ABSTRACT:Ring-opening copolymerizations of succinic anhydride (SAn, 1) or maleic anhydride (MAn, 2) with propylene oxide (PO) were carried out by using magnesium diethoxide (Mg(OEt) 2 ) as a catalyst. The unsaturated polyester (P2a) was found to have only Z-configuration around a C=C double bond from its 1 H and 13 C NMR spectra. Isomerization reaction of P2a from Z-to E-configuration was performed in 1,2-dichloroethane with a catalytic amount of morpholine. Thus unsaturated polyesters, P2b-e, having the same molecular weight but the different ratio of Z-/E-configuration could be optionally prepared from one original polymer P2a by controlling isomerization reaction time. Biodegradability of these polyester samples was evaluated from their biochemical oxygen demand (BOD) values in the presence of an activated sludge. Polyester P2a was hardly degraded during measurement. However, polyesters P2b-e, partially containing E-configuration of the C=C double bond, degraded considerably faster than P2a itself. The biodegradability of saturated polyester P1 was also examined to compare with the P2-series.KEY WORDS Biodegradability / Unsaturated Polyester / Geometrical Isomer / Ring-Opening Copolymerization / Cyclic Acid Anhydride / Propylene Oxide / Synthetic polymeric materials have provided many advantages in our daily life for the last century, and become one of the most important materials. When once almost all of synthetic polymers are disposed after use, however, those cause serious environmental problems. Thus, biodegradable polymers have received much attention in recent years as one of the answer to solve the problems. In fact, biodegradable polymers, especially aliphatic polyesters, have been widely investigated by many scientists in the world.In spite of a large number of studies on biodegradability of polyesters, little attention has been given to unsaturated polyesters. 1-6 Tokiwa and Suzuki reported that a few unsaturated polyesters containing 2-butenediol unit could be hydrolyzed by lipase. 1 On the other hand, slightly cross-linked unsaturated polyesters, poly(hexamethylene fumarate) and poly(cis-2-butene fumarate), were hardly hydrolyzed by lipase.A carbon-carbon double bond in unsaturated polyesters has two geometrical isomers (Z-and Econfiguration), and such difference should affect their biodegradability. In controlling the biodegradation rate of polyester, it is very helpful to make geometrical effects clear. In our previous paper, 6 it was shown that in comparison with saturated polyesters, the ef- † To whom correspondence should be addressed. ficient degradation was prevented by introducing Zconfiguration of C=C double bond in the unsaturated polyesters but introducing E-configuration did not affect so remarkably. However, the variety of samples was limited because of the difficulty in preparation of samples having the same molecular weight and the different Z/E ratio. Although polycondensation method of unsaturated acid anhydrides with diol in the presence of acid as a catalyst was employed in prev...
ABSTRACT:Unsaturated polyesters, P1a and P2a, having different molecular weight were synthesized by solution polycondensation of maleic anhydride (MAn) with ethylene glycol (EG). Furthermore, unsaturated polyesters, poly(ethylene maleate/fumarate) (P1b-e and P2b-e), which have various ratios of different Z-/E-configuration at the C=C double bond were readily delivered from P1a and P2a, respectively, in 1,2-dichloroethane by using morpholine as a catalyst for isomerization. In order to discuss separately the effects of molecular weight of the samples on their biodegradability from the effects due to configuration of C=C double bond, several Z-or E-rich oligomeric model compounds having methyl esters as the terminal groups were prepared. The biodegradability of these polyester samples and oligomeric model compounds was evaluated from biochemical oxygen demand (BOD) values in the presence of an activated sludge. As the number-average molecular weight of both oligomeric model compounds and unsaturated polyesters was higher, their biodegradability was lowered by introducing C=C double bond, especially, by that of Z-configuration.KEY WORDS Biodegradability / Unsaturated Polyester / Geometrical Isomer / Polycondensation / Maleic Anhydride / Ethylene Glycol / Synthetic polymeric materials have provided many advantages in our daily life for the last century, and become one of the most important materials. When once synthetic polymeric materials are disposed, however, those often caused serious environmental problems. Thus biodegradable polymers which were completely decomposed to CO 2 and H 2 O in nature have received much attention in recent years as one of the answers to solve the problems. In fact, biodegradable polymers, especially aliphatic polyesters, have been widely investigated by many scientists in the world.In spite of a large number of studies on biodegradability of polyesters, little attention has been given to unsaturated polyesters. 1-7 Tokiwa and Suzuki reported that a few unsaturated polyesters containing 2-butenediol unit could be hydrolyzed by lipase. 1 On the other hand, slightly cross-linked unsaturated polyesters, poly(hexamethylene fumarate) and poly(cis-2-butene fumarate), were hardly hydrolyzed by lipase.A carbon-carbon double bond in unsaturated polyesters has two geometrical isomers (Z-and Econfiguration) and such difference should affect their biodegradability depending on the substrate specificity of enzyme. In controlling the biodegradation rate of polyester, it must be useful to make geometrical effects clear. In our previous paper, 6, 7 it was shown that in comparison with saturated polyesters, the ef- † To whom correspondence should be addressed . ficient degradation was prevented by introducing Zconfiguration of C=C double bond in the polyesters but introducing E-configuration did not do so remarkably. In addition to biochemical oxygen demand (BOD) measurement of polymer samples, dimethyl esters derived from the corresponding acids, maleic and fumaric acid, were measured. It was revealed...
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