Siloxanes reactions with

The reaction is of practical importance in the vulcanization of siUcone mbbers (see Rubber compounding). Linear hydroxy-terrninated polydimethyl siloxanes are conveniently cross-linked by reaction with methyldiethoxysilane or triethoxysilane [998-30-1]. Catalysts are amines, carboxyflc acid salts of divalent metals such as Zn, Sn, Pb, Fe, Ba, and Ca, and organotin compounds. Hydroxy-terrninated polysiloxanes react with Si—H-containing polysiloxanes to... 

During the aqueous hydrolysis of dichlorosilanes there is always a very important side reaction. It is the self-condensation of silanols which are formed initially during the hydrolysis. These reactions also give rise to the formation of cyclic siloxanes together with the linear oligomers or polymers (Reaction Scheme III). The amount of cyclic products usually depends on the hydrolysis conditions and the degree of the self-condensation attained as well as concentration considerations. 

Amine-terminated siloxane oligomers have also been utilized in the synthesis of various siloxane-amide and siloxane-imide copolymers, High molecular weight siloxane-amide copolymers have been synthesized by the solution or interfacial co-polymerization of siloxane oligomers with sebacoyl chloride or terephthaloyl chloride respectively 1S5,165). In some reactions diamine chain extenders have also been utilized. Thermal and dynamic mechanical characterization of these copolymers have shown the formation of multiphase systems160). Compression molded films displayed very good elastomeric properties. 

Preparation of siloxane-carbonate segmented copolymers by interfacial polymerization involves the reaction of carboxypropyl-terminated siloxane oligomers with bisphenol-A and phosgene, in the presence of a strong base and a phase transfer catalyst, in water/methylene chloride solvent system l50 192), as shown in Reaction Scheme XIV. 

Synthesis of hydrolytically stable siloxane-urethanes by the melt reaction of organo-hydroxy terminated siloxane oligomers with various diisocyanates have been reported i97,i98) -yhg polymers obtained by this route are reported to be soluble in cresol and displayed rubber-like properties. However the molecular weights obtained were not very high. A later report56) described the use of hydroxybutyl terminated disiloxanes in the synthesis of poly(urethane-siloxanes). No data on the characterization of the copolymers have been given. However, from our independent kinetic and synthetic studies on the same system 199), unfortunately, it is clear that these types of materials do not result in well defined multiphase copolymers. The use of low molecular weight hydroxypropyl-terminated siloxanes in the synthesis of siloxane-urethane type structures has also been reported 198). 

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. 

The products were identified by comparing the retention times of the reaction products with commercial compounds, and by GC-MS analysis in a Hewlett-Packard 5973/6890 GC equipped with an electron impact ionization at 70 eV detector and a cross-linked 5% PH ME siloxane (0.25 mm coating) capillary column. The reaction products were separated from the catalyst with filter syringes and analyzed in an Agilent 4890D and a Varian 3400 GC equipped with a flame ionization detector, and CP-Sil 8CB (30 m x 0.53 mm x 1.5 pm) and DB-1 (50 m x 0.52 mm x 1.2 pm) columns, respectively. Decane was used as an internal standard. The catalyst was thoroughly washed after reaction with acetonitrile, acetone and water, and dried overnight under vacuum at 40°C. 

Poly(methyl 3-(l-oxypyridinyl)siloxane) was synthesized and shown to have catalytic activity in transacylation reactions of carboxylic and phosphoric acid derivatives. 3-(Methyldichlorosilyl)pyridine (1) was made by metallation of 3-bromopyridine with n-BuLi followed by reaction with excess MeSiCl3. 1 was hydrolyzed in aqueous ammonia to give hydroxyl terminated poly(methyl 3-pyridinylsiloxane) (2) which was end-blocked to polymer 3 with (Me3Si)2NH and Me3SiCl. Polymer 3 was N-oxidized with m-ClC6H4C03H to give 4. Species 1-4 were characterized by IR and H NMR spectra. MS of 1 and thermal analysis (DSC and TGA) of 2-4 are discussed. 3-(Trimethylsilyl)-pyridine 1-oxide (6), l,3-dimethyl-l,3-bis-3-(l-oxypyridinyl) disiloxane (7) and 4 were effective catalysts for conversion of benzoyl chloride to benzoic anhydride in CH2Cl2/aqueous NaHCC>3 suspensions and for hydrolysis of diphenyl phosphorochloridate in aqueous NaHCC>3. The latter had a ti/2 of less than 10 min at 23°C. 

Polymers derived from the preceding type of reaction with nitriles,5 amines,6 and phosphines,7 have been reported. Green8 has reported the preparation of a resin-type material composed of at least 10 repeat units from the reaction between decaborane and adiponitrile (NC(CH2)4CN). Also reported,9 is the inclusion of flexible siloxanes and ether linkages into a diamine, and of their subsequent reaction with decaborane to give adduct polymers (see 2, 3). 

A similar strategy was also applicable for the synthesis of six- and eight-membered siloxanol-ring systems. Hydrolysis of z-PrRSiCl2 (R = Ph, o-Tol) with ZnO and KOH provided the six-membered siloxane rings as a mixture of two constitutional isomers cis-trans-(i-PrRSiO)3 (539, R = Ph 540, R = o-Tol) and Wzr-(z-PrRSiO)3 (541, R = Ph 542, R = o-Tol) which were separated by preparative HPLC. Subsequent reaction with HC1/A1C13 and hydrolysis of the chloro intermediates yielded the same product for both isomers, namely Wzr-[z-Pr(OH)SiO]3 543, implying that isomerization occurs under these conditions (Scheme 75).484... 

From such silanol-functional cyclics, the polycyclic (ladder) siloxanes are made in a controlled manner. Thus, the reaction of (7-PrSi(0H)0)4 with ((-PrPhClSiO)2 in pyridine was described, leading to the formation of tetraphenyl tricyclic ladder siloxane. Dephenylchlorination with A1C13/HC1, and the hydrolysis allowed isolation of tetrahydroxyl tricyclic ladder siloxane in good yield. Using a similar reaction starting from tetrahydroxyl ladder siloxane, the first pentacyclic ladder siloxane was obtained.38 Abe et al. describe the synthesis of... 

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