Poly mesomorphic state

Studied in ref. [26] is the effect of HFC reaction conditions on the configuration sequences in POCS-4. Since the mesomorphous state in PMCS-4 is formed in stereoregular trans-tactic polymers only [27, 32] and spatial configuration of initial monomers is not always fully preserved in poly-mers, the effect of HFC conditions on transformation of =Si-CI and =Si-OH centers in initial corn-pounds has been studied. The detected fact of cyclosiloxanes partial inversion at Cl atoms substitution at silicon was expected, as reported before [33, 34], More detailed description of reflex correlation was carried out in ref. [35], Symbols and mark projections of units and bonds to the pla-ne perpendicular to the cycle plane. 

Unlike poly-decaorgano-cyclohcxasiloxanes which form the mesomorphic state independent of the chain tactidty, pofy-octaorgano-tetrasiloxaiKs can exist in the mesomorphic state only in tra ns lactic configuration. 

Aharoni et al have combined the above technique with X-ray diffraction to elucidate the conformational nature of the x- and y-alkylene segments in the crystalline and mesomorphic states of poly(ester-amides) ... 

The second way of forming nanoparticles of PE-surfs is to use water-soluble block-copolymers with one complexable (ionic) block and one non-com-plexable (nonionic) block. For example, the mesomorphous complexes (solid state) between poly(ethylene oxide)—b-poly(ethylene imine)s and dodecanoic acid can easily by dispersed in water to form nanoparticles [117]. The nanoparticles are of core-shell type and have sizes around 200 nm. Their cores are formed by poly( ethylene imine) dodecanoate while their shells consist of poly(ethylene oxide). It was found that the shapes of the nanoparticles depend on the PEI block. They are, for example, prolate if the PEI is linear and spherical if the PEI is branched. 

The work presented in the next section concerns the immobilization of retinoic acid by three polyamino acids poly(-L-lysine), poly(-L-arginine) and poly(-L-histidine). The mesomorphous structure of these complexes, which are prepared as nano-particles, has been examined. Then we will report on the physicochemical characteristics of water-soluble complexes formed between PEO-PLL block copolymers and retinoic acid. The structure in the solid-state and solution are discussed. Further the dissociation of the complex when changing the pH is reported. Finally, the immobilization of retinoic acid by PEI with different molecular weights is presented. 

The mesogenic structure of a benzoic acid dimer has been introduced as a noncovalent cross-linker for polysiloxanes [79]. Polymer 57 exhibits a smectic C phase due to the dynamics of H-bonding. In contrast, mesomorphic order is locked in the solid state of poly[(4-acryloyl)benzoic acid] by polymerization in its mesophase [128]. No liquid-crystalline state is observed for this material because of the lack of flexibility of the structures. Main-chain-type polymeric liquid-crystal associates are formed from carboxyl-bifunctionalized aromatic compounds [129]. 

Summary Symmetrically substituted poly(di- -alkylsilane)s with side chains of from 4 to 6 methylene units and poly(di-n-butylsilylenemethylene) were investigated using solid-state NMR to obtain information on the molecular mobility of main and side chains in the different crystalline and mesomorphic phases. In addition, pressure-volume-temperature (pVT) measurements were carried out to investigate the dependence of the phase behavior on both temperature and pressure. 

Fig, 23. Plot of the isotropization temperature T, as a function of the degree of polymerization of atactic poly[oxy(decamethylcyclohexasiloxane-2,8-diyl)] and X-ray spectra in mesomorphic and isotropic states... 

Completely rigid rod-like molecules such as poly(4-oxybenzoyl) or poly( p-phenylene terephthalate) tend to be highly crystalline and intractable, with melting points above the decomposition temperature of the polymers (>450°C). The problem of thermotropic MCLCP design is to disrupt the regularity of the intractable para-linked aromatic polymers to the point at which mesomorphic behaviour is manifested below the decomposition temperature and the materials can be processed in fluid yet ordered states. The disruption must not, however, be taken to the stage where conventional isotropic fluid behaviour is preferred. These requirements that the polymer must retain some rod-like nature but at the same time be melt-processable below 400-450°C have limited thermotropic MCLCPs mainly to polymers based on the linear ester or ester/amide bonds. With polyester/ polyesteramides, disruption is normally achieved by the th ee copolymerization techniques outlined in Fig. 8.1, i.e. frustrated chain packing, flexible spacers and non-linear links. 

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