Polymeric fibers and microporous films by photo‐crosslinking of triphenylene‐derived liquid crystals

Abstract

Two series of photoreactive discotic liquid crystals consisting of a triphenylene core and six cinnamate units with one (TPC1 n) or two (TPC2 n) n‐alkoxy groups (C nH2n+1O; n = 10–14), respectively, as peripheral groups are synthesized. Both of them are polymerized into fibers up to 2 mm long by UV irradiation in liquid paraffin in the columnar LC temperature ranges. The fiber structures seem to be preconstructed in liquid paraffin. In addition, TPC2 n are shown to form microporous films up to 15 μm in diameter by simply casting the solutions of some solvents followed by drying for several minutes in air at room temperature. Photoirradiation of the films in the LC temperature range converts them to polymeric ones while preserving the microporous and hexagonally ordered structure. From comparison with TPC1 n and the hydrogenated derivative of TPC2 12, the porous film‐forming property is suggested to result from the combination of the double bond of the cinnamoyl group and the two long alkoxy chains on the phenyl ring. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 605–612

Thermoreversible helical fibers from photoreactive triphenylene-derived liquid crystals in liquid paraffin

“…TPC1 p -12 gave more linear crescent-shaped products while from TPC1 p -14 and TPC1 p -16 , most products were tangled. In fact, sometimes insoluble product from TPC1 p -12 was obtained as reported previously [ 23 ]. As discussed in the section on expected reaction mechanisms below, this may be due to the higher reactivity of TPC1 p -12 as considering the higher orderliness seen in Fig.…”

“…For the LC phase determination, X-ray diffraction (XRD) was performed by changing the temperature. The phase transition behaviors are summarized in Table 1 with those of TPC1 p -n (n = 12, 14) reported previously [ 23 ]. From the DSC measurements of TPC1 p -6 , an endothermic change was observed at 166 °C on the heating process as seen in Table 1 .…”

“…Two new triphenylene derivatives, TPC1 p -n (n = 6, 16), were prepared from hexahydroxytriphenylene and the corresponding substituted cinnamic acid chloride following the previous procedure [ 23 ]. The optical textures were studied by polarized optical microscopy (POM), and the phase transition temperatures and the heats of phase transition were determined by differential scanning calorimetry (DSC).…”

“…The TPC s forming the Col r phase are stacked with the molecular axis inclined to the column axis, as indicated by A. In the previous report [ 23 ], it was proposed that [2+2] photocyclization of molecules assembled in the Col r structures in a film form led to crosslinking and changed to a Col h -like morphology with overlapping molecules. As polymerization proceeds, the original Col r order collapses and the cross-linking reaction stops, as shown in B.…”

“…We developed photoreactive columnar LC compounds and investigated the effect of UV irradiation in liquid paraffin with no additives at the temperature in LC state [ 23 ]. They were triphenylene derivatives, TPC1 p -n and TPC2 mp -n ( Fig.…”