Effect of Ionic Liquid on Structure and Properties of Polysquaraines

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• 作者：Mei-Chan Ho ; Ching-Hsun Chao ; Chun-Hua Chen ; Ren-Jye Wu ; Wha-Tzong Whang
• 刊名：Macromolecules
• 出版年：2012
• 出版时间：April 10, 2012
• 年：2012
• 卷：45
• 期：7
• 页码：3010-3016
• 全文大小：458K
• 年卷期：v.45,no.7(April 10, 2012)
• ISSN：1520-5835

文摘

Polycondensation of 4-bis[2-(1-methylpyrrol-2-yl)vinyl]-2,5-didodecyloxybenzene and squaric acid yielded the polysquaraine SQ with two isomeric subunits鈥?,3-addition (zwitterionic) and 1,2-addition (diketonic) moieties鈥攊n the main chain structure. The former featured a C鈥揙/C鈺怬 infrared (IR) absorption frequency at 1622 cm^鈥?; the latter, a C鈺怬 signal at 1716 cm^鈥?. Traditional synthesis yielded SQ as a powder with metallic luster that could not be cast as a polymer film from solution. When the ionic liquid [Oct₃NMe][TfO] (IL) was present in the cosolvent of BuOH and benzene (1:3), however, the resulting SQI_x polymers (x = 0.01鈥? wt %) did not precipitate from solution, making it possible to cast continuous free-standing films with a large area (>1 脳 1 cm²). A greater content of IL in the solution favored the formation of the 1,3-addition zwitterionic subunits in the SQI_x polymer main chains, thereby changing the physical and optical properties of the polysquaraine, as evidenced in IR and optical absorption spectra. The features in the UV鈥揤is鈥揘IR absorption spectra of SQ and SQI_x were dependent on the IL concentration and the nature of the solvent. Among our synthesized SQI_x polymers, SQI_0.01 and SQI_0.1 formed flexible free-standing films with metallic luster, smooth surfaces, and good semiconductivities (2.27 脳 10^鈥? and 4.74 脳 10^鈥? S/cm, respectively). X-ray diffraction patterns revealed that the presence of IL in the polymerization medium increased the SQI_x interchain packing distance. SQI_0.01 and SQI_0.1 possessed thermal stabilities comparable with that of SQ. Our successful use of IL in the preparation of SQI_x polymers appears to have great potential for application in ionic liquid鈥搑elated organic or polymeric preparation and processing.