Zwitterionic chain polymerizations of cyanoacrylates

The lecture reviews recent studies on vinyl and vinylidene compounds, chiefly alkyl cyanoacrylates. It emphasizes the kinetics, especially the distinctive SINT (slow-initiation-no-termination) pattern, and the composite mechanism of initiation by tertiary amines. The need for corroboration of interpretations, clarification of ambiguities and extensions is emphasized.     

The polymerization of styrene by perchloric acid at 0°

Polymerization of styrene by HClO₄ in CH₂Cl₂ at 0° at various [M]₀/[HClO₄]₀ ratios has been studied. At low values of this ratio, the reaction is second order in HClO₄ whereas it is first order at the values commonly used in kinetic studies. The rates are strongly increased by the addition of the salt benzyl trimethyl ammonium hexafluoroantimoniate, the effect being greater the lower the monomer concentration. Molecular weight distributions in the polymers formed under various conditions support the conclusion that at very low [M]₀/[HClO₄]₀ ratios the polymerization is predominantly ionic in character, and the higher order in [HClO₄]₀ is anomalous.     

An Exceptional Set in the Ergodic Theory of Markov Maps of the Interval

It is known that a Markov map T of the unit interval preservesa measure µ, say, equivalent to Lebesgue measure, andthat almost every point of the interval has a forward orbitunder T that is uniformly distributed with respect to µ.In the opposite direction the main result of this paper statesthat there is a set of points having Hausdorff dimension 1 whoseforward orbits are in a certain sense very far from being sodistributed. 1991 Mathematics Subject Classification: 58F08,28A80.     

Novel affinity chromatographic system for the single-step purification of glycosaminoglycans from complex systems using volatile buffers

A new system for the isolation and purification of glycosaminoglycans (GAGs) and related molecules from complex systems such as plasma is described. Affinity chromatography which exploits the very high affinity between the polymeric base Polybrene and sulphated polysaccharides was used. A novel volatile buffer system composed of ammonium formate and formic acid, which allows the complete recovery of samples, was developed, and elution conditions were optimised for the separation and purification of GAGs of different charge densities. Using this system the losses associated with dialysis and desalting, frequently necessary preliminaries to further analysis, are avoided.