Aggregative tendency

A wide variety of stmetures exist in the cyanine, merocyanine, and oxonol classes of dyes. Properties that may affect toxicity vary widely also. These include solubihty, propensity to be oxidized or reduced, aggregation tendency, and diffusion through membranes. Specific acute toxicity data are Hsted in Table 2, and the LD q data vary widely with the test used. 

There are numerous examples of tin(II)-oxygen compounds which demonstrate the high aggregation tendency of this type of compounds119,120. A typical... 

Dendrimers have also been found useful in the construction of thin films containing isolated fullerenes [85, 86]. Such materials could eventually find practical application in sensors and/or optoelectronic devices [87]. Generally, monolayers prepared from C60 are ill-defined due to the aggregation tendency of fullerenes. The covalent attachement of C60 to bulky dendritic frameworks... 

Pukdnszky B, Fekete E (1997) Aggregation tendency of particulate fillers determination and consequences, paper presented at Eurofillers 1997, September 7-11, Manchester... 

Some investigations on the solvent effect concerning the aggregation tendency of surfactant in nonpolar media have been made in mixed solvent systems. These yield information on the relative stability of a particular miceliar structure in one of the solvent components with respect to the other. Also inversion of the micellar structure has been observed in such cases where nonpolar, aprotic solvents were mixed with those giving rise to hydrophilic interactions, i.e., which are in general structure forming. 

The monophthalocyanines 106 and 107 show a weak aggregation tendency in chloroform. The latter has a self-dimerization constant of 1,175 M-1. By contrast, the donor-acceptor bis(phthalocyanine) 99 exhibits a much stronger aggregation tendency with a dimerization constant of 1.1 x 106 M-1 in chloroform. It is believed that in addition to the hydrophobic effect, the two phthalocyanine halves of compound 99 may be considered as donor and acceptor subunits that interact with each other. As revealed by electron microscopy, 99 forms one-dimensional nanoaggregates through intermolecular interactions between its complementary donor and acceptor phthalocyanine units as shown in Fig. 8. The dimerization constant of 99 is about one order of magnitude lower than that observed for the hetero-dimerization of 106 and 107, which may be due to the cyclophane step that hinders the formation of columnar aggregates of double phthalocyanine dimer. 

The cac values were estimated as the first inflexion point from the curves and they are equal to 2xlO g/L for sample 9 and lO g/L for sample 10, respectively. These relatively low values can be explained by the presence on the polysiloxane side-chain of the azobenzenic hydrophobic groups with a high aggregation tendency (H-type or J-type - Fig. 18) [33, 34]. 

Marinsky J. A. and Reddy M. M. (1990) Vapor-pressure osmometric smdy of the molecular weight and aggregation tendency of a reference-soil fulvic acid. Anal. Chim. Acta 232, 123-130. 

One can see from Fig. 6 that 1-propanol is in excess around a central 1-propanol molecule whereas water is in excess around a central water molecule. Hence both components of this mixture have self-aggregation tendencies and two types of clusters are present in this mixture one of them is enriched in alcohol and the other one in water. All An j have extremes... 

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