Presentations

本報では熱硬化型のエラストマー素材としてポリリシノール酸、生分解性を有する熱可塑型エラストマーとして12-ヒドロキシ酸系共重合体について、その合成と物性について概説した。 １．熱硬化型ポリエステルエラストマー　 「ポリリシノール酸」 　ヒマシ油より得られるリシノール酸を原料にリパーゼ（油脂分解酵素）を触媒として80℃、96h反応を行うことで分子量約10万の高分子量ポリリシノール酸を合成した。得られたポリリシノール酸は低温性に優れ、生分解性を有する液状のポリマーであった。さらに汎用の架橋剤により速やかに架橋・硬化し、優れたエラストマー性能を発現した。 ２．種子油由来の熱可塑性エラストマー「ポリ( 12HD-co -12HS )」 　種子油より得られる12-ヒドロキシステアリン酸(12HS)および12-ヒドロキシドデカン酸(12HDA)を原料にリパーゼを触媒として共重合体を合成した。12HS含量の増加とともに弾性率は低下し、20mol%以上で優れたエラストマー性能が発現した。さらに合成した共重合体は優れた生分解性を示した。

The enzymatic ring-opening polymerization (ROP) behavior of cyclic thioester was studied and compared with that of cyclic oxyester. It was found that the cyclic oxyester polymerized significantly faster than the cyclic thioester by the lipase. A living nature of the polymerization was observed for the ROP of cyclic thioester, and the rate-determining step was determined to be the deacylation of the enzyme-activated monomer by the propagating thiol chain.

Poly[poly(ethylene glycol-co-cyclic acetal)] (PECA) hydrogel consisting of degradable cyclic acetal segments and hydrophilic poly(ethylene glycol) segments was synthesized. A toxicity study of PECA and degradation products upon BMSC viability showed that there was little effect of PECA molecular weight on cell viability. Bulk PECA hydrogels were incubated in PBS buffer at 37°C during long term in vitro degradation, with results indicating that approximately 40% of the hydrogel dry mass was lost after 5 months. Results further confirmed that there was minimal change in pH during degradation. BMSCs were encapsulated in PECA hydrogel and were observed by fluorescence microscopy. Cells were viable inside PECA hydrogels after 14 days incubation. This work demonstrates that PECA hydrogels may be a viable biomaterial for cell transplantation as well as other biomedical applications.

Cyclic oligo(tetramethylene carbonate) was synthesized by the condensation of butane-1,4-diol and diphenyl carbonate in a toluene solution using immobilized lipase from Candida antarctica (lipase CA) as an environmentally benign catalyst. The cyclic oligo(tetramethylene carbonate) was readily polymerized by lipase CA in bulk to produce poly(tetramethylene carbonate) (PTeMC) with a molecular weight of 119,000. When the conversion was exceeded about 90 %, the degradation reaction was more pronounced than the propagation reaction, and the molecular weight of the polymer was gradually decreased. It was also found that PTeMC was amorphous as determined by DSC, and the contact angle of the PTeMC film was 83ｏ(±1.3ｏ). Sufficient cell viability and cell attachment of the PTeMC film were demonstrated

Chemical recycling of poly (butylene succinate) (PBS) was studied using a lipase with respect to the ring-size of the oligomer. It was found that PBS was degraded in a dilute toluene solution using a lipase (Novozym 435) to produce cyclic oligomers mainly consisting of dimer and trimer. The cyclic dimer produced a higher molecular weight polyester than cyclic trimer by the ring-opening polymerization. And differences between cyclic dimer and trimer on the ring-opening polymerization were analyzed. The cyclic dimer was exclusively obtained by sublimation under reduced pressure.

The poly(L-lactic acid) (PLLA)-based polymer blend, PLLA/polyethylene (PE), into repolymerizable oligomer was carried out using montmorillonite K5 (MK5) with the objective of developing a selective chemical recycling process. The PLLA in the PLLA/PE polymer blend was selectively degraded by MK5 in a toluene solution at 100 °C for 1 h to produce the LA oligomer (OLLA) having a molecular weight of a few hundreds. The PE remained unchanged by MK5 and was quantitatively separated by the reprecipitation method. The OLLA was repolymerized using a conventional chemical catalyst to produce a high-molecular weight PLLA.

