Backbone composition

Table 8. Possible variations in the backbone composition of polyorganosiloxanes ...

Detailed information on the copolymerization of cyclic trifluoropropylmethyl-siloxane trimer and octamethylcyclotetrasiloxane is also very limited in the open literature26 27 . Recently, preparation of various amine terminated (dimethyl-tri-fluoropropyl,methyl)siloxane oligomers with varying molecular weights and backbone compositions has been reported 69115 ll7). Table 11 shows various properties of the oligomers produced as a function of composition. These types of modification play very important roles in determining the solubility characteristics and hence the compatibility of resultant polysiloxanes with other conventional organic monomers... 

Resultant multiphase copolymers displayed properties ranging from soluble thermoplastic elastomers and engineering polymers to intractable thermosets, depending on the backbone composition and orientation, and especially the level of ODA incorpora-... 

During the reactions backbone compositions of the siloxane oligomers employed have been varied between all dimethylsiloxane to 50/50 by weight dimethylsiloxane/ diphenylsiloxane and dimethylsiloxane/(trifluoropropyl,methyl)siloxane. Block molecular weights of the siloxane oligomers have been kept between 3,000-5,000 g/mole, whereas the overall level of siloxane incorporation into the copolymers have been varied between 0 and 60 weight percent. In most cases the ratio of terephthalate to... 

After these preliminary studies, McGrath and co-workers have used ethylpiperazine terminated siloxane oligomers with varying molecular weights and backbone compositions throughout their studies 69 114,11S). Modifications of epoxy resins with siloxane oligomers were performed in two steps as depicted in Reaction Scheme XXIII. 

As expected, the terminal functional groups mainly determine the reactivity of these siloxane oligomers towards other reactants. The variations in the backbone composition have critical effects on the glass transition temperature, solubility parameter, thermal stability and surface behavior of the resulting oligomers(12,13). 

Roberts, R. W., and D. M. Crothers, Stability and properties of double and triple helices Dramatic effects of RNA or DNA backbone composition. Science 258 1463-1466,... 

Characterization of the poly(macromonomers) prepared by homopolymerization has proved that they provide a useful probe for discussing the structural characteristics of the star and brush polymers. Graft copolymers have been and will be a most important area of application of the macromonomer technique since a variety of multi-phased and microphase-separated systems can easily be designed just by an appropriate combination of a macromonomer and a conventional monomer. In general, however, characterization of their absolute MW, branch/backbone composition as well as their distributions remain to be studied in more detail. 

In contrast to cellulases, the hemicellulases encompass a much broader suite of activities. In addition to analogue versions of endo-, exo-, and glycosidase cellulase activities, multiple debranching activities are needed to handle the high complexity of the heterogeneous hemicelluloses (Table 33.3). The varied backbone composition of hemicelluloses also adds complexity. Xylans, xyloglucans, man-nans, and numerous other minor polysaccharide chains form the backbone for different hemicelluloses. 

Eqs. (8) and (11) are important because they predict a direct relationship between a failure property and network structure. If the Equations hold, then the following experimental results would be expected (1) l o for a series of networks of the same chemical composition will reflect only differences in crosslinking, and (2) 2 /n for chemically different networks of the same will reflect the differences in their backbone composition. Experiments such as these have been performed on a variety of elastomers e.g., polyurethanes,... 

Extending this 1,3-butadiene analogy to an all BN backbone composition, Power reports the synthesis of diboron species R(R2N)BB(NR2)R. a structure determination for a compound... 

The inhibition by PGA-based glycopolypeptides was compared with that by recombinantly synthesized glycopolypeptides in order to assess the effects of backbone composition on inhibitory potency. In spite of their similar molecular... 

EMA omo was also fractionated with F-22 to confirm that chlorodifluoromethane is too good a solvent for this copolymer the results are given in table 9.9. Using very small pressure increments, fourteen fractions were obtained with modest polydispersities. No discernible trend was detected with the backbone composition of the fractions indicating that F-22 was only able to discriminate on the basis of molecular weight and not on the basis of... 

Comb polymer with a poly(methacrylic acid) backbone and polyacrylonitrile side chains Comb polymer with unspecified backbone composition and statistical ethylene/vinyl chloride copolymer side chains... 

Comb poiymer with a poiy(methacryiic acid) backbone and poiyacryionitriie side chains Comb poiymer with unspecified backbone composition and statisticai ethyiene/vinyi chioride copoiymer side chains... 

Backbone Composition Because the side chains tether one end to... 

Solid and void fraction Pore size Backbone entity size Pore connectivity Backbone connectivity [nterfacial characteristics Backbone composition and structure... 

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