Photochromic langmuir monolayers

Genson KL, Holzmuller J, Villacencio OF, McGrath DV, Vaknin D, Tsukmk VV. Langmuir and grafted monolayers of photochromic amphiphilic monodendrons of low generations. J Phys Chem B 2005 109 20393-20402. 

Scheme 11 Chemical structure of hairy rod" poly(L-glutamate)s used to obtain photochromic monolayers and Langmuir-Blodgett films. 81,85-91 ...

The monolayer also provides an environment of variable dielectric so that intermolecular association between photoactive molecules can readily occur. For example, molecular association of pyrene within a Langmuir-Blodgett film is clearly seen through time-resolved fluorescence measurements on the picosecond timescale [92], Attenuated total reflectance studies of dyes in cast films can similarly reveal their positions and photophysical interactions [93], Photochromism in a monolayer assembly has been attributed to excitation of ion-pair charge transfer complexes formed within the array [94]. 

These exceptional characteristics have been used later in several interesting applications. An elastic polymer film containing the same MV2 + salts as part of the main chain was found to be photochromic and results indicate that data can be written optically X > 365 nm) and erased thermally [212]. The photo-chromism was also observed in monolayer assemblies (Langmuir-Bloodgett films) made of mixtures of N,N hexadecyl-4,4 -bipyridinium salts of TFPB-and arachidic acid [213, 214, 215]. 

Blair et al. have also carried out Langmuir film balance measurements on monolayers of the photochromic polyamides mentioned above, namely the 3,3 - and 4,4 -poly-(azodibenzoyl-trans-2,5-monomer unit was observed and interpreted as resulting from azo trans to cis isomerization. The differences between the pressure-area curves of the meta(3,3 -) and para (4,4 -)polyamides were interpreted on the assumption that the meta compound has a helical structure and that the para compound is linear. 

Menzel, H., McBride, J. S., Weichart, B., and Riither, M. Langmuir Blodgett Films ol Photochromic Polyglutamates 8. Structure of the Monolayers at the Air/Water Interface. Thin Solid Films 284-285, 640 (1996). 

Seki, T., Fukuda, K., and Ichimura, K. Photocontrol of polymer chain organization using a photochromic monolayer. Langmuir, 15, 5098 (1999). 

Menzel, H. Langmuir-Blodgett films of photochromic polyglutamates. 7. The photomechanical effect in monolayers of polyglutamates with azobenzene moieties in the side chains. Macromol. Chem. Phys., 195, 3747 (1994). 

J. F. Masson, P. A. Liddell, S. Baneiji, T. M. Battaglia, D. Gust, K. S. Booksh, Nondestructive monitoring of the photochromic state of dithienylethene monolayers by surface plasmon resonance, Langmuir, 21, 7413-7420 (2005). 

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