Ring-opening polymerization silicones

Ahn, H. W. Clarson, S. J., Synthesis of Isotactic Rich Poly(methylphenylsiloxane) by Living Anionic Ring-Opening Polymerization. Silicon 2011, 3,157-161. 

Sakurai, H. Yoshida, M. Synthesis of Polysilanes by New Procedures Part 1 Ring-opening Polymerizations and the Polymerization of Masked Disilenes. In Silicon-based Polymers The Science and Technology of their Synthesis and Application-, Jones, R. G., Ando, W., Chojnowski, J., Eds. Kluwer Dordrecht, 2000 pp 375-399. 

Chojnowski, J. Cypryk, M. Fortuniak, W. Kazmierski, K. Rozga-Wijas, K. Scibiorek, M. Controlled Synthesis of All Siloxane Architectures by Ring-Opening Polymerization. In Synthesis and Properties of Silicones and Silicone-Modified Materials Clarson, S. J., Fitzgerald, J. J., Owen, M. J., Smith, S. D., Van Dyke, M. E., Eds. AGS Symposium Series 838 American Chemical Society Washington, DC, 2003 pp 12-25. 

Time-of-flight secondary ion mass spectroscopy (TOF-SIMS)15 has been used for observing the initiating species in anionic ring-opening polymerizations of D3. The PDMS mass spectrum shows peaks of varying intensity with local maxima every 3 silicon repeat units. This distribution is attributed to the relative concentrations of the three initiating species, II, 12 and 13, shown in equation 2 which can be determined from the peak intensities. 

There are several reports in recent literature on the application of silicon-containing compounds as the initiators of cationic ring-opening polymerization. This apparently is related to the attempts to prepare block copolymers containing polysiloxane or polysilane segments. (CfL SiCFAgClCL system was used to initiate cationic polymerization of tetrahydrofuran... 

The syntheses of siloxanes with vinyl groups at the silicon atoms of the chain was performed by anionic ring-opening polymerization of vinyl group-containing cyclotri- or cyclotetrasiloxanes (03, 04 ) with alkyl lithium compounds as initiators. The polymerizations were terminated by chlorosilanes with additional silico- or carbofunctional groups or octyl groups. In the block copolymerizations we used 03 or 04 and hexamethylcyclotrisiloxane (D3) (Scheme 1 and 2). 

The usual method for obtaining linear silicone polymers is by ring-opening polymerization reactions on cyclic... 

The silicone fluids are normally chain-blocked linear polymers, manufactured by ring-opening polymerization, as described in Section 3.4. The dimethylsiloxane polymers are by far the most important, but to make fluids for high-temperature use, phenytmethylsiloxane units are also included in the polymer. 

Elastomers and nonsilanol terminated fluids are produced by base-catalyzed polymerization of low-molecular weight siloxanes. Polydimethylsiloxanes are also produced by ring opening polymerization of D3, D4, and D5. In the presence of MM or MDDM (endcapper), silicones MD M are formed otherwise, silanol terminated polysiloxanes may be obtained. 

Mechanism of Equilibration. The generally accepted mechanism for the base-catalyzed ring-opening polymerization of cyclosiloxanes involves attack of the basic catalyst at the silicon atom (15). It has been proposed, and generally accepted, that the active species is a partially dissociated siloxanolate anion (13). In the results presented in this chapter, significant differences in reaction rates were observed as the corresponding cation of the siloxanolate species was varied. The more rapid disappearance of D4 and aminopropyldisiloxane in the presence of these catalysts increased in the following order ... 

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