【作者】 李璇；

【导师】 杨玉良；

【作者基本信息】 复旦大学 ， 高分子化学与物理， 2009， 博士

【摘要】 现代科技的发展日新月异,结构简单、组成单一的高分子材料往往难以满足对性能日益广泛和苛刻的要求。新型高分子材料的分子设计及现有的聚合物材料的共混改性已经成为高分子材料高性能化的研究重点。可以通过改变聚合物分子量、共聚物组成、分子链构型等分子参数和调节温度、剪切等加工工艺获得不同尺寸和形状的新型功能材料。聚合物的相行为及其动力学研究与高分子材料内部结构的形态生成与控制密切相关,因而直接影响到材料的最终性能。结构复杂、组成多样的聚合物体系能够赋予新材料优异的结构与性能,但额外增加的分子参数与工艺条件将使材料的设计更为复杂和难以控制。理论研究可以帮助人们理解多组分聚合物体系相分离的控制因素,预测多相复杂结构聚合物体系有序或部分有序结构,设计理想的新型材料。目前为止,高分子理论的研究还没有在复杂嵌段高分子材料结构性能、复合改性、加工成型等方面进行过系统的阐述。本论文试图通过不同的理论方法,包括平衡热力学理论和相分离动力学等,对上述问题给出初步的解答。将聚合物的微观结构与高分子材料的宏观性能与流变行为相联系,重点考察了多组分聚合物体系的相行为和力学性能。在以下几个方面展开研究:剪切场下复杂嵌段高分子的相行为;嵌段高分子相分离动力学机理及流变行为;嵌段高分子的结构与组成对有序无序相转变温度（ODT）的影响;预测共聚物组成与结构对多元共混高分子体系热力学相容性与相分离形态的影响;两亲性嵌段共聚物在选择性溶液中的自组装行为。第一章:绪论部分,对本文涉及到的理论方法和研究内容作出了阐述。第二章:由于高分子材料的加工不仅仅是为了成型这样一个单纯的物理过程,同时也是一个性能调控过程,因此对温度场、外部流场等导致高分子复杂流体的相结构及其流变学的研究一直是凝聚态物理及高分子科学的前沿领域。本章中利用DSCFT耦合可变形元胞算法描述剪切的边界条件,研究了高分子聚合物的不同链拓扑结构,例如A/B均聚物共混物与AB二嵌段共聚物、线型ABC与星型ABC三嵌段共聚物,在稳态剪切场下的相行为。并考察了具有不同链结构的线型嵌段共聚物嵌段在振荡剪切场下的相行为,分别阐述了线型ABC三嵌段共聚物、（AB）_n型多嵌段共聚物在振荡剪切场中形成三种层状相取向（平行相Parallel,垂直相Perpendicular,纬向垂直相Transverse）所需的剪切条件。第三章:材料科学的研究中,一个重要目的就是希望能够通过已知微观结构得到其宏观的力学性能。虽然,已有部分理论工作可以用于材料力学性能的预测,但是关于嵌段共聚物的结构—性能方面的理论研究仍然比较匮乏。我们在动态自洽场理论的基础上,将应变场作为一种外场的影响自然地引入到自洽场理论的单链传播因子q（r,s）中,可以得到体系的应力—应变关系,并且由此计算得到的力学性能包含了高分子链拓扑结构的信息,可以用以考察聚合物的微观结构对材料动态力学性能的影响。首先研究了三嵌段共聚高分子相分离得到有序相结构中的应力分布情况;然后根据单链传播因子q（r,s）解出的应力与应变曲线进行线性拟和得到储能模量G’。利用G’对微相结构的变化很敏感的特点,比较了AB两嵌段共聚物与A/B共混物的的熔体淬冷后的相分离机理,并与先前实验的图案和其他理论结果进行了比较,证实了算法的可靠性;最后,比较了线型ABC和星型ABC三嵌段高分子由于链拓扑结构的不同导致的相分离机理上的差异。第四章:研究了共聚物的分子参数与有序无序相转变温度（ODT）之间的关系,对改善材料的加工性能具有潜在的应用价值。因为储能模量G’与相分离微相结构紧密关联,所以可以利用模量G’的改变追踪相转变中形态的细微变化。我们在动态自洽场方法DSCFT的基础上,通过缓慢改变Flory-Huggins相互作用参数X模拟了实验中的温度扫描过程并得到相应的X_ODT。研究了共聚物的分子参数对相互作用能X^N_ODT的影响。分别就多嵌段共聚物的拓扑结构和多分散指数对体系ODT行为的影响进行了详细的研究和讨论。动态自洽场方法DSCFT比从热力学平衡相形态上判断ODT或OOT更加灵敏,在转变点附近受浓度涨落的影响也较小。第五章:聚合物共混改性是实现高分子材料高性能化、精细化、功能化和发展新品种的重要途径之一。随着共混组分数的增加以及高分子链拓扑结构的复杂性增加,共混物内部能够相分离形成各种不同的复杂结构。本章利用Flory-Huggins格子平均场理论和动态自洽场方法DSCFT,研究了聚合物的组成与结构对多元共混高分子体系热力学相容性和平衡相形态的影响。预测了几种聚丙烯/弹性体/塑料三元共混体系的相容性,提出改善体系相容性的建议,并与实验结果进行了比较验证;另外,通过动态自洽场方法DSCFT模拟了聚丙烯多元共混体系的形态,对相分离过程中得到的特殊形态和各形态出现的条件作出阐述。模拟结果表明:体系的形态受共聚物的组成影响很大。通过调节共聚物的组成与嵌段结构,可以得到多种复杂的多相形态。第六章,聚合物与溶剂的混合溶液体系可以看做多组分聚合物共混的另一种形式,其涵盖了涂料、胶粘剂、生物降解及医用缓释材料等诸多研究领域而得到人们的广泛关注。木章应用SCFT自洽场理论研究了两亲性嵌段共聚物在选择性溶液中的自组装行为,重点讨论了“crew-cut”型两亲性嵌段高分子中嵌段的多分散指数对自组装形态的影响以及具有复杂拓扑结构如星型（star）、梳形（comb-coil）的两亲性嵌段高分子的稀溶液自组装形态。另一方面,由于合成技术的不断发展,星型、环型、（超）接枝分子结构与常见的线型分子结构在自组装过程中具有明显的区别,验证了分子结构能显著影响自组装过程、自组装体的形态和不同形态间的演变。本章的理论研究为制备和控制两亲性嵌段高分子在溶液中的自组装形态提供了一定的理论依据。更多还原

