Crystal Growth in Gels from the Mechanisms of Crystal Growth to Control of Polymorphism: New Trends on Theoretical and Experimental Aspects

Abstract

A gel can be considered to be a two-phase (liquid and solid) system, which lacks flow once it reaches a stationary state. The solid phase is usually a tridimensional polymeric mesh, while the liquid phase is usually found in three forms: contained in great cavities, retained in the capillary pores between micelles, or adsorbed on the surface of a micelle. The influence of the use of gels in crystal growth is diverse and depends on the type of gel being used. A decrease in solubility of any solute in the liquid may occur if the solvent interacts extensively with the polymeric section, hence, the nucleation in gels in these cases apparently occurs at relatively low supersaturations. However, if the pore size is small enough, there is a possibility that a higher supersaturation is needed, due to the compartmentalization of solvents. Finally, this may also represent an effect in the diffusion of substances. This review is divided into three main parts; the first evaluates the theory and practice used for the obtainment of polymorphs. The second part describes the use of gels into crystallogenesis of different substances. The last part is related to the particularities of protein crystal polymorphism, as well as modern trends in gel growth for high-resolution X-ray crystallography.

Exploiting and controlling gel-to-crystal transitions in multicomponent supramolecular gels

“…Conceptually, it might be possible to induce different polymorph formation depending on the conditions used. [29][30][31][32] Additionally, in multicomponent systems, this method can be used to change the properties of the gel phase and access materials with improved, unusual and interesting properties. 19,28 Growing crystals in a dipeptide-based gel phase has been shown to protect the crystals against degradation.…”

Application of Polymers as a Tool in Crystallization—A Review

“…They found that the dense hydroxyapatite layer and hydroxyapatite/dicalcium phosphate dehydrate layer prevented the diffusion of calcium ions from the calcium nitrate solution, thus inhibiting the formation of Ca 3 (PO 4 ) 2 in the gel phase. Velásquez-González et al discussed the theory and practice used for the preparation of polymorphs, use of gels into crystallogenesis of different substances, particularities of protein crystal polymorphism and also modern trends in gel growth for high-resolution X-ray crystallography [ 17 ]. In turn, Choi et al provided evidence for synthetic biomimicry similar to bio-polymerization mechanisms to steer disorder-to-order transitions via solvent plasticization-like behavior [ 18 ].…”

Counter-Diffusion System as an in Vitro Model in the Investigation of Proteins Involved in the Formation of Calcium Carbonate Biominerals

“…This is achieved when the radius of the crystal nucleus grow to the critical size. Nucleation here is stochastic and occurs when the required energy of the system is reached between the increasing free energy of nucleus formation and decreasing energy of solidification . As the nanochemistry progressed over the years, the CNT was reviewed and reconsidered .…”

“…Biomineralization in the CDS mostly depends on the diffusion of solutes through the gel matrix, which regulates the supersaturation at the crystallization site allowing for delayed precipitation and growth of calcium carbonate. The mineralization site at CDS is convection-free . The system is adjustable for manipulations for many cases, allowing the introduction of additives, as counterions or low-molecular weight molecules.…”