Thermodynamic and lamella models relationship for the eutectic system benzoic acid – cinnamic acid

Abstract

The present investigation reveals the relationship between excess thermodynamic functions and the growth habits of the eutectic phases from the melt by continuous melt-growth technique. Excess thermodynamic functions computed for different compositions of the benzoic acid -cinnamic acid eutectic system have been found consistent with the criteria of spontaneity and Planck formulation, and their reliability has been ascertained by the application of Guggenheim lattice theory. The results on the kinetics of anisotropic growth of the eutectic phases from the melt, evidentially evince the dislocation mechanism. Evidences have been obtained for a parabolic variation of mechanical strength with growth velocity of the eutectic material grown anisotropically from the melt at different intervals, which offer supporting complement to the dislocation mechanism governing the dependence of growth velocity on supercooling ∆T in the solidus -liquidus interface in a form : V = k(∆T ) 2 . A moderate anisotropic growth region has been explored by unique results of strength properties and microscopic results as well, to growing a layer of lamellae in a unidirectional lamina. An anisotropic eutectic composite lamellae lamina developed by moderate growth velocity (7.3 x 10 -8 m 3 s -1 ), is of greater interest offering optimum hardness, approximately varying between three-and eight fold average increase in different modes of the mechanical strength in comparison to its isotropic growth carried out in an ice-bath (~273K), and manifold superior to its constituent phases irrespective of the growth mode. The directional lamina of uniform microstructural parameter lamellae, indicates that there is a perfect lamella-matrix equilibrium for which excess thermodynamic functions do vanish.

Distinguishing Cocrystals from Simple Eutectic Mixtures: Phenolic Acids as Potential Pharmaceutical Coformers

“…According to our literature survey, among all mixtures, 58 systems are immiscible in the solid state. This subclass comprises simple eutectics of all considered types of phenolic acids including their precursors, namely, benzoic acid 26,55−67 and cinnamic acid 57,68,69 and their hydroxylated analogues. 26,62−66,70−77 Although in simple eutectics the nonsubstituted benzoic acids are dominant, there are, however, some interesting exclusions.…”

“…According to our literature survey, among all mixtures, 58 systems are immiscible in the solid state. This subclass comprises simple eutectics of all considered types of phenolic acids including their precursors, namely, benzoic acid ,− and cinnamic acid ,, and their hydroxylated analogues. ,− ,− Although in simple eutectics the nonsubstituted benzoic acids are dominant, there are, however, some interesting exclusions. Indeed, examples of solid state associates formed by these coformers include many pharmaceutically relevant complexes, such as a carbamazepine-cinnamic acid molecular complex and benzoic acid cocrystals with many various APIs and drug-like compounds such as aromatic amides (isonicotinamide, 4-(1 H -pyrazol-1-ylmethyl)­benzamide), amines (1,2-diaminobenzene, 1,2-diaminobenzene), diazepams (nevirapine), methylxanthines (caffeine, etofylline), and other heterocycles (trimethroprim, flucytosine).…”

Characteristics of the binary faceted eutectic: benzoic acid – salicylic acid system

“…Viscosity measurements Viscosities of various compositional melts representing the entire system were measured relative to the reference liquid p-xylene [6] in a liquid paraffin bath with an accuracy of ±0.05 K in the temperature range 391-408 K. The viscometer employed for the experimental purpose was reported earlier [16].…”

“…Implicit in this approach is the concept that an acceptable composite material may consist of two or more materials combined to give a performance in service which is superior, and possibly unique in some specific respects, to the properties of the homogenous materials [6][7][8][9]. An acceptable composite material can be obtained by adopting the anisotropic moderate melt growth route.…”

Growth Reinforcing Composite Materials from Liquid Phase: Mechanical and Microstructural Parameters Relationship Essentially Evincing the Predominance of an Akin Mass Composition over the Domain of Compositions

“…Nucleation studies of binary organic systems being transparent in nature were performed following the procedure referred earlier (Sharma et al, 2004a). A nearly constant amount (4.0 g) of each composition of the systems was carefully taken into different pyrex tubes of uniform internal diameters.…”