Liquid crystal polymer, functional polymers

A multifunctional cholesteric liquid crystal polymer functionalized with amine has been synthesized and tested for biomedical applications [104]. 

Optically active polymers are important functional materials for several industrial and bio-m ical applications and are extensively used as chiral catalysts for asymmetric synthesis, packing materials of chromatographic columns and chiral materials for the preparation of liquid crystal polymers (7). Polymers such as poly hydroxy alkanoates (PHAs), naturally occurring microbial optically active polyesters, are important materials in biomedical applications owing to their biodegradability (2). In synthetic polymer chemistry, synthesis of optically active polymers has been one of the most challenging tasks. Most synthetic chiral polymers are prepared from optically pure starting materials which are, except when isolated from nature, in limited supply and difficult to prepare (7, 3). 

The term photochromism can be defined as a light-driven reversible transformation between two isomers possessing different absorption spectra.111,21 The two isomers differ from one another not only in their absorption spectra, but also in their geometrical structures, oxidation/reduction potentials, refractive indices, and dielectric constants. When such photochromic chromophores are incorporated into functional molecules, such as polymers, host molecules, conductive molecular wires, or liquid crystals, the functions can be switched by photoirradiation.[3 61 Photostimulated reversible changes in refractive index can also be applied to optical waveguide switching.171 This chapter reviews applications of photochromic chromophores, especially diar-ylethene derivatives, in various photo switching molecular systems. 

All Liquid Crystal Polymers are characterised by the fact that they contain stiff meso-genic groups, often inserted in flexible chain systems (so called "spacers") and connected to them by linking functional groups the mesogenic unit is inserted either in the main chain or in the side chains or (in exceptional cases) in both. We shall discuss MCLCPs and SCLCPs. A schematic representation of common structures of LCPs is displayed in Fig. 6.14 (Jansen, 1996). An example of a SCLCP with disc-like mesogens is displayed in Fig. 6.15 (Franse et al., 2002, 2004). 

Functionally Terminated Liquid Crystal and Photoresist Polymers... 

The living ROMP reactions of norbornene and norbornene derivatives have been used to make a variety of polymers possessing unusual properties. Copolymerization of selected functionalized norbornenes with norbornene has been used to synthesize star polymers and side-chain liquid crystal polymers. " This chemistry has also resulted in the preparation of phase separated block copolymers that contain uniform sized metal or semiconductor nanoparticles. The... 

Hybrid composite materials (HCM) represent the newest group of various composites where more than one type of fibre is used to increase cost-performance effectiveness, i.e., in a composite system reinforced with carbon fibres the cost can be minimised by reducing its content while maximising the performance by optimal partial replacement with an another fibre or by changing the orientations. HCM include nanocomposites [31], functionally gradient materials [32], Hymats (hybrid materials) [33], interpenetrating polymer networks (IPN) [34], and liquid crystal polymers [35]. 

The nature of liquid crystal polymers means that there ate two aspects to the synthesis. Firstly, conventional synthesis to provide the monomeric unit(s) and secondly, the polymerisation reaction that yields the desired liquid crystal polymer. The syntheses of the monomer units are, in general, analogous to those discussed above with the additional requirement of introducing a polymerisable functional unit at some point in the monomer material. 

The characteristic functionalities of naturally occurring polymers are, in most cases, related to their specific chiral structure. In nature, proteins, nucleic acids, and polysaccharides are constructed of readily available chiral monomers such as sugars and amino acids. Both natural and synthetic chiral polymers are finding application as chromatographic supports, polymeric reagents and catalysts, chiral membranes, and materials for preparation of cholesteric liquid crystal polymers (471,472). 

Miller, M. M. Cowie, J. M. G Tail, J. G Brydon, D. L. Mather, R. R. Fibres from polypropylene and liquid-crystal polymer blends using compatibUizing agents. 1. Assesment of functional and nonfunctional polypropylene-acrylic acid compatibihzers. Polymer 1995, 36, 3107-3112. 

The molybdenum neopentyUdene complex Mo(CHBu )(NR)(OBu )2 is the active catalyst used in a fascinating development for the synthesis of 11-Vt semiconductor clusters (ZnS, CdS, PbS) and silver and gold nanoclusters of predictable size within microdomains in films of block copolymers prepared by ROMP. Block copolymers of norbomene and a functionalized norbomene that wiU complex with a metal-containing compound were prepared and characterized as monodisperse materials. The functionalized component (amine, alkoxide, or thiolate) then sequestered the metal and the metallated block copolymer was cast into a film which was subsequently treated with H2S to convert the metal into the sulfide. The molybdenum complexes have also featured in the development of the synthesis of side-chain liquid crystal polymers by living ROMP.98 99... 

Just as for biological beings, the liquid crystalline phase structure and simultaneously the functionality of liquid crystalline elastomers are strictly limited to a defined temperature regime. Similar to low molar mass liquid crystals and LC polymers this temperature regime is determined by the chemical constitution of the polymer networks. For the synthesis and investigation of liquid crystalline elastomers the basic concepts of liquid crystals, LC polymers, and polymer networks have to be brought together. 

The concept for the design of supramolecular liquid crystals and supramolecular polymers has opened new fields in materials and polymer science, which are ever expanding. New stable and dynamic structures are generated by self-organization of these materials. Related functional polymeric materials such as dendrimers [140-143], block copolymers [144], polymer blends [145,146], rotaxanes [147-149], anisotropic gels [150-152], metallo-supramolecular polymers [153,154], nanoobjects [155,156] as well as supramolecular polymers are also obtained by self-assembly of multicomponents through noncovalent interactions. 

As consumer products become smaller and offer more services to the user, one frequent consequence is that they contain increasing numbers of physically smaller components. A typical example of this trend is the hearing aid where the emphasis is on providing a more powerful and efficient device which will improve the wearer s quality of life. The Acuris P hearing aid from Siemens incorporates a moulded interconnect device (MID) made from Ticona s Vectra E820i LDS liquid crystal polymer (TCP). This novel plastic permits complex, fine-line circuit patterns to be laser-etched and then plated. The MID itself, whose function is to connect the microphone module to other electronic components in the unit, is approximately 3 mm wide and 25 mm long. 

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