Synthesis and Characterization of Poly(pyridinium salt)s with Organic Counterions Exhibiting Both Thermotropic Liquid-Crystalline and Light-Emitting Properties

Abstract

Two poly(pyridinium salt)s with bulky organic counterions (tosylate and triflimide) were synthesized by either the ring-transmutation polymerization reaction of 4,4′-(1,4-phenylene)bis(2,6diphenylpyrylium tosylate) with 1,12-diaminododecane on heating in dimethyl sulfoxide (DMSO) at 145-150 °C for 24 h or the metathesis reaction of the corresponding tosylate polymer with lithium triflimide in a common organic solvent such as acetonitrile. Their polyelectrolyte behavior in DMSO was determined by solution viscosity measurements, and their chemical structures were determined by Fourier transform infrared and Fourier transform NMR spectroscopy. They were characterized for their thermotropic liquidcrystalline properties with a number of experimental techniques. Poly(pyridinium salt) with tosylate as a counterion had a crystal-to-smectic phase transition at 116 °C that persisted up to its decomposition temperature. The corresponding polymer with triflimide as a counterion had not only lower crystal-tosmectic phase transition at 80 °C but also a smectic-to-isotropic transition at about 180 °C. Both of these transitions were well below its decomposition temperature. It had better thermal stability than that of the corresponding tosylate polymer. Their fluorescence property in solutions of tetrahydrofuran and methanol as well as in the solid state was also included in this study.

Synthesis and characterization of poly(pyridinium salt)s with oxyalkylene units exhibiting amphotropic liquid–crystalline and photoluminescence properties

“…7). Its T m value was marginally higher than that (182 C) of an analogous polymer containing 9 methylene units in the main chain [23], but much higher than that (116 C) of an analogous polymer containing 12 methylene units in the main chain [24]. Note here that poly(pyridinium salt)s with either tetrafluoroborate or triflate as counterions do not exhibit thermotropic LC properties because of their thermal decomposition prior to melting transitions [22,23].…”

“…The smectic-to-isotropic phase transition (T i ) for each of the polymers II-1eII-3 was not detected by DSC measurement presumably because of the broadness of this transition that occurs frequently in many polymers [23,24]. Attempts Table 4 Thermal properties of polymers I-2, II-2, I-3 and II-3 to determine this transition for each of these polymers by POM studies also failed, since the observation of the disappearance of weak birefringence phase was quite problematic.…”

Combined main-chain/side-chain ionic liquid crystalline polymer based on ‘jacketing’ effect: Design, synthesis, supra-molecular self-assembly and photophysical properties

“…For instance, the emission peak positions for the poly(BImBHCS-X) (X" = Br", BF 4 ", PF 6 " and TFSI") samples were located at 420 and 435 nm indicating an obvious bathochromic shift when compared to PBBHCS. This shift originated from the extended planar conjugated system of imidazole heterocycle and biphenyl group [64,65]. In Figure 12b, the spectra of these samples in thin films showed some new transitions which corresponded to the obvious emission peaks at 360, 420 and 485 nm, respectively.…”

“…Compared to PBBHCS, the slight bathochromic shift of the characteristic absorption peak for the poly(BImBHCS-X) was found. The results come from the extended planarization of the imidazole heterocycle and biphenyl group [64,65].…”

“…For comparison, the UV-Vis spectrum of PBBHCS is also included Figure 12. Emission spectra of MCSC-ILCPs poly(BImBHCS-X) (X" =Br", BF 4 ", PF 6 " and TFSI") and PBBHCS at excitation wavelength of 290 nm: (a) in CH 2 Cl 2 and (b) in thin films derived from the electron richness of the imidazole heterocycle [64,65]. In addition, the positions of the other two emission peaks present at 420 and 485 nm for poly(BImBHCS-Br), poly(BImBHCS-BF 4 ), poly(BImBHCS-PF 6 ) and poly(BImBHCS-TFSI) changed little compared to that of PBBHCS.…”