TY  - JOUR
AU  - Cmok, Luka
AU  - Mattiazzi, Simon
AU  - Drevensek-Olenik, Irena
AU  - Sebastian, Nerea
AU  - Gak Simić, Kristina
AU  - Trišović, Nemanja
AU  - Vilfan, Mojca
PY  - 2023
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/5955
AB  - We report on observations of optical switching in bent-core liquid crystals possessing azocinnamoyl groups in both elongated side arms. UV-activated switching was observed in two of the synthesised materials, both of which were studied optically and with dielectric spectroscopy. Polarising microscopy was used to measure the changes in optical transmittance, and while no illumination effect was seen in the nematic phase, visible changes were observed in the smectic phase, most pronounced in the close vicinity of the smectic to nematic-phase transition. Switching dynamics was characterised, and we found that the average switching time varies strongly with temperature. The relaxation process is faster (below (Formula presented.)) and exhibits no significant temperature dependence. Dielectric measurements have shown that the observed smectic C phases were not polar with the molecules possessing a rather small electric dipole moment. Upon illumination, small differences in the dielectric permittivity were observed only in the smectic phase, suggesting that the illumination effect can be attributed to changes in the molecular conformational and orientational order.
PB  - Taylor and Francis Ltd.
T2  - Liquid Crystals
T1  - Optical switching of bent-core liquid crystals with azocinnamoyl units
DO  - 10.1080/02678292.2023.2179120
ER  - 

@article{
author = "Cmok, Luka and Mattiazzi, Simon and Drevensek-Olenik, Irena and Sebastian, Nerea and Gak Simić, Kristina and Trišović, Nemanja and Vilfan, Mojca",
year = "2023",
abstract = "We report on observations of optical switching in bent-core liquid crystals possessing azocinnamoyl groups in both elongated side arms. UV-activated switching was observed in two of the synthesised materials, both of which were studied optically and with dielectric spectroscopy. Polarising microscopy was used to measure the changes in optical transmittance, and while no illumination effect was seen in the nematic phase, visible changes were observed in the smectic phase, most pronounced in the close vicinity of the smectic to nematic-phase transition. Switching dynamics was characterised, and we found that the average switching time varies strongly with temperature. The relaxation process is faster (below (Formula presented.)) and exhibits no significant temperature dependence. Dielectric measurements have shown that the observed smectic C phases were not polar with the molecules possessing a rather small electric dipole moment. Upon illumination, small differences in the dielectric permittivity were observed only in the smectic phase, suggesting that the illumination effect can be attributed to changes in the molecular conformational and orientational order.",
publisher = "Taylor and Francis Ltd.",
journal = "Liquid Crystals",
title = "Optical switching of bent-core liquid crystals with azocinnamoyl units",
doi = "10.1080/02678292.2023.2179120"
}

Cmok, L., Mattiazzi, S., Drevensek-Olenik, I., Sebastian, N., Gak Simić, K., Trišović, N.,& Vilfan, M.. (2023). Optical switching of bent-core liquid crystals with azocinnamoyl units. in Liquid Crystals
Taylor and Francis Ltd...
https://doi.org/10.1080/02678292.2023.2179120

Cmok L, Mattiazzi S, Drevensek-Olenik I, Sebastian N, Gak Simić K, Trišović N, Vilfan M. Optical switching of bent-core liquid crystals with azocinnamoyl units. in Liquid Crystals. 2023;.
doi:10.1080/02678292.2023.2179120 .

Cmok, Luka, Mattiazzi, Simon, Drevensek-Olenik, Irena, Sebastian, Nerea, Gak Simić, Kristina, Trišović, Nemanja, Vilfan, Mojca, "Optical switching of bent-core liquid crystals with azocinnamoyl units" in Liquid Crystals (2023),
https://doi.org/10.1080/02678292.2023.2179120 . .

