Influence of alkoxy tail length on the self‐organization of hairy‐rod polymers based on mesogen‐jacketed liquid crystalline polymers

Abstract

A series of hairy‐rod polymers, poly{2,5‐bis[(4‐alkoxyphenyl)oxycarbonyl]styrenes} (P‐OCm, m = 1, 2, 4, 6, 8, 10, 12, 14, 16, and 18) were designed and successfully synthesized via free radical polymerization. The chemical structure of the monomers was confirmed by elemental analysis, 1H NMR and 13C NMR. The molecular characterizations of the polymers were performed with 1H NMR and gel permeation chromatography. The phase structures and transitions of the polymers were investigated by the combination of techniques including differential scanning calorimetry, wide‐angle X‐ray diffraction, polarized optical microscopy, and rheological measurement. The experimental results revealed that the self‐assembly behaviors of P‐OCm changed with the increase in m. First, the P‐OCm (m = 1, 2) showed only a stable liquid crystalline phase above Tg. Second, with the increasing length of alkoxy tails, the P‐OCm (m = 4, 6, 8) presented a re‐entrant isotropic phase above Tg and a liquid crystalline phase at higher temperature. Third, the P‐OCm (m = 10, 12, 14, 16, 18) exhibited an unusual re‐entrant isotropic phase which was separating SmA (in low temperature) and columnar phases (in high temperature). It was the first time that mesogen‐jacketed liquid crystalline polymers formed smectic phase, re‐entrant isotropic phase, and columnar phases in one polymer due to the microphase separation and the driving force of the entropy. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Synthesis and liquid crystalline behavior of 2,5-disubstituted styrene-based random copolymers: Effect of difference in length of the rigid core on the mesomorphic behavior of mesogen-jacketed liquid crystalline polymers

“…When the sample was heated to 140 C, the diffraction peaks disappeared and the scattering halo appeared, indicating that the sample becomes isotropic. Further increasing the temperature to 260 C, one peaks appeared about 3.07 (d ¼ 2.87 nm), indicating a transition from isotropic to columnar phase [36]. In the high 2q region of 10e35 , at lower temperature range the WAXD patterns only rendered one peaks (as shown in Fig.…”

“…6(a), (b), (c) and (d), respectively. So, the phase transitions of P 1 eP 5 followed the sequence of smectic A phase 4 re-entrant isotropic phase 4 columnar phase [36].…”

“…4(a). Last, after T1, one transition peak appeared at 217 C for P 1 , which was caused by the phase transition from isotropic phase to column nematic phase (T2) [36]. For P 2 eP 5 , the T2 were difficultly detected by DSC because the thermal heat was small.…”

“…After water was added into the residue, the crude solid product was first collected by filtration and dried under vacuum, and then purified using column chromatography on silica gel with chloroform as eluant. The M-OC18 was synthesized according to our work [36]. The characterization data of these monomers were as follows and …”

“…In our previous studies, our group has proved that the P-OC18 formed the smectic A phase, re-entrant isotropic phase and columnar phases with the increasing of temperature [36]. The P-C18 presented the stable smectic A phase [37].…”