| Summary: | 碩士 === 國立成功大學 === 化學工程學系 === 84 === In this study three types of aminoazobenzenes such as
4-Nitro-4'-N-(n-Octyl)azobenzene; 4-Nitro-4'-N-(n-Lauryl)
azobenzene and 4-Nitro-4'-N,N-bis(n-Lauryl)azobenzene were
prepared to study the monolayers properties on water surface.
The monolayers of these aminoazobenzenes on water are found
to be unstable.Therefore, stearic acid (SA) was added to improve
their stability on water surface. It shows that the film
stability and degree of molecular aggregation varies with the
ratio of the aminoazobenzene and SA. <4-Nitro-4'-N-(n-Octyl)
azo-benzen> shows the better stability and less aggregation
monolayer with a ratiobetween 2:1 and 1:1. The phases and phase
transitions of monolayer depends onthe length of substituted
group, temperature and the kind as well as concentration of
ions in the subphase. In this system, both reducing
temperature andincreasing the length of substituted group could
improve the stability of monolayer.The monolayer of mono-
substituted aminoazobenzenes show expanded film ina wide range
of surface pressure. However, that of di-substituted
aminoazoben-ze ne shows expanded phase. The addition of Cd2+
ions into the subphase showsbetter stable monolayer comparing
with Ca2+ ions reported elsewhere. The stability of monolayer
increases with increasing ion concentration. Finally,
thecrystal morphology of these aminoazobenzenes were also
studied by using differential scanning calorimetry (DSC) and
polarized optical microscope. 4-Nitro-4'-N,N-bis(n-Lauryl)
azobenzene shows smectic liquid crystal phase. 4-Nitro-4'-N-(n-
Octyl)azobenzene shows both smectic and nematicliquid crystal
phases. However, 4-Nitro-4'-N-(n-Lauryl)azobenzene shows only
two types of crystalline butno liquid crystal phase.
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