Highly Oriented and Crystalline Films of a Phenyl-Substituted Polythiophene Prepared by Epitaxy: Structural Model and Influence of Molecular Weight
Highly Oriented and Crystalline Films of a Phenyl-Substituted Polythiophene Prepared by Epitaxy: Structural Model and Influence of Molecular Weight
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DOI：
10.1021/acs.macromol.6b00495
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发表时间：
2016-05-10
期刊：
影响因子：
5.5
通讯作者：
Brinkmann, Martin
中科院分区：
文献类型：
--
作者：
Hamidi-Sakr, Amer;Schiefer, Daniel;Brinkmann, Martin
据报道，绝大多数基于具有直链或支链烷基侧链的聚（烷基噻吩）的半导体聚合物在其结晶相中是π堆叠的。然而，在区域规则的聚（3-（2，5-二辛基苯基）噻吩）（PDOPT）中，由于存在庞大的2，5-二辛基苯基侧基，因此不存在π-π相互作用。在这项工作中，高水平的结晶度和取向的PDOPT在萘基板上对齐的薄膜中创建的侧链的缓慢定向外延结晶。取决于分子量，获得边缘和平坦的层状晶体。至于聚（3-己基噻吩）（P3 HT），电子显微镜成像显示从延伸到折叠链结晶PDOPT的M-n约为12.7 kDa的过渡。高取向度和结晶度导致具有良好限定的电子振动结构的紫外-可见吸收和光致发光的高各向异性。单晶状电子衍射图案进一步用于细化PDOPT的结构模型（a = 29.09埃，B = 10.45埃，c = 7.72埃，α = β = γ = 90度，空间群P21/c）。独特的是，结晶PDOPT的特征在于完全平坦化的链，尽管聚噻吩主链之间不存在π-堆叠。辛基侧链是指状交叉的并且在致密的子电池中结晶，将其与其它半导体聚噻吩例如I型聚（3-己基噻吩）和聚（2，5-双（3-十二烷基-2-基）噻吩并[3，2-B]噻吩）的亚电池进行比较，以绘制总结晶度和侧链堆积密度之间的趋势。
The large majority of semiconducting polymers based on poly(alkylthiophene)s with either linear or branched alkyl side chains are reported to pi-stack in their crystalline phases. In regioregular poly(3-(2,5-dioctylphenyl)thiophene) (PDOPT), however, pi-pi interactions are absent due to the presence of the bulky 2,5-dioctylphenyl side groups. In this work, high levels of crystallinity and orientation are created in thin films of PDOPT aligned on substrates of naphthalene by slow directional epitaxial crystallization of the side chains. Depending on molecular weight, both edge-on and flat-on lamellar crystals are obtained. As for poly(3-hexylthiophene) (P3HT), electron microscopy imaging reveals a transition from extended to folded chain crystallization in PDOPT for M-n approximate to 12.7 kDa. The high orientation and crystallinity result in high anisotropy in UV-vis absorption and photoluminescence with well-defined vibronic structures. The single-crystal-like electron diffraction patterns are further used to refine a structural model of PDOPT (a = 29.09 angstrom, b = 10.45 angstrom, c = 7.72 angstrom, alpha = beta = gamma = 90 degrees, and space group P21/c). Uniquely, crystalline PDOPT features perfectly planarized chains despite the absence of pi-stacking between polythiophene backbones. The octyl side chains are interdigitated and crystallize in a dense subcell which is compared to that of other semiconducting polythiophenes, e.g. form I poly(3-hexylthiophene) and poly(2,5-bis(3-dodecyl-2-yl)thieno[3,2-b]thiophene), to draw a trend between overall crystallinity and density of the side chain packing.