Methyl- siloxane polymers

Poly(ether.siloxanes) contain a poly(methyl.siloxane) polymer, which may be branched, and poly(eiher)-blocks. Its structure may be linear or comblike. The blocks are connected by Si-O-C- or Si-C- bridges., Si-0-C- linked products can, for example, be produced by reacting branched dimethyl(chloro)siloxy-lerminated poly(methyl-siloxanes) (see Section 4.3.3) with monohydroxy-functional polyCethers. 

Siloxane polymers and copolymers TABLE 13. The homologous series of pyrolysis products of cyclolinear methyl-siloxane polymers (from Reference 178 reproduced by permission of Elsevier) ... 

Lee, M. K. Meier, D. J., Synthesis and Properties of Diarylsdoxane and (Aryl/ Methyl)Siloxane Polymers 1. Thermal Properties. Polymer 1994, 34, 4882-4892. 

Random block methyl-siloxane polymer containing Meldola blue -0.15 Vvs. SCE, pH 7 Cast onto graphite 40 pA cm- mM-= 162, 236, 237... 

The poly(diphenyl siloxane) chain is a rigid molecule because of the interaction of the phenyl substituents. Only a single melting temperature in the range of 247 °C to 260 °C has been reported for the homopolymer.(141,159,160) Other diaryl siloxane and aryl methyl siloxane polymers also have relatively high melting temperatures.(161)... 

Many of the unique properties of siUcone oils are associated with the surface effects of dimethylsiloxanes, eg, imparting water repeUency to fabrics, antifoaming agents, release liners for adhesive labels, and a variety of poHshes and waxes (343). Dimethylsilicone oils can spread onto many soHd and Hquid surfaces to form films of molecular dimensions (344,345). This phenomenon is greatly affected by even small changes in the chemical stmcture of siloxane in the siloxane polymer. Increasing the size of the alkyl substituent from methyl to ethyl dramatically reduces the film-forming abiUty of the polymer (346). The phenyl-substituted siUcones are spread onto water or soHd surfaces more slowly than PDMS (347). 

Finkelmann et al. 256 274,2781 have also investigated the synthesis and the characteristics of siloxane based, crosslinked, liquid crystalline polymers. This new type of materials displays both liquid crystallinity and rubber elasticity. The synthesis of these networks is achieved by the hydrosilation of dimethylsiloxane-(hydrogen, methyl)siloxane copolymers and vinyl terminated mesogenic molecules in the presence of low molecular weight a,co-vinyl terminated dimethylsiloxane crosslinking agents156 ... 

Synthesis of comb (regular graft) copolymers having a PDMS backbone and polyethylene oxide) teeth was reported 344). These copolymers were obtained by the reaction of poly(hydrogen,methyl)siloxane and monohydroxy-terminated polyethylene oxide) in benzene or toluene solution using triethylamine as catalyst. All the polymers obtained were reported to be liquids at room temperature. The copolymers were then thermally crosslinked at 150 °C. Conductivities of the lithium salts of the copolymers and the networks were determined. 

It is surprising that poly(siloxane)/PC copolymer and SAN can form a transparent blend because the refractive index of poly(di-methyl siloxane) (PDMS) is around 1.4, which is very different from that of SAN (25). Moreover, PDMS can form a transparent blend with SAN that would not form a transparent blend with PC. Refractive indices of some polymers are summarized in Table 10.6. 

Since there had not been any measurements of thermal diffusion and Soret coefficients in polymer blends, the first task was the investigation of the Soret effect in the model polymer blend poly(dimethyl siloxane) (PDMS) and poly(ethyl-methyl siloxane) (PEMS). This polymer system has been chosen because of its conveniently located lower miscibility gap with a critical temperature that can easily be adjusted within the experimentally interesting range between room temperature and 100 °C by a suitable choice of the molar masses [81, 82], Furthermore, extensive characterization work has already been done for PDMS/PEMS blends, including the determination of activation energies and Flory-Huggins interaction parameters [7, 8, 83, 84],... 

