Polysiloxane, linear synthesis

Finkelmann, H. and Rehage, G. Investigations on liquid crystalline polysiloxanes, I, Synthesis and characterization of linear polymers. Makromol. Chem. Rapid Commun. 1, 31 (1980)... 

Engel M, Hisgen B, Keller R, Kreuder W, Reck B, Ringsdorf H, Schmidt HW, Tschmner P (1985) Synthesis, structure and properties of liquid crystalline polymers. Pure Appl Chem 57 1009-1014 Finkelmann H (1982) Polymer Liquid Crystals. Academic ftess. New York Finkelmann H, Rehage G (1980) Investigations on liquid crystalline polysiloxanes, 1. Synthesis and characterization of linear polymers. Makromol Chem Rapid Commun 1 31-34 Finkelmann H, Rehage G (1984) Liquid crystal side chain polymers. Liquid crystal polymers II/III. Adv Polym Sci 60/61 99-172... 

Chojnowski, J. Cypry k, M. Synthesis of Linear Polysiloxanes. In Silicon-Containing Polymers. The Science and Technology of Their Synthesis and Applications, Jones, R. G., Ando, W., Chojnowski, J., Eds. Kluwer Dordrecht, 2000 Chapter 1, pp 3—41. 

Weber, W. P. Paulasaari, J. Cai, G. Synthesis of Linear Copolysiloxanes with Regular Microstructures and Synthesis of Soluble Polysiloxanes with Trifunctional RSi03/2 (T) or Tetrafunctional Si04/2 (Q) Units. 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. ACS Symposium Series 838 American Chemical Society Washington, DC, 2003 pp 72-78. 

Chojnowski J, Cypryk M (2000) Synthesis of Linear Polysiloxanes. In Jones RG, Ando W, Chojnowski J, editors. Silicon-Containing Polymers. Dordrecht Kluwer Academic Publishers, pp. 3 1... 

Beside the synthesis of linear polysiloxanes, hydrosilylation was also nsed to obtain liquid crystalline elastomers. This can be performed in two ways, either a one pot reaction involving a diolefln together with the functionalized mesogen or a two step process involving first the synthesis of a linear polysiloxane, bearing adequate functions for a further crossfinking. For example, a photosensitive group such as benzophenone could be introduced (Fig. 5, x and y are theoretical values). In order to ensure a full conversion in silane, the time of reaction was increased here to 65 h [17]. 

The next step in the synthesis of silicone polymers is the hydrolysis of dimethyldichlorosilane, giving HCl and a mixture of cyclic and linear oligomeric polysiloxanes... 

The equilibrium 20 is important not only in the synthesis of linear polysiloxanes but also in their applications. The effects of water vapor on inducing chain cleavage at high temperature are not only reduced molecular weights but also a dramatic increase in the rates of chemically induced stress relaxation at 250 °C in cross-linked poly(dimethylsiloxane) networks under load (70). Slow hydrolytic bond cleavage in cross-linked networks is seen even in studies of stress relaxation in air at room temperature, and appreciable rates of stress relaxation in the loaded networks are measured at temperatures as low as 70 (7i). The stress relaxation is greatly accelerated... 

The linear polymers can be reconverted to the cyclic compounds particularly if initiator concentration is too high and if the initiator is not removed or neutralized at the end of the reaction. However, it is the triumph of polymer chemists that in spite of these challenges polysiloxanes with molecular weights in the range of 2-5 million can be prepared quite routinely. The PDFs are not very narrow and no method seems to be yet available that allows synthesis of polysiloxanes with narrow molecular-weight distributions. 

Hahn, B., and Percec, V., Synthesis of linear and cyclic chiral smectic liquid crystalline polysiloxanes with 2,5-disubslituted 1,3,2-dioxaborinane ba.sed mesogens, Polyni. Prepn, 29, 16 n (mS). 

This paper will summarize work performed in our laboratory on the synthesis of hybrid materials using cyclic oligo- and linear polysiloxanes in conjunction with polystyrenes, acrylates and methacrylates synthesized by ATRP. Architectural variation will also be discussed including linear, graft and star polymers. 

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