【作者】 于洋；

【导师】 魏志勇；

【作者基本信息】 大连理工大学 ， 高分子材料， 2019， 博士

【摘要】 不可再生石油资源的濒临枯竭与环境污染的日益严重已经成为人类主要面临的两大难题。近些年来,生物基可降解脂肪族聚酯越来越多的得到社会、科学和经济领域的关注,它不仅可以降低人们对石油资源的依赖,还可以减少高分子材料对环境的破坏。大量的脂肪族二元酸和二元醇小分子可以直接从生物质中提取或由微生物发酵而获得。这些生物基小分子能够在分子水平上被精确地设计,合成具有石油基聚合物性能的材料。因此,生物基脂肪族聚酯被认为是最有希望的石油基材料替代品之一,必将成为人类生产生活中的重要组成部分。在实际应用中,人们通常通过共聚合方法制备无规结构的脂肪族共聚酯,这样不仅可以将两种均聚酯的性质进行综合,还可以通过调节共聚组分比例来控制共聚酯的各项性能。由于无规共聚物的化学单元是完全无规连接在一起的,因此表现出复杂的结晶行为。无规共聚物的热力学性质、结晶性质以及相转变规律仍有许多问题亟待解决。本论文以生物基脂肪族二元酸和二元醇为单体设计合成了多种性能优异的、化学结构可控的饱和脂肪族共聚酯以及不饱和脂肪族共聚酯。系统研究了共聚单元链长、奇偶性、不饱和双键的几何构象结构等因素对共聚酯物理性能的影响,并提出了理论模型以便于深入了解共聚单元化学结构对共聚物相态行为的调控规律,主要研究内容与结果如下:(1)采用1,6-已二醇、丁二酸与不同碳链长度的二元酸,设计合成了四个系列生物基偶-偶脂肪族共聚酯。通过多种手段的表征,确认四个系列共聚酯均为异质同二晶体系。四个系列共聚酯中,晶型转变点处的共聚单元组成随共聚二元酸碳链长度的变化而改变。具有更长碳链长度的二元酸具有更强的结晶竞争能力,即使在含量较小的情况下,也能够控制共聚酯的晶体结构。此外,基于Wendling-Suter理论计算得到了共聚单元相互插入时的吉布斯自由能,进一步定量分析了共聚单元相互插入的难易程度。结果表明,共聚二元酸链长对共聚单元的相互插入起决定性作用。基于以上研究,完善了“链长插入-排斥模型”,这一模型有助于理解脂肪族聚酯碳链长度对异质同二晶行为的调控规律。(2)通过调控单体二元醇链长以及二元酸链长设计合成了五种生物基奇-偶脂肪族共聚酯,并对奇-偶脂肪族共聚酯的共结晶行为进行了深入研究。发现在奇-偶共聚酯中存在一个严格异质同晶体系,严格异质同晶是一种非常罕见的结晶行为。此外,发现共聚二元醇的链长对异质同二晶行为同样会产生重要影响。此部分工作结合偶-偶脂肪族共聚酯的研究,提出了异质同晶与异质同二晶体系中共聚单元“竞争性”与“相容性”的概念,这有助于深入理解脂肪族聚酯中化学结构与共结晶行为之间的关系。此外,通过关联共聚酯的异质同二晶行为与材料机械性能之间的关系,发现共聚单元间的“竞争性”与“相容性”可以预测共聚物机械性能的变化,为设计合成所需要力学性能的聚酯提供了新的思路和方法。(3)采用顺-2-丁烯-1,4-二醇、1,4-丁二醇以及丁二酸共聚,合成了包括全组分范围的聚(丁二酸丁二酯-共-丁二酸顺丁烯二酯)(PBScBS)生物基共聚酯。在优化的反应条件下制备了高分子量的线性PBScBS不饱和聚酯,反应过程中顺-2-丁烯-1,4-二醇的非共轭顺式双键没有发生交联以及异构化副反应。通过对PBScBS共聚酯的热性能以及结晶行为的分析研究,表明PBScBS不饱和聚酯为异质同二晶体系。PBScBS具有优异的机械性能,表现出了良好的韧性。PBScBS中两种共聚单元之间仍然存在较大的“竞争性”与“相容性”的差异,这是由于顺-2-丁烯-1,4-二醇单元的插入带来的几何构象效应导致的。PBScBS中的“竞争性”与“相容性”直接影响了其球晶形态,尤其是对环带间距产生了微妙的影响。此外,PBScBS中共聚单元间的“竞争性”与“相容性”仍然可以用来预测共聚物机械性能的变化,表明“竞争性”与“相容性”对共聚物的力学性能的影响规律在不饱和聚酯中仍然适用。(4)采用生物基来源的反式-β-氢黏康酸、富马酸和1,4-丁二醇共聚合成了全生物基的聚(反式-β-氢黏康酸丁二酯-共-富马酸丁二酯)(PBHBF)不饱和共聚酯。研究了不同组分下的聚合反应条件(催化剂用量、第二阶段反应温度以及时间)对产物的影响,找到了最优的反应条件,制得了高分子量的PBHBF,反应过程中无支化以及异构化等副反应发生。PBHBF呈现了异质同二晶特征,聚酯的熔点、结晶温度、玻璃化转变温度以及结晶度可以通过改变共聚单元组成来调控。PBHBF聚酯具有良好的热稳定性,宽的加工窗口。相比于低密度聚乙烯和其他常见的聚酯材料,PBHBF表现出类似的或更优异的力学性能。因此,具有优异综合性能的高分子量PBHBF在实际应用中有望作为环境友好型材料取代石油基的聚酯材料。(5)成功制备了高分子量、立构可控的聚(马来酸丁二酯-共-富马酸丁二酯)(PBMF)不饱和共聚酯。通过对PBMF的化学结构与物理性能的系统研究,阐明了几何构象结构对不饱和聚酯性能的影响。通过控制PBMF聚酯的立构结构可以调控其热性能、结晶性能以及机械性能。随着马来酸含量的增加PBMF聚酯从硬质塑料逐渐变为柔性弹性体,拓宽了 PBMF聚酯的应用范围。此外,发现PBMF可以作为一种具有化学选择性的功能化聚酯平台,含有功能性基团的伯胺分子可以与马来酸的顺式双键进行迈克尔加成反应,而富马酸的反式双键被完全保留下来。因此,通过绿色温和的迈克尔加成反应可以将多种功能性基团选择性地接枝到PBMF聚酯主链上,展现了其广阔的应用前景。更多还原

【Abstract】 The fossil resource depletion and environmental pollution have become the two primary challenges.Biobased degradable polyesters are materials with the required ecological advantages to offer alternative solutions for such challenges,which have witnessed increasing interest in society,academia and economy fields.A large number of small molecules such as aliphatic dicarboxylic acids and diols can be produced directly from agricultural and forestry products or by microbial fermentation.Moreover,these biobased small molecules can be precisely designed at the molecular level to synthesize materials with properties similar to those of petroleum-based polymers.Therefore,biobased aliphatic polyesters are considered as the most promising alternative to petroleum-based materials,which would become an integral part of human society.In practice,aliphatic polyesters are usually prepared into random copolyesters by copolymerization,which can not only combine the