Yasukatsu Maeda

Ring-opening copolymerization of succinic anhydride with ethylene oxide initiated by magnesium diethoxide

Abstract The ring-opening copolymerization of succinic anhydride (SA) with ethylene oxide (EO) was carried out by using mainly magnesium diethoxide (ME) as an initiator. ME was superior with respect to polymerization yield and number-average molecular weight (Mn) of the copolymers obtained. The copolymers were found to be alternating copolymers independent of feed monomer molar ratio. The yield and the Mn of the copolymers increased with the polymerization temperature and the time within 48 h. There was a maximum of Mn at a time of 48 h, at 100°C. The Mn of the alternating copolymers was as high as 1.3 × 104. The Mn of the copolymers increased proportionally with the increase of monomer/initiator molar ratio (M/I) up to M/I = 400. From analysis of the end-groups of low Mn of copolymers by 1H n.m.r., these copolymers were a mixture of two copolymers having different end groups. One had ethyl ester group connecting with SA at either end group, the other had ethyl ester group connecting with SA and hydroxyl group connecting with EO.

Study of biodegradability of poly(δ-valerolactone-co-L-lactide)s

The biodegradability of poly(δ-valerolactone-co-L-lactide)s was studied both with enzymatic (lipase from Rhizopus arrhizus) and nonenzymatic hydrolyses. The hydrolyzability was evaluated by recording the amount of the hydrolyzed water-soluble products. The enzymatic hydrolysis was considerably affected by copolymer composition. The copolyester, the most susceptible to enzymatic hydrolysis, was the one containing a 90 mol % δ-valerolactone unit. The copolymers were also nonenzymatically hydrolyzed at 70°C. The results were similar to those of enzymatic hydrolysis, confirming the influence of copolymer composition on the hydrolyzability. However, the L-lactide rich copolymers were more susceptible to hydrolysis. These results suggest that poly(δ-valerolactone) is easily degraded by lipase, whereas poly(L-lactide) is degraded through simple hydrolysis.

Synthesis and characterization of novel biodegradable copolyesters by transreaction of poly(ethylene terephthalate) with copoly(succinic anhydride/ethylene oxide)

Poly(ethylene terephthalate)/copoly(succinic anhydride/ethylene oxide) copolymers, (PET/PES copolymers) were synthesized by the transreaction between PET and PES and characterized with GPC, 1 H NMR, and DSC. Most of the copolymers obtained were random copolymers. The films cast of these copolymers were transparent. The thermal, mechanical properties, and biodegradability of the copolymers obtained were studied with respect to the composition and lengths of aliphatic and aromatic units in the copolymers. In the copolymers having high PET content, the melting points, due to the PET segment, were observed by DSC measurement, although the fusion heats of the copolymers were small. The enzymatic hydrolyzability by a lipase from Rhizopus arrhizus and biodegradability by activated sludge of the copolymers decreased with an increase in PET content. When the length of succinic acid unit in the copolymer was below 2, the hydrolyzability of the copolymers decreased considerably. The tensile strengths of the cast films prepared from the copolymers synthesized by the transreaction increased with an increase in PET content, whereas, the elongations at break decreased. Their tensile strengths were half, and the elongations were double compared to those of PET homopolymer film.

Synthesis and biodegradability of novel copolyesters containg γ-butyrolactone units

