Catalyzed ring-opening polymerization materials

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. 

An alternative approach to such materials involves acid-catalyzed ring-opening polymerization of macrocyclic stannasiloxane rings to produce waxy solids. The molecular weight of these materials could not be determined. 

The above discussions have focused on commercial materials. The next section highlights some recent approaches to useful SiC precursors currently underdevelop in the academic community. Two groups have developed polycarbosilane syntheses based on metal catalyzed ring opening polymerization [28,40,41] ... 

The rate of disappearance of the starting materials was followed as one approach to determine the effect of catalyst type and concentration on the rate of the ring-opening polymerization. Results are presented in this chapter for the potassium-siloxanolate-catalyzed system, as well as for the analogous tetramethylammonium- and tetrabutylphosphonium-siloxanolate-catalyzed systems. 

Polymer 149, prepared by ring-opening polymerization (ROMP) of the corresponding functionalized norbornene, provides a clear illustration of the potential of this kind of materials. This resin catalyzes (12% molar) the reaction of linear aliphatic aldehydes with unsaturated ketones to provide 1,4-dicarbonyl compounds (153, Scheme 10.23) and was used for four consecutive cycles without any detectable decrease in performance [358]. A similar dimethylthiazolium structure supported on 2% cross-linked PS-DVB (150) was studied as catalyst for the acyloin condensation of a large variety of aldehydes [364], Catalyst 150 is used in 10 mol.% and the reaction takes place in ethanol at room temperature, with triethylamine as the base, to afford the corresponding a-hydroxyketones in excellent yields. Remarkably, the catalyst can be reused 20 times without losing its activity. 

The most common polymer family to be attached to sohd inorganic materials is aliphatic polyesters, such as poly(E-caprolactone) (PCL). PCL is a thermoplastic, bioresorbable (via hydrolysis), and semicrystalline polymer that is synthesized by the ring-opening polymerization (ROP) of s-caprolactone monomer (Khan et al., 2010). As depicted in Fig. 3.2(e), this in situ polymerization scheme can be catalyzed by tin(II)2-ethylhexanoate(Sn(Oct)2) or boron trifluoride dimethyletherate(BF30(CH3)2)... 

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