Catalyzed ring-opening polymerization

This scheme is remarkably close to the coordination insertion mechanism believed to operate in the metal alkoxide-catalyzed ring-opening polymerization of cyclic esters (see Section 2.3.6). It shares many features with the mechanism proposed above for the metal alkoxide-catalyzed direct polyesterification (Scheme 2.18), including the difficulty of defining reaction orders. 

Poly(tetramethylene oxide) polyols (see Scheme 4.4) are a special class of polyethers syndiesized via acid-catalyzed ring-opening polymerization of tetrahy-drofuran. Although less susceptible to side reactions, the synthesis of these C4 ethers is less flexible in terms of product composition and structure. Thus, because of diis syndietic route, only two-functional glycols are available and copolymers are not readily available. Molecular weights of commercial C4 glycols range up to about 3000 g/m. 

Scheme 4.12 Conventional synthesis of polyether polyols via base-catalyzed ring-opening polymerization of alkylene oxides.

Co/Zn double metal cyanide catalyzed ring-opening polymerization of propylene oxide effect of cocataiysts on polymerization behavior... 

Various cyclic esters have been subjected to hpase-catalyzed ring-opening polymerization. Lipase catalyzed the ring-opening polymerization of 4- to 17-membered non-substituted lactones.In 1993, it was first demonstrated that medium-size lactones, 8-valerolactone (8-VL, six-membered) and e-caprolactone (e-CL, seven-membered), were polymerized by lipases derived from Candida cylindracea, Burkholderia cepacia (lipase BC), Pseudomonas fluorescens (lipase PF), and porcine pancreas (PPL). °... 

Optically active polyesters were synthesized by lipase CA-catalyzed ring-opening polymerization of racemic 4-methyl or ethyl-e-caprolactone. The (5 )-isomer was enantioselectively polymerized to produce the polyester with >95% ee. Quantitative reactivity of 4-substituted e-caprolactone using lipase CA as catalyst was analyzed. The polymerization rate decreased by a factor of 2 upon the introduction of a methyl substitutent at the 4-position. Furthermore, 4-ethyl-8-caprolactone polymerized five times slower than the 4-methyl-8-caprolactone. This reactivity difference is strongly related to the enantioselectivity. Interestingly, lipase CA displayed 5 -selectivity for 4-methyl or ethyl-8-caprolactone, and the enantioselectivity was changed to the (f )-enantiomer in the case of 4-propyl-8-caprolactone. 

Base and acid catalyzed ring opening polymerization of cyclotri-siloxane, -[Me2SiO]3- [e.g. reaction (10)], is a well-known method of generating high molecular weight polysiloxanes. 

Rochow et al. (27-28) have examined acid catalyzed ring opening polymerization as an approach to the formation of polysilazanes. 

Lipase-Catalyzed Ring-Opening Polymerization of Cyclic Monomers... 

Here, lipase-catalyzed ring-opening polymerization of cyclic compounds giving polymers other than polyesters is described. l,3-Dioxan-2-one, six-membered cyclic carbonate, was polymerized in the presence of lipase catalysts (Fig. 13)... 

S)-Isopropylmorpholine-2,5-dione, six-membered depsipeptide, was polymerized by lipase PC and PPL catalysts [112]. High temperature (100°C or 130°C) was required for the polymerization, yielding biodegradable poly(de-psipeptide). During the polymerization, the racemization of the valine residue took place. Demonstrated was PPL-catalyzed ring-opening polymerization of ethylene isopropyl phosphate, five-membered cyclic phosphate [113]. 

Kress, J. D. Leung, P. G. Tawa, G. J. Hay, P. J. Calculation of a Reaction Path for KOH-Catalyzed Ring-Opening Polymerization of Cyclic Siloxanes. In Silicones and Silicone-Modified Materials Clarson, S. J., Fitzgerald, J. J., Owen, M. J., Smith, S. D., Eds. AGS Symposium Series 729 American Chemical Society Washington, DC, 2000 pp 81—97. 

Suzuki et al. [14] reported the Pd-catalyzed ring-opening polymerization of a cyclic carbamate in the presence of an initiator, which also acts as a core molecule, to afford a hyperbranched polyamine. The polymerization was proposed to be an in situ multibranching process, wherein the number of propagating chain ends increase with the progress of the polymerization. 

Brunelle, D. J. and Serth-Guzzo, J. Titanate-catalyzed ring-opening polymerization of cyclic phthalate ester oligomers, Polym. Prep., 40(1), 566 (1999). 

Nomura N, Taira A, Tomioka T, Okada M (2000) A catalytic approach for cationic living polymerization Sc(OTf)3-catalyzed ring-opening polymerization of lactones. Macromolecules 33 1497-1499... 

Albertsson A-C, Srivastava RK (2008) Recent developments in enzyme-catalyzed ring-opening polymerization. Adv Drug Deliv Rev 60 1077-1093... 

Loeker EC, Duxbury CJ, Kumar R, Gao W, Gross RA, Howdle SM (2004) Enzyme-catalyzed ring-opening polymerization of e-caprolactone in supercritical carbon dioxide. Macromolecules 37 2450-2453... 

Feng Y, Kniifermann J, Klee D, Hdcker H (1999) Lipase-catalyzed ring-opening polymerization of 3(S)-isopropylmorpholine-2,5-dione. Macromol Chem Phys 200 1506-1514... 

Recent Developments in Metal-Catalyzed Ring-Opening Polymerization of Lactides and Glycolides Preparation of Poly lactides, Polyglycolide, and Poly(lactide-co-glycolide)... 

Recent Developments in Metal-Catalyzed Ring-Opening Polymerization... 

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