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Fig. 3.24 Excitation of a
soliton in the polyacetylene
chain
single ones and vice versa. This can be used to create switches by incorporating a
switchable molecular fragment capable of rearranging the conjugation chain into
the original conjugated system. One possible fragment of this type is the molecule
of 1,1-N,N-dimethyl-2-nitro-ethanamine, which, being embedded in the trans-
polyacetylene chain, can undergo phototransformations upon light absorption and
rearrange the conjugation chain (Fig.
3.25
). Herewith:
After the passage of a soliton in the main chain and the substitution of double
bonds by single ones and vice versa, no photoisomerization will occur, which
can serve as an indicator of the soliton transmission.
Isomerization reaction, initiated before the passage of the soliton in the main
chain, changes the electronic structure of not only the switching fragment but
also of the adjacent region of the chain (breaks the conjugation chain) and thus
makes subsequent passage of the soliton impossible.
The concept of soliton switching can be generalized to multiple conjugated quasi
one-dimensional chains, along which solitons can propagate. One such example is
