Structure–property relationships determining the spontaneous polarization in FLC‐polymers

Abstract

Communications ADVANCED MATERIALSobserved at high temperatures. The experimental values of i(, at high temperatures are not reproduced well by the two models mentioned above. Above 180 K the measured susceptibility is larger than the calculated one. The mechanism of the spin-spin coupling in the dimer 1 in this temperature range remains to be discussed. Further studies are necessary before this system can be understood completely. E.xperimental4-amino-4-carboxyl-2,2,6,6-tetramethylp1peridine-l-oxyl(2) and the dinitroxylamide (2) were prepared from 4-0~0-2.2,6,6-tetramethylpiperidine as described in our previous work [lo]. The magnetic susceptibilities were determined with an AC Susceptometer Model 7000 in an external field of 5.027 Oe. The measurements were carried out with about 100 mg of the powder samples over a temperature range from 4.2 K to 300 K for the dimer 1 and 4.3 K to 150 K for the monomer 2. The diamagnetic contributions of the radicals xd = -1 . 4~ (emulmol) for the monomer 2 and xd = -2.6 x (emuimol) for the dimer 1, which are calculaled using Pascal's constants (1 I] and the values from Yamanchi [12], are used to correct the measured susceptibilities to obtain the paramagnetic susceptibilities xg.

Solving the Structure of a Metal‐Substituted Aluminum Phosphate Catalyst by Electron Microscopy, Computer Simulation, and X‐ray Powder Diffraction

“…13.52 ( S , 1 H),8.52 (s, 1 H), 7.73 (d, J = 16.1 Hz, 1 H), 7.55 (d, J = 8.4 Hz, ML,: An ethanolic solution containing copper acetate or vanadyl sulfate (1 mmol) was added to a hot ethanolic solution of L (2 mmol). The color of the reaction solution changed from yellow to green.…”

Liquid‐Crystalline Colloidal Particles

“…Many LC-acrylate monomers which give rise to nematic phases are known, however, only very few acrylate monomers to obtain chiral smectic C* phases (the precondition for the ferroelectric phase) are known because research on this topic had nearly exclusively focused on ferroelectric polysiloxanes. [7][8][9][10] Concerning the phase sequence, we were aiming at LC-polymers with a T g -value above room temperature. If ferroelectric LC-phases were encountered, a moderate transition temperature between smectic C* and smectic A phase and a high spontaneous polarization was desirable.…”

“…M1 is known to give a LC polyacrylate with a broad nematic range; [11] M2 is an azobenzene-containing monomer which allows the preparation of photoswitchable LC-polymers; M3 gives rise to one of the few reported ferroelectric polyacrylates with moderate phase transition temperatures; [7,12,13] M4 was newly synthesized in analogy to ferroelectric polysiloxanes. [9] The phase behavior of the polymers P1, P3 and P4 (radical polymerization of M1, M3 and M4), as well as that of the copolymers CoPo (copolymerization of M1 and the azobenzene-containing monomer M2) was characterized by DSC and polarizing microscopy. It was done with the bulk polymer obtained from larger agglomerates remaining as residue after the centrifugation of the dispersion polymerization batches.…”

Behavior and properties of side chain thermotropic liquid crystal polymers

“…The reported value ofPs = 420 nC/cm2 (at T = 15 1 "C) for polymer VI (Fig. 12) is very likely the highest value so far achieved with FLCPs [42]. The influence of the polymer molecular weight on the spontaneous polarization has been studied in a polyacrylate series [21] as well as in a polysiloxane series [ 181.…”