Backbone composition, siloxane oligomers

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... 

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. 

Synthesis and characterization of well-defined, a,w-terminated difunctional siloxane oligomers are discussed. Detailed procedures on the preparation of primary amine- and hydroxy-terminated oligomers are given. Control of the average molecular weight (Mn) and also the possible variations in the backbone structure and composition are explained. The effect of these variations on the physical, thermal and chemical properties of the resulting materials are discussed. Characterization of these oligomers by FT-IR, NMR and UV spectroscopy, potentiometric titration and DSC are summarized. 

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). 

---