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Preparation and characterization of polydimethylsiloxanes with narrow molecular weight distribution

✍ Scribed by H.J. Hölle; B.R. Lehnen

Publisher
Elsevier Science
Year
1975
Tongue
English
Weight
387 KB
Volume
11
Category
Article
ISSN
0014-3057

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✦ Synopsis

The preparation of polydimethylsiloxanes (PDMS) of narrow molecular weight distribution (MWD) by anionic polymerization of hexamethyicyclotrisiloxane (D3) in an improved polymerization apparatus is described. Using (CH3)2Si(OLih as initiator and (CH3hSiCI (TMCS) as terminating agent, polymers with only methyl groups were obtained with molecular weights ranging from 2 x 103 to 2 × 10 6. Kinetic investigations were performed only so far as necessary for controlling the polymerization under the chosen experimental conditions (solvent: n-hexane, solvating agent: hexamethylphosphortriamide (HMPT), polymerization temperature: 25°). The molecular weights of the polymers were determined by light-scattering and, after calibration, by viscometry and GPC. The non-uniformities of the samples with symmetrical MWD were estimated using the 4a-method. The GPC apparatus had been calibrated with polystyrene and poly-a-methylstyrene samples of extremely small non-uniformity.

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