Impact of Tunable Oligophosphonates on Barium Sulfate Crystallization

Abstract

Calixarenes can be used as well-defined scaffolds for investigating structure-activity relationships of additives and their impact on crystallization. In this work we present the crystal growth modification of barium sulfate by p-phosphonic acid calix[n]arene, which vary in size, n = 4, 5, 6 and 8, and thus vary in the size of the internal cavity for the same functionality in the upper rim. The tetrameric, hexameric and octameric macrocycles induce nanoparticle formation with clear superstructure. In the case of the hexameric calix[6]arene, the initial mesocrystalline superstructure fuses over time forming almost hollow spheres, while the mesocrystals formed in the presence of the tetramer and octamer are stable over an extended period. The pentameric calix[5]arene forms more disordered aggregates of single crystals. Thermogravimetric data show that a significant proportion of the weight of the barium sulfate containing solid is the macrocycle, regardless of the choice of macrocycle.

Overview of the Synthesis of Salts of Organophosphonic Acids and Their Application to the Management of Oilfield Scale

“…Calixarenes bearing phosphonic acid groups have been shown to induce the mesocrystal formation of barium sulfate, despite being relatively low-molecular-weight additives. These calixarenes are a synthesis in three steps from the parent calixarene by bromination of the aromatic rings, substitution with a phosphonodiester, and reaction of this with bromotrimethylsilane to give the calixarene tetraphosphonic acid, as shown in Figure . − …”

An azobenzene-based photoswitchable crystal growth modifier

“…7 To improve understanding of additive-crystal interactions, we, and others, have studied the impact of sequences of additives with systematically changed structures. 4,[8][9][10][11][12] Given that subtle changes in additive structure can have a large impact on crystal growth, we became interested in the idea of using a "switchable" additive, inspired by the remarkable range of stimuli-responsive materials that have been developed. 13 These materials have applications in light powered engines, 14 photo-responsive liquid crystals, 15 polymers, 16 molecular electronics, 17 holographic optical data storage, 18 and so on.…”

The many roles of mellitic acid during barium sulfate crystallization

“…6,7 There has been much work conducted in the area of mesocrystals and their formation in the presence of polymeric species. [8][9][10][11] We have, in the past, shown that small molecules can stabilise barium sulfate and that this is most likely due to self-assembly of the organic molecule [12][13][14] resulting in the steric stabilisation required. Formation of meso-crystals is also possible by charge stabilisation of nanoparticles 15,16 rather than steric stabilisation since the general mechanism relies on any form of stabilization of the initial nanoparticle before formation of the mesocrystal and/or fusion to an iso-oriented crystal.…”