Crystalline dispersions

The investigation of semi-solid objects such as lipid membranes [34], liquid crystalline dispersions [35, 36], drug delivery systems [37], food [38] and also... 

The concept of interfacial mesophases promoting spontaneous emulsification (21.22) can be applied to the Tagat TO - Miglyol 812 system, where stable liquid crystalline dispersion phases are adequate to promote the process of self-emulsification. The stability of the resulting emulsion systems can also be accounted for by liquid crystalline interface stabilisation (23.24). Phase separation of material as observed above 55f surfactant, in conjuction with the increased viscosities of such systems, will inhibit the dynamics of the self-emulsification process and hence the quality of self-emulsified systems declines when the surfactant concentration is increased above 55. ... 

It is considered that penetration of water into this liquid crystalline dispersion In association with gentle agitation results In the observed self-emulslflcatlon. 

With the aid of X-ray diffraction, it was observed that the formation of amorphous dispersion, instead of crystalline dispersion of drug, in the drug-excipient solid solution contributed to quicker dissolution and a higher amount of total drug release in the dissolution test. Furosemide (Fig. 2) was shown to form amorphous dispersions in the solid solution with either polyvinylpyrrolidone (PVP) or crospovidone, as evidenced by X-ray diffraction (26,27). The extent of amorphous dispersions... 

Studies with adatoms and microcrystals have clearly shown that the electronic structure of these systems are profoundly different from those of the corresponding bulk material. Electrocatalytic activation can be expected only as the structure of the material is substantially changed (cf. Raney metals). The case of DSA has shown how widely the properties of a material can be varied as it is obtained in a poorly crystalline, dispersed, non-stochiometric form. 

Functionalized LCP may be used as comonomers in thermoset formulations. Upon cure, liquid-crystalline thermosets (LCT) are obtained, with a morphology characterized by the presence of liquid-crystalline dispersed domains. 

Depending on conditions during processing and storage, a crystalline microstructure develops in many foods that can significantly impact food propaties. Some important characteristics of the crystalline dispersion include the crystalline phase volume, mean size and size distribution of crystals, shape and surface characteristics of the particles, polymorphic characteristics, and any network structure that forms between... 

It should be chemically, physically, and thermally stable, with a low melting point. On solidification, it should crystallize rapidly and maintain the drug as a fine crystalline dispersion. The carrier and drug should be miscible in the liquid to avoid irregular crystallization and subsequent variability in dissolution rate. 

Crystalline dispersions of several niobate crystals or barium titanate (up to 70 vol %) in a silicate glass phase form transparent ferroelectric glass ceramics. The small size of the crystals ( 500 A) accounts for transparency. 

CDC are defined only by their size (most scientists agree on sizes below 1 pm others set 0.5 pm as the upper limit). CDC are very heterogeneous in all other aspects (e.g., thermodynamic stability, chemical composition, and the physical state, including solid, liquid, or liquid-crystalline dispersions) [ 1 ]. The most prominent examples are nanoparticles, nanoemulsions, nanocapsules, liposomes, nanosuspensions, (mixed) micelles, microemulsions, and cubosomes. Some CDC have reached the commercial market. Probably the best known example is the microemulsion preconcentrate of cyclosporine (Sandimmun-Neoral), which minimized the high variability of pharmacokinetics of the Sandimmun formulation. In addition, intravenous injectable CDC have been on the commercial market for many years. Examples include nanoemulsions of etomidate (Etomidat-Lipuro) and diazepam (Diazepam-Lipuro) [2-4], mixed micelles (Valium-MM, Konakion), and liposomes (AmBisome) [5]. 

In other cases where crystalline interactions are favorable for dissolution, crystalline dispersions can be manufactured to provide enhanced wetting. This section describes examples of both types of dispersions, with a focus on the influence of formulation to achieve the desired attributes. 

B. Senyuk, N. Behabtu, B.G. Pacheco, T. Lee, G. Ceriotti, J.M. Tour, M. Pasquali, LI. Smalyukh, Nonlinear photoluminescence imaging of isotropic and liquid crystalline dispersions of graphene oxide. ACS Nano 6, 8060- 066 (2012)... 

R. Jalili, S.H. Aboutalebi, D. Esrafilzadeh, R.L. Shepherd, J. Chen, S. Aminorroaya-Yamini, K. Konstantinov, A.I. Minett, J.M. Razal, G.G. Wallace, Scalable one-step wet-spinning of graphene fibers and yams from liquid crystalline dispersions of graphene oxide towards multifunctional textiles. Adv. Funct. Mater. 23, 5345-5354 (2013)... 

Spicer, P. T. (2005). Progress in liquid crystalline dispersions Cubosomes. Current Opinion in Colloid Interface Science, 10(5-6), 274-9. 

Ce ions in the surface defects of DDalumina or non-crystalline dispersed phase. 

Quantification of the degree of crystallinity present initially, induced during storage or processing in amorphous pharmaceuticals by pXRD is well established. The powder pattern of a partially crystalline dispersion includes Bragg peaks associated with the prominent crystal faces superimposed to the amorphous halo. The intensity... 

Richer information from variable temperature and hetero-nuclear re-laxometry (e.g., F Ti/rinearest neighbor distance) Molecular mechanism of miscibihty from 2D-correlation contours (strength, i.e., distance of drug-polymer H-bonding) Convoluted spectral profile of partially crystalline dispersions due to overlapping sharp signals of crystalline fraction and the broad peaks of the amorphous fraction Expensive, time and resource intensive technique... 

In this chapter we concentrate on applications of thermal analysis in basic and applied research, leading to better understanding of the processes involved in the formation and transformation of crystalline dispersions both from electrolyte solutions and in confined spaces such as emulsions and microemulsions. 

Crystalline dispersions are formed by a succession of precipitation processes, nucleation, crystal growth, flocculation, and various aging processes (Fig. 1). In this section we present a short review of the thermodynamic principles that define these processes. For a comprehensive treatise on the subject the reader is directed to Ref. 10. 

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