Control of polymerization processes of 10,12‐pentacosadiynoic acid LB films

Abstract

Studies have been carried out on K r F cxcimer laser light (EX), X-ray or electron beam (EB) induced polymerization of 10,12-pentacosadiynoic acid (PDA) Langmuir-Blodgett (LB) films in relation to molecular density or molecular arrangement of the films using X-ray diffraction analysis, infrared (IR) spectroscopy and Raman spectroscopy. The molecular arrangement or density of the PDA LB films was controlled by subphase conditions whcn the films were built up, such as pH, temperature of a subphase or salt concentration in the subphase. Polymerization sensitivity of the PDA LB film was affected by the arrangement or molecular density. On low density (A type) films the polymerization occurred by irradiation with EX, X-ray or EB, but on high density (B type) films the polymerization occurred only when the irradiation was carried out by high energy beams such as X-ray or EB. Decomposition of polymerized films was observed further by excessive irradiation of EX or X-ray, but not on the B type films. It was revealed by X-ray diffraction analysis that in the A type film, the PDA molecules bent to a larger extent than those in the B type film and the polymerization proceeded topochcmically, that is, the thickness decrcased little after EB irradiation in a helium atmosphere. On the other hand, in the B type film, the thickness decreased by about 10% as a result of EB irradiation. By IR reflection-absorption (RA) and Raman measurements, it was confirmed that conjugated diacetylenic bonds disappeared and conjugated double and new conjugated triple bonds appeared after high energy beam irradiations. These results support the supposition that 1,4-polymerization, i.e. polydiacetylene type polymerization, occurs easily in the A type film and 1,2-or 3,4-polymerization, i.e. polyacetylene type polymerization, occurs in the B type film, and that the polymerized A type film was decomposed at the polydiacetylenic bond when the irradiation continued further. It was also shown that the polyacetylene type polymer was obtained only when the B type film was irradiated with the high energy beam.

Carboxylate−Counterion Interactions and Changes in These Interactions during Photopolymerization of a Long-Chain Diacetylene Monocarboxylic Acid at Air−Water Interfaces: External Infrared Reflection Absorption Spectroscopic Study

“…In addition, a shoulder of the isotherm at about 0.24 nm 2 /molecule suggests that there occurs either a partial collapse of the S phase or a transition from the S phase to another solid phase. The isotherms measured in the presence of both the Ba 2+ and Pb 2+ ions give similar features to those observed for a low density form of a DA monolayer on a subphase containing the Ca 2+ ion . The isotherms at first show a slow rise ascribable to an LE phase and/or an LE/LC transition and then a rather sharp rise, indicating a transition from the LC phase to an S phase.…”

“…The isotherms measured in the presence of both the Ba 2+ and Pb 2+ ions give similar features to those observed for a low density form of a DA monolayer on a subphase containing the Ca 2+ ion. 18 The isotherms at first show a slow rise ascribable to an LE phase and/or an LE/LC transition and then a rather sharp rise, indicating a transition from the LC phase to an S phase. Shoulders observed for the isotherms at a molecular area of about 0.25 nm 2 /molecule (19 mN/m) on the Ba 2+ subphase and at about 0.26 nm 2 /molecule (27 mN/m) on the Pb 2+ subphase suggest that either a partial collapse of the solid phase or a transition from the S state to another solid phase takes place at these molecular areas.…”

Characterization of 10,12-pentacosadiynoic acid Langmuir–Blodgett monolayers and their use in metal–insulator–metal tunnel devices

“…The surface tension (and indirectly the film integrity) was efficiently controlled using the KSV NIMA LB Trough controller. For polymerization purposes, the monolayers were exposed to 245 nm UV radiation for 15 min using a UV bench lamp [ 17 ].…”

Advanced Biomimetic Approach for Crystal Growth in Nonaqueous Media: Morphology and Orientation Control of Pentacosadiynoic Acid and Applications

“…If the distance between the diacetylene moieties is less than 0.5 nm, topochemical polymerization proceeds in the organized states by irradiation of UV light, γ-rays, and electron beams . In previous works, films of crystalline DAs were obtained by casting, Langmuir–Blodgett techniques, and vacuum vapor deposition methods. − However, morphology and orientation control of DAs based on crystal growth through solution processes were not studied in previous works. Our challenge here is morphology and orientation control of PCDA crystals through biomimetic approaches, the subsequent topochemical polymerization, and their applications to OFET and thermochromic devices.…”