Poly(propyleneimine) Liquid Crystal Codendrimers Bearing Laterally and Terminally Attached Promesogenic Groups

Abstract

The synthesis, chemical characterization, and liquid crystalline behavior of two new series of poly(propyleneimine) (DAB) codendrimers are described. Both series were obtained by grafting onto the fourth-generation dendrimer (DAB−(NH2)32) various proportions of two types of promesogenic units: one of them laterally attached and the other terminally attached. Both series differ in the terminally attached promesogenic unit, being chiral in series 1 and achiral in series 2. X-ray diffraction studies show that these compounds exhibit nematic or lamellar mesophases. For intermediate proportions, the smectic C mesophase, which was not exhibited by the homodendrimers, appears. Thus, the evolution between a nematic and an orthogonal lamellar mesophase occurs through a tilted mesophase. The chiral centers in series 1 permit the appearance of chiral nematic (N*) and chiral smectic C (SmC*) mesophases, which are studied. Deuterium NMR experiments reveal that the nematic formed by one codendrimer is uniaxial and not the anticipated biaxial nematic.

Connector type‐controlled mesophase structures in poly(propyl ether imine) dendritic liquid crystals of identical dendrimer generations

“…A long spacer is critical in order to make the peripheral mesogenic moieties independent of the influence of the dendritic core, to derive a stable mesophase structure 22a, …”

Novel morphologies for laterally decorated metaparticles: molecular dynamics simulation

“…The core mimics either a solid nanoparticle (e.g., gold nanoparticle [6,7]) or averaged in time shape of a dendritic scaffold [4,5]. It was found experimentally that the most important aspects of decoration are as follows: the surface density of mesogens on the outer shell of MP, the length of a spacer, and the exact way mesogens are attached chemically to the spacer [4][5][6][7][8][9][10][11]. In particular, both terminal and lateral attachment can be realised chemically [4,5,[8][9][10][11] [depicted schematically in figure 1 (a) and (b)] and the difference between the morphologies observed in these two cases are in the focus of this study.…”

Fluorinated liquid crystalline dendrimers

“…These modulated smectic mesophases had been previously described for low-molecular-weight mesogens bearing fluorinated terminal chains [54] as well as for some non-fluorinated codendrimers. [55,56] Similarly to the previously described codendrimers that self-assembled in a frustrated SmA + phase, the authors attributed the presence of this modulated smectic A phase (SmÃ) to the segregation produced between semifluorinated and perhydrogenated chains. [49] In particular, the layers of the resulting mesophase were reported to exhibit undulation in a direction perpendicular to the layer normal as a consequence of the dissymmetry originated by the nanosegregation of both moieties.…”