High‐molecular‐weight PTeMC and PHMC were prepared by the lipase‐catalyzed polymerization of butane‐1,4‐diol or hexane‐1,6‐diol and diphenyl carbonate via the formation of a cyclic dimer by a green process. Cyclic carbonate dimers were prepared by the lipase‐catalyzed condensation of diphenyl carbonate with butane‐1,4‐diol or hexane‐1,6‐diol in dilute toluene solution using an immobilized lipase from Candida antarctica, and was followed by the ring‐opening polymerization of the cyclic dimer in bulk with the same lipase to produce PTeMC with = 119 000 g · mol?1 and PHMC with = 399 000 g · mol?1, respectively. Additionally, enzymatic polymerization of cyclic carbonate dimer was analyzed with respect to the Km and Vmax for the lipase.
Enzymatic hydrolysis of poly(butylene succinate) (PBS) and poly(butylene succinate‐co‐L ‐lactate) (PBSL) has been studied by using a lipase originated from Pseudomonascepacia. It has been found that the drawn fibers of PBSL are readily hydrolyzed by the action of the lipase, while those of PBS undergo little enzymatic hydrolysis. Since the polymer films of PBS and PBSL are readily hydrolyzed under the same conditions, the enzymatic hydrolysis should depend not only on the crystallinity but also on the molecular orientation. The molecular weight of the samples gradually decreases with incubation time, because nonspecific hydrolysis occurs on the main chains of both PBS and PBSL even in the absence of lipase. The enzymatic hydrolysis of PBS and PBSL gives 4‐hydroxybutyl succinate (HBS) as the main product with traces of succinic acid and butane‐1,4‐diol together with L ‐lactic acid in the case of PBSL. In addition, the hydrolysis rate of the carboxyl end‐capped PBS is much slower than that of the original or hydroxyl end‐capped PBS. These results imply a hydrolysis mechanism involving the preferential exo‐type chain scission from the carboxyl terminals.
Mass remaining of various PBS and PBSL samples as a function of time. 相似文献
Unnatural‐type syndiotactic and atactic poly[(R,S)‐3‐hydroxybutanoate]s [P(3HB)s] were enzymatically transformed into a reactive cyclic 3HB oligomer of molecular weight ca. 500 in an organic solvent, such as toluene, using immobilized lipase from Candida antarctica at 40°C for 24 h. It was confirmed that similar results were obtained for both syndiotactic and atactic P(3HB)s. On the other hand, the acidic degradation of these polymers using a protonic acid, such as p‐toluenesulfonic acid, exclusively produced the linear 3HB oligomer instead of the cyclic oligomer. The formation of the cyclic oligomer was regarded as the characteristic feature of the lipase‐catalyzed degradation in organic media. The cyclic oligomer obtained readily reacted with alcohol as a nucleophile, and using lipase, to produce the alkyl ester of the 3HB oligomer. 相似文献
Summary: Novel biodegradable copolymers derived from succinate, butan‐1,4‐diol, and butan‐1,4‐diamine were synthesized by two‐step polycondensation reactions. The obtained copolymers had a periodical‐sequence structure consisting of ester and amide units, and the melting temperatures of the periodic copolymers increased with an increase in amide content. The crystalline structure of the periodic copolymers differs from that of butylene succinate homopolymer (PBS), and these results suggest that the periodically introduced amide units are included in the crystalline phase forming a novel crystalline structure.
Periodic copolyester‐amides derived from succinate, butane‐1,4‐diol, and butan‐1,4‐diamine 相似文献
This article summarizes the enzyme‐catalyzed synthesis and chemical recycling of biodegradable aliphatic polyesters and poly(carbonate ester)s directed towards establishing green polymer chemistry. Lipase catalyzes the condensation polymerization of a hydroxy acid, diacid with diol, diacid anhydride with oxirane, and polyanhydride with diol, or the ring‐opening polymerization of lactones of small to large rings, and a cyclic diester to produce the corresponding polyesters. Also, lipase catalyzes the condensation polymerization of a dialkyl carbonate with diol, and the ring‐opening polymerization of a cyclic carbonate to produce the corresponding polycarbonates. These polyesters and polycarbonates were selectively degraded by lipase to produce repolymerizable oligomers. These chemical recycling systems using an enzyme will establish a novel methodology for sustainable polymer recycling. Finally, current trends in green polymer production using enzymes are discussed. 相似文献
18O‐Substituted propane‐1,2‐diols and meso‐butane‐1,2‐diols were synthesized and fed to growing cells of Lactobacillus brevis. Propan‐1‐ol and butan‐2‐ol, prepared from such diols through diol‐dehydratase‐catalyzed dehydration followed by intracellular reduction, were analyzed for their 18O‐content. For each propane‐1,2‐diol enantiomer, partial retention or complete loss of the isotope appeared to be related to the mode of substrate binding. Specific retention of the O‐atom linked to the (R)‐configured C‐atom of meso‐butane‐1,2‐diol indicates that the diol dehydratase handles this substrate like (R)‐propane‐1,2‐diol. 相似文献
A model of linear isothermal polymerization of two bi‐functional monomers, one of which has alike functional groups of different reactivities, is presented. The model has been applied to the polymerization of 2,4‐toluenediisocyanate (TDI)a and butane‐1,4‐diol carried out in solution at 86 or 101°C. The rate constant K of the reaction between an isocyanate group in position 4 of TDI and a hydroxy group, the ratio κ of reactivities of groups in position 4 relative to that in position 2, and the ratio kφ of reactivities of an isocyanate group in the monomer relative to that at the end of an oligomer chain, have been evaluated from experimental data to be 6.51·10–4 dm3·mol–1·s–1, 1.47, and 1.55 at 86°C, and 17.2·10–4 dm3·mol–1·s–1, 1.55, and 1.62 at 101°C, respectively. 相似文献
