tethering a chiral alkyl chain as a side-chain unit (P1, Fig. 8.3). The conjugated
polymers exhibited an optical activity in the cast films with circular dichroism
(CD) and CPL activities corresponding to the π-πà transition in the π-conjugated
main chain. The cast films afforded a bisignate split CD profile in the π-πà transition
region of the main chain, suggesting a one-handed helical inter-chain π-stacking
structure based on the exciton coupling theory [23]. Although the chiral alkyl chain
unit was introduced in the side chain through the photochromic moiety, the chirality
information was transferred to the inter-polymer main-chain interactions, displaying
the CPL activity in the film state in a similar manner to other conjugated polymers
modified with chiral side-chain units [24–27]. The photochromic unit in the conjugated polymers P1-o maintained the photo-responsiveness in the cast films. The
fluorescence and CPL of the π-conjugated main chain were readily quenched by
means of UV irradiation through energy transfer from the main chain to the photogenerated closed-ring moiety of diarylethene in the side chain. The CPL activity was
recovered by the cyclo-reversion reaction of the diarylethene moiety upon visible
light irradiation and the ON-OFF photo-switching behavior was repeated over
10 cycles.
8.3 Photo-Switching of CPL Based on Pyrene-Bearing
Photo-Responsive Foldamer
The inter-chromophoric interactions usually provide the most significant contributions to the chiroptical property in molecular systems as explained by the exciton
coupling theory [23, 28]. As a rough framework of the theory, the chiral arrangement
UV
vis
n
n
CPL-ON
CPL-OFF
(S)-P1-o
(S)-P1-c
Fig. 8.3 Structure and photoreaction of photo-responsive chiral conjugated polymer P1
8 Photo-Switching of Circularly Polarized Luminescence
179
polymers exhibited an optical activity in the cast films with circular dichroism
(CD) and CPL activities corresponding to the π-πà transition in the π-conjugated
main chain. The cast films afforded a bisignate split CD profile in the π-πà transition
region of the main chain, suggesting a one-handed helical inter-chain π-stacking
structure based on the exciton coupling theory [23]. Although the chiral alkyl chain
unit was introduced in the side chain through the photochromic moiety, the chirality
information was transferred to the inter-polymer main-chain interactions, displaying
the CPL activity in the film state in a similar manner to other conjugated polymers
modified with chiral side-chain units [24–27]. The photochromic unit in the conjugated polymers P1-o maintained the photo-responsiveness in the cast films. The
fluorescence and CPL of the π-conjugated main chain were readily quenched by
means of UV irradiation through energy transfer from the main chain to the photogenerated closed-ring moiety of diarylethene in the side chain. The CPL activity was
recovered by the cyclo-reversion reaction of the diarylethene moiety upon visible
light irradiation and the ON-OFF photo-switching behavior was repeated over
10 cycles.
8.3 Photo-Switching of CPL Based on Pyrene-Bearing
Photo-Responsive Foldamer
The inter-chromophoric interactions usually provide the most significant contributions to the chiroptical property in molecular systems as explained by the exciton
coupling theory [23, 28]. As a rough framework of the theory, the chiral arrangement
UV
vis
n
n
CPL-ON
CPL-OFF
(S)-P1-o
(S)-P1-c
Fig. 8.3 Structure and photoreaction of photo-responsive chiral conjugated polymer P1
8 Photo-Switching of Circularly Polarized Luminescence
179