Ring-opening polymerization complexes

The concentration of the lactam in the final product is determined by (3.11). Cyclic dimers can also form, and these also take part in the polymerization12 the reactions are acid catalyzed. The kinetics of this ring-opening polymerization with the three reactions in (3.10)—(3.12) is complex. The reaction rate constants and equilibrium constants have been described by several authors,5 6,8,12 28 and more pragmatic approaches for describing the reaction kinetics have also been given.28,31,33... 

Table 2 Ring-opening polymerization of lactones initiated by lanthanide complexes (CL = e-caprolactone LA = lactide TMC = trimethylene carbonate). 

In another example, a polymer-supported chromium porphyrin complex was supported on ArgoGel Cl and then employed for the ring-opening polymerization of 1,2-cyclohexene oxide and C02 [95], This complex showed higher activity than a C02-soluble equivalent, and the solid nature of the catalyst meant that recycling of the catalyst was much easier. 

Five-coordinate aluminum alkyls are useful as oxirane-polymerization catalysts. Controlled polymerization of lactones102 and lactides103 has been achieved with Schiff base aluminum alkyl complexes. Ketiminate-based five-coordinate aluminum alkyl (OCMeCHCMeNAr)AlEt2 were found to be active catalyst for the ring-opening polymerization of -caprolactone.88 Salen aluminum alkyls have also been found to be active catalysts for the preparation of ethylene carbonate from sc C02 and ethylene oxide.1 4 Their catalytic activity is markedly enhanced in the presence of a Lewis base or a quaternary salt. 

Figure 12.4 Oxygenated heteroqrcles used for ring-opening polymerization by immobilized rare-earth metal complexes.

We have reported a gas phase and solution phase study comparing mono-and dinuclear CF" complexes as catalysts for the ring opening polymerization of propylene oxide. (Adapted from Schon et al., 2004)... 

Abraham GA, Gallardo A, Lozano AE, San RJ (2000) E-caprolactone/ZnCL complex formation characterization and ring-opening polymerization mechanism. J Polym Sci A Polym Chem 38 1355-1365... 

Ring-Opening Polymerization of Epoxide with Various Aluminum Complexes as Initiators in the Presence of a Lewis Acid... 

For sodium/hexamethylene-l,6-bis-carbamidocaprolactam system, Sibal et al. [64] found the value of the constant k in Equation 1.4 to be 17.5. Note that the values of the constant k in Equation 1.4 that defines the relative complex viscosity rise during anionic ring opening polymerization of caprolactam are comparable for both caprolactam-magnesium-bromide/isophthaloyl-bis-caprolactam and sodium/hexamethylene-l,6-bis-carbamidocapro-lactam as the catalyst/initiator systems even though the kinetic constants for anionic polymerization for these systems are extremely different (see Table 1.2). 

Complex viscosity during ring opening polymerization, Pas Complex viscosity of the monomer, Pas... 

The PEO salt complexes are generally prepared by direct interaction in solution for soluble systems or by immersion method, soaking the network cross-linked PEO in the appropriate salt solution [52-57]. Besides PEO, poly(propylene)oxide, poly(ethylene)suceinate, poly(epichlorohydrin), and polyethylene imine) have also been explored as base polymers for solid electrolytes [58]. Polyethylene imine) (PEI) is prepared by the ring-opening polymerization of 2-methyloxazoline. Solid solutions of PEI and Nal are obtained by dissolving both in acetonitrile (80 °C) followed by cooling to room temperature and solvent evaporation in vacuo. Polyethyleneimine-NaCF3S03 complexes have also been explored [59],... 

The mass spectra [17] give a grossly simplified picture of the complex mixture which can result from a ring-opening polymerization. Knotted isomers can have almost identical mass spectra, dominated by the parent ion. With the reversibility of metathesis, the polyolefin mixture near equilibrium is expected to contain a large variety of knotted and linked species. 

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