Chain crosslinking

Once cured, PDMS networks are essentially made of dimethylsiloxane polymeric chains crosslinked with organic linkages. The general and inherent molecular properties of the PDMS polymers are therefore conferred to the silicone network. Low surface energy and flexibility of siloxane segments are two inherent properties very useful in adhesion technology. 

Kloosterboer, J. G. Network Formation by Chain Crosslinking Photopolymerization and its Applications in Electronics. Vol. 84, pp. 1 —62. 

If we were to have an isolated polymer chain with a single nuclear spin attached to each segment (the marked chain) crosslinked into an unmarked network, the second moment of the NMR line of that spin species would carry information relating to the separation of chain segments, and to their relative orientation with respect to the field direction. If the network were to be subjected to a bulk deformation, these geometrical parameters would be altered, and hence we would expect a corresponding change in the value of the experimentally measured... 

Chain crosslinking, causing increase in molecular weight. 

Figure 5.7 Calculated dependence of the weight-average degree of polymerization of molecules, (P)w, and hard clusters, (Pc)w, on conversion in a stoichiometric Adh) + B2(h) + B2(s) system (h - hard, s - soft). The system corresponds to a mixture of short and hard chains crosslinked with a tetrafunctional crosslinking agent...

Dusek, K., Network formation by chain crosslinking (co)polymerization, in Haward, R. N. (ed.), Development in Polymerization, Vol. 3, Applied Science Publ., Barking, 1982, pp. 143-206. 

Chain crosslinking (co)polymerlzatlon involving a polyvinyl monomer represents a process where the application of the branching theory based on a (perturbed) tree-like model falls due to strong cycllza-tion. Strong cyclization is characteristic for these systems not because of a special configuration of the monomers but because of... 

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

Photopolymerization and photocrosslinking processes have been in use for many years in the electronics industry, for example in the making of printed circuit boards and in the fixation of color dots in TV tubes. More recent applications of light-induced chain crosslinking polymerization processes are the replication of optical discs (1,2) of aspherical lenses (3,4) and the in-line coating of optical fibers (5,6). 

The work that follows pertains primarily to actin networks. Many proteins within a cell are known to associate with actin. Among these are molecules which can initiate or terminate polymerization, intercalate with and cut chains, crosslink or bundle filaments, or induce network contraction (i.e., myosin) (A,11,12). The central concern of this paper is an exploration of the way that such molecular species interact to form complex networks. Ultimately we wish to elucidate the biophysical linkages between molecular properties and cellular function (like locomotion and shape differentiation) in which cytoskeletal structures are essential attributes. Here, however, we examine the iri vitro formation of cytoplasmic gels, with an emphasis on delineating quantitative assays for network constituents. Specific attention is given to gel volume assays, determinations of gelation times, and elasticity measurements. 

Such a network can be described as a series of spiral silicon-oxygen chains crosslinked with each other by oxygen bonds. If some of the oxygen aLoms are replaced wiLh organic snbsLiuients. a linear polymer will result ... 

How do we take into account its eventual internal rotations How do we distinguish between tetrafunctional (four elastically active chains) and trifunctional (three elastically active chains and one dangling chain) crosslinks ... 

Since the crosslinking density a is the probability of any unit to be cross-linked, the number of additional crosslinked units on an, v-mcric chain, crosslinked to the first chain, is expected to be equal to a. multiplied by the number of remaining crosslinkable groups (.v— 1). Thus, the expected number of additional chains crosslinked to the. v-meric chain, which is crosslinked to the first randomly chosen chain, is a(s— 1). Averaging over all chain sizes will give the average expectance of additional chains v. 

A more stable, asbestos-like phase (/3-S03) has infinite helical chains of linked S04 tetrahedra (12-XXVI), and the most stable form, a-S03, which also has an asbestos-like appearance, presumably has similar chains crosslinked into layers. 

The acetates, unlike the acetates of transition metals like Cr , Fe ", and Ru , do not adopt oxo-centred structures with M3O cores. Instead, [Ln(OAc)3.1.5(H20)] (Ln = La-Pr) have structures with acetate-bridged chains crosslinked by further acetate bridges [Ln(OAc)3. (H2O)] (Ln = Ce-Pr) have one-dimensional polymeric structures with acetate bridges and [Ln(OAc)3.4H20)] (Ln = Sm-Lu) are acetate-bridged dimers. 

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