properties of the two homopolyesters,but also control the properties of copolyesters by adjusting composition.Random copolymers,with two or more different types of chemical units joined together at random,exhibit a complex phase behavior.Up to date,however,the thermodynamic properties,crystallization properties and phase transition laws of random copolyesters are still poorly understood.In this work,a variety of saturated aliphatic copolyesters and unsaturated aliphatic copolyesters with controllable chemical structures and excellent properties were synthesized from the biobased aliphatic dicarboxylic acids and diols.The influences of dicarboxylic acid or diol chain length,odd-even effect,and conformational geometric effect of unsaturated double bond on the physical properties of copolyesters were systematically studied,furthermore new theoretical models were proposed to give an insight into the mechanism of how does the chemical structure factor regulates the phase behavior of copolymer.The main results were summarized as follows:(1)Four series of biobased even-even copolyesters were designed and synthesized by 1,6-hexanediol,succinic acid and another comonomeric diacid with gradual increases in chain length.Isodimorphism was confirmed for all the copolyesters by means of several characterization and analysis methods.The hexamethylene succinate(HS)composition of crystal type transition point for the four copolyesters was different depending on the comonomeric diacid chain length.The comonomer diacid with longer chain length had stronger competitive ability in controlling the cocrystallization even when they were present in a minor proportion.Moreover,the mutual insertion content of comonomers was quantificatively investigated by the defect Gibbs energy calculated from Wendling-Suter method.It indicated that the chain length of comonomer could exert a decisive influence on the degree of mutual insertion of comonomers.Moreover,the chain length inclusion-exclusion model on the basis of the Wendling-Suter theory was proposed to give an insight into the mechanism of how does the chain length of comonomers regulate the isodimorphism behavior.(2)Five series of biobased odd-even copolyesters varied with chain length of dicarboxylates and diols were designed and prepared,and the cocrystallization behavior of these five odd-even copolyesters were studied systematically.A new strict isomorphism copolyester was revealed,which was a very rare crystallization behavior for copolymer.In addition,the chain length of comonomeric diols can also exert a considerable influence on the isodimorphic behavior of copolyesters.This part in combination with the even-even copolyester study,we constructed the concept of "competition" and "miscibility" for isomorphism and isodimorphism in order to shed some insight on the relationships between the chemical structure and cocrystallization.Furthermore,a close dependence between the mechanical properties with"competition" and "miscibility" in such copolyesters was observed and discussed.Hence,the present study regarding the effect of comonomeric chain length on the "competition" and"miscibility" provided a guidance in the selection of comonomers for preparation of aliphatic copolyesters with desirable performances.