Cyclic carbonate polymerization

Detailed investigations of the mechanism of five-membered cyclic carbonate polymerization initiated with tin and zirconium alkoxides were carried out by Kricheldorf et... 

A haloalkyl carbonate structure is formed by the initial ring-opening reaction of the monomer with alkyl halide, which was shown by using ethyl 3-iodopropyl carbonate as the initiator for cyclic carbonate polymerization. The obtained polymer contained both ethyl and iodopropyl end-groups. 

Macroinitiators such as polymeric Li, Na, and K alkoxides can also be used for the initiation of the six-membered cyclic carbonate polymerization. Thus, besides living vinyl polymers, hydroxyl group-terminated polymers of poly (tetrahydrofuran) (PTHF), poly(oxyethylene), and poly(dimethylsiloxane) (PDMS) were transformed to alkoxides by treatment with scc-BuLi or K-naphthalene and used as initiators. The use of these macroinitiators enables the identification of side reactions, as shown by Keul and Hocker for polystyrene lithium (PS Li ). The addition of the macro initiator to the monomer, to maintain a high excess of monomer, minimizes side reactions. Transformation of the polystyryl... 

Darensbourg s group and Yang et al. have reported the use of effective salen complexes of aluminum as catalysts for six-membered cyclic carbonate polymerization. ... 

According to the second method of carbonate block copolymer synthesis, sequential monomer polymerization is proceeded with transformation of the active center. The block copolymers are prepared in three steps. First, the polymerization of one monomer is carried out. After complete conversion of the first monomer the transformation of active centers is performed, and the initiation of the polymerization of the second monomer is proceeded. For example, this approach was applied for obtaining poly(styrene-l7-neopentyl carbonate).After completion of the styrene living polymerization, carbanionic centers were transformed into alkoxide ones via reaction with EO and then the ROP of neopentyl carbonate polymerization was performed. In the case of block copolymers of methyl methacrylate with neopentyl carbonate living PMMA, prepared according to GTP, was used as a macroinitiator for DTC polymerization. A silyl keteneacetal active center was transformed to an alkoxide one. Depending on the functionality of the macroinitiator (A) used for cyclic carbonate polymerization, two types of block copolymers can be obtained A-B or B-A-B. 

The recent most important finding in the field of polymerization of cychc ah-phatic carbonates has been the observation made by Takata and Endo, that cyclic carbonates polymerize with a considerable expansion in volume [10]. 

A novel chemoenzymatic route to polyester polyurethanes was developed without employing highly toxic isocyanate intermediates. First, diurethane diols were prepared from cyclic carbonates and primary diamines, which were subsequently polymerized with dicarboxylic acids and glycols by using lipase CA as catalyst, yielding the polyurethanes under mild reaction conditions. 

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)... 

More active zinc phenoxide initiators of the type [Zn(0Ar)2(Et20)2]956 were found to catalyze both the copolymerization of CHO with C02 and the terpolymerization of CHO, PO, and C02 attempts to copolymerize PO and C02 yielded predominantly cyclic carbonates. For example, (332) copolymerizes CHO and C02 at 80 °C and 800 psi to give a copolymer containing 91% syndiotactic polycarbonate linkages (and 9% polyether junctions due to the non-insertion of C02) with good activity (>350g polymer/g [Zn] in 69 h).957 However, the polymerization is not well-controlled (Mw/Mn>2.5). Variation of the phenoxide ligands revealed that (333) is 4 times... 

Cyclic aromatic disulfides, polymerization reactions of, 23 706 Cyclic (arylene) disulfides, 23 712 Cyclic batch adsorption processes, 1-613 Cyclic bis(arylene tetrasulfide)s, 23 712 Cyclic carbon, polymer materials with, 15 177... 

Shibasiki Y, Sanada H, Yokoi M, Sanda F, Endo T (2000) Activated monomer cationic polymerization of lactones and the application to well-defined block copolymer synthesis with seven-membered cyclic carbonate. Macromolecules 33 4316-4320... 

Polymerization of a cyclic carbonate ester yields a linear polycarbonate [Kuhling et al., 1989 Rokicki, 2000], For example, the cyclic oligomer (m — 2-20 in Eq. 7-85) of the... 

AS is very rare for a polymerization process. The only other reported instances of positive AS values are those for the polymerizations of the cyclic octamers of sulfur and selenium and cyclic carbonate oligomers (Sec. 7-5c) [Brunelle et al., 1989]. All other polymerizations involve a decrease in entropy because of the decreased disorder for a polymer relative to its monomer. The positive AS values for the cyclic siloxane, S, and Se probably result from the high degree of flexibility of the linear polymer chains due to the large-sized atoms that they contain. This flexibility leads to greater degrees of freedom in the linear polymer compared to the cyclic monomer. 

Cyclic carbonates are not commercially available and have to be synthesized prior to use. As a result, commercially available carbonates such as diethyl carbonate [55-57] or diphenyl carbonate [93] were evaluated in polycondensation reactions with diols to prepare polycarbonates since they allow a broader spectrum of polymers to be accessed. Unfortunately, polymerizations employing diethyl carbonate require the use of an excess diethyl carbonate [55]. Nevertheless, polymers with molecular weight of 40kDa were achieved within 16 h. Also, the polymerization of diphenyl carbonate with butane-1,4-diol or hexane-1,6-diol via the formation of a cyclic dimer produced polymers with molecular weights ranging from 119 to 339kDa [93]. 

Among the more common thermoplastics from ring opening polymerization of interest in composite processing are polylactams, polyethers, polyacetals, and polycycloolefins. It has also been shown that polycarbonates can be produced from cyclic carbonates [22], Anionic ring opening polymerization of caprolactam to nylon 6 is uniquely suited to form a thermoplastic matrix for fiber-reinforced composites, specifically by the reaction injection pultrusion process [23-25]. The fast reaction kinetics with no by-products and the crystalline... 

In addition to the formation of hydroperoxides, other reactions are known to occur simultaneously. The formation of polyperoxides, carbon-to-carbon polymerization, and the formation of epoxides and cyclic peroxides have been proposed or demonstrated in lipid oxidation. 

Cyclic carbonates are prepared in satisfactory quality for anionic polymerization by catalyzed transesterification of neopentyl glycol with diaryl carbonates, followed by tempering and depolymerization. Neopentyl carbonate (5,5-dimethyl-l,3-dioxan-2-one) (6) prepared in this manner has high purity (99.5%) and can be anionically polymerized to polycarbonates with mol wt of 35,000 (39). 

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