Mass liquid-crystalline mixture

For polymer concentrations < 3 % the mixtures remain isotropic during polymerisation and become a rubbery mass that is too viscous to stir in the later stages of heating. In contrast polymer concentrations of 5-10% form yellow green stir-opalescent solutions within 30 minutes of the dissolution of the terephthalic acid. Such solutions remain stirrable throughout the polymerisation despite the higher concentrations — an indication of the liquid-crystalline nature of the medium. 

Pure j3-methylglutaric anhydride melts at 46°.6 The jS-methylglutaric anhydride obtained in this preparation varies in its appearance at 25° from an almost completely crystalline mass to a mixture of about one-third solid and two-thirds liquid. However, the submitter has found that product of either appearance can be converted to methyl hydrogen /3-methylglutarate in 80-85% yield. Further purification is troublesome, and the product of the present procedure is pure enough for most purposes. 

Jakob, E-, Wolarz, E., Bialecka-Florjanczyk, E., Bauman, D., and Haase, W. Dielectric relaxation in a mixture of a side-chain liquid crystalline polymer and a low molecular mass a/o dye. Mol. Cryst. Liq. Cryst. 258, 253 (1995). 

If liquid sulfur, after the chemical equilibrium has been established (12 h at 120 C or 1 h at 250 °C), is rapidly quenched to low temperatures and inune-diately extracted with carbon disulfide the polymeric will remain undissolved while Ss and S fWill dissolve. After filtration, most of the Ss will crystallize out on cooling of the solution to -78 C while S together with some Ss remains in solution. It is not possible to isolate S i completely free of Ss-Therefore, in the literature the mixture Ss+S t has often been simply termed S f but in this chapter we will differentiate between S f on the one hand and mixtures of S f with Ss on the other hand ( Ss-I-S r ). If a solution of Ss+S s is evaporated in a vacuum a yellow resin-like mass is obtained which solidifies at low temperatures as a glass but decomposes at room temperature within a few days to a crystalline mixture of Ss and S [19]. 

According to the elastic continuum theory of liquid crystals which was introduced in Chapter 1, the three kinds of deformations can be described by three elastic constants, An(splay), / (twist) and / (bend). In the case of small molecular mass liquid crystals, the three constants are mainly determined by the chemical composition of the liquid crystalline molecules. Among them, K22 is the smallest while the other two are approximately close. All three elastic constants are of the order of 10 12 N. The elastic constants of some important liquid crystals are listed in Table 6.1. Each kind of liquid crystals is a mixture of R5-pentyl and R6-hexyl homologues in the ratio of 40 60. The data are obtained at the temperature of T = Tc — 10 °C where Tc is the clear temperature. 

In principle, liquid crystalline polymers can be applied in displays. Unfortunately, the response of them to the external fields isn t satisfactory because their viscosity is greater than the small molecular mass liquid crystals by a few orders of magnitude. In fact, only when the temperature is near the glass transition temperature, can the response be measured in seconds. Apparently, this is far from the real requirement. One may mix the liquid crystalline polymer with small molecular mass liquid crystal for such a purpose, but the mixture doesn t show an advantage over the small molecular mass liquid crystal displays. The ferroelectric liquid crystalline polymer is an exception. It works with a very fast effect and can achieve a display with a response time of a few milliseconds or a fewr tens of milliseconds. 

De Souza and Nes (1968) have isolated a crystalline mixture of unsaturated 24-ethylcholesterols from the blue-green alga Phormidium luridum. Various techniques were used for identification of the compounds—column and gas-liquid chromatography, as well as UV, mass, NMR, and infrared spectrometry. The positions of unsaturation were corroborated with an infrared band at 1033 cmfor A unsaturation and a shoulder near 1050 cm for a A unsaturated component. A weak band at 968 cm corresponded to a trans-A component. 

Liquid crystals are intermediate states of matter or mesophases, halfway between an isotropic liquid and a solid crystal. In nature, some substances, or even mixtures of substances, present these mesomorphic states. These liquid crystalline phases exhibit a local disorder ( liquid-like behavior) and are dynamic at a molecular level, but a long-range order exists, which endows it with unique rheological, mass transport, and optical properties. Liquid crystals offer a number of useful properties for the drug delivery. Solubilization of drug in the liquid crystalline is similar to the solubilization of drug in micelles. Simultaneously, increase in viscosity of the system helps to provide more... 

Definition of terms related to polymer blends, composites, and multiphase polymeric materials This recommendation defines the most commonly used terms encountered when dealing with polymer blends and composites and is limited to mixtures in which the components differ in chemical composition or molar mass or both and in which the polymer forms the continuous phase. Many of the multiphase systems are in fact biphasic systems with a multitude of finely dispersed phase domains. Crystalline and liquid crystalline multiphase systems are the subject of other documents. 

Conoscopy is known to be prone to artifacts because of its sensitivity to the symmetry of the refractive index, which might be tampered due to surface effects and flow phenomena. By using deuterium NMR spectroscopy. Severing et al. [11] confirmed phase biaxiality in a polymeric liquid crystal similar to that studied earlier by Leube. To evaluate different parameters that bias the formation of a biaxial nematic phase and gain a more general picture of the phase biaxiality in nematic liquid crystalline polymers, the investigations were expanded to side-chain polymers of different chemical constitutions as well as to mixtures of polymers and low molar mass liquid crystals [12],... 

Tetrahydrofurfuryl chloride. Place 204 g. (194 ml.) of freshly distilled tetrahydrofurfuryl alcohol (b.p. 177°) and 174 g. (178 ml.) of dry pyridine in a 1-litre three-necked flask, fitted with a dropping funnel, mechanical stirrer and thermometer. Cool in an ice bath, stir vigorously and add 250 g. (153 ml.) of freshly distilled thionyl chloride at the rate of 3-5 drops per second. A pasty crystalline mass begins to separate and the temperar ture commences to rise rapidly when one-third to one-half of the thionyl chloride has been added subsequently the mass largely redissolves and a dark brown liquid forms. Remove the ice bath when the addition is complete and stir the mixture for 3-4 hours. Pour the reaction product into a large separatory funnel and extract with seven 250 ml. portions of ether break up any lumps that may form with a glass rod. Remove the ether from the combined extracts by distillation, wash the residue with three 50 ml. portions of water, dry with anhydrous magnesium sulphate and distil under reduced pressure. The yield of tetrahydrofurfuryl chloride, b.p. 47-48°/15 mm., is 180 g. 

Since the acetaldehyde cannot be separated by fractional distillation from the ether in which it has been collected, it is converted into the crystalline aldehyde-ammonia. The contents of the two receivers are transferred to a small filter jar which is cooled in a freezing mixture, and ammonia gas is led in from a cylinder. The delivery tube for the current of ammonia is a straight calcium chloride tube with its wide end deeply submerged in the liquid. To break up the crystalline mass which is formed, this tube is frequently moved to and fro. The jar is kept covered with a clock-glass (bored), piece of cardboard, or copper gauze. On account of the ether which evaporates, all flames in the vicinity must be extinguished. 

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