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一种新型含炔基的聚合2-乙基-2-噁唑啉引发剂的合成

A Novel Initiator Containing Alkyne Group for the Polymerization of 2-Ethyl-2-oxazoline

  • 摘要: 本文利用2-苯基-1,3-二氧六环-5-醇合成了含有一个炔基和两个三氟甲磺酸酯基的三官能团引发剂.首先,2-苯基-1,3-二氧六环-5-醇与炔丙溴反应制得含炔基的中间体.然后在稀盐酸和四氢呋喃水溶液中反应制得含双羟基的中间体,最后在四氯化碳中与三氟甲磺酸酐反应制得新型引发剂.该引发剂的结构由核磁共振氢谱确认.并且用该引发剂引发2-乙基-2-噁唑啉的聚合,得到窄分布的聚合物.作为对比,本文同时合成了一种含两个甲苯磺酸基的引发剂,由于两个甲苯磺酸基之间存在较大的空间位阻,该引发剂聚合所得的聚(2-乙基-2-噁唑啉)分布较宽,并且在反应后的体系中存在大量的未反应的引发剂.为了进一步研究位阻效应对2-乙基-2-噁唑啉聚合的影响,合成了一种线性的含一个甲苯磺酸基的引发剂,用该引发剂引发聚合体系中仍有大量未反应的引发剂存在,说明位阻效应和亲电平衡均会影响2-乙基-2-噁唑啉的阳离子开环效率.聚合物分子量及分子量分布通过核磁共振氢谱,基质辅助激光解吸电离-时间飞行质谱和尺寸排阻色谱表征.

     

    Abstract: A novel trifunctional initiator with one alkyne and two trifluoromethanesulfonate moieties was synthesized from a protected alcohol 5-hydroxyl-2-phenyl-1, 3-dioxane. The alkyne functionalized intermediate with two protected alcohol groups was synthesized by reacting with propargyl bromide. The alcohol groups were cleaved using a mixture of tetrahydrofuran and hydrochloric acid aqueous solution. In the last step the initiator was synthesized using triflic anhydride in carbon tetrachloride. The initiator was characterized by 1H NMR and used for the polymerization of 2-ethyl-2-oxazoline which gives polymers with narrow distribution. For comparison a similar initiator with two tosylates was prepared and used for the polymerization of the monomer 2-ethyl-2-oxazoline, the resulting product has a wide molecular weight distribution and most of the initiator remains unreacted after 24 h which may be due to the steric hindrance between the two tosylate groups. To further explore the steric hindrance phenomenon, a linear tosylate initiator was synthesized, but still some of the initiator remains unreacted, illustrating that both steric hindrance and electrophilic balance affect the efficiency of the cationic ring-opening polymerization. All of the polymers were characterized in detail by using 1H NMR, matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy, and size exclusion chromatography to confirm the purity and distribution of the polymers.

     

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