School of Chemistry, University of Bristol, Bristol BS8 1TS, UK.
Chemistry. 2013 Jul 8;19(28):9186-97. doi: 10.1002/chem.201300463. Epub 2013 Jun 3.
With the aim of accessing colloidally stable, fiberlike, π-conjugated nanostructures of controlled length, we have studied the solution self-assembly of two asymmetric crystalline-coil, regioregular poly(3-hexylthiophene)-b-poly(2-vinylpyridine) (P3HT-b-P2VP) diblock copolymers, P3HT23-b-P2VP115 (block ratio=1:5) and P3HT44-b-P2VP115 (block ratio=ca. 1:3). The self-assembly studies were performed under a variety of solvent conditions that were selective for the P2VP block. The block copolymers were prepared by using Cu-catalyzed azide-alkyne cycloaddition reactions of azide-terminated P2VP and alkyne end-functionalized P3HT homopolymers. When the block copolymers were self-assembled in a solution of a 50% (v/v) mixture of THF (a good solvent for both blocks) and an alcohol (a selective solvent for the P2VP block) by means of the slow evaporation of the common solvent; fiberlike micelles with a P3HT core and a P2VP corona were observed by transmission electron microscopy (TEM). The average lengths of the micelles were found to increase as the length of the hydrocarbon chain increased in the P2VP-selective alcoholic solvent (MeOH<iPrOH<nBuOH). Very long (>3 μm) fiberlike micelles were prepared by the dialysis of solutions of the block copolymers in THF against iPrOH. Furthermore the widths of the fibers were dependent on the degree of polymerization of the chain-extended P3HT blocks. The crystallinity and π-conjugated nature of the P3HT core in the fiberlike micelles was confirmed by a combination of UV/Vis spectroscopy, photoluminescence (PL) measurements, and wide-angle X-ray scattering (WAXS). Intense sonication (iPrOH, 1 h, 0 °C) of the fiberlike micelles formed by P3HT23-b-P2VP115 resulted in small (ca. 25 nm long) stublike fragments that were subsequently used as initiators in seeded growth experiments. Addition of P3HT23-b-P2VP115 unimers to the seeds allowed the preparation of fiberlike micelles with narrow length distributions (L(w)/L(n) < 1.11) and lengths from about 100-300 nm, that were dependent on the unimer-to-seed micelle ratio.
为了获得胶体稳定、纤维状、具有受控长度的π共轭纳米结构，我们研究了两种不对称结晶-螺旋、区域规整的聚（3-己基噻吩）-b-聚（2-乙烯基吡啶）（P3HT-b-P2VP）嵌段共聚物的溶液自组装，即 P3HT23-b-P2VP115（嵌段比=1:5）和 P3HT44-b-P2VP115（嵌段比约为 1:3）。在对 P2VP 嵌段具有选择性的各种溶剂条件下进行了自组装研究。嵌段共聚物是通过末端叠氮的 P2VP 和炔基末端官能化的 P3HT 均聚物的铜催化叠氮-炔环加成反应制备的。当嵌段共聚物在 THF（两种嵌段的良溶剂）和醇（P2VP 嵌段的选择性溶剂）的 50%（v/v）混合物溶液中通过共溶剂的缓慢蒸发进行自组装时；通过透射电子显微镜（TEM）观察到具有 P3HT 核和 P2VP 冠的纤维状胶束。发现胶束的平均长度随着 P2VP 选择性醇溶剂（MeOH<iPrOH<nBuOH）中烃链长度的增加而增加。通过将嵌段共聚物在 THF 中的溶液透析到 iPrOH 中，可以制备出非常长（>3μm）的纤维状胶束。此外，纤维的宽度取决于链扩展的 P3HT 块的聚合度。通过紫外/可见光谱、光致发光（PL）测量和广角 X 射线散射（WAXS）的组合，证实了纤维状胶束中 P3HT 核的结晶度和π共轭性质。对 P3HT23-b-P2VP115 形成的纤维状胶束进行强烈超声处理（iPrOH，1h，0°C）会导致形成小（约 25nm 长）的棒状片段，随后将其用作种晶生长实验的引发剂。将 P3HT23-b-P2VP115 单体添加到种子中，可以制备具有窄长度分布（L(w)/L(n) < 1.11）和长度约为 100-300nm 的纤维状胶束，其长度取决于单体-种子胶束的比例。
