Investigations of the structures and molecular processes in polar Langmuir-Blodgett superlattices

Miscellaneous · Wed Jan 01 00:00:00 EST 1992

OSTI ID:5182857

Walsh, S P

The principle focus of this research was to prepare polar ultrathin films using an alternating monolayer adaptation of the traditional Langmuir-Blodgett (LB) technique, and to investigate the role that structure (physical and chemical) plays upon the outward manifestation of this internal polarization: pyroelectricity. A specially designed film trough was prepared such that two separate monolayers could be independently manipulated. Alternating bilayer assemblies were be prepared by translating the deposition substrate above and below the surface of the floating monolayers as needed without disruption of the stability of the Langmuir films. Long chain diacetylenic acid and amine amphiphiles were prepared. The diacetylenic amine compound was thoroughly investigated at the gas-water interface. Common conditions of monolayer stability for the acid/amine amphiphile pairs and the concept of isoelectric deposition were developed. Homogeneous and heterogeneous LB assemblies were prepared. Chemical and structural investigations were performed using a combination of x-ray diffraction and FTIR spectroscopic techniques. The melting temperatures of the unpolymerized structures were dependent on organization and ionization of the individual molecules. Solid state polymerization of the diacetylenic multilayers was found to somewhat disrupt the organization of the assemblies, but to suppress monolayer melting. The pyroelectric response in such structures was molecular, not chemical, in nature with the polarization changing as a result of molecular librations. Electrical characterizations of the assemblies showed the thin films to behave as good dielectrics. Pyroelectric responses of the ionized assemblies containing free counter ions were unexpectedly low. It was felt that the low values were due to either a damping of the librational moments by the presence of the counter ions, or that the mobility of these ions offset the librational dipoles of these polar groups.

• Research Organization: Case Western Reserve Univ., Cleveland, OH (United States)
• OSTI ID: 5182857
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
36 MATERIALS SCIENCE
SUPERLATTICES
POLYMERIZATION
PYROELECTRIC EFFECT
STRUCTURAL CHEMICAL ANALYSIS
ALKYNES
AMINES
POLARIZATION
THIN FILMS
CHEMICAL REACTIONS
FILMS
HYDROCARBONS
ORGANIC COMPOUNDS
400201* - Chemical & Physicochemical Properties
360606 - Other Materials- Physical Properties- (1992-)
360602 - Other Materials- Structure & Phase Studies