(3)Biobased copolyesters poly(butylene succinate-co-cis-butene succinate)(PBSeBS)with various compositions were synthesized using cis-2-butene-1,4-diol,1,4-butanediol and succinic acid for the first time by optimized methods,achieving linear random copolyesters without isomerization or cross-linking side reactions.Isodimorphism was confirmed for PBScBS by means of several characterization and analysis methods.The tensile properties of PBScBS were assessed,suggesting all the copolyesters exhibited high elongations at break and outstanding toughness.More importantly,significant differences of "competition" and"miscibility" between comonomer units existed in PBScBS,which resulted from the conformational geometric effect of cis-double bonds in cis-2-butene-1,4-diol.The "competition,,and "miscibility" directly affect the band spherulites of PBScBS,especially to the band spacings.Meanwhile,in unsaturated copolyesters,the laws of dependence of mechanical properties with"competition" and "miscibility" still apply.(4)Fully biobased poly(butylene hydromuconoate-co-butylene fumarate)(PBHBF)unsaturated copolyesters were successfully synthesized from trans-β-hydromnconic acid,fumaric acid,and 1,4-butanediol by a melt polycondensation.Polymerization conditions(catalyst amount,reaction temperature and reaction time)were changed to improve PBHBF and molecular weight.The optimized strategy was considered to be applicable for preparing high molecular mass unsaturated polyesters without isomerization or cross-linking side reactions.On the basis of studies for thermal and crystallization properties,PBHBF showed an isodimorphism character,and in sum,the degree of crystallization and glass transition,melting,and crystallization temperatures could be effectively adjusted though the control of comonomer composition.PBHBF showed a good thermal stability and a broad processing window.In all cases,PBHBF exhibited excellent mechanical performances at room temperature similar to,or even better than,those of low density polyethylene and the most popular aliphatic polyesters.Due to the potential biodegradability and excellent thermomechanical properties,these fully renewable unsaturated polyesters are expected to be alternatives to the fossil fuel-derived polyesters and polyethylene for practical applications.(5)A universal method for the facile synthesis of stereochemistry-controllable poly(butylene maleate-co-butylene fumarate)(PBMF)copolyesters was presented.The microstrUcture and physcial properties of PBMF were systematically investigated to illuminate the respective conformational geometric effect of cis and trans isomers on the physical properties of copolyesters.These stereochemistry-controllable copolyesters transform from rigid plastics into flexible elastomers with the variation of the stereochemistry composition.The variation of the stereochemistry composition of PBMF allowed the crystallization,thermal and mechanical properties to be tailored over a broad range.Finally,the prepared unsaturated copolyesters were further exploited as a chemoselective polymer platform to incorporate various functional groups through a green and mild Michael addition reaction onto the backbone,showing the potential of PBMF for a wide variety of applications.更多还原