单分散聚芴熔融结晶形态
文献类型：学位论文
| 作者 | 刘健 |
| 学位类别 | 博士 |
| 答辩日期 | 2015-04 |
| 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 | 闫东航 |
| 关键词 | 单分散聚芴 大面积连续结晶膜 片层结构 相转变 |
| 中文摘要 | 共轭高分子以其优异的性能在有机电子器件领域表现出了极大的应用前景。大量研究表明器件性能与薄膜凝聚态结构息息相关。特别是对于有机薄膜晶体管（OTFTs）和有机光伏电池（OPVs）来说，大面积连续的高结晶性薄膜往往会带来好的器件性能。由于高分子分级结晶行为的影响，高分子的多分散性会显著影响薄膜的结晶性。鉴于此，本论文以一种得到广泛研究的共轭高分子——聚芴（PFO）作为研究对象，选取三种不同分子量的单分散聚芴，通过熔融结晶的方法来制备大面积连续的高结晶性薄膜，系统性的研究了单分散聚芴的热结晶行为、晶体相结构及其光物理性质，并研究分子量对于聚芴结晶的影响，总结了聚芴的熔融结晶规律，给出了不同分子量聚芴相图。本论文主要研究成果如下： 1. 对于十六聚体聚芴（F16），直接从溶液中滴涂得到的为含β相的薄膜，薄膜保有部分F16针状单晶的形貌。通过两步热退火得到了片层状晶体，为一种新相（β’相）。其属于正交晶系Pmc21空间群，晶胞参数为 a = 1.30 nm, b = 2.22 nm, c = 3.36 nm。晶胞含有4条链，密度为1.06 g/cm3。片晶中分子主链平行于片层平面，烷基侧链垂直于片层。通过熔融结晶的方法得到了球晶，球晶也是β’相，由片晶组成，球晶内分子链平行于半径方向，烷基侧链垂直于基底。与β相相比，β’相为F16的热力学稳定相。 2. 对于三十二聚体（F32）和六十四聚体（F64）聚芴，直接从溶液中滴涂得到含β相的无规薄膜。 通过熔融结晶的方法得到了大面积连续的纳米纤维晶薄膜。结晶薄膜保有部分液晶薄膜的织构特点。薄膜内部存在片层结构。薄膜结晶过程为从晶核开始的辐射生长，最终形成球晶状结构，并且球晶边界处有一定程度的相互融合。结晶薄膜为α相，其晶胞参数为a=2.60 nm、b=2.38 nm和c=3.32 nm。与β相相比，α相为F32和F64的热力学稳定相。 3. 在F32与F64 α相纳米纤维薄膜中，分子链平行于纤维宽度方向，芴环堆积方向为纤维长轴方向。F32与F64分子在纳米纤维晶中为伸直链构象。 4. 通过对以上工作的总结，我们得到了不同链长聚芴相图。发现分子链长可以影响聚芴熔融结晶相，对于F16得到的为β’相，对于F32和F64得到的为α相。通过两相形貌图的对比，我们总结出了聚芴熔融结晶的规律。F16倾向于表现小分子的结晶特点，形成的是典型的片层状晶体；F32与F64表现出了高分子的结晶特点，形成的是纳米纤维晶薄膜，但薄膜仍表现出了层状结构特点。并且我们推测这种链长对相的影响和片层状结构在其他高分子体系中也会出现。 |
| 英文摘要 | Conjugated polymers have great application prospect due to the high performance in organic electronic devices fields. Mounts of studies have demonstrated that the devices performance is highly relative with the condensed structure of films. Especially for organic thin film transistors (OTFTs) and organic photovolatics (OPVs), large-area continuous highly crystalline films can produce high device performance. Because of the influence of the fractionated crystalline behaviour of conjugated polymers, the polydispersity of polymers vastly hinders the increasing of film crystallinity. With this motivation, a widely-used conjugated polymers – Poly(9,9-diotclyfluorene) (PFO) was chosen as the studied object in this dissertation. We selected three monodisperse PFO with different molecular weights. Large-area continuous highly crystalline films were prepared by melt crystallization. Moreover, the thermal-crystalline behaviour, phase structure and photophysical property of monodisperse PFO were systematically investigated. Besides, we also investigated the effect of molecular weights on PFO crystallization. The melt-crystalline discipline of PFO was summarized, and the phase diagram of monodisperse PFO with different molecular weights was given. The main results of this dissertation are as follows: 1. For monodisperse PFO with 16 repeating units (F16), thin films containing β phase were prepared by directly dropping from solution, and the films preserve some of shape of needle-like single crystal prepared by solution crystallization of F16. Lamellar crystals, which is a novel phase (named as β’ phase), were prepared by two-step thermal annealing. The β’ phase have orthorhombic unit cell parameters of a = 1.30 nm, b = 2.22 nm and c = 3.36 nm with space group Pmc21, there are 4 chains in the unit cell and its density is 1.06g/cm3. In these crystals, the molecular backbone chains are packed parallel to the lamellar plane with the alky side chains vertical to lamella. Besides, the β’ phase spherocrystals were prepared by melt crystallization. The spherocrystals were composed of lamellar crystals, in which the backbone chains are packed parallel to the radius direction with the alky side chains normal to the substrates. Compared to the β phase, β’ phase is the thermal stable phase for F16. 2. For monodisperse PFO with 32 and 64 repeating units (F32 and F64, respectively), random thin films containing β phase were prepared by directly dropping from solution. Large-area continuous nanofibril thin films were prepared by melt crystallization. Crystalline films preserve some of texture characteristic of liquid crystalline films. There is lamellar structure in the crystalline films. The crystallization process undergoes radial growth from nucleus to form spherulite-like structure, moreover, to a certain extent, there is fusion at the boundary of spherulite-like structures. The crystalline films are α phase with orthogonal unit cell parameters of a = 2.60 nm, b = 2.38 nm and c = 3.32 nm. Compared to the β phase, α phase is the thermal stable phase for F32 and F64. 3. In the α phase nanofibril films of F32 and F64, the backbone chains are parallel to the width direction of nanofibrils with fluorenes stacking along the length direction. F32 and F64 remain extended in the nanofibrils. 4. The phase diagram of PFO with different chain lengths was obtained by summarizing above results. We found that the chain lengths can affect the melt-crystallized phases, the melt crystallization of F16 produces β’ phase, while for F32 and F64, it turns into α phase. The discipline of melt crystallization of PFO was summarized by comparing the morphology of these two phases. F16 tends to display the crystalline feature of micromolecule and produces typical lamellar crystals. Nevertheless, for F32 and F64, the characteristics of macromolecule are shown to form crystalline nanofibril films, but the films still represent the characteristic of lamellar structur |
| 语种 | 中文 |
| 公开日期 | 2016-05-03 |
| 源URL | [http://ir.ciac.jl.cn/handle/322003/64474]  |
| 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 | 刘健. 单分散聚芴熔融结晶形态[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. |
入库方式： OAI收割
来源：长春应用化学研究所
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