Aliphatic polythionoesters were prepared by the one-pot thionoesterification of polycaprolactone, polypentadecanolactone, poly (butylene succinate) and poly (butylene adipate) using diphosphorus pentasulfide and hexamethyldisiloxane. And their physico-chemical properties as well as enzymatic degradabilities and chemical recyclabilities were evaluated.

Poly(diester-urethane) (PDEU) was prepared by the lipase-catalyzed polymerization of diethyl adipate and urethanediol which was prepared by the reaction of ethylene carbonate and amino alcohol. Also, poly(ester-urethane) (PEU) was prepared by the polymerization of hydroxyl carboxylic acid containing urethane linkage. Their polymerization behavior, mechanical properties, chemical recyclabilities and biodegradabilities were studied and compared with respect to the molecular structure.

アニオン性界面活性剤は優れた機能を発揮することから現在最も広く使用されている。しかし、多価金属イオンと不溶性の塩を形成し、洗浄力が著しく低下することが知られている。さらに、環境問題から界面活性剤は優れた生分解性とバイオベース由来原料の使用が求められる。これまでに著者らは、フマル酸オリゴマーが良好な金属イオン封鎖能と生分解性を有することを報告した。そこで、本報ではフマル酸オリゴマーを親水基に用い、長鎖アルキル基を導入することにより、金属イオン封鎖能と生分解性を併せ持つ界面活性剤を、グリーンなプロセスにより得た。さらに、得られた界面活性剤の界面活性能や金属イオン封鎖能といった機能及び生分解性について評価を行った。

プラスチックは優れた利便性から急速な発展を遂げ、金属材料やセラミックスとともに欠くことの出来ない材料となっている。その反面、廃プラスチックの処理、石油資源の枯渇やCO2濃度増大などの問題が顕在化し、生分解性プラスチックの開発や植物資源を利用した素材開発が強く求められるようになっている。本報では生分解性を併せ持つエラストマー素材を指向し、種子油より得られる12-ヒドロキシステアリン酸(12HS)および12-ヒドロキシドデカン酸(12HD)を原料に共重合ポリエステルを合成し、その特性について検討を行った。

優れた抗菌性と界面活性を有する第四級アンモニウム塩型カチオン性界面活性剤は多くの分野で使用されているが、循環型社会構築の観点から、環境調和性、高機能性、生分解性、さらにはリサイクル性が求められる。本報では、第四級アンモニウム塩に生分解性とリサイクル性を付与する目的で、分子内にカーボネート結合を有するジェミニ型カチオン性界面活性剤を設計し、それらのグリーンプロセスによる合成と機能について検討を行った。

Chemically recyclable and biodegradable polyesters were prepared using biobased and potentially biobased compounds, and their sustainable recyclabilities were studied using an environmentally benign catalyst, such as an enzyme or clay catalyst. Diol-diacid type green polyesters were prepared by the lipase-catalyzed polymerization of succinic, adipic, fumaric, maleic and itaconic acid with their reduction products of butane-1,4-diol, hexane-1,6-diol and 2-butene-1,4-diol. A high-molecular weight polyester was produced via the lipase-catalyzed ring-opening polymerization of the cyclic oligomer/monomer which was prepared by the condensation of the diol and diacid/diester in a dilute organic solution. The produced polyester was equally degraded into the repolymerizable cyclic oligomers by lipase (Figure 1). Furthermore, it was confirmed that no cis/trans isomerization of the fumarate, maleate and itaconate units occurred during the polymerization and recycling processes using a lipase. Also, the unsaturated polyesters were readily crosslinked by the conventional organic peroxides.

The nivel synthesis of a high molecular weight polythioester using an enzyme was studied. The enzyme-catalyzed polymerization may become one of the environmentally benign methods that meet the green chemistry requirements since no hazadous substance is used or generated. It is also an attractive method since polythioesters with a variety of molecular structures can be synthesized.

酵素及び微生物を用いたグリーンプラスチックのケミカルリサイクルについてまとめた

Environmentally benign poly(carbonate/ester-urethane) (PC/LU) was synthesized by the reaction of enzymatically prepared oligocarbonate diol and lactide oligomer end-capped by trimethylene glycol with hexamethylene diisocianate. Thermal and physical properties of PC/LUs were measured. And the enzymatic degradation of PC/LU was also evaluated.

Poly(ester-urethane) was synthesized from bio-based amino acid using an enzyme. Thermal and physical properties as well as chemical recyclability and biodegradability of poly(ester-urethane) were evaluated.