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- W2499156945 abstract "The synthesis of difunctionalized aminopropyl-terminated poly(dimethylsiloxane) via equilibrium polymerization of the cyclic tetramer in the presence of the functionalized disiloxane was demonstrated. The use of tetramethylammonium and tetrabutylphosphonium siloxanolate anionic catalysts for these reactions was studied. The reactions of the tetramethylammonium and tetrabutylphosphonium catalysts were limited to ~80 °C because of the known transience of these species at higher temperatures. The disappearance of the cyclic tetramer and disiloxane was monitored by HPLC (high-pressure liquid chromatographic) and GC (gas chromatographic) techniques, which indicated that the tetramethylammonium and tetrabutylphosphonium catalysts were much more efficient than the potassium catalyst, even when the potassium catalyst was used at much higher(e.g., 160 °C) temperatures. This behavior may be related to the higher degree of dissociation and, possibly, the enhanced solubility of the tetramethylammonium and tetrabutylphosphonium catalysts relative to the much more studied potassium catalyst. The number-average molecular weight was independent of the catalyst concentration and was influenced only by conversion and the molar ratio of the tetramer to the disiloxane. GPC (gel permeation chromatographic) characterization was also possible by derivatizing the amine to ketimine functionalities. Supercritical-fluid-fractionation studies of the functionalized siloxanes yielded samples with relatively narrow molecular weight distributions, which were compared with polysiloxane standards produced in our laboratory. The number-average molecular weights determined by titration methods and those determined by GPC experiments were in excellent agreement." @default.
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- W2499156945 date "1989-05-05" @default.
- W2499156945 modified "2023-09-27" @default.
- W2499156945 title "Synthesis and Fractionation Studies of Functionalized Organosiloxanes" @default.
- W2499156945 doi "https://doi.org/10.1021/ba-1990-0224.ch008" @default.
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