Alternating Copolymerization of Aziridines and Cyclic Anhydrides

夏天

任伟民

硕士

大连理工大学

聚酯酰胺;;交替共聚;;可控聚合;;环状酸酐;;氮丙啶衍生物

聚酯酰胺是一种主链上既含有酯键又含有酰胺键的高分子聚合物。它结合了聚酯优良的生物降解性和聚酰胺优良的机械性能,在生物医学材料领域和智能材料领域有广阔的应用前景。本文开发了一种新型合成聚酯酰胺的方法,即通过环状酸酐与氮丙啶衍生物的交替共聚反应制备聚酯酰胺。相比于传统的缩聚法和开环聚合法,本论文开发的合成方法有如下优势:单体合成简单且种类丰富;通过改变两种聚合单体的组合方式可方便地调控聚酯酰胺结构;聚合过程简单高效可控。论文取得的具体结果如下:(1)发展了氮丙啶衍生物的高效合成方法。先通过苯甲醛与醇胺类化合物缩合后用硼氢化钠还原的方法制备氨基醇,再经过环化反应合成苄基保护的氮丙啶衍生物。该方法具有原料价廉易得、反应条件温和及收率较高的特点。同时,醇胺类化合物丰富的来源使得合成的氮丙啶衍生物具有多样化结构,也为调控聚酯酰胺性能提供了可能性。(2)实现了氮丙啶衍生物与环状酸酐交替共聚反应。以2-甲基-N-苄基氮丙啶(MBnAz)和邻苯二甲酸酐(PA)为单体,苄醇为引发剂,对催化剂的筛选结果显示,大位阻有机碱7-甲基-1,5,7-三氮杂二环[4.4.0]癸-5-烯(MTBD)展现出良好的催化活性,反应10 h,MBnAz的转化率达到73%,生成的共聚物分子量为13.5 kg/mol,分子量分布为1.14。电喷雾质谱(ESI-MS)结果表明聚合物具有完全交替的酯键-酰胺键结构。对反应过程进一步研究,发现聚合物的数均分子量与单体的转化率呈正相关线性关系,且始终保持较窄的分子量分布,表明聚合反应具有良好的可控性。二次加料实验进一步证明该反应具有活性聚合的特征。原位红外光谱跟踪实验证实聚合反应无诱导期,酯键和酰胺键对应的特征吸收峰同步增长。热性能测试显示该聚合物玻璃化转变温度为118℃,分解温度可达到257℃。底物拓展实验发现,多种氮丙啶衍生物和环状酸酐均能发生良好的聚合反应,生成的相应聚合物均呈现完全交替结构,显示此合成聚酯酰胺的方法具有良好的普适性。(3)实现了N-对甲苯磺酰基氮丙啶与环状酸酐的高效聚合反应,在聚合物主链引入酯键和酰胺键得到聚酯酰胺。以4-二甲基吡啶(DMAP)为引发剂,2-甲基-N-对苯基磺酰基氮丙啶(MTsAz)和PA聚合反应0.5 h,MTsAz转化率达到95%,聚合物分子量为21.1 kg/mol,分子量分布为1.15。ESI-MS谱图显示所得聚合物端基为DMAP且具有两组结构,分别为氮丙啶衍生物和酸酐的交替结构和氮丙啶衍生物的均聚结构。

Poly(ester-amide)s,of which the main chains contain alternatively distributed ester and amide,have been widely applied in the area of biomedicine materials,smart materials etc,due to their good biodegradable and mechanical properties.Herein,we developed a novel strategy of synthesizing poly(ester-amide)s via the copolymerization of cyclic anhydrides and aziridine derivatives.Compared with the conventional synthetic methods,such as the byproduct unavoidable polycondensation or monomer structures limited ring opening polymerization,the newly developed method showed many advantages including easily access to aziridine derivatives,tunable structures of the resultant copolymers,efficient and controllable copolymerization behaviors.The detail comments are as follows:(1)An efficient method for synthesizing aziridine derivatives was developed.The benzyl protected aziridine derivatives were synthesized through the condensation of benzaldehyde and hydramine compounds,the corresponding product was reduced by sodium borohydride(NaBH_4),followed by the cyclization reaction and afforded the corresponding aziridine derivatives.This synthetic method exhibited many advantages including readily available starting materials,moderate reaction condition and high product yields.The easily accessible hydramines enriched structures of the resultant copolymers,which provided the chance of tuning the properties of the resulting polymers.(2)The alternating copolymerization of the anhydrides and aziridine derivatives were successfully obtained usingorganic base/benzyl alcohol(BnOH)as catalyst.With the 2-methyl-N-benzylaziridine(MBnAz)and phthalic anhydride(PA)as model monomers,and BnOH as initiator,the organic base N-methyl-1,5,7-triazabicyclododecene(MTBD)exhibited excellent activity in catalyzing the copolymerization after catalyst screening experiments.The conversion of MBnAz reached to 73%after the copolymerization for 10 h,affording the resulted copolymers with the molecular weight(M_n)of 13.6 kg/mol and a narrow distribution of molecular weight(D)of 1.14.The MALDI-TOF spectrum revealed the perfectly alternating structures of the copolymers.The study on the polymerization process exhibitedthe linear increase in M_n with monomer conversion,accompanied with the narrowD,indicating well-controlled nature of the copolymerization.Furthermore,the second-feed experiment exhibited the living copolymerization character of the copolymerization.The in-situ IR experiment proved no induce period of the copolymerization,the synchronously increase in the intensity of the peaks representing ester and amide.The glass transition temperature of the PA/MBnAz copolymers was determined as 118℃,with the decomposition temperature up to 257℃.The aziridine derivatives with different structures can copolymerize with anhydrides,providing the corresponding copolymers with alternating structures,suggesting the excellent universality of this method for obtaining poly(ester amide)s with diverse structures.(3)The efficient polymerization of N-p-toluenesulfonylaziridine and cyclic acid anhydride to poly(ester amide)s with ester bond and amide bond in the main chain was obtained.Using 4-dimethylaminopyridine(DMAP)as the initiator for 2-methyl-N-p-toluenesulfonylaziridine(MTsAz)and PA polymerization for 0.5 h,the conversion rate of MTsAz reached to 95%,the molecular weight of the polymer was 21.1 kg/mol,and the molecular weight distribution was1.15.The electrospray mass spectrogram shows that the DMAP is the terminal part of resulting polymer with a two-component structures.The polymer has an alternating structures of aziridine derivatives and anhydrides and also with a homopolymerization structures of aziridine derivatives,respectively.