A new liquid crystal phase, denoted modulated helical nanofilament (HNF(mod)), is formed from a very simple class of biphenyl carboxylates lacking the benzylidene aniline moieties typically found in HNF mesogens. The HNF(mod) phase represents a novel kind of nanoparticle possessing stacked aromatic rings, with potential applications in organic electronics.
Helical nanofilaments (HNFs) have attracted much interest because of their unique optical properties, but there have been many hurdles to overcome in using them for the practical applications due to their structural complexity. Here we demonstrate that the molecular configuration and layer conformation of a modulated HNF (HNFs(mod)) can be studied using a physicochemical confinement system. The layer directions affected by the chemical affinity between the mesogen and surface were drastically controlled in surface-modified nanochannels. Furthermore, an in situ experiment using grazing-incidence X-ray diffraction (GIXD) was carried out to investigate in detail the structural evolution through thermal transitions. The results demonstrate that the HNF(mod) structure can be perfectly controlled for functional HNF device applications, and a combined system with chemical and physical confinement effects will be helpful to better understand the fundamentals of soft matter.
We have investigated the various morphological changes of helical nanofilament (HNF; B4) phases in multiscale nanochannels made of porous anodic aluminum oxide (AAO) film. Single or multihelical structures could be manipulated depending on the AAO pore size and the higher-temperature phase of each molecule. Furthermore, the nanostructures of HNFs affected by the chemical affinity between the molecule and surface were drastically controlled in surface-modified nanochannels. These well-controlled hierarchical helical structures that have multidimensions can be a promising tool for the manipulation of chiral pores or the nonlinear optical applications.
Eine neue flüssigkristalline Phase, bezeichnet als moduliertes helikales Nanofilament (HNF(mod)), wird aus einer einfachen Klasse von Biphenylcarboxylaten gebildet, denen die für HNF‐Mesogene typischen Benzylidenanilin‐Einheiten fehlen. Die HNF(mod)‐Phase ist ein neuartiges Beispiel eines Nanopartikels mit gestapelten aromatischen Ringen mit Anwendungspotenzial in der organischen Elektronik.
Using
a unique one-pot convergent anionic polymerization strategy,
18 (polystyrene)star-b-(polyisoprene)linear-b-(polystyrene)star (S
n
IS
n
) pom-pom
triblock copolymers were synthesized varying a range of architectural
parameters including PS arm molecular weight (M
n,star), the number of arms contained in the star (n), and the PI midblock molecular weight (M
n,PI). A selected series of five of these 18, in which M
n,star was held approximately constant between
14.3 and 16.5 kDa, but with the numbers of arms in the star and PI
midblock molecular weight varied, were selected for detailed characterization
using rheology, AFM, and SAXS. The five selected all shared PS as
the minority component, with star volume fractions (f
PS) varying between 0.11 and 0.22. All samples showed
clear phase separation, with three of the five adopting a highly ordered
hexagonal packing of cylinders (HPC) confirmed through SAXS and AFM.
The remaining two systems were limited to liquid-like packing of cylindrical
domains (LLP). Longer midblock molecular weights and increased numbers
of arms in the star both showed a propensity to hinder formation of
a highly ordered hexagonal lattice. Increasing the number of arms
in the star also favored transitions to a disordered phase at lower
temperatures when overall S
n
IS
n
molecular weight was held constant. The behavioral
trends identified suggest interfacial packing frustration plays a
prominent role in determining the ability of the system to develop
highly ordered periodic structures. The chain crowding produced by
the PS star architecture intrinsically favors interfacial curvature
toward the majority PI component, contrary to that intrinsically favored
by the block composition alone. In the two systems in which the frustration
was architecturally most severe (largest n of 7.1,
highest M
n,PI of 191 kDa), evolution of
a hexagonal lattice could not be induced, even after significant thermal
annealing. The pom-pom architecture itself also appears to have a
significant impact on entanglement relaxation dynamics, with development
of HPC morphologies only possible at elevated temperatures.
The synthesis and characterisation of a main-chain chiral smectic liquid crystalline thiol-ene polymer system is described. The chemical structure is designed based on the structure of W317, a mesogen with a large electroclinic effect in the Smectic A* (SmA*) phase. The novel thiol-ene monomer K0902 has a large surface electroclinic effect with an unexpected small electroclinic effect in the SmA* phase. The corresponding thiol-ene oligomer poly-K0902 is characterised by gel permeation chromatography (GPC), differential scanning calorimetry (DSC), polarised optical microscopy (POM), X-ray diffraction (XRD) and shows an expected I-SmA*-Glass phase sequence, but the electroclinic angle is relatively small.
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