R. Tabone, M. Barra / Dyes and Pigments 88 (2011) 180e186
185
4. Conclusions
The rate of thermal cis-to-trans isomerisation of 1-phenyltriazenes
derived from cyclic amines (i.e., trisubstituted triazenes) in doped
PMMA and PS films in the glassy state can be described by a first-order
rate law, whereas that for isomerisation of DPT (a disubstituted tri-
azene) fits a biexponential function. Rate dependence on substrate
structure (1-phenyltriazenes series) and on polymer matrix polarity
(all substrates), in agreement with theoretical simulations (DPT) and
previous solution studies (1-phenyltriazenes series), is consistent with
geometrical isomerisation involving rotation around the N]N bond
via a dipolar transition state. In the case of 1-phenyltriazene deriva-
tives, isomerisation rate constants determined in PMMA and PS films
are found to be directly proportional to rate constants for isomerisation
in acetonitrile and benzene solutions, respectively. Kinetic data pre-
sented herein should prove useful in the design of triazene-based
photoresponsive materials.
Acknowledgments
We gratefully acknowledge partial funding from the Natural
Sciences and Engineering Research Council (NSERC) of Canada.
Fig. 6. Plot of observed rate constants for isomerisation of 1-phenyltriazene deriva-
tives in poly(methyl methacrylate) films versus reported values for isomerisation in
acetonitrile solution.
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1
Predominant photolytic decomposition precluded indeed the analysis of
N-substituted DPT derivatives such as 3-methyl-1,3-diphenyltriazene [22], to study
further the role of unsymmetrical disubstitution at N3 on the isomerisation
mechanism.
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