Molecular addressing? Studies on light-induced reorientation in liquid-crystalline side chain polymers

Anderle, Klaus; Birenheide, Richard; Werner, Martin; Wendorff, Joachim H.

doi:10.1080/02678299108030382

Cited by 153 publications

(75 citation statements)

References 9 publications

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“…The mesogenic azobenzene, upon illumination in the violet-UV range, undergoes trans-cis isomerization, which takes place on the nanosecond timescale and the nanometre length scale. Due to the strong molecular anisotropy in the trans-configuration, the molecular transition dipole moment will be essentially parallel to the main molecular axis; hence selective pumping with linearly polarized light will change the molecular orientational distribution, eventually reorienting the molecules in the plane perpendicular to the polarization of the pump light [4]. Such an effect will depend on the pump power density, wavelength, and polarization.…”

Section: Introductionmentioning

confidence: 99%

Molecular relaxation in a photosensitive liquid-crystalline polymeric glass former

Cristofolini

Facci

Camorani

et al. 1999

J. Phys.: Condens. Matter

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Abstract. We have measured the relaxation to equilibrium in the supercooled nematic phase upon approach to T g of a fragile liquid-crystalline photosensitive polymeric glass former. Perturbation is introduced in a non-conventional way by optical pumping (orientation) of the nematic polydomain phase. Relaxation back to equilibrium is followed both on the microscopic scale, by means of depolarized time-resolved Raman experiments, and on the macroscopic scale, by means of quartz crystal microgravimetry.

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Section: Introductionmentioning

confidence: 99%

Molecular relaxation in a photosensitive liquid-crystalline polymeric glass former

Cristofolini

Facci

Camorani

et al. 1999

J. Phys.: Condens. Matter

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“…All of these issues can be studied in a specific class of materials, namely side-chain liquid crystalline polymers with an azobenzene moiety attached to the main chain via a flexible molecular spacer [3][4][5]. In polyacrylates and poly-methacrylates the pumping of the photo-isomerization transition yields several potentially useful optical effects with very high sensitivity [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Slow dynamics in an azopolymer molecular layer studied by x-ray photon correlation spectroscopy

et al. 2010

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We report the results of X-ray photon correlation spectroscopy (XPCS) experiments on Langmuir Blodgett multilayers of a photosensitive azo-polymer. Time correlation functions have been measured at different temperatures and momentum transfers (q) and under different illumination conditions (darkness, UV or visible). The correlation functions are well described by the Kohlrausch-Williams-Watts (KWW) form with relaxation times that are proportional to q -1 , which in other systems have been explained in terms of intermittent rearrangements [L. Cipelletti et al., Phys. Rev. Lett. 84, 2275-2278] or random dipolar interactions within an elastic medium [J.-P. Bouchaud and E. Pitard, Eur. Phys. J. E 6, 231-236 (2001)]. The characteristic relaxation times follow the well known Vogel-Fulcher-Tammann law describing the temperature dependence of the bulk viscosity of this polymer. UV photoperturbation accelerates the relaxation dynamics, in qualitative agreement with the fluidification effect of UV photo-perturbation previously observed by surface rheometry, and is used to drive the system out of equilibrium. Transient dynamics is characterized, by the variance  of the two-times correlation functions. A clear peak in  appears at a well defined time  C which scales with q -1 and with the ageing time, in a similar fashion as previously reported in colloidal suspensions [O. Dauchot et al., Phys. Rev. Lett. 95, 265701 (2005)]. From an accurate analysis of the correlation functions we could demonstrate a temperature dependent cross-over from KWW compressed to simple exponential behaviour, which is modified by the fluidification due to the optical pumping of the cis-trans isomerisation of the side-chain azobenzene group.

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“…10,11 These studies clearly indicate that cooperative motions are possible in amorphous polymers, even below T g , and that the polarity of the groups involved in the cooperative motions is an important factor. Similarly, the photoinduced orientation of azobenzene groups has been used to reorient non photochromic groups in liquid crystalline (LC) polymers [12][13][14][15] or to align LC molecules in Langmuir-Blodgett films. 16,17 The nature of the matrix in the doped polymer systems is also a factor that influences the angular reorientation of azobenzene derivatives.…”

Section: Introductionmentioning

confidence: 99%

Photoinduced Orientation of Azobenzene Chromophores in Amorphous Polymers As Studied by Real-Time Visible and FTIR Spectroscopies

et al. 1998

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ABSTRACT:In situ dynamical study of the photoinduced orientation of the DR1 azobenzene derivative in a doped PMMA matrix and in p(DR1A-co-MMA) copolymers was carried out using real-time visible and infrared spectroscopies. The different mechanisms occurring during the photoisomerization cycles were highlighted by following the time dependence of the normalized average absorbance (T 0), the normalized linear dichroism (T2) and the order parameter (P2) during the orientation (laser on) and the relaxation (laser off) periods. The thermal cis-trans back-relaxation and the angular redistribution were followed separately from the T0 and T2 relaxation curves, respectively. The orientation and relaxation curves were fitted by the Kohlrausch-Williams-Watts (KWW) function in order to compare the rate constant and the distribution width for various samples. On one hand, the chromophore-matrix interactions were investigated in doped systems by changing the tacticity of the PMMA matrix. On the other hand, the chromophore-chromophore interactions in functionalized polymers were studied by changing the concentration of azobenzene units in copolymer systems.

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Molecular addressing? Studies on light-induced reorientation in liquid-crystalline side chain polymers

Cited by 153 publications

References 9 publications

Molecular relaxation in a photosensitive liquid-crystalline polymeric glass former

Molecular relaxation in a photosensitive liquid-crystalline polymeric glass former

Slow dynamics in an azopolymer molecular layer studied by x-ray photon correlation spectroscopy

Photoinduced Orientation of Azobenzene Chromophores in Amorphous Polymers As Studied by Real-Time Visible and FTIR Spectroscopies

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