Semidilute solutions of liquid-crystalline polymers

Abstract

Solution properties of two liquid crystalline side-chain polymers of different architecture have been investigated by static and dynamic light scattering. Dilute solutions of these polymers showed common flexible chain behavior, and no indications for a significant chain rigidity were observed. In semidilute solution the concentration dependence of the osmotic modulus revealed stronger repulsion than common linear macromolecules. Furthermore, a chain-length dependence was observed. Both effects can be explained by the thickness of the polymer chain. At high concentrations an excess low-angle scattering and a slow mode of motion were detected, indicating formation of large clusters. The first appearance of these clusters was found at the same concentration for samples of different molar mass. This leads to the suggestion that attractive interactions between mesogenic groups are responsible for cluster formation. Further information on the structure of the clusters was obtained by studying fractal dimension and depolarized scattered light.

Chiral liquid-crystalline polyacrylates from (S)-(-)-2-methyl-1-butanol. Synthesis, mesomorphic properties and light scattering

“…They are in agreement with the few results published in PLCs 15,16 , where ρ is in the range from 1.7 to 2.1, typically for polydisperse linear chains in good solvents. In this way, the behavior is typical for flexible macromolecules in both solvents indicating that mesogenic groups do not affect the chain stiffness.…”

“…The weight averaged molecular weight w M , radius of gyration R g , and second virial coefficient A 2 of the polymers in different solvents could be extracted from the intercept and the corresponding initial slopes 14,15 . The intensity time correlation functions obtained by PCS, which can be related to the relaxation rate Γ, were analyzed by the method of cumulants 11 .…”

“…An extrapolation of D app to zero angle gives the translational diffusion coefficient D c at concentration c. D c was then extrapolated linearly to c=0 according to the equation (1) 14,15 .…”

Macromolecular Anisotropic Association in Isotropic Solutions of a Liquid Crystal Side Chain Polymer

“…[14] Second, the presence of dynamic depolarized light scattering reveals the existence of non-spherical supramolecular species. Similar observations on semi-dilute solutions of side chain liquid crystalline polymers, concerning both the excess low-q intensity and the presence of depolarized light scattering, were reported by Richtering et al [2] These findings do not relate with pre-transitional spatial heterogeneities observed in nematic liquid crystals in the isotropic region. [14] The orientation relaxation function of Figure 2 is clearly related to the slow process (cf.…”

“…In solution, lyotropic phases may not be observed due to the formation of supramolecular aggregates. [2] SCLCP's based on a polynorbornene backbone were prepared via ring opening metathesis polymerization (ROMP) with one pendant mesogenic group per repeating unit. [5] Due to the living character of this polymerization, resulting in a direct relation between initiator to monomer ratio, well-defined degrees of polymerization are available.…”