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Elastic Nanocomposite Structures Formed by Polyacetylene–Hemicyanine Mixed Films at the Air–Water Interface
journal contribution
posted on 2013-10-24, 00:00 authored by Luisa Ariza-Carmona, María
T. Martín-Romero, Juan J. Giner-Casares, Marta Pérez-Morales, Luis CamachoA mixed film of 10,12-pentacosadiynoic
acid (DA) and an amphiphilic
cationic hemicyanine (SP) in the ratio 1:1 has been fabricated. This
mixed film has been proved to be completely homogeneous due to the
good compatibility between both molecules, i.e., hydrophobic regions
sized and polar regions of opposite charge. This adequate balance
between the vertical sections of the hydrophobic and hydrophilic groups
allows the formation of an ion pair between them. In this mixed film,
DA molecules organize in monolayer instead of trilayer as occurs for
pure DA film. Surface pressure measurements (isotherms and compression–expansion
cycles), Brewster angle microscopy, reflection spectroscopy, and PM-IRRAS
prove this structure. Using BAM to reveal the structure of this mixed
film, circular domains with internal anisotropy because the ordered
alignment of hemicyanine groups (strong self-aggregation) are observed.
Under UV irradiation a new polyacetylene (PDA) form was fabricated
in a homogeneous mixed monolayer despite of the distance measured
between the DA molecules by the presence of SP dye. The polymerization
takes place only in the circular domains. Under expansion the domains
forming during compression and after UV irradiation form a nanocomposite
stable material with partially elastic outer region.