Novel Amphiphilic Styrene-Based Block Copolymers for Induced Surface Reconstruction

This paper describes the synthesis of amphiphilic block copolymers by living radical polymerization (NMP) of new styrene-like monomers. The polar monomers (ethylene oxide side chains and free hydroxyl- or amino-groups after deprotection) were polymerized in a “protected form” to adjust the solubility of the monomers. In this way high molar mass polymers with a narrow polydispersity (around or below 1.2) were accessible. In the bulk state hydrophobic and hydrophilic domains demix. By exposing thin films of these polymers to vacuum (air) or alternatively to water or a hydrophilic surface it becomes possible to switch the surface polarity reversibly between contact angles of about 105° and 83°…

Functional Liquid Crystalline Polymers: Ferroelectric Polymers and Liquid Crystalline Elastomers and Ionomers

Abstract The incorporation of different functional groups in liquid crystalline polymers opens the way to a variety of interesting new materials, which may be used for non-linear optics, as piezo-elements or as two-phasic composite materials.

Micro- and nanostructuring of oligo- and polythiophenes in two and three dimensions

Abstract Oligothiophenes bearing methacrylic functionalities were two-dimensional-structured by stamping techniques. The localised monomer was hardened by radical polymerisation in UV light. The structures in micrometre- and nanometre-scale were characterised electrochemically by SECM. An inverse polymer opal with extremely high inner surface and periodicity was obtained by localising the photosensitive oligothiophene within an opal template of SiO 2 beads. Cyclic voltammetry of the oligothiophenes in aprotic solvents was carried out to examine possible electrochemical conversions. A self-assembling technique for lateral and vertical structuring of polythiophenes with pendant sulfonate and …

Physicochemical characterization of octakis(alkyloxy)-substituted Zn(ii)-phthalocyanines non-covalently incorporated into an organogel and their remarkable morphological effect on the nanoscale-fibers

A series of octakis(alkyloxy)-substituted Zn(II)-phthalocyanines were efficiently incorporated into an organogel made of (1R,2R)-trans-1,2-bis(dodecanoylamino)cyclohexane by means of multiple cooperative non-covalent interactions, and SEM revealed the formation of unique brush-like nanostructures.

Liquid Crystalline Elastomers—Characterization as Networks

Abstract This paper summarises the properties of archiral and chiral liquid crystalline (LC) elastomers, the latter of which have found interest due to their piezoelectric properties. In addition the formation of new LC elastomers by a radical polymerization of acrylate groups covalently linked to LC polymers was investigated. This was done concerning the progress of the crosslinking reaction, concerning the influence of the crosslinking on the LC phases and concerning the network properties (swelling ratio and elastic modulus) of the resulting elastomers. It turns out that the networks prepared in this way are very soft and their crosslinking density is low. This can be explained assuming …

Ferroelectric LC-elastomers

Ferroelectric liquid crystalline elastomers combine the rubber elasticity of polymer networks with liquid crystalline phases and ferroelectric ordering. Ferroelectric switching leads therefore to a deformation of the polymer network and an elastic stress. The coupling between both effccts can be varied by changing the topology of the netpoints.

Gelling and the collective dynamics in ferroelectric liquid crystals

Dielectric spectroscopy has been applied to investigate the dynamic behaviour of a ferroelectric liquid crystal in the smectic C* and smectic A phases confined in gel matrices of a fibre like (1D) or platelet like (2D) structure. These gel matrices were obtained from semicarbazide or bis-acylurea derivatives, which self assemble because of their H-bonding motif. The confinement strongly influences the magnitude of the spontaneous polarization and the collective fluctuations of the director detected as the Goldstone-mode. It is thus possible to detect gelation by dielectric spectroscopy. By this method it was possible to follow the destruction and restoration of the gel structure induced by …

Applications of Liquid Crystalline Elastomers

This chapter focuses on recent developments in the field of liquid crystalline elastomers (LCEs) that bring these materials closer to the world of real applications, concentrating on their actuation properties. First, we briefly introduce different LCE materials that show actuation behavior and explain how they can be synthesized. In the second part, we focus on materials in which a shape change is triggered by a phase transition. In particular, we discuss how the chemistry of the polymeric material influences the strength and direction of the shape change. We review the efforts made to trigger the actuation event by stimuli other than temperature variation. Subsequently, we summarize prepa…

Combined LC-polymers possess the structural properties of both LC main chain and LC side chain polymers. Beneath this structural speciality, their broad LC-phases and their polymorphism (different smectic phases and one nematic phase as a function of temperature) make them interesting. Crucial to an understanding of them is the fact that main chain and side chain mesogens orient parallel to each other and interact cooperatively to form the LC-phase. Due to this synergism the temperature range of the LC-phase is much broader than that of the corresponding LC main chain and LC side chain polymers. This interplay of main chain and side chain mesogens allows structures to be designed with prefe…

Ferroelectric liquid-crystalline elastomers

Photo-crosslinking in freely-suspended films of ferroelectric lc-polymers

Ferroelectric block copolymers

A block copolymer consisting of polystyrene and a side chain ferroelectric liquid crystalline polymer was synthesized using polymer analogous chemistry on a monodisperse poly(styrene-b-isoprene). Composition was adjusted to give lamellar microstructure after addition of the mesogenic side groups. If placed in an LC cell without orientation of domains, no ferroelectric response was observed. After shearing the thin film, presumably due to alignment of lamellae, a bistable ferroelectric switching could be detected.

