Dielectric and IR Spectroscopy of the Macromolecular Reaction of Anhydridization in a Functionalized Side-Chain Liquid Crystalline Copolymer Containing Acrylic Acid Groups

Abstract

The anhydrization reaction has been investigated in functionalized side-chain random liquid crystalline (LC) copolymers containing cyanobiphenyl mesogenic and acrylic acid (38 mol %) groups. Heat treatment of the LC copolymer at 130 °C for 5-200 h is accompanied by formation of intra-and intermolecular anhydrides and network structures causing an increase of the glass transition and clearing temperatures. The influence of annealing on the reorientational dynamics of the copolymers was investigated by broad-band dielectric relaxation spectroscopy. The local dynamics of the side group involving spacer motion (γ relaxation) and mesogen rotation about the long axis (β relaxation) do not depend on the annealing time. At the same time a considerable (more than 2 orders of magnitude) decrease in the relaxation rates of the cooperative δ and R processes was observed due to a gradual increase in the main-chain rigidity during the annealing. The molecular mechanism of all relaxation processes detected is discussed.

Molecular mobility of CU(II)-containing liquid crystalline ionomers: dielectric relaxation and thermally stimulated depolarization currents

“…Fig. 2 also shows the 2log t m ¼ wð1=TÞ plots in the subglass state for P1 with 38( of AA (curves 4, 5) [31]. One can see that curve 4 is placed between curve 1 and 2 corresponding to the b and the g 1 processes, respectively.…”

“…2. Dependences of 2log t on inverse temperature in the range of the a (6,7) and 2d (8,9) processes for P1 (6,8) and P3 (7,9) and in the range of the sub-glass processes (1-5) for PM-5-CAB (curves 1, 2) [25,27], PM-5-PhB (curves 1-3) [28,30], and for P1 with 38( AA (curves 4, 5) [31]; the points at 2log t ¼ 22:2 are the T m values obtained from the global curves. modes).…”

Molecular dynamics in semifluorinated side-chain polyesters as studied by broadband dielectric spectroscopy

“…Since the aliphatic spacer itself is nonpolar, its mobility can be dielectrically active only if some adjacent polar group is connected to it, for example an oxygen atom. It has been pointed out in side-chain liquid crystalline polymers [39e43] and related studies [44] that the process is observed for polymer systems with at least four spacer units. This agrees well with our observation that the g B -relaxation is only observed in polymer 7, which has six eCH 2 e spacer units.…”

Dielectric Relaxation in Isotropic/Liquid Crystalline Block Copolymers: Effect of Nanoscale Confinement on the Local β and γ Dynamics

“…It is known that the bulk (unconfined) side-chain LC polymers with cyanobiphenyl mesogen fragment and with four carbon methylene spacer reveal two local modes (called β and γ) related to the motion of mesogen and spacer, respectively. 11 Moreover, any chemical modification of chain structure (copolymer structure, H-bond, or/and network formation), which does not touch the side chain directly, does also not affect its local motion. 11 Thus, we expect to observe these local modes in the PS/LC block copolymers.…”