Solvent Polarity-Modulated Molecular Alignment of Linear Diacetylenic Acid Films by Solution Shearing

Abstract

Directional alignment of functional molecules has important implications in various areas. Here, films of well-aligned linear diacetylenic acid, 10,12-pentacosadiynoic acid, were prepared by the solution-shearing method and photopolymerized to give well-aligned poly­(ene-yne) films. Depending on the polarity of the solvent used in the shearing process, the direction of molecular alignment and the resultant polymer chains varied as a function of the polarity of the solvent used so that they oriented mainly parallel to the shearing direction when a nonpolar solvent was used and mainly perpendicular to the shearing direction when a polar solvent was used. The presence of H-bonded cyclic carboxyl dimers or solvated acid monomers in the solution is suggested to contribute to the different behaviors. Highly anisotropic field-effect mobilities were measured for transistors based on these films as conducting channels, with the highest mobility of 1.63 cm2 V–1 s–1 obtained for films prepared from hexane solution.

Guided Assembly of Linear Diacetylenic Acid Molecules by Solution Shearing: An Odd–Even Effect in Film Morphology and Charge Transport Properties

“…According to a previous report, shearing of the linear C 12 DAC 8 COOH molecules from hexane solution yielded thin films with the diacetylene units tilted along the shearing direction and so was the poly(eneyne) backbone upon polymerization. 21 In the current work, 2 mg/mL acids in hexane were coated onto the phenyltrichlorosilane (PTS)-modified SiO 2 /Si substrates at the speed of 0.50−0.05 mm/s and at a surface temperature of 33−38 °C using the solution-shearing method. The same films were prepared on PTS-modified quartz substrates for the UV absorption measurement.…”

“…The silicon wafers with a 300 nm SiO 2 surface layer were cleaned by Piranha solution and rinsed thoroughly with pure water, IPA, and acetone in sequence. The cleaned silicon wafers were soaked in 1% solution of phenyltrichlorosilane (PTS) in dry toluene for 1 h to give the PTS-modified SiO 2 /Si substrate . Shearing was carried out on a custom-made blade coater.…”

“…The cleaned silicon wafers were soaked in 1% solution of phenyltrichlorosilane (PTS) in dry toluene for 1 h to give the PTS-modified SiO 2 /Si substrate. 21 Shearing was carried out on a custom-made blade coater. A silicon wafer (10 × 10 cm 2 ) modified with octadecyltrichlorosilane (ODTS) was used as the shearing blade and mounted on a stepper motor by suction via a vacuum pump.…”

“…UV spectra were obtained from a Hewlett-Packard 8453 spectrophotometer. The degree of alignments was evaluated from the dichroic ratio D from polarized UV−vis absorption spectra, 21 where D is defined by I ∥ /I ⊥ , with I ∥ and I ⊥ being the absorbances with polarization parallel and perpendicular to the shearing direction, respectively. An optical microscope (OM) (OLYMPUS, BX51) and Raman spectrometer (Princeton Instruments, Acton SP2500) were equipped with a polarizer.…”

Hexa-peri-hexabenzocoronene derivatives carrying dovetailed alkyl and diacetylenic side chains: a synthesis, characterization, and polymerization study

“…1(a)), where m and n represent the spacer group and the terminal alkyl chain around the DA units, respectively. We showed that the columnar packing of HBC cores can help align the DA-containing side chains along the column and get polymerized [26][27][28][29][30] to give conjugated poly(eneyne) chains as conducting channels for transistor application. The position of the DA unit along the alkyl chain nevertheless appeared to affect the polymerization profoundly.…”