| Περίληψη: | Dendrimers are a class of monodisperse polymeric macromolecules with a well
defined and highly branched three-dimensional architecture. Their
well-defined structure and structural precision makes them outstanding
candidates for the development of new types of multifunctional super-molecules and materials with applications in medicine and pharmacy, catalysis, electronics, optoelectronics, etc. Liquid Crystalline Dendrimers (LCDrs) are a relatively new class of super-molecules which are based on the functionalization of common dendrimers with mesogenic (liquid crystalline) units. The combination of the fascinating molecular properties of the common dendrimers with the directionality of the mesogenic units have
produced a novel class of liquid crystal forming super-mesogens (LCDRs) with
unique molecular properties that allow novel ways of supramolecular self-assembly and self-organisation.
This work is mainly concerned with the computational modelling of LCRs. A
coarse grain strategy is adopted for the development of computational
tractable models which take explicitly into account the specific architecture, the extended flexibility and the shape anisotropy of the mesogenic units of LCDRs. The developed force field applies easily to a
variety of dendritic architectures. Utilizing Monte Carlo computer
simulations we study the structural and conformational behavior of single LCDrs and of systems of LCDrs either in confined geometries or in the bulk. Special emphasis is given on the modeling of the response of LCDRS on externally applied alignment fields. External fields might be fictitious aligning potentials which mimic electric
or magnetic fields or fields induced by the confining substrates.
The surface alignment of liquid crystalline dendrimers (LCDrs) is a key factor for many of their potential applications. We present results from Monte Carlo simulations of LCDrs adsorbed on flat, impenetrable aligning
substrates. A tractable coarse-grained force field for the inter-dendritic and the dendrimer-substrate interactions is introduced. The developed force field is based on modifications of well-known interaction potentials that can be used either with MC or with molecular dynamics simulations. We investigate the conformational and ordering properties of single, end-functionalized LCDrs under homeotropic, random (or degenerate) planar and nidirectional planar aligning substrates. Depending on the anchoring constrains to the mesogenic units of the LCDr and on temperature, a variety of stable ordered LCDr states, differing in their topology, are observed and analyzed. The influence of the dendritic generation and core functionality on the surface-induced ordering of the LCDrs are examined.
The study has been extended to system of LCDrs confined in nano-pores of different shapes and sizes under several anchoring conditions. Two basic confining geometries (pores) considered in this work: slit and cylindrical pores. In each confining geometry, different anchoring conditions are
imposed. The Isobaric-Isothermal (NPT) Monte Carlo Simulation is used to investigate the thermodynamic and structural properties of these nano-confined systems. The ransmission of orientational and positional ordering from the surface to the middle region of the pore depends on the size of the pore as well as on temperature and on anchoring strength. In the case of cylindrical pore, alignment propagation is short ranged compared to
that of slit-pore.
As a benchmark of our coarse-grained modelling strategy, we have extended
and tested our coarse grained Force Field for the study of Janus-like dendrimers confined on planar substrates. The obtained results indicate the capability of our model to capture successfully the highly amphipilic nature of these class dendrimers and their self-organisation properties.
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