【Abstract】 Simply structured and homogeneous macromolecular materials are falling short of the urgent demands of developing advanced materials with excellent properties,as the modern techniques are growing rapidly.Designing novel molecular structure or blending of the existing polymers have become the focus of obtaining advanced materials.It is possible to acquire new function materials,which has diversified sizes and shapes,by tuning molecular parameters such as molecular weight、molecular architecture、copolymer compostion and processing conditions such as temperature、external shear field,etc.The study on phase behaviors and rheological properties has close relationship with macromolecular materials’ pattern formation and properties,which ultimately linked to the performance of these materials.Complex polymer systems not only provide people with novel materials capable of performing various purposes and possessing excellent properties,but also add extra parameters and conditions to confuse the material design.Therefore,theoretical study which is able to help people understand the governing factors of the behaviors of multicomponent polymer systems,assist in the designing of advanced materials.People are now paying more attention to the set up of appropriate theorectial methods to predict、design and control the process of obtaining ordered multiphase complex polymer systems.Till recently,there is still lack of a systematic description of the relation between complex polymer structure and property、composite modification、processing conditions.In this dissertation,we managed to give a primary answer to the previous questions by combining different theoretical methods,such as equilibrium thermodynamics and phase separation dynamics,etc.The link beween microscopic molecular structures and macroscopic properties and rheological behaviors enables us to study the phase behavior and mechanical properties of complex polymer systems.The results are presented in the following parts:complex block copolymers under external shear;phase separation dynamics and rheological properties of block copolymers;the effect of molecular structure and composition on Order-Disorder Transition temperation;prediction of miscibility and morphology of multicomponent polymer blends;self assembly of amphiphilic copolymers in dilute solutions.Chapter 1,gives the overview of the theoretical methods and research purposes.Chapter 2,external field effects and their resulting properties have long been studied in the frontier of condensed matter and macromolecular science.For instance, polymers can be oriented in the external flow field.We combine DSCFT scheme with variable cell shape method in the description of boundary conditions,and applied to the study of topological effect,such as differences between A/B blends and AB diblock、linear ABC and star ABC triblock copolymers,on the behavior of these copolymers under simple shear flow.After that,topologically different linear copolymers are treated under the oscillatory shear.The results are able to give the shearing conditions for the appearance of lamellae orientations such as Parallel, Perpendicular and Transverse.Chapter 3,one of the most important goals in the material research is to obtain macroscopic properties and rheological behaviors from known micro structures. There are few theoretical methods capable of predicting mechanical properties,yet the researches on the structure-property relation of block copolymers are still fancy. We obtain the stress-strain relations by introducing the deformation field into the DSCFT functions and sinle chain propagator q(r,s).Therefore,the topological information is naturally put into the calculation which enables the study of the relation between micro structures and rheological properties.At first,we give the stress distribution of triblock copolymers.Then,storage modulus G’,which is sensitive to the possible structure change,is calculated by linear fit of stress-strain curves,and is used to compare the differences between AB diblock and A/B blend in the phase separation mechanism.Finally,the DSCFT scheme is applied to distinguishing of one step,two step separation mechanism in linear and star ABC triblock copolymers.Chapter 4,the study on ODT and OOT of block copolymers is able to help to the design of processing conditions in the industry.Variable cell shape DSCFT proposed in this dissertation not only take into account the relation between storage modulus G’ and interaction parameters x~N,but topological and polydispersity effects on the ODT of block copolymers.Chapter 5,polymer blends,which exhibit outstanding microstructure and excellent properties,have become more and more important in the advanced material design.In this chapter,Flory-Huggins mean field theory and DSCFT scheme is used to investigate the component and topological structure effects on the miscibility and equilibrium morphologies of polymer blends.Miscibility of ternary blend systems such as PP/Elastomer/Plastic are predicted and verified by previous experimental results.Possible advices are given for the improvement of the miscibility.Then, DSCFT scheme is applied to the study of pattern formation of PP multiphase systems.We give detailed description of the particular morphologies and conditions for these morphologies to occur.The simulation results show that the composition of the copolymers have fundamental impact on the pattern formation of the blend system.Chapter 6,polymer and solvent mixtures can be regarded as another type of multicomponent blends,which had covered areas of paints,coatings,adhesives and biodegradable materials.In this chapter,SCFT is applied to study self-assembly of amphiphilic block copolymers in selective solvents.The polydispersity effect of "crew-cut" AB diblock copolymers and different architectures such as star、comb-coil on the self-assembled morphologies in solution has been investigated.The theoretical results provide useful guidance to the synthesis and preparation of various types of aggregates in dilute solutions.更多还原