Abstract Copolymers were synthesized by ring-opening polymerization of γ-butyrolactone (BL) with cyclicesters. Comonomers used were l -lactide (LLA), glycolide (GL), β-propiolactone (PL), δ-valerolactone (VL) and e-caprolactone (CL). Tetraphenyl tin was used as an initiator. The copolymerization was carried out in bulk at 140°C for 4 days and the polymers were characterized by 1H n.m.r., 13C n.m.r., g.p.c. and d.s.c. The BL contents of the copolymers varied in the range 0 and 26 mol%. The number average molecular weights were from 1.3 × 103 to 1.5 × 105. When a small amount of the BL unit was introduced into the polymer chain, increased flexibility and excellent biodegradability were imparted to the polymer. However, excess of BL resulted in low molecular weight polymers with substantially low yields. D.s.c. measurements showed that the copolymers had one single endothermic peak at lower temperatures than those of the Tms of each homopolymer. The BL rich copolymers were shown to be amorphous. The statistical nature of the synthesized copolymers was confirmed with n.m.r. analysis. The copolyesters were hydrolyzed in distilled water at 70°C and their hydrolyzability was found to be affected by the chemical structure and polymer composition. The hydrolyzability of glycolide or lactide copolymers was high in comparison with other copolyesters. The BL-rich copolyesters were easily hydrolyzed. The copolymers were also hydrolyzed with lipases from Rhizopus arrhizus, R. delemar and Candida cylindracea in phosphate buffer solution (pH 7.0) at 37°C. Copolymers without substituents, such as the poly(BL-co-e-caprolactone)s, were easily enzymatically hydrolyzed. It is noteworthy that the non-enzymatic hydrolysis was not affected by the presence of substituents.

Synthesis of a new biodegradable copolyesteramide: poly(L-lactic acid-co-ε-caprolactam)

Novel copolyesteramides were synthesized by reacting L-lactic acid (LLA) with e-caprolactam (CLM) in the presence of Fe, Sn or Zn powder as a catalyst. The molecular weight of the copolymers was 3.7 × 10 3 when using tin as a catalyst. For the purpose of increasing the molecular weight of the copolymer, azeotropic removal of water from the reaction mixture was performed; the molecular weight increased to 8.4 × 10 3 . The biodegradability of the copolymers was evaluated by using a standard activated sludge. One of the copolyesteramides (mole ratio LLA/CLM = 45/55, Mn = 8.4 × 10 3 ) was degraded up to 50% after 33 d in contact with an activated sludge.

Properties and biodegradability of chain-extended copoly(succinic anhydride/ethylene oxide)

Chain-extension reactions were carried out using titanium-iso-propoxide (TIP) as a catalyst for a series of polyesters or copolyesterethers with low molecular weights (M n =1500–10,000) synthesized by the ring-opening copolymerization of succinic anhydride (SA) with ethylene oxide (EO). The copolymers having aM n from 25,000 to 50,000 of different properties were obtained. Both the melting point (T m ) and the fusion heat (δH), which indicate the crystallinity of the copolymers, rose with an increase in SA content in the copolymers. Semitransparent films were prepared by compression molding of the copolymers. The biodegradation of the copolymer films was evaluated by enzymatic hydrolysis by lipases and by an aerobic gas evolution test in standard activated sludge. The hydrolyzability of these copolymers by three kinds of lipases was affected by their copolymer composition SA/EO, form, andM n . The copolyesterether (SA/EO=43/57,M n =48,900) was more easily biodegraded by standard activated sludge compared to the polyester (SA/EO=47/53,M n =36,300).

Synthesis and biodegradation of copolyesterether of copoly(succinic anhydride/ethylene oxide) with triblock copolymer of poly(oxyethylene)-poly(oxypropylene)-poly(oxyethylene)