TY  - CONF
AU  - Gak Simić, Kristina
AU  - Trišović, Nemanja
AU  - Cmok, Luka
AU  - Drevenšek-Olenik, Irena
PY  - 2022
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/6771
AB  - V prispevku predstavljamo sintezo in karakterizacijo serije tekočih kristalov z upognjeno sredico. Upognjeno sredico sestavljajo 3 benzenski obroči povezani z azocinamoilno skupino in še 2 povezana z fotoobčutljivim AZO mostom. Dolžini stranskih repov so bili v vseh primerih enake (C12H25–), medtem ko smo na centralnem in zunanjih benzenskih obročih z substitucijo funkcionalnih skupin spreminjali električne lastnosti spojin in njihov način spontanega urejanja. V
nasprotju z spojino, ki je vsebovala “gole” benzenske obroče smo v primerih z funkcionalnimi skupinami dosegli večjo prostorsko porazdelitev naboja ter nove - drugačne makroskopsko urejene faze.
Pri karakterizaciji smo se osredotočili predvsen na efekte fotoizomerizacije. Znano je, da v azocinamoilnih funkcionalnih skupinah prihaja do več fotokemičnih procesov, poleg cis-trans prehoda še do ciklizacije in foto-Fries reorganizacije. Preučili smo fazni diagram tekoče kristalnih faz, ki jih tvorijo te spojine, odkrili da ena izmed spojin tvori zanimivo smektično B7 fazo. UV osvetlitev vzorcev povzroči spremembe v ureditvi, opazili smo, da se v planarno urejenih celicah te spremembe hitre in ponovljive, ter da znižajo temperaturo faznega prehoda iz smektične v nematsko fazo. V poizkusih, kjer je bil material samo nanšen na stekleno povšino, smo opazili tipično Schliren teksturo, katera se je ob UV osvetlitivi stabilizirala in je ostala stabilna tudi po več mesecih. Razlog za to smo pripisali dimerizaciji cinamoilnih funkcionalih grup, ki so preprečile cis-konformaciji da se relaksira nazaj v trans-konformacijo, predvidevamo, da zaradi omejene geometrije takšen proces ni možen v planarnih celicah.
PB  - V Ljubljani : Fakulteta za matematiko in fiziko
C3  - Zbornik povzetkov / 12. konferenca fizikov v osnovnih raziskavah, Terme Čatež, 11. november 2022
T1  - Fotoobčutljivi azocinamoilni tekoči kristali z upognjeno sredico
T1  - Photosensitive azocinnamoyl liquid crystals with a bent core
SP  - 31
UR  - https://hdl.handle.net/21.15107/rcub_technorep_6771
ER  - 

@conference{
author = "Gak Simić, Kristina and Trišović, Nemanja and Cmok, Luka and Drevenšek-Olenik, Irena",
year = "2022",
abstract = "V prispevku predstavljamo sintezo in karakterizacijo serije tekočih kristalov z upognjeno sredico. Upognjeno sredico sestavljajo 3 benzenski obroči povezani z azocinamoilno skupino in še 2 povezana z fotoobčutljivim AZO mostom. Dolžini stranskih repov so bili v vseh primerih enake (C12H25–), medtem ko smo na centralnem in zunanjih benzenskih obročih z substitucijo funkcionalnih skupin spreminjali električne lastnosti spojin in njihov način spontanega urejanja. V
nasprotju z spojino, ki je vsebovala “gole” benzenske obroče smo v primerih z funkcionalnimi skupinami dosegli večjo prostorsko porazdelitev naboja ter nove - drugačne makroskopsko urejene faze.
Pri karakterizaciji smo se osredotočili predvsen na efekte fotoizomerizacije. Znano je, da v azocinamoilnih funkcionalnih skupinah prihaja do več fotokemičnih procesov, poleg cis-trans prehoda še do ciklizacije in foto-Fries reorganizacije. Preučili smo fazni diagram tekoče kristalnih faz, ki jih tvorijo te spojine, odkrili da ena izmed spojin tvori zanimivo smektično B7 fazo. UV osvetlitev vzorcev povzroči spremembe v ureditvi, opazili smo, da se v planarno urejenih celicah te spremembe hitre in ponovljive, ter da znižajo temperaturo faznega prehoda iz smektične v nematsko fazo. V poizkusih, kjer je bil material samo nanšen na stekleno povšino, smo opazili tipično Schliren teksturo, katera se je ob UV osvetlitivi stabilizirala in je ostala stabilna tudi po več mesecih. Razlog za to smo pripisali dimerizaciji cinamoilnih funkcionalih grup, ki so preprečile cis-konformaciji da se relaksira nazaj v trans-konformacijo, predvidevamo, da zaradi omejene geometrije takšen proces ni možen v planarnih celicah.",
publisher = "V Ljubljani : Fakulteta za matematiko in fiziko",
journal = "Zbornik povzetkov / 12. konferenca fizikov v osnovnih raziskavah, Terme Čatež, 11. november 2022",
title = "Fotoobčutljivi azocinamoilni tekoči kristali z upognjeno sredico, Photosensitive azocinnamoyl liquid crystals with a bent core",
pages = "31",
url = "https://hdl.handle.net/21.15107/rcub_technorep_6771"
}

Gak Simić, K., Trišović, N., Cmok, L.,& Drevenšek-Olenik, I.. (2022). Fotoobčutljivi azocinamoilni tekoči kristali z upognjeno sredico. in Zbornik povzetkov / 12. konferenca fizikov v osnovnih raziskavah, Terme Čatež, 11. november 2022
V Ljubljani : Fakulteta za matematiko in fiziko., 31.
https://hdl.handle.net/21.15107/rcub_technorep_6771

Gak Simić K, Trišović N, Cmok L, Drevenšek-Olenik I. Fotoobčutljivi azocinamoilni tekoči kristali z upognjeno sredico. in Zbornik povzetkov / 12. konferenca fizikov v osnovnih raziskavah, Terme Čatež, 11. november 2022. 2022;:31.
https://hdl.handle.net/21.15107/rcub_technorep_6771 .

