Spacers polymers

As sparse as the dataset describing mainchain nematic LCP blends with conventional polymers is, it is rich compared to the almost non-existent data on the blending of other types of LCPs-side chain polymers, flexible spacer polymers, smectics, etc. 

Investigations in the past years have proved that applying the concept of flexible spacer, polymers can be synthesized systematically, which exhibit the l.c. state. Owing to the flexible linkage of the mesogenic molecules to the polymer main chain, very similar relations can be expected with respect to 1-l.c., like chemical constitution and phase behavior, or dielectric properties and field effects for the l.c. side chain polymers. This will be in contrast to main chain polymers, where the entire macromolecule, or in case of semiflexible polymers parts of the macromolecules, form the l.c. structure. The introduction of a flexible spacer between backbone and mesogenic group can be performed in a broad variety of chemical reactions. Some arbitrarily... 

Ceramic materials, including sapphire, have been used extensively in HPLC pumps for more than 20 years as pistons and check valve components. These materials have also been used to construct heads because of their good chemical stability. The use of ceramics is limited, however, because of high cost and brittleness. Although many systems have one material as the primary construction material, the wetted surfaces of a pumping system can contain several other materials. Therefore, for material-sensitive applications, all the materials in the HPLC eluent flow path should be considered. Materials that may be encountered are polymeric materials for pump seals such as fluoropolymers, polypropylene, and Teflon sapphire pump pistons and check valve seats ruby check valve balls Kalrez, KelF, or ceramic washers and spacers polymer-based transducer components and in older systems connections and joints made with silver solder. 

The shorter biphenyl group has been used with alkyl spacers, Polymers 15 and 16 of Table 1, to give both smectic and nematic polymers depending on the direction of the linking ester group 20,22,26) found that if the mesogen is... 

The effect of reversing ester groups, which has already been briefly discussed, should be mentioned again here. In the case of the azo and azoxy polymers made from carboxy-terminated flexible spacers, polymers with stable mesophases were formed. In contrast, polymers made from oxy terminated spacers had no mesophase. While this behavior is an extreme case, when comparisons are possible it seems that polymers made with the carboxy-terminated spacers almost always have wider ranges... 

Van Dijk-Wolthuis WNE, Tsang SKY, Kettenes-van den Bosch JJ, Hennink WE. A new class of polymerizable dextrans with hydrolyzable groups hydroxyethyl methacrylated dextran with and without oligolactate spacer. Polymer 1997 38 6235-6242. 

Furuya, H., Asahi, K., and Abe, A., An odd-even effect in the mesophasic behavior of dimer liquid crystals due to the bond orientation of a phenylene unit incorporated in the flexible spacer, Polym. 7,18, 779-782 (1986). 

Giomez, M. A., Roman, R, Marco, C., Del Pino, J., Fatou, J. G. (1997). Relaxations in Poly(tetramethylene terephtaloy l-bis-4-oxybenzoate) Effect of Substitution in the Mesogenic Unit and in the Flexible Spacer. Polymer, 38(21), 5307-5311. 

In the case of gen 9, the values o for spacers contain and from O.33-0.43 cussion of odd-even paper of this serie although the degree order parameter is spacer polymers as cer lengths do inde degree of orderly,2 ASxN/AStotal observ just reflects the p polymers. 

Komuro K, Kawakami Y (1999) Synthesis and characterization of side-chain liquid crystalline polycarbosilanes with siloxane spacer. Polym Bull 42 669-674... 

Jeon In-Yup, Tan Loon-Seng, Baek Jong-Beom. (2007). Synthesis of Linear and Hy-perbranched Poly(esterketone)s Containing Flexible Oxyethylene Spacers. Polym. Sci. A, 45(22), 5112-5122. 

Because such polyether spacer polymers are also of interest in other fields of polymer-supported immobilization, the first reports published on the synthesis of polystyrene graft copolymers date back to almost one decade agp [111,112]. In fact, these graft supports have been applied successfidly in f ds where insoluble polymers with homogeneous phase reacticais are advantageous, e.g., for phase-transfer reactions [113-116]. 

A common feature of different types of liquid crystal polymers (LCPs), e.g., thermotropic side-chain or main-chain (either stiff or with flexible spacers) polymers, is their slowed-down dynamics compared to low molecular weight liquid crystals (LCs). Often polymers can be quenched to a glassy state in which the liquid-crystalline order is preserved but motions are completely frozen out. Such liquid-crystalline glasses provide a unique opportunity to determine, in principle, the full orientational distribution function, whereas only its second moment is available from motionally averaged NMR spectra. Thus LCP studies have made fundamental contributions to LC science. 

The effect of the flexibility of the spacer on the glass transition temperature and formation of the mesophase is illustrated in Table 6.3 on the example of a comparison of aliphatic and oxyethylene groups with the same length and identical mesogenic groups. For close values of the glass transition temperatures of polymers 1,2, and 3 and 4, the LC phase is not realized for the polymers with the more flexible spacers (polymers 1 and 3). In this case, the hypothetical Tol is apparently below the experimentally found 7g (cf. Fig. 6.4). However, if Tg is decreased even more (polymer 5) so that Tg is below 7 cl. then formation of the mesophase is possible. 

Huang W, Han CD (2006b) Dispersion characteristics and rheology of organoclay nanocomposites based on a segmented main-chain liquid-crystalline polymer having side-chain azopyiidine with flexible spacer. Polymer 47(12) 4400 410... 

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