The photopolymerization properties and the surface pressure dependence of excitonic absorption of polydiacetylene (PDA), i.e., poly-(heptacosa-10,12-diynoic acid), are investigated by in situ reflection spectra of a monolayer at a N2 gas–water (pure water, CdCl2 aqueous solution) interface. The electronic structure of the initially appearing PDA is strongly dependent on the packing condition of diacetylene monomer, the blue- and red-form PDAs that initially appear in loose and close packing conditions, respectively. A reversible color change induced by a change in surface pressure is found for the first time in a partially polymerized PDA monolayer on pure water, in which blue and red form PDAs appear predominantly at low and high surface pressures, respectively. Further, two metastable phases, observed at wavelengths about 40 nm longer than those of the blue form, are thought to be induced by the rheological process of the substitutional sidegroups. Our results suggest that these color changes are closely related to a strain on the acetylenic backbone structure which is induced by the deformation of substitutional alkyl sidegroups.
The Raman and infrared spectra of 1-chloro-, 1-bromo-, and 1-iodopropanes, CH3CH2CH2X (X=Cl, Br, and I), and 1-chloro-, 1-bromo-, and 1-iodobutanes, CH3CH2CH2CH2X (X=Cl, Br, and I), were measured for the gaseous, liquid, glassy, and crystalline states. The normal vibration frequencies were calculated, a consistent set of force constants explaining the frequencies of basic halogenoalkanes being assumed. The rotational isomerism was studied on the basis of the spectral observations and the normal coordinate calculations. The enthalpy differences among the rotational isomers were examined.
A process for fabricating alignment-free, printable, organic thin-film transistors is presented. This process utilizes a self-assembly phenomenon in which soluble nanomaterials such as metallic nanoparticles and organic molecules are self-assembled into a device structure. To demonstrate this process, solution-processed source∕drain electrodes were self-aligned to a gate electrode using a hydrophobic self-assembled monolayer (SAM) optically patterned onto the gate electrode using a backsubstrate exposure technique. An organic semiconductor film deposited on the patterned SAM was selectively ordered and substantially self-aligned to the gate electrode. This process is called self-aligned self-assembly. A field-effect mobility of 0.15cm2∕Vs and potential minimum channel length of 3μm were experimentally demonstrated when pentacene molecules and silver nanoparticles were used as the semiconductor and electrode materials, respectively.
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