Ring-opening polymerization of cyclic carbonates by alcohol-acid catalyst

Abstract

Ring‐opening reactions of 1,3‐dioxepan‐2‐one (1) and 1,3‐dioxan‐2‐one (2) with several alcohols were examined. The reactions proceeded without trifluoroacetic acid (TFA) in low conversions, while they proceeded smoothly with TFA to afford the ring‐opened adducts and oligomers. Ring‐opening polymerizations of 1 and 2 were also carried out by alcohol–acid catalysts to afford the corresponding polycarbonates (Mn = 2500−6800). The molecular weights increased with increase of the conversions of 1 and 2. The observed polymerization rates of 1 and 2 were determined as 24.4 × 10−6 and 0.8 × 10−6 s−1, respectively. Mechanistic aspects were studied by NMR spectroscopy. The methylene protons α and β to the carbonate moieties shifted to lower fields in 0.06–0.11 ppm in the 1H‐NMR spectra by the addition of TFA. Downfield shifts of the carbonyl carbon signals of 1 and 2 were observed in 3.94–4.15 ppm in the 13C‐NMR spectra. These results strongly suggest that the cyclic carbonates are activated by TFA. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2463–2471, 1998

Synthesis and Characterization of OH-Terminated Poly(trimethylene carbonate)s by Alcohol-Initiated Ring-Opening Polymerization in Melt Bulk without Using Any Catalyst

“…Benzyl alcohol was chosen as an initiator for the purpose of comparison with literature. 18 Such alcohols as 1,4-butanediol, ethanol, isopropanol or t-butanol were selected as initiators in order to examine the effect of alcohol structure on the ROP of TMC. ½M=½I: molar ratio of TMC to t-butanol, C%: TMC conversion, ¼ M n,th =M n,NMR Â 100 %, M n,th ¼ ½M=½I Á MW TMC Á Conversion%, the amount of TMC: 1000 mg. ½M=½I: molar ratio of TMC to ethanol, C%: TMC conversion, ¼ M n,th =M n,NMR Â 100 %, M n,th ¼ ½M=½I Á MW TMC Á Conversion%, the amount of TMC: 1000 mg.…”

“…In contrast, the similar reaction proceeded difficultly in solution in the absence of TFA at 0 C or 50 C, with very low conversion of monomer. 18 As can be seen, TFA is not indispensable in the ROP under the above polymerization conditions.…”

“…16,17 On the other hand, considering the catalysis mechanism of Lewis acid of such metal complexes, trifluoroacetic acid (TFA) has been also chosen as a catalyst of the ROP of seven-or six-number cyclic carbonates in order to reduce the harmfulness of metal residue. 18 In fact, in the absence of such catalysts, the ringopening reactions of seven-numbered cyclic carbonate also occurred. 18 Dong reported that the conversion of monomers did not decrease when SnOct 2 was used much less.…”

“…18 In fact, in the absence of such catalysts, the ringopening reactions of seven-numbered cyclic carbonate also occurred. 18 Dong reported that the conversion of monomers did not decrease when SnOct 2 was used much less. 4 Shiomi synthesized PCL-b-PEG-b-PCL triblock by the bulk ROP of "-caprolactone initiated with hydroxy groups at both chain ends of PEG without any catalyst at 200 C. 10 These observations show that a catalyst seems to be not indispensable in the ROP under suitable polymerization conditions.…”

Synthesis and characterization of functional six-membered ring carbonates for the preparation of orthogonal couplers

“…It is possible to polymerize selectively bifunctional ring carbonates, composed of a five-and a six-membered ring carbonate, to prepare polycarbonates and polyhydroxyurethanes by controled ringopening reactions [4,17]. Acid catalysed ring-opening polymerization initiated by alcohol needs temperatures between 0 °C and 50 °C [22]. Furthermore ring carbonates can be polymerized via enzymatic ring-opening polymerization [23].…”