Keogh S M, Hedderman T G, Rüther M G, Lyng F M, Gregan E, Farrell G F, Chambers G, Byrne H J
FOCAS Institute/School of Physics, Dublin Institute of Technology, Kevin St, Dublin 8, Ireland.
J Phys Chem B. 2005 Mar 31;109(12):5600-7. doi: 10.1021/jp044755u.
Hybrid systems of the conjugated organic polymer poly(p-phenylene vinylene-co-2,5-dioctyloxy-m-phenylene vinylene)(PmPV) and HiPco single-walled carbon nanotubes (SWNTs) are explored using spectroscopic and thermal techniques to determine specific interactions. Vibrational spectroscopy indicates a weak interaction, and this is further elucidated using differential scanning calorimetry (DSC), confocal laser scanning microscopy, temperature-dependent Raman spectroscopy, and temperature-dependent infrared spectroscopy of the raw materials and the composite. An endothermic transition is observed in the DSC of both the polymer and the 0.1% HiPco composite in the region of 50 degrees C. Also observed in the DSC of the composite is a double-peaked endotherm at -39 and -49 degrees C, which does not appear in the polymer. The Raman spectroscopy of the polymer upon increasing the temperature to 60 degrees C shows a diminished cis-vinylene mode at 1575 cm(-1), with an increase in relative intensity of the trans-vinylene mode at 1630 cm(-1). Partially irreversible change in isomerization suggests increased order in the polymer. This change in the polymer is also manifest in the Raman composite spectrum upon increase of the temperature to 60 degrees C, where the spectrum becomes abruptly dominated by nanotubes. Raman spectroscopy of the composite shows no change at -35 degrees C; however, infrared absorption measurements suggest that the transition at -35 degrees C derives from the polymer side chains. Here the composite at -35 degrees C shows a change in the absorbance of the polymer side chain aryl-oxide linkage at 1250 cm(-1) and alkyl-oxide stretch at 1050 cm(-1). Infrared spectra thus suggest that the transitions in the lower temperature region around -35 degrees C are side chain-induced, while Raman spectra suggest that the transition at 60 degrees C is backbone-induced. Furthermore, temperature cycling induces an irreversible decrease in the mean fluorescence intensity of the polymer, coupled with a further reduction in the mean fluorescence intensity of the composite. This suggests that an increase in crystallization of the composite is supported and enhanced by an increase in ordering of the polymer. Implications are discussed.
利用光谱和热学技术对共轭有机聚合物聚（对苯撑乙烯-co-2,5-二辛氧基间苯撑乙烯）（PmPV）与HiPco单壁碳纳米管（SWNTs）的混合体系进行了研究，以确定特定的相互作用。振动光谱表明存在弱相互作用，通过差示扫描量热法（DSC）、共聚焦激光扫描显微镜、温度依赖拉曼光谱以及原材料和复合材料的温度依赖红外光谱对其进行了进一步阐释。在聚合物和0.1% HiPco复合材料的DSC曲线中，在50℃左右观察到一个吸热转变。在复合材料的DSC曲线中还观察到在-39℃和-49℃处有一个双峰吸热峰，而在聚合物中未出现。将聚合物温度升高至60℃时的拉曼光谱显示，1575 cm⁻¹处的顺式亚乙烯基模式减弱，1630 cm⁻¹处的反式亚乙烯基模式相对强度增加。异构化过程中部分不可逆的变化表明聚合物的有序度增加。当温度升高至60℃时，聚合物的这种变化在复合材料的拉曼光谱中也有体现，此时光谱突然以纳米管为主导。复合材料在-35℃时拉曼光谱无变化；然而，红外吸收测量表明，-35℃处的转变源于聚合物侧链。在此，-35℃时的复合材料在1250 cm⁻¹处聚合物侧链芳氧基键的吸光度以及1050 cm⁻¹处烷氧基伸缩振动有变化。因此，红外光谱表明，-35℃左右较低温度区域的转变是由侧链引起的，而拉曼光谱表明60℃处的转变是由主链引起的。此外，温度循环导致聚合物平均荧光强度不可逆下降，同时复合材料的平均荧光强度进一步降低。这表明聚合物有序度的增加支持并增强了复合材料结晶度的提高。文中讨论了其影响。