The ring‐opening polymerization of (R,S)‐β‐butyrolactone (BL) in bulk was analyzed with respect to the polymer structure of the resulting poly[(R,S)‐3‐hydroxybutanoate)] [P(3HB)] by isolation of the pure form using preparative supercritical CO2 fluid chromatography. It was confirmed that the four‐membered BL was polymerized in bulk by lipase to yield the corresponding cyclic, hydroxy‐ and crotonate‐terminated P(3HB)s. The relative ratios of the three types of polymers depended on the lipase concentration as well as on the monomer conversion. It was also confirmed that both cyclic and linear P(3HB) polymer species were subject to hydrolysis, and inter‐ and intramolecular transesterification by lipase to produce two series of polymers having linear and cyclic structures with higher and lower molecular weight. The formation of the cyclic P(3HB) iss regarded as the characteristic feature of the lipase‐catalyzed polymerization of BL. 相似文献
New heat‐reversibly crystalline poly‐(alkylated phenylene oxide)s are described. the oxidative polymerization of 2,5‐dimethylphenol catalyzed by (1,4,7‐triisopropyl‐1,4,7‐triazacyclononane) copper dichloride produced poly(2,5‐dimethyl‐1,4‐phenylene oxide), which showed heat‐reversible crystallinity with a high melting point at ca. 300°C, although the isomeric polymer, poly(2,6‐dimethyl‐1,4‐phenylene oxide), never recrystallizes once melted. The polymerization of 2,5‐diethylphenol and 2,5‐dipropylphenol gave the polymers consisting of 1,4‐phenylene oxide units; the latter polymer possessed heat‐reversible crystallinity, however, the former one did not. 相似文献
Enzymatic degradation and polymerization using an enzyme were analyzed with respect to the establishment of a sustainable chemical recycling system for poly(ε‐caprolactone) (PCL) which is a typical biodegradable synthetic plastic. As the typical example, the enzymatic degradation of PCL having an Mn of 110 000 using lipase CA in toluene containing water at 70°C for 6 h afforded a unimodal oligomer having an Mn of about 1 000 quantitatively consisting of linear and cyclic oligomers. This was again polymerized by lipase CA in toluene under restricted water concentration to produce PCL having an Mn of greater than 70 000. 相似文献
The enantiomeric ratio E of enzyme‐catalyzed (Candida antarctica lipase and lipase PS) and chemo‐catalyzed (L ‐proline‐based diamines) acylation reactions of 1‐(naphthalen‐2‐yl)ethanol, 2‐phenylpropanol, and 2‐benzylpropane‐1,3‐diol is dependent on solvent and temperature. Plots of ln E vs. 1/T showed the presence of inversion temperatures (Tinv). The Tinv values for the bio‐catalyzed and the chemo‐catalyzed reactions are fairly in agreement, and correspond as well to the TNMR values obtained by variable‐temperature 13C‐NMR experiments on the substrates in the same solvent of the resolution. This result demonstrates that clustering effects in the substrate solvation manage the chemical and the enzymatic enantioselectivity, and, moreover, that the solute? solvent cluster is always the real reacting species in solution for chemical as well as for enzymatic reactions. 相似文献
A stereospecific synthesis of (2S)‐3‐(2,4,5‐trifluorophenyl)propane‐1,2‐diol from D ‐mannitol has been developed. The reaction of 2,3‐O‐isopropylidene‐D ‐glyceraldehyde with 2,4,5‐trifluorophenylmagnesium bromide gave [(4R)‐2,2‐dimethyl‐1,3‐dioxolan‐4‐yl](2,4,5‐trifluorophenyl)methanol in 65% yield as a mixture of diastereoisomers (1 : 1). The Ph3P catalyzed reaction of the latter with C2Cl6 followed by reduction with Pd/C‐catalyzed hydrogenation gave (2S)‐3‐(2,4,5‐trifluorophenyl)propane‐1,2‐diol with >99% ee and 65% yield. 相似文献
Enzymatic degradation of poly(ε‐caprolactone) has been successfully carried out in supercritical carbon dioxide (scCO2). Candida antarctica lipase smoothly catalyzed the hydrolytic degradation in scCO2 to give oligo(ε‐caprolactone). The degradation in the presence of acetone (5 vol.‐%) produced the oligomer of smaller molecular weight (less than 500) compared to that prepared without the additive. Matrix‐assisted laser desorption/ionization‐time of flight (MALDI‐TOF) mass spectrometry analysis showed that the degradation product was of a mixture of linear and cyclic oligomers. The addition of a very small amount of water also promoted the degradation of the polyester. 相似文献
The direct enzymatic synthesis of a cyclic trimethylene carbonate (1,3‐dioxane‐2‐one) monomer with/without a methyl substituent was carried out using dimethyl or diethyl carbonate and 1,3‐diol with the objective of producing aliphatic poly(trimethylene carbonate), a typical biodegradable synthetic plastic. The lipase‐catalyzed condensation of dimethyl or diethyl carbonate with aliphatic 1,3‐diols using immobilized Candida antarctica lipase (lipase CA) in an organic solvent at 70 °C afforded the corresponding methyl‐substituted and unsubstituted cyclic trimethylene carbonates. The cyclic trimethylene carbonates obtained by the reaction of dimethyl or diethyl carbonates with 1,3‐propanediol and 2‐methyl‐1,3‐propanediol were polymerized by lipase to produce the corresponding polycarbonates.
Total TMC yield as a function of the reaction time. 相似文献