The thermal properties and biodegradability of the block copolyesterethers with copoly[succinic anhydride (SA)/ethylene oxide (EO)], synthesized by ring-opening copolymerization as a hard segment and the triblock copolyethers of poly(oxyethylene)-poly(oxypropylene)-poly(oxyethylene)(PN) as a soft segment, were studied. The block copolyesterethers synthesized from higher than 8000 number-average molecular weight (M n ) of copoly(SA/EO)s showed a microphase separation structure as determined by the thermal properties [melting point (T m ) and glass transition (T g )], at any polymer composition [EO/propylene oxide (PO)] or the determination of M n of PN. A decrease in the M n of copoly(SA/EO) or an increase in PO content in PN resulted in depression of heats of fusion (ΔH) of these block copolyesterethers. The enzymatic degradation of the block copolyesterethers by the lipase from Rhizopus arrhizus showed a substantial increase with a decrease in their ΔH, whereas it was depressed with an increase in the M n of polyoxyethylene or polyoxypropylene segment in the block copolyesterethers. The block copolyesterethers were degraded by microorganisms in activated sludge. The biodegradability of the block copolyesterethers showed a pronounced drop, with an increase in the polyoxyethylene chain length or polyoxypropylene content in PN. The polycondensation was also conducted without a catalyst at 190°C, similarly, to the reaction catalyzed with Ti[OCH(CH 3 ) 2 ] 4 at 170°C. The effect of the residual titanium on the biodegradability of the block copolyesterethers was negligible.

Synthesis and biodegradation of copolyesterether of copoly(succinic anhydride/ethylene oxide) with polyether

The thermal properties and biodegradability of block copolyesterethers based on copoly[succinic anhydride (SA)/ethylene oxide (EO)] (polymer composition range SA/EO 42/58-49/51 mol %), synthesized by ring-opening copolymerization and poly( ethylene glycol) (PEG) or poly(propylene glycol) (PPG), were studied. The block copolyesterethers synthesized from higher than 7000 molecular weight (M n ) or high SA content copoly(SA/EO), SA/EO = 48/52 or 49/51, and PEG showed melting points and fusion heats (ΔH) similar to those of the prepolymers without leading to a microphase-separation structure. Enzymatic degradability of the block copolyesterethers synthesized from biodegradable copoly(SA/EO) with a low SA content (SA/EO = 42/58 mol %) and PEG was significantly smaller compared to that of the chain-extended copoly(SA/EO) used as a prepolymer. On the other hand, the block copolymers synthesized by an equimolar amount of copoly(SA/EO) and PPG showed evidence of a microphase-separation structure. An increase in propylene glycol (PG) content interfered with the formation of a microphase-separation structure. However, the block copolyesterethers including nonbiodegradable copoly(SA/EO), with a high SA content (SA/ EO = 49/51 mol %), and PPG were found to be enzymatically degradable. In the biodegradation testing with standard activated sludge, the block copolyesterethers were degraded by microorganisms in activated sludge. The relationship between polymer composition and the biodegradation rate by activated sludge shows a similar trend to that of enzymatic hydrolysis.

Studies on poly [acrylamide-co-(ε-caprolactone)] synthesis, characterization and biodegradability

The synthesis, characterization, hydrolysis and biodegradation of a copoly(ester amide), poly[acrylamide-co-(e-caprolactone)], are described. The hydrogen transfer copolymerization of acrylamide (AA) with e-caprolactone (CLN) in the presence of butyllithium or calcium hydride as initiators has been investigated. The calcium hydride was effective for the synthesis of the copoly(ester amide) in a wide range of polymer composition (AA/CLN = 10:90 to 90:10). The copoly(ester amide) was readily hydrolyzed in th presence of hydrochloric acid (0,1 n) at 125°C in an autoclave (e.g. AA/CLN = (e.g AA/CLN = 59:43, degradation 93%). Furthermore, the copoly(ester amide) was hydrolyzed enzymatically by lipase from Rhizopus arrhizus. The behavior of the enzymatic hydrolysis differed to the non-enzymatic hydrolysis. The enzymatic hydrolyzability was remarkable in the range of the AA repeating unit (β-alanine unit) from 10 to 40 mol-% e.g. AA/CLN = 27:73, degradation 44%), wile, the degradability for non-enzymatic hydrolysis rose with increasing AA repeating unit content. The biodegradation of the copoly(ester amide) was evaluated using a standard activated sludge (e.g. AA/CLN = 27:73 biodegradation 45%). The relationship between the biodegradation and the polymer composition was similar for the standard activated and the enzymatic hydrolysis.