Yu.Ya. Nel'kenbaum

On the nature of the activity of the systems C2H5AlCl2-alcohol in the cationic polymerization of olefins☆

A study has been made of some physico-chemical properties and of the activity of the systems C2H5AlCl2-alcohol in isobutylene polymerization (transformation of isobutylene models). A quantum chemical calculation has been carried out for some models of active centres in these systems. The calculated data agree with the experimental results, which points to the carbocationic activity of alcohol.

Compatibility of isobutylene polymers with polysiloxanes

The compatibility of isobutylene polymers and copolymers with various polyorganosiloxanes has been investigated. Over the wide range of temperature investigated and the entire range of ratios of components thermodynamic compatibility was observed solely for polydiethylsiloxanes with Mn = 550–725. The compatibility was verified by means of a combination of physical and physico-chemical methods, including inter alia electron microscopy, ESR, and rheological analysis. It was found that an increase in MW for polydiethylsiloxanes leads to diminished compatibility with polyisobutylene. In particular, the polymer with Mn = 1500 proved to be only partially compatible.

Interrelationship of the acid and catalytic properties of complexes of aluminum chloride with proton donors

Conclusions1.According to the data of quantum chemical calculations, complexes of HCl with RnAl· Cl3−n possess high acid strength, which depends little on the ligand surroundings of aluminum. The experimental behavior of the complexes as catalysts of cationic processes agrees with the calculated data.2.For complexes of weak proton donors H2O and ROH with RnAlCl3−n, calculation predicts a low acid strength, depending on the nature of the Lewis acid. The acid-catalytic properties of the complexes and the selectivity of the action are associated with the cooperative interaction with the substrate, an important role in which is played by the counterion of the complex.

Influence of aromatic hydrocarbons on the ultrasonic degradation of polyisobutylene

Abstract When ultrasonic degradation of polyisobutylene is conducted in aromatic hydrocarbons, the process is accompanied by polymerization of the latter by a complex mechanism. Transformations of arenes do not affect the kinetics of degradation, but alter properties of the degradation product.

Cationic copolymerization of isobutylene with chloronorbornene

Abstract Polymers are formed during copolymerization of isobutylene with chloronorbornene in the presence of Lewis acids. Polyisobutylene blocks in these polymers are separated by individual molecules of chloronorbornene. Polymers containing OH groups that can interact with di-isocyanates were obtained by hydrolysis of homo- and copolymers of chloronorbornene. Copolymers have a heat stability and adhesive strength which is higher compared with homopolymers.

The type of reactive centres present in the alkylaluminium aquo-complex used in the electrophilic polymerization of olefins☆

Calculation and experimental results (the physical and chemical properties, and the activity in the isobutylene polymerization) concerning the nature of the reactive centres of aquo-complexes C2H5AlCl2·H2O are described. These compounds are shown to digress from the analogous complexes with HCl and not to be an H acid, but are characterized by a low Lewis acidity. An initiation of the isobutylene polymerization over C2H5AlCl2·H2O presumes a prior C2H5AlCl2 reaction with H2O in the presence of the monomer and the formation of an alumoxane aquo-complex as the actual initiator. The transformation of the alkylaluminium dichloride aquo-complex to that of alumoxane has been proved by direct methods (IR spectroscopy, the use of isobutylene models, C2H5AlCl2·D2O), as well as by analyses of the dependences of the isobutylene (IB) polymerization (the polymer yield and the initial process rates as a function of the H2O content of the aquo-complex); an initiation scheme of the IB polymerization by the alumoxane aquo-complex which is characterized by a sufficiently large strength of the acid centres (H0 ⩽ − 8) is suggested. In contrast with the AlCl3 complexes, C2H5AlCl2·H2O is highly selective in the IB polymerization when the latter is present in a mixture with other olefines; the selectivity drops rapidly on changing from an inert solvent (hexane) to a polar (CH2Cl2). It is concluded that the C2H5AlCl·H2O complexes forming in the absence of IB differ in type of reactive centres from those forming in situ and those based on AlCl3.