| 题名 | 两嵌段共聚物增容剂非对称对共混薄膜界面性质的影响 |
| 作者 | 蒋放 |
| 学位类别 | 硕士 |
| 答辩日期 | 2015-05 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 中国科学院长春应用化学研究所 |
| 导师 | 石彤飞 ; 卢宇源 |
| 关键词 | 薄膜 高分子共混 不对称嵌段共聚物 界面性质 Monte Carlo模拟 |
| 中文摘要 | 高分子薄膜在许多方面都有着广泛的应用，例如：民用塑料袋等产品、选择性渗透膜、光电器件、生物医药材料等。随着科学技术的不断发展，单一组分的薄膜已经不能满足人们对高分子薄膜的需求，人们通常将两种或多种均聚物共混来制备性能优异的高分子薄膜。然而，大多数均聚物很难相容，且嵌段共聚物能够改善均聚物共混薄膜体系各组分间的界面性质和相容性，因此，通常向均聚物共混薄膜体系中添加嵌段共聚物作为增容剂。在理论方面，因为高分子链间和链内的相互作用非常复杂，所以在其理论研究中需要引入大量的数学或物理近似；在实验方面，因为单分散的样品合成上非常困难，价格上也非常昂贵，且很难改变体系中粒子间的相互作用参数，所以无法系统而深入地研究这些参数对增容效果的影响。但是，计算机模拟克服了上述困难；事实上，目前计算机模拟已经成为了人们探究高分子物理学领域宏观现象分子机理必不可少的研究方法和手段。通常情况下，高分子共混体系要求计算机模拟的粒子数很大，从而计算模拟的时间很长，往往超出了我们能够接受的范围；但是，如果我们只关注其热力学性质，那么可以选用运算相对较快的格子Monte Carlo模拟方法。另一方面，因为我们模拟的是薄膜体系，因此也消除了一个维度的粒子数限制，从而我们可以利用Monte Carlo模拟方法来研究均聚物/嵌段共聚物/均聚物三元共混薄膜体系的基本热力学性质，特别是，平衡后嵌段共聚物高分子链的基本性质。 在本论文中，为了描述均聚物/嵌段共聚物/均聚物三元共混薄膜体系的基本热力学性质，特别是嵌段共聚物非对称性对其界面性质的影响，我们利用Monte Carlo模拟方法，从分子链水平上研究了非对称两嵌段共聚物增容剂对共混薄膜界面性质的影响，考察了共聚物链长非对称性和A、B两种不同组分间相互作用能的非对称性对界面性质的影响，重点对比了体系中分子链尺寸、密度分布、均聚物间的界面宽度、界面附近嵌段共聚物的取向行为以及中心界面区域内分子链的自由能等物理量受对称性的影响，具体研究工作如下： 1. 两嵌段共聚物链长的非对称性对界面性质的影响：（a）随着均聚物链长的增长，嵌段共聚物的增容效果相对较差，具体表现为嵌段共聚物高分子链的均方回转半径，均方末端距，嵌段间的均方距离等随均聚物链长的增长而变小；（b）当嵌段共聚物链长较长时，对称与非对称高分子的均方回转半径等物理量相当，而当嵌段共聚物较短时，非对称比对称高分子的均方回转半径等物理量小很多，这说明：当链长较长时，高分子链仍然分布于界面；但是当非对称嵌段共聚物较短时，非对称的嵌段共聚物高分子链很容易被链长较长的共聚物组分拽到其本体中，而非界面处；因此，当嵌段共聚物较长时，非对称性对增容效果的影响较小，而当嵌段共聚物较短时，非对称高分子的增容效果差很多。 2. 相互作用强度非对称性对界面性质的影响：（a）当εAB较小时，嵌段共聚物会比较均匀的分布在整个体系中，但是随着相互作用能的增大，聚集在界面附近的嵌段也逐渐增加，同时由于焓的原因，界面也越平整。另外，体系中εAB越大，共聚物在z方向上的拉伸程度越强，取向也越明显。（b）相互作用强度的非对称性（增强某一组分自身的相互作用强度）可使得高分子链的拉伸和取向加强，从而使嵌段共聚物的增容作用增大。 |
| 英文摘要 | Compatibilizing effect of copolymers in binary blends of two homopolymers has been an attracting subject for the researchers. Homopolymers of different types are usually immiscible, and block copolymers containing both types of monomers can be used to modify the interfacial properties of immiscible homopolymer blends. Theorietically, due to the complexity of the interaction in this system, the results from the theory study were usually obtained under the approximate circumstances. Experimentally, preparation of monodisperse samples is difficult and expensive. On the other hand, it is difficult to change the interaction energy between the segment as well as the chain structure. Fortunately, computer simulation can overcome these problems, it is known that the computer simulation has been used to be not only a complement of experimental and theoretical methods, but also a valuA-Ble tool to study the polymer chain dynamics, glass transition, and phase behavior for the polymer system. In this paper, we focus on the thermodynamic properties of homopolymer / block copolymer / homopolymer film system, rather than dynamic behavior, so we use Monte Carlo simulation for this system. In this paper, we employ Monte Carlo simulations to research the effects of chain length on interface of polymer / block copolymer / homopolymer film system. The productive results are as follows. 1. Effects of the chain length asymmetry on interface properties: (a)Compatibilizing effect of diblock copolymers becomes worse as homopolymer chain length increases, which can be showed that square gyration radius, square end-to-end distance and square distance between block center of copolymers all decrease. (b)When the chain length of copolymers is relatively long, physical quantities of symmetry and asymmetry copolymers are similar, such as square gyration radius. When the chain length of copolymers is relatively short, asymmetry copolymers’ physical quantities are smaller than symmetry copolymers’. In other words, copolymers are distributed in interface when chain length are relatively long, and asymmetry copolymers concentrate in homopolymer phase when chain length are relatively short. Therefore, when chain length are relatively long, asymmetry copolymers don’t change compatibilizing effects. And when chain length are relatively short, compatibilizing effects of asymmetry copolymers is worse. 2. Effects of the interaction energy on interface properties: (a)When εAB is smaller, copolymers will distribute in system homogeneously. And when εAB is increasing, proportion of copolymers in interface is also increasing. Meanwhile interface is more flat because of enthalpy effects. Stretching and orientation effects of copolymer also increase as εAB increase. (b) Asymmetry of interaction energy(i.e., increase monomers attraction potential)could increase retching and orientation effects of copolymer, which makes compatibilizing effect better. |
| 语种 | 中文 |
| 公开日期 | 2016-05-03 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.ciac.jl.cn/handle/322003/64456]  |
| 专题 | 长春应用化学研究所_长春应用化学研究所知识产出_学位论文 |
| 推荐引用方式 GB/T 7714 | 蒋放. 两嵌段共聚物增容剂非对称对共混薄膜界面性质的影响[D]. 中国科学院长春应用化学研究所. 中国科学院研究生院. 2015. |
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