Ferroelectric liquid-crystalline elastomers

Oriented liquid-crystalline (LC) elastomers (polar monodomains, concerning the direction of polarisation) have been prepared from polar monodomains of ferroelectric LC-polysiloxanes by a radical photocrosslinking process. Attempts to perform ferroelectric switching lead in these soft elastomers to an elastic stress which prohibits—for low voltages—a complete reorientation of the polar axis (ferroelectric switching). A ferroelectric switching can, however, be observed for high voltages. The loop of hysteresis of this switching is asymmetric concerning the zero point of the driving voltage. Piezoelectric measurements show that these elastomers combine an elastic memory for one polar state wit…

New Developments in Soft Lithography

Abstract The burgeoning area of soft lithography is reviewed with special emphasis on developments within the past three years. Applications in electronics have driven such developments, but more recently, other kinds of device structures and 3D prototyping have also found application, in part, through soft lithography. Microcontact printing (μCP), “lift off” μCP nano transfer printing (nTP), micromolding in capillaries (MIMIC), solvent assisted micromolding (SAMIM), replica molding (REM), and microtransfer molding are the main soft lithography schemes discussed.

Polyelectrolytes on block copolymer surfaces

Soft lithography and properties of amphiphilic block copolymers are combined in a new technique for the generation of patterned substrates, which can be used in different ways as templates for further processing. In these processing steps the deposition of polyelectrolytes, metals and grafting from polymerizations are used for the construction of different structures.

Simple chiral urea gelators, (R)- and (S)-2-heptylurea: their gelling ability enhanced by chirality.

Abstract We present the first report on the synthesis of chiral ureas, ( R )- and ( S )-2-heptylurea, and their gelling behaviors. The ureas were prepared by the reactions of chiral amines and phenyl carbamate in the presence of triethylamine. On cooling from homogeneous solutions, the chiral ureas form gels in water and various nonpolar organic solvents, such as cyclohexane, toluene, and tetrachloromethane, while the racemate gelatinize only toluene and tetrachloromethane among the solvents we examined. The gelling ability of the enantiomeric urea is higher than the racemate, as the critical gelling concentrations in toluene, for example, were 0.2% and 0.7% (wt/wt), respectively. The enhan…

Tailored Semiconducting Polymers: Living Radical Polymerization and NLO-Functionalization of Triphenylamines

This paper describes the preparation of various polymers with triarylamine side groups. High molecular weight materials were obtained by free radical polymerization utilizing the gel effect. Polymers with a marrow polydispersity and a predetermined molecular weight could be prepared by living radical polymerization. The T g could, thereby, be controlled between 50 and 140°C either by using different monomers or by varying the molecular weight. Living radical polymerization allowed in addition the preparation of block copolymers. The triarylamine side groups could be transformed into NLO-chromophores by reaction with tetracyanoethylene. This leads to the incorporation of tricyanoethylene. Th…

Temperature dependence of surface reorganization characteristics of amphiphilic block copolymer in air and in water studied by scanning force microscopy

We have investigated the surface reorganization characteristics of a novel amphiphilic diblock copolymer, poly(acetic acid-2-(2-(4-vinyl-phenoxy)-ethoxy)-ethylester)-block-polystyrene (PAEES-b-PS), in response to varying interfaces from air to water and vice-versa at various temperatures. The surface reorganization characteristics of the block copolymer films was monitored by scanning force microscopy, in order to delineate the kinetically controlled morphological process of surface reorganization of a diblock copolymer, with a particular emphasis on the phase contrast signal which allowed the determination of local composition patterns of PAEES-b-PS at the surface. Upon heating a water-an…

Dielectric and electro-optical studies of a ferroelectric copolysiloxane.

This paper reports an extensive study of the static (spontaneous polarization, ${\mathit{P}}_{\mathit{s}}$, tilt angle \ensuremath{\theta}, and pitch) and dynamic properties of a ferroelectric liquid-crystalline polymer. It is shown that a ferroelectric liquid-crystalline polymer (diluted polysiloxane) exhibits physical behavior similar to that of a low-molar-mass liquid crystal in terms of contrast ratio, pitch of the helix, and relationship between ${\mathit{P}}_{\mathit{s}}$ and \ensuremath{\theta}. The degenerated collective modes for the director rotation are shown to split into two modes at the Sm-A--Sm-${\mathit{C}}^{\mathrm{*}}$ phase transition temperature using dielectric spectros…

Oligothiophenes for Pattern Formation by Stamping

Oligothiophene monomers with a fixed length varying from 3 to 5 thiophene rings were prepared by Stille coupling. They were functionalised with one or two methacrylate groups to allow polymerization and cross-linking. These monomers can be patterned with the help of soft silicon stamps (e.g., with the micro-injection moulding in capillaries process) on substrates like glass or flexible polymer foils. If a photoinitiator has been added, they can then be hardened by exposure to UV-light through the transparent stamp. Afterwards the stamp can be removed. This allows the preparation of several centimeters long oligothiophene lines of a width varying between 50 and 0.5 μm. These lines of semicon…