Studies of the Aggregation of Dyes. A Spectrophotometric Method of Determining the Aggregation Numbers of Dyes

Abstract

The aggregation of dyes in an aqueous or alcoholic solution has been studied spectroscopically by a method named the "maximum slope method."The method can ascertain the molar absorptivity and formation constant of dye aggregate when a simple equilibrium model between a monomer and an n-mer is assumed to be operative, and when the absorptivity of monomer is given.Further, the molar absorptivities of the monomer and the polymers and the formation constants of the polymers are adjusted, in order to minimize the mean deviation, by an other method, named the "minimum deviation method." Using the latter method, the parameters of an equilibrium system including a monomer and several polymers can also be calculated.Aggregations of Benzopurprine 4B and Sky Blue FF in aqueous salt solutions were studied by the above two methods.Aggregations of these dyes in aqueous alcoholic solutions were also discussed.

Micellar Effects on Dediazoniation and on Azo Coupling Reactions

“…Although there exists a wealth on information concerning the effects of micelles on the properties of azo dyes in the micellar (16)(17)(18)(19)(20)(21)(22)(23) and in the submicellar concentration ranges (24,25), very few studies have been devoted to explore the effects of micelles on the rates of azo coupling reactions (1)(2)(3)(4). The main results of these studies are, in most instances, limited to the statement that they are strongly affected by the formal charge of reactants, i.e., the arendiazonium ion and the coupling partner, in keeping with Hartley's sign rule (26,27).…”

pH-dependent complexation of hydroxypropyl-beta-cyclodextrin with chlorin e6: effect on solubility and aggregation in relation to photodynamic efficacy

“…Loftsson et al . demonstrated that the permeability of a drug–CD complex could be decreased by an increase in viscosity of the adjacent liquid layer at the permeable surface . The formulations with inclusion complex are expected to produce higher viscosity of the microenvironment due to the presence of significant amount of HP‐β‐CD.…”

The role of inorganic electrolyte (salt) in cellulosic fibre dyeing: Part 2 theories of how inorganic electrolyte promotes dye uptake

“…From the perspective of the five dye classes used for cellulosic fibre dyeing, studies of electrolyte-induced aggregation have focussed predominantly on direct dyes 158,[188][189][190][191][192][193][194][195][196][197] and reactive dyes [198][199][200][201][202][203][204] ]. For example, the extent of aggregation of direct dyes increases with increasing amount of inorganic electrolyte, as illustrated by the data presented in Figure 18.…”

“…), which, by extension, F I G U R E 1 8 Effect of inorganic electrolyte concentration on equilibrium constant of aggregation, K n , of C.I. Direct Red 2; drawn using data from 188 BURKINSHAW can be considered to reflect the relative solubility of each type of dye anion under the particular dyebath conditions employed. Thus, as discussed below, the fact that different amounts of added inorganic electrolyte are typically used to apply vat dye, sulphur dye, azoic coupling component, direct dye and direct dye anions to cotton (Figure 11) and other types of cellulosic fibre stems from the fact that the anionic dye/dye precursors display different levels of solubility within the particular dyebaths that are utilised for their exhaust application.…”