Synthesis of Poly(Tetramethylene Ether) Glycol Containing Ester Linkages Derived from Castor Oil and Properties of Recyclable Polyurethanes Prepared Therefrom

以蓖麻油为原料合成了含酯键的聚四亚甲基醚[或聚四氢呋喃]二醇{HO-CH[（CH 2）5CH 3] CH 2 CH =CH（CH 2）7-C（=O）O-[（CH 2）4 O]n-1-（CH 2）4-OC（=O）-（CH 2）7-CH= CH-CH 2 CH [（CH 2）5CH 3]-OH; PTHF-RA-OH}。该多元醇与2倍量的4，4 ′-二苯基甲烷二异氰酸酯反应，再与1，4-丁二醇扩链，得到了一种含可降解酯基的新型聚氨酯。所得聚氨酯（PTHF-RA-BD-PU）的热性能和力学性能与由聚四氢呋喃二醇（PTHF-OH）或聚四氢呋喃二醇（PTHF-OH）制备的聚氨酯（PTHF-BD-PU）相似。PTHF-RA-BD-PU在四氢呋喃/乙醇（9/1 v/v）溶剂中，在少量水存在下，用氢氧化钾处理，使蓖麻油酸酯键发生水解反应，得到PTHF-OH和蓖麻油酸封端的聚氨酯低聚物的混合物，用二氯甲烷萃取，PTHF-OH的回收率在90%以上产率基于PTHF-RA-BD-PU的聚（四氢呋喃）链段。以脂肪酶为催化剂，对PTHF-RA-BD-PU进行酶降解。PTHF-RA-BD-PU在37 ℃的磷酸盐缓冲溶液（pH7.4）中与薄膜样品的非均相反应和在45 ℃的N，N-二甲基甲酰胺中的均相反应均导致PTHF-RA-BD-PU的分子量降低。这可能是由于PTHF-RA-BD-PU的蓖麻油酸酯基团的脂肪酶催化水解。

Ricinoleic acid derived from castor oil was utilized for the preparation of ester linkages-containing poly(tetramethylene ether) [or poly(tetrahydrofuran)] glycol {HO-CH[(CH2)5CH3]CH2CH=CH(CH2)7-C(=O)O-[(CH2)4O]n-1-(CH2)4-OC(=O)-(CH2)7-CH=CH-CH2CH[(CH2)5CH3]-OH; PTHF-RA-OH}. This polyol was reacted with two-fold amount of 4,4’-diphenylmethane diisocyanate followed by the chain-extension reaction with1,4-butanediol to give a new polyurethane with degradable ester moieties. The obtained polyurethane (PTHF-RA-BD-PU) exhibited similar thermal and mechanical properties to those of the polyurethane (PTHF-BD-PU) prepared from poly(tetramethylene ether) [or poly(tetrahydrofuran)] glycol (PTHF-OH). The treatment of PTHF-RA-BD-PU with potassium hydroxide in tetrahydrofuran/ethanol (9/1 v/v) solvent in the presence of a small amount of water caused hydrolysis reaction of the recinolate ester linkages to give the mixture of PTHF-OH and the urethane oligomers capped with recinoleic acid moieties.The extraction of PTHF-OH with methylene chloride from the mixture resulted in the recovery of PTHF-OH in over 90% yield based on the poly(tetrahydrofuran) segments of PTHF-RA-BD-PU. Enzymatic degradation of PTHF-RA-BD-PU was carried out with lipase as a catalyst. Both of the heterogeneous reaction with film specimens in water using phosphate buffer solution (pH 7.4) at 37 oC and the homogeneous reaction in N,N-dimethylformamide at 45 oC caused the decrease in the molecular weight of PTHF-RA-BD-PU. This is probably due to the lipase-catalyzed hydrolysis of the recinolate ester groups of PTHF-RA-BD-PU.