Trapping of Cyclics

It was also found that the diluents added after the end-linking were more easily removed, possibly because they were less entangled with the network structure, and this could correspond to differences in diluent chain conformations. Such comparisons can thus provide valuable information on the arrangements and transport of chains as constrained within complex network structures [20]. 

Some of these data can also be used to estimate values of the diffusion coefficient D, either in sorption or in extraction [191, 192], Of particular interest are differences in values obtained on these linear chains and the corresponding cyclics, as described in Section 9.3.3. 

The cyclic diluents can also be sorbed into the networks after the end-linking process [191] or they can be present during the process [193-195]. In the latter case, some are permanently trapped as will be described below, making difficult the calculation of diffusion coefficients from the extraction data. In the former case, however, D is readily calculable. For both the cyclic and linear chains, D was found to decrease with increase in Afd, and with decrease in Mc, as expected. The cyclics were found to have values of D larger than those for the linear chains, presumably because their greater compactness facilitates their transport through the network structure. 

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Figure 4.12 Sketch of the trapping of cyclics during the end-linking preparation of a network.292 Reproduced by permission of the American Chemical Society.

Scheme 15 Mechanism for the DIB/D mediated decarboxylation and trapping of cyclic amino acids...

Figure 9. Trapping of cyclic molecules during end-linking preparation of a network. (Reproduced from reference 47. Copyright 1987 American Chemical...

Rolf D, Benneck JA, Gray GR (1983) Reductive cleavage of glycosides. Stereochemistry of trapping of cyclic oxonium ions. J Carbohydr Chem 2 373-383... 

TRAPPING OF CYCLIC OLIGOMERS WITHIN NETWORK STRUCTURES... 

Clarson, S. J. Mark, J. E. Semiyen, J. A., Studies of Cyclic and Linear Poly(dimethylsiloxanes) 24. Topological Trapping of Cyclic Polymers into Unimodal and Bimodal Model Network Structures. Polym. Comm. 1987,28, 151-153. 

DeBolt, L. C. Mark, J. E., Models for the Trapping of Cyclic Poly(dimethylsiloxane) (PDMS) Chains in PDMS Networks. Macromolecules 1987,20,2369-2374. 

Huang, W. Frisch, H. L. Hua, Y. Semiyen, J. A., A Study of the Properties and Topological Trapping of Cyclic Poly(dimethylsiloxane) in Poly(2,6-dimethyl-1,4-phenylene oxide) Networks. J. Polym. Set, Part A Polym. Chem. 1990,... 

Galiatsatos, V. Eichinger, B. E., An Interpretation of the Topological Trapping of Cyclic Poly(dimethylsiloxane) in PDMS Network Structures. Polym. 

Clarson, S.J.,Mark, J.E., and Semiyen, J.A. (1986) Studies of cyclic and linear poly(dimethylsiloxanes) Effect of ring size on the trapping of cyclic polymers into network structures. Polymer Communications, 27,244-245. 

Trapping of cyclics present during the end linking of linear-chains into network structures. Polymer Communications, 26,53-55. 

Huang, W., Frisch, H.L., Hua, Y., and Semiyen, J.A. (1990) A study of the properties and topological trapping of cyclic poly(dimethylsiloxane) in poly(2,6-dimethyl-l,4-phenylene oxide) networks. Journal of Polymer Science Part A-Polymer Chemistry, 28,1807—1812. 

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