking copolymerization.

Seebach and coworkers prepared salen derivatives possessing two to eight st)ryl groups for crosslinking copolymerization with styrene [71]. The salen cores were derived from ( R,Rj-l,2-diphenylethylenediamine or 2-cyclohexane-... 

Figure 12. Network formation in chain crosslinking copolymerization (Reproduced with permission from Ref. 49. Copyright 1982 Applied Science Publishers).

The crosslinking copolymerization of unsaturated polyesters with styrene is utilized industrially for the production of surface coatings. More extensive are applications in fiber-reinforced plastics where the unsaturated polyesters are used as a matrix for inorganic and organic fibers (see Example 5-20). Areas of application are (large) parts in boats, vehicles, and sport equipment construction. 

These superabsorbents are synthesized via free radical polymerization of acrylic acid or its salts in presence of a crosslinker (crosslinking copolymerization). Initiators are commonly used, water-soluble compounds (e.g., peroxodi-sulfates, redox systems). As crosslinking comonomers bis-methacrylates or N,hT-methylenebis-(acrylamide) are mostly applied. The copolymerization can be carried out in aqueous solution (see Example 5-11 or as dispersion of aqueous drops in a hydrocarbon (inverse emulsion polymerization, see Sect. 2.2.4.2). 

The following example describes the synthesis of a superabsorbent via crosslinking copolymerization of acrylic acid (sodium salt) with A/,A/ -methylenebis(acrylamide). 

Dusek,K. Inhomogeneities induced by crosslinking in the course of crosslinking copolymerization, pp. 245-260. In Polymer networks, structure, and mechanical properties. See Ref. (260). 

Divinylbenzene (DVB) also behaves as a non-conjugated diene it can remain difunctional only upon the interruption of conjugation in the aromatic ring. This, of course, does not occur. Non-conjugated dienes are used in crosslinking copolymerizations for the preparation of insoluble three- dimensional macromolecules (especially DVB for ion-exchanger backbones) and for scientific purposes. 

Fig. 24 Experimental results for the weight-average molecular weight development during the emulsion crosslinking copolymerization of styrene (St)/divinylbenzene (DVB) and methyl methacrylate (MMA)/ethylene glycol dimethacrylate (EGDMA). Data from [323]...

Method of crosslinking Copolymerization with crosslinking monomers Crosslinking of water-soluble polymer Irradiation of radioactive ray Self-crosslinking Introduction of crystal structure... 

Despite the small r values for copolymerization of styrene and the 1,2-vinyl units of polybutadiene, it is expected at styrene conversions over 95% that crosslinking copolymerization of styrene and rubber will occur. In addition, the allylic radicals formed in initiation Reaction 3 start graft copolymers of styrene monomer and polybutadiene double bonds. The existence of allylic radicals in our system is corroborated by the work of Fischer (22). In graft copolymerization, the 1,2- configuration is preferentially incorporated into the copolymer (16, 17, 18, 19) as in Structure 6. Networks are apparently formed... 

The second approach implies that the MWD equations for a multicomponent monomer system are treated as those of a homopolymer. These ideas appeared in the literature under slightly different names but around the same period, when more researchers started studying copolymerization systems (e.g., Ballard et al. [20]). Hamielec s group formalized this approach under the name of pseudokinetic rate constants method (PKRCM) and illustrated its use for linear, branched, and crosslinked copolymerization systems [21], as well as for batch, semibatch, and continuous reactors [22], Ray s group also made use of what they referred to as apparent rate constants [23]. The group of Morbidelli used a similar idea that they termed as pseudohomopolymer approach [24]. 

The modeling of homopolymerization as well as linear and nonlinear (chain transfer to polymer and crosslinking) copolymerizations can be represented with the same polymerization scheme shown in Figure 12.1. The kinetic... 

Intramolecular cyclization vs. branching during crosslinking copolymerization... 

Phase separation during the crosslinking copolymerization in the presence of diluents... 

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