LANGMUIR-BLODGETT-FILM ORGANIZATION RESULTING FROM ASYMMETRICAL OR PARTIAL TYPES OF MONOLAYER TRANSFER - COMPARISON FOR AMPHIPHILES OF DIFFERENT GEOMETRICAL SHAPES
A. Angelova et R. Ionov, LANGMUIR-BLODGETT-FILM ORGANIZATION RESULTING FROM ASYMMETRICAL OR PARTIAL TYPES OF MONOLAYER TRANSFER - COMPARISON FOR AMPHIPHILES OF DIFFERENT GEOMETRICAL SHAPES, Langmuir, 12(23), 1996, pp. 5643-5653
The problem of whether the Langmuir-Blodgett (LB) technique is capable
of producing ordered films of molecular arrangement different from a
bulk phase one is addressed for amphiphiles of rod-like and disk-like
geometrical shapes. Low-angle X-ray diffraction and morphological char
acterization are performed for LB films deposited by means of asymmetr
ical and partial types of monolayer transfer. The influence of thermod
ynamic parameters, steric molecular peculiarities, and intermolecular
interactions on the efficiency and mechanism of the monolayer transfer
is considered. Molecular overturning to a multibilayer (''bulk'') arr
angement is established for the case of Z-type (one-direction up-strok
e) deposition of the rod-like amphiphile, and a crystalline body-cente
red orthorhombic (''bulk'') structure for the case of partial (''mixed
'' XY type) LB transfer of the diskotic films. Symmetrical Y-type depo
sition is found to result in almost defect-free multilayers over large
scales of film surface examination. For both kinds of amphiphiles stu
died, the asymmetrical and partial types of LB transfer are less effec
tive, as compared to the Y-type, in inducing periodic thin film organi
zations, distinct from the bulk phase structures of the amphiphiles.