Gak Simić, Kristina, Trišović, Nemanja, Cmok, Luka, Drevenšek-Olenik, Irena, "Fotoobčutljivi azocinamoilni tekoči kristali z upognjeno sredico" in Zbornik povzetkov / 12. konferenca fizikov v osnovnih raziskavah, Terme Čatež, 11. november 2022 (2022):31,
https://hdl.handle.net/21.15107/rcub_technorep_6771 .

TY  - JOUR
AU  - Gak Simić, Kristina
AU  - Rybak, Paulina
AU  - Pociecha, Damian
AU  - Cmok, Luka
AU  - Drevenšek-Olenik, Irena
AU  - Tóth-Katona, Tibor
AU  - Trišović, Nemanja
PY  - 2022
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/5218
AB  - A series of bent-core liquid crystals possessing the azocinnamoyl unit in both elongating side arms was synthesized. The chain length was kept fixed for each molecule (C12H25), whereas the substituents at the central and outer rings were varied. The LC phases were assigned by polarizing optical microscopy, differential scanning calorimetry and X-ray diffraction. The investigated compounds are suitably diverse to reveal some aspects of the relationship between molecular structure and the mesomorphic properties. Namely, non-substituted parent compound is crystalline only and the methyl group in position 2 or the chlorine atom in position 4 of the central ring suppresses LC phase formation. Introduction of the strong electron-withdrawing nitro group between the side arms on the central ring leads to a B7 phase. Compounds possessing a bromine atom or two chlorine atoms in the neighbourhood of the ester groups form LC phases typical for rod-like molecules, namely a nematic – smectic phase sequence. The results are compared with those reported for the azobenzoyl analogues.
PB  - Elsevier B.V.
T2  - Journal of Molecular Liquids
T1  - Introducing the azocinnamic acid scaffold into bent-core liquid crystal design: A structure–property relationship study
SP  - 120182
VL  - 366
DO  - 10.1016/j.molliq.2022.120182
ER  - 

@article{
author = "Gak Simić, Kristina and Rybak, Paulina and Pociecha, Damian and Cmok, Luka and Drevenšek-Olenik, Irena and Tóth-Katona, Tibor and Trišović, Nemanja",
year = "2022",
abstract = "A series of bent-core liquid crystals possessing the azocinnamoyl unit in both elongating side arms was synthesized. The chain length was kept fixed for each molecule (C12H25), whereas the substituents at the central and outer rings were varied. The LC phases were assigned by polarizing optical microscopy, differential scanning calorimetry and X-ray diffraction. The investigated compounds are suitably diverse to reveal some aspects of the relationship between molecular structure and the mesomorphic properties. Namely, non-substituted parent compound is crystalline only and the methyl group in position 2 or the chlorine atom in position 4 of the central ring suppresses LC phase formation. Introduction of the strong electron-withdrawing nitro group between the side arms on the central ring leads to a B7 phase. Compounds possessing a bromine atom or two chlorine atoms in the neighbourhood of the ester groups form LC phases typical for rod-like molecules, namely a nematic – smectic phase sequence. The results are compared with those reported for the azobenzoyl analogues.",
publisher = "Elsevier B.V.",
journal = "Journal of Molecular Liquids",
title = "Introducing the azocinnamic acid scaffold into bent-core liquid crystal design: A structure–property relationship study",
pages = "120182",
volume = "366",
doi = "10.1016/j.molliq.2022.120182"
}

Gak Simić, K., Rybak, P., Pociecha, D., Cmok, L., Drevenšek-Olenik, I., Tóth-Katona, T.,& Trišović, N.. (2022). Introducing the azocinnamic acid scaffold into bent-core liquid crystal design: A structure–property relationship study. in Journal of Molecular Liquids
Elsevier B.V.., 366, 120182.
https://doi.org/10.1016/j.molliq.2022.120182

Gak Simić K, Rybak P, Pociecha D, Cmok L, Drevenšek-Olenik I, Tóth-Katona T, Trišović N. Introducing the azocinnamic acid scaffold into bent-core liquid crystal design: A structure–property relationship study. in Journal of Molecular Liquids. 2022;366:120182.
doi:10.1016/j.molliq.2022.120182 .

Gak Simić, Kristina, Rybak, Paulina, Pociecha, Damian, Cmok, Luka, Drevenšek-Olenik, Irena, Tóth-Katona, Tibor, Trišović, Nemanja, "Introducing the azocinnamic acid scaffold into bent-core liquid crystal design: A structure–property relationship study" in Journal of Molecular Liquids, 366 (2022):120182,
https://doi.org/10.1016/j.molliq.2022.120182 . .