Synthesis by Ring-Opening Polymerization

If desired, the linear oligosiloxanes, and indeed any linear polydimethylsiloxane, can be converted into cyclosiloxanes by base-catalyzed pyrolysis. If this reaction is carried out under equilibrating conditions and the products are fractionally distilled with removal only of the most volatile compound, D3, the entire mixture can be converted to this valuable intermediate. This procedure is frequently used to obtain pure D3 and D4, useful for polymer synthesis by ring-opening polymerization. 

In polyester synthesis via ring-opening polymerizations, metal catalysts are often used. For medical applications of polyesters, however, there has been concern about harmful effects of the metallic residues. Enzymatic synthesis of a metal-free polyester was demonstrated by the polymerization of l,4-dioxan-2-one using Candida antarctica lipase (lipase CA). Under appropriate reaction conditions, the high molecular weight polymer (molecular weight = 4.1 x 10" ) was obtained. 

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. 

Over the years we have developed methods for the direct synthesis of hydrolytically and/or enzymatically degradable microspheres by ring-opening polymerization of e-caprolactone and lactides [6-12]. The diameters of these microspheres are usually less than 3 xm. In this chapter we discuss... 

The number average diameter of microspheres obtained from polymers synthesized, by emulsification of polymer solutions followed by solvent extraction and/or solvent evaporation methods, can be controlled by choosing the appropriate conditions at which particles are produced. However, by this method particles with 15 p,m and with D D > 1.9 are produced. Spray drying did not provide poly(L-Lc) particles with regular spherical shape. Direct synthesis of poly(L-Lc) microspheres by ring-opening polymerization with stepwise monomer addition can be used as a method of choice for the production of microspheres with diameters controlled to ca. 6 p.m and with diameter polydispersity parameter < 1.20. 

Many of the common condensation polymers are listed in Table 1-1. In all instances the polymerization reactions shown are those proceeding by the step polymerization mechanism. This chapter will consider the characteristics of step polymerization in detail. The synthesis of condensation polymers by ring-opening polymerization will be subsequently treated in Chap. 7. A number of different chemical reactions may be used to synthesize polymeric materials by step polymerization. These include esterification, amidation, the formation of urethanes, aromatic substitution, and others. Polymerization usually proceeds by the reactions between two different functional groups, for example, hydroxyl and carboxyl groups, or isocyanate and hydroxyl groups. 

Thus, the second approach to the synthesis of poly(organophosphazenes) involves the introduction of the organic (or organometallic) side groups at the cyclic trimer level, followed by ring-opening polymerization of the substituted cyclic trimer to the high polymer (reaction (ll)).23... 

M. Okada, Y. Yamakawa, and H. Sumitomo, Chemical synthesis of (1 3)-/i-D-glucopyranan by ring-opening polymerization of a 1,3-anhydro sugar derivative, Macromolecules, 24 (1991) 6797-6799. 

Y. Choi, T. Yoshida, T. Mimura, Y. Kaneko, H. Nakashima, N. Yamamoto, and T. Uryu, Synthesis of sulfated octadecyl ribo-oligosaccharides with potent anti-AIDS virus activity by ring-opening polymerization of a 1,4-anhydroribose derivative, Carhohydr. Res., 282 (1996) 113-123. 

G. Borjihan and T. Uryu, Synthesis of 3-acetamido-3-deoxy-(l - 5)-u-D-xylofuranan by ring-opening polymerization of a l,4-anhydro-3-azido-a-D-xylopyranose derivative, Macromolecules, 31 (1998) 5572-5576. 

Y. S. Choi, T. Uryu, and T. Yoshida, Synthesis of block copolysaccharides by ring-opening polymerization of anhydro sugar derivatives, Macromol. Chem. Phys., 198 (1997) 2875-2888. 

T. Uryu, K. Hatanaka, K. Matsuzaki, and H. Kuzuhara, Chemical synthesis of amino-group-containing (1 - 6)-o -D-glucan derivatives by ring-opening polymerization of... 

Synthesis of Cyclic Polymers by Ring-Opening Polymerizations. 154... 

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