The adsorption of polymer dispersants of the polyisobutenylsuccinimide series has been studied at the solid/xylene interface. Carbon black was studied as a model solid. Adsorption isotherms were determined, the enthalpy of adsorption was measured by calorimetry, and the thickness of the adsorbed layer was obtained from small-angle neutron scattering. The paper emphasizes the structure−properties relationships with the help of a series of polyisobutenylsuccinimides having different polyamine groups and different polymer architectures, simple diblock (PIBSI) and comblike structure (polyPIBSI). The polyamine part ensured a strong adsorption on the solid surface, which increased in strength with the number of amine groups. In the same way, changing the diblock structure for a comblike one led to an enhanced affinity of the polymer for the solid surface. The adsorption was enthalpic but the Gibbs free energy of adsorption remained moderate because of a large entropy loss during adsorption. There was an enthalpy−entropy compensation phenomenon. Below a concentration of 70 mmol/m3, the polymers adsorbed as a 30 Å thick monolayer and the adsorption phenomenon was irreversible, due to the polymeric nature of the polar part. A drastic increase of adsorbed amount took place for higher concentrations. The formation of reverse hemimicelles was assumed as the origin of this phenomenon. The supplementary adsorption was reversible, showing that the polymer−polymer interactions were weaker than the polymer−surface interactions.

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Hexaazaisowurtzitane or cage molecules have attracted attention concerning their synthesis because hexanitrohexaazaisowurtzitane (HNIW or CL20) is presently the most powerful energetic compound. The synthesis of hexaazaisowurtzitanes was considered to be limited solely to the condensation of certain benzylamines with glyoxal. Here, we present the synthesis and characterization of seven novel non-benzylic hexaazaisowurtzitanes, such as hexapropargylhexaazaisowurtzitane. The substituents on the six nitrogen atoms are different to those of the benzyl or substituted benzyl groups to which previous syntheses were limited. X-ray structures are given for the hexapropargyl and hexa-2-thienylmethylene derivatives. Steric strains limit the synthesis with alpha-substituted benzyl and allyl derivatives. The reaction mechanism and the role of the intermediate diimines are discussed. Some of the novel hexaazaisowurtzitanes are potential precursors of hexanitrohexaazaisowurtzitane.

The kinetics of quaternisation by methyl iodide of 33 substituted pyridines was measured in acetonitrile at 30 'C; the reactions were followed by n.m.r. with a competitive technique. The relative rate constants were similar to those observed i n other polar aprotic solvents. Steric effects exist for all the ortho-substituents and can be estimated from the deviation from the B r ~n s t e d plot. A scale of ortho-steric parameters (SO) is proposed. There is no significant dependance of SO on the Dougard-Decroocq solvent parameters and a complete lack of correlation between So and the electronic effects of substituents. The relative So values agree with other experimental estimations of the steric size of substituents. The So parameters are discussed in terms of substituent structure in connection with the Taft-Kutter-Hansch €. and Charton u parameters. The general applicability of a unique scale of steric parameters is discussed.