Dimethyl-1,4-silphenylene

The second calculation is more involved. The only values of Co listed in Table 2 that are relatively free of error in setting W = 0 are those for poly(dimethyl siloxane) and poly(tetramethyl-p-silphenylene silo-xane) since for these polymers Tq 0 and the modified Vogel expression reduces to the simpler Vogel equation. Unfortunately, these materials are also studied far from their T, a and T,... 

Besides poly(siloxanes), a few other silicone containing polymers have been synthesized. One such polymer is poly(dimethy-1,4-silphenylene). Thermal decomposition of this polymer at 400° C in argon [3] generates methane, dimethylsilane, benzene, dimethylphenylsilane, HSi(CH3)2-C6H4-SiH(CH3)2, H(Si(CH3)2-C6H4)2-H, dimethyl-diphenylsilane, and C8H4-(Si(CH3)2-C6H4)2H. 

Cyanopropylphenyldimethylsiloxane(50% cyanopropylphenyl and 50% dimethyl) 3-cyanopropyl-silphenylene co-polymer (equivalent to 70% dicyanopropyl) 40 230 290... 

Silphenylene-Siloxane Copolymers.—The thermal properties vctsus structure for poly(tetramethyl-p-silphenylensesiloxane) and (tetramethyl-p-silphenylene/di-methylsiloxane) block copolymers have been compared. The homopolymer has a m.p. of 160°C, heat of fusion of 54.4 J/g and Tg of —20°C. The Tg of the copolymer varies monotonically with inojeased dimethylsiloxane content, from — 20 to —123 °C. Data have been reported on the crystallization kinetics and morphology of blends of fractionated poly(tetramethyl-p-silphenylenesiloxanes). The chemical degradation of poly(tetramethyl-/ -silphenylenesiloxane/dimethyl-siloxane) block copolymers by HF has been reported. In 48% HF at 30 °C, preferential attack occurs at the Si—O bond, particularly those of the MejSi—O non-crystalline components, in copolymers containing 15, 35, and 52% poly-dimethylsiloxane. - Further data have been reported on the crystal structure and fold conformation of poly(tetramethyl-/>-silphenylenesiloxane)s, obtained from X-ray diffraction studies. ... 

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