Amrutha S R, Jayakannan M
Speciality Polymers, Chemical Sciences & Technology, Regional Research Laboratory, Thiruvananthapuram - 695 019, India.
J Phys Chem B. 2006 Mar 9;110(9):4083-91. doi: 10.1021/jp056522o.
In the present work, we have demonstrated a facile approach to increase the luminescence of the poly (p-phenylenevinylene)s via controlling the molecular aggregates induced by pi-stacking. We have synthesized new bulky tricyclodecane (TCD) substituted PPVs: poly(2-methoxy-5-tricyclodecanemethyleneoxy-1,4-phenylenevinylene) (MTCD-PPV), poly(bis-2,5-tricyclodecanemethyleneoxy-1,4-phenylenevinylene) (BTCD-PPV), and a series of symmetrically substituted bulky PPV copolymers (P-1-P-7) covering the entire composition range from 0 to 100 mol %. The structures of the monomers and polymers were confirmed by 1H NMR and FTIR, and the molecular weights were determined by gel permeation chromatography. The composition analysis by NMR revealed that the bulky monomer was highly reactive and the incorporation of bulky units in MEH-PPV increased irrespective of the feed ratio. The polymers possess good solubility, high molecular weights, good thermal stability, and so forth. The molecular weights of the PPV copolymers were also significantly affected by the bulky substitution: the higher the incorporation of bulky units, the lower the molecular weight. The absorption and emission studies revealed that there was no influence on the MEH-PPV by TCD substitution in solution whereas in the solid state the photoluminescence intensity of PPV increased more than 10 times. The luminescence increase in PPV was observed throughout the entire bulk and was not confined to any particular domain in the polymer. The bulky PPV copolymers showed that both the luminescence intensity (in film) and quantum yields (in solution) increased with an increase in the extent of BTCD incorporation in the MEH-PPV and attained a maximum for 50% BTCD. The TCD unit has thus proved to be an efficient bulky susbstituent for PPV as it controls the pi-stack-induced molecular aggregates in the polymer chains by increasing the interchain distances. The new bulky PPV copolymers are highly soluble, thermally stable, and highly luminescent besides being economically cheap compared to the other materials reported so far for the bulkier approach in pi-conjugated materials.
在本工作中，我们展示了一种简便的方法，通过控制由π-堆积诱导的分子聚集体来提高聚对苯撑乙烯（PPV）的发光性能。我们合成了新型的大位阻三环癸烷（TCD）取代的PPV：聚（2-甲氧基-5-三环癸烷基亚甲基氧基-1,4-苯撑乙烯）（MTCD-PPV）、聚（双-2,5-三环癸烷基亚甲基氧基-1,4-苯撑乙烯）（BTCD-PPV）以及一系列对称取代的大位阻PPV共聚物（P-1 - P-7），其涵盖了从0到100摩尔％的整个组成范围。单体和聚合物的结构通过1H NMR和FTIR得以确认，分子量通过凝胶渗透色谱法测定。NMR的组成分析表明，大位阻单体具有高反应活性，并且无论进料比如何，MEH-PPV中引入大位阻单元的比例都会增加。这些聚合物具有良好的溶解性、高分子量、良好的热稳定性等。PPV共聚物的分子量也受到大位阻取代的显著影响：大位阻单元的引入比例越高，分子量越低。吸收和发射研究表明，在溶液中TCD取代对MEH-PPV没有影响，而在固态下PPV的光致发光强度增加了10倍以上。在整个本体中都观察到了PPV发光的增加，并且不限于聚合物中的任何特定区域。大位阻PPV共聚物表明，随着MEH-PPV中BTCD引入比例的增加，发光强度（在薄膜中）和量子产率（在溶液中）均增加，并在BTCD含量为50％时达到最大值。因此，TCD单元已被证明是一种有效的PPV大位阻取代基，因为它通过增加链间距离来控制聚合物链中由π-堆积诱导的分子聚集体。与迄今为止报道的用于制备更庞大π共轭材料的其他材料相比，新型大位阻PPV共聚物除了经济成本低之外，还具有高溶解性、热稳定性和高发光性。
