ABSTRACT
Highly functional macromolecules with a well-defined architecture are the key to designing efficient and smart materials, and these polymeric systems can be tailored for specific applications in a diverse range of fields. Herein, the formation of a new liquid crystalline polymeric network based on the crosslinking of dendrimeric entities by the CuI-catalyzed variant of the Huisgen 1,3-dipolar cycloaddition of azides and alkynes to afford 1,2,3-triazoles is reported. The polymeric material obtained in this way is easy to process and exhibits a variety of properties, which include mesomorphism, viscoelastic behavior, and thermal contraction. The porous microstructure of the polymer network determines its capability to absorb solvent molecules and to encapsulate small molecules, like organic dyes, which can be released easily afterwards. Moreover, all these properties may be easily tuned by modifying the chemical structure of the constituent dendrimers, which makes this system a very interesting one for a number of applications.
Subject(s)
Dendrimers/chemistry , Liquid Crystals/chemistry , Polymers/chemistry , Algorithms , Chemical Phenomena , Chemistry Techniques, Synthetic , Liquid Crystals/ultrastructure , Mechanical Phenomena , Models, Theoretical , Molecular Structure , X-Ray DiffractionABSTRACT
The synthesis and characterisation of a family of block codendrimers consisting of highly versatile mesogenic and carbazole-containing 2,2-bis(hydroxymethyl)propionic acid (bis-MPA) dendrons are reported. The liquid-crystal behaviour was investigated by means of differential scanning calorimetry, polarised-light optical microscopy and X-ray diffraction. Depending on the chemical structure of the constituent dendrons, the codendrimers show lamellar or columnar mesophases. On the basis of the experimental results, models both at the molecular level and in the mesophase are proposed. The physical properties of the block codendrimers derived from the presence of the carbazole moiety in their structure were investigated: photoluminescence in solution and in the mesophase, electrochemical behaviour and hole transport. Electrodeposition of carbazole dendrons afforded a globular supramolecular conformation in which the mesogenic molecular side plays a key role.
ABSTRACT
A polymer network is prepared by the thiol-yne photopolymerization of multifunctional dendrimer with a tetrathiol crosslinker. The network obtained shows a liquid crystalline phase at room temperature, which has been characterized by optical microscopy, differential scanning calorimetry, and X-ray diffraction. Photoinduced deformation of uniaxially aligned free-standing films of the photocrosslinked material has been demonstrated.
Subject(s)
Dendrimers/chemical synthesis , Liquid Crystals/chemistry , Sulfhydryl Compounds/chemistry , Calorimetry, Differential Scanning , Dendrimers/analysis , Light , Photochemical Processes , Polymerization , Temperature , X-Ray DiffractionABSTRACT
A set of chiral discotic phenylacetylenes have been synthesized by 3-fold Sonogashira coupling between different ethynylbenzenes and triiodobenzenes. The resultant bulk materials are fully characterized by polarized optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffraction. The octopolar nature of the target compounds is studied by UV-vis absorption spectroscopy and hyper-Raleigh scattering in solution. Optimization of the donor-acceptor substitution yields both high hyperpolarizability values and appreciable mesomorphic properties. A simple thin film device for second harmonic generation has been prepared from the nitro-substituted liquid crystalline derivative.
ABSTRACT
In this tutorial review we describe some studies concerning liquid crystal dendritic polymers. We have chosen to present several representative examples that illustrate the diverse kinds of LC dendritic structures, namely: dendrimers, dendrons, dendronized polymers and hyperbranched polymers. We review their synthesis, mesogenic properties and the way that they are arranged to form supramolecular liquid crystal assemblies.
Subject(s)
Dendrimers/chemistry , Liquid Crystals/chemistry , Polymers/chemistry , Dendrimers/chemical synthesis , Models, Molecular , Molecular Structure , Polymers/chemical synthesisABSTRACT
Discotic liquid crystals based on triindole, a novel redox active central core, have been synthesized and their mesomorphic behaviour investigated.
ABSTRACT
The synthesis and characterization of two families of ionic liquid crystal dendrimers consisting of the ammonium salts of the commercially available poly(amidoamine) (G = 0-5) and poly(propylene imine) (G = 1-5) dendrimers and three long-chain carboxylic acids are reported. The liquid crystalline behavior was investigated by means of differential scanning calorimetry, polarizing light optical microscopy, and X-ray diffractometry. The thermal stability of the ionic materials was further studied by NMR. Most of the dendrimers show lamellar mesomorphism, and two of them exhibit columnar mesomorphism. On the basis of the experimental results, we propose models both at the molecular level and in the mesophase for all the materials.
