A. Lio et al., ATOMIC-FORCE MICROSCOPE STUDY OF CHROMATIC TRANSITIONS IN POLYDIACETYLENE THIN-FILMS, Journal of vacuum science & technology. B, Microelectronics and nanometer structures processing, measurement and phenomena, 14(2), 1996, pp. 1481-1485
Despite decades of study, the exact mechanism for chromatic transition
s in polydiacetylene materials remains somewhat elusive. The mechanism
of the blue to red color transition for overcompressed mixed lipid th
in films of 10,12 pentacosadiynoic acid has been investigated by atomi
c force microscopy. Blue layers were prepared by the horizontal Langmu
ir-Schaefer deposition method. The red form was attained by thermal an
nealing of blue films !thermochromism). The blue films reveal micro-si
zed domains. Each domain shows a stripelike morphology on top of a nea
rly complete layer. The polymer backbone direction shows a high degree
of order. A partial disorder is shown to exist along the interbackbon
e direction. Our study of the red form films indicates that changes oc
cur in the micron-scale morphology of the films. Interestingly the alk
yl side chains rearrange into a completely ordered structure and remai
n ordered well beyond the transition temperature (70 degrees C < T < 9
0 degrees C). Our results strongly suggest that the reorganization of
the side chains is the origin of the thermochromic effect for these fi
lms. (C) 1996 American Vacuum Society.