Siloxane Polymers. The synthesis of the ferrocene-modified siloxane polymers (A - E) has been described previously (25,27,32). Briefly, the methyl(2-ferrocenylethyl)-siloxane polymers were prepared by the hydrosilylation of vinylferrocene with the methylhydrosiloxane homopolymer or the methylhydrosiloxane-dimethylsiloxane copolymers (m n ratios of 1 1, 1 2, and 1 7.5 see Figure 1) in the presence of chloroplatinic acid as a catalyst. The methyl(9-ferrocenylnonyl)siloxane-dimethylsiloxane (1 2) copolymer was prepared via hydrosilylation of 9-ferrocenyl-l-nonene with the methylhydrosiloxane-dimethylsiloxane (1 2) copolymer. The molecular weight range of these ferrocene-modified siloxane polymers is approximately 5,000-10,000. Purification of the polymers was achieved by reprecipitation from chloroform solution, via dropwise... 

Dimethylpolysiloxane occurs as a clear, colorless, viscous liquid. It is a mixture of fully methylated linear siloxane polymers containing repeating units of the formula (CH3)2SiO that are terminated with trimethylsiloxy end-blocking units of the formula (CH3)3SiO—. It is soluble in most aliphatic and aromatic hydrocarbon solvents, but it is insoluble in water. Note Dimethylpolysiloxane is frequently used in commerce as such, or as a liquid containing silica (usually 4% to 5%), which must be removed by high-speed... 

Methyl-( -ferrocenylethyl)- and methyl-[ -(r,3 -dimethylferrocenyl)ethyl]siloxane polymers 53 and 54, respectively were prepared by the hydrosilylation of vinyl-ferrocene and l,T-dimethylferrocene-3-vinylferrocene with methyl hydrosiloxane (molecular weight was originally reported to be 2270) or methylhydrosiloxane-dimethylsiloxane copolymer (molecular weight was originally reported to be 2000 — 2100) in the presence of chloroplatinic acid as a catalyst. The synthetic route is given in Seheme 10-25 [62], The reaction was monitored by IR spectroscopy until the complete disappearance of the Si-H absorption at 2161 cm". ... 

The PhEur 2005 and USP 28 describe simethicone as a mixture of fully methylated linear siloxane polymers containing repeating units of the formula [-(CH3)2SiO-] , stabilized with trimethylsiloxy end-blocking units of the formula [(CHsls SiO-], and silicon dioxide. It contains not less than 90.5% and not more than 99.0% of the polydimethylsiloxane [-(CH3)2SiO-] , and not less than 4.0% and not more than 7.0% of silicon dioxide. The PhEur 2005 additionally states that the degree of polymerization is between 20-400. 

The gas-phase tram-alkylation reaction was performed in an automated micro-flow apparatus containing a quartz fixed-bed reactor (i d. 10 mm) at lO Pa [16 vol% benzene (1, p.a., dried on molsieve), 3.2 vol% diethylbenzene (2, consisting of 25% ortho, 73% meta, 2% para isomers, dried on molsieve), N2 balance (50 mL/min), WHSV =1.5 h ] with 2.0 mL of the tube reactor filled with catalyst particles (500-850 pm sieve fraction, typically 1.4 g). Two separate saturators were connected to the inlet of the reactor for the supply of 1 and 2. The partial vapor pressure of 1 and 2 was controlled by adjusting the temperature of the saturator-condensers and the N2 flow rate. After equilibration for 30 min at the applied reaction temperatures (473 K and 673 K, heating rate 10 K/min) within a dry N2 flow (50 mL/min), benzene (1) and diethylbenzene (2) were passed throu the reactor. To prevent condensation of both reactants and products prior to GC analysis [Hewlet Packard 5710 A, column CP-sil 5CB capillary liquid-phase siloxane polymer (100% methyl) 25 m x 0.25 mm, 323 K, carrier gas N2, FID, sample-loop volume 1.01 pL], tubes were heat-traced (398 K). FID sensitivity factors and retention times were determined using ethene (99.5 %, dried over molsieve) and standard solutions of 1, 2, and ethylbenzene (3, 99%) in methanol (p.a.). The conversion of 2 was measured as a function of time [8]. 

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