ATOMIC-FORCE MICROSCOPE STUDY OF CHROMATIC TRANSITIONS IN POLYDIACETYLENE THIN-FILMS

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.