TY  - THES
A1  - Tomczyk, Jaroslaw
T1  - Photoinduced optical anisotropy in films of photochromic star-shaped liquid crystals
Y1  - 2013
CY  - Potsdam
ER  - 
TY  - JOUR
A1  - Tomczyk, Jaroslaw
A1  - Sobolewska, Anna
A1  - Nagy, Zsuzsanna T.
A1  - Guillon, Daniel
A1  - Donnio, Bertrand
A1  - Stumpe, Joachim
T1  - Photo- and thermal-processing of azobenzene-containing star-shaped liquid crystals
JF  - Journal of materials chemistry : C, Materials for optical and electronic devices
N2  - A new class of star-shaped, liquid crystalline, low-molecular weight compounds functionalized with photochromic azobenzene and mesogenic groups was investigated in terms of light-induced anisotropy. The behaviour of the materials under the action of light with simultaneous or subsequent thermal treatment was examined with respect to the induction of anisotropy. The unconventional UV light treatment prior to the irradiation with linearly polarized light allowed induction of very high values of anisotropy (D = 0.77) at room temperature. Moreover, the simultaneous action of light and temperature led to the induction of higher values of dichroism in comparison with anisotropy generated by the standard procedure. Subsequent thermal treatment led to dewetting and the formation of 3D macroscopic stripe- and dome-like structures for one of the investigated compounds. Despite photoinduction of anisotropy by a single beam, the formation of polarization and surface relief gratings by two-beam interference pattern was also investigated.
Y1  - 2013
U6  - https://doi.org/10.1039/c2tc00627h
SN  - 2050-7526
VL  - 1
IS  - 5
SP  - 924
EP  - 932
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Nagy, Zsuzsanna T.
A1  - Heinrich, Benoit
A1  - Guillon, Daniel
A1  - Tomczyk, Jaroslaw
A1  - Stumpe, Joachim
A1  - Donnio, Bertrand
T1  - Heterolithic azobenzene-containing supermolecular tripedal liquid crystals self-organizing into highly segregated bilayered smectic phases
JF  - Journal of materials chemistry
N2  - Synthesis, self-organization, and optical properties of supermolecular tripedal liquid crystals incorporating various prototypical mesogenic units such as alkoxy-azobenzene (AZB), alkoxy-biphenylene (BPH) or alkoxy-cyanobiphenyl (OCB) derivatives are reported. Different molecular systems were designed in order to sequentially incorporate the smectogenic-like alkoxy-azobenzene-based chromophore within the molecular structure, whose relative proportion is selectively varied by exchanging with the other mesogens. A divergent synthetic mode was elaborated for their synthesis, starting from the regioselective functionalization of the phloroglucinol-based (PG) inner core. This methodology allowed the preparation of several sets of unconventional tripedal oligomers with conjugated heterolithic structures (made of different blocks, e.g. PG(6)AZB(x)BPH(3-x) and PG(6)AZB(x)OCB(3-x), x = 1 or 2) along the homolithic parents (all identical blocks, e.g. PG(z)AZB(3), z = 6 or 11, z is the number of methylene in the spacer between PG and the protomesogen, PG(6)BPH(3), and PG(6)OCB(3)), respectively. Essentially all the synthesized systems behave as thermotropic liquid crystals and show various types of highly segregated multilayered smectic phases, or, in one case, a nematic phase, depending on the nature of the constitutive anisotropic blocks and on the molecular topology (homolithic versus heterolithic, mesogenic ratio x : 3 - x). The effects of these structural modifications on the mesomorphism (mesophase structures, temperature ranges, and thermodynamic stability) have been investigated by differential scanning calorimetry and small-angle X-ray diffraction experiments combined with dilatometric measurements. Models describing the various supramolecular organizations of these tripedes into such multilayered structures are proposed and discussed. Preliminary results of the investigations of their optical properties will also be presented.
Y1  - 2012
U6  - https://doi.org/10.1039/c2jm33751g
SN  - 0959-9428
VL  - 22
IS  - 35
SP  - 18614
EP  - 18622
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  -