Rudolf Lukáš

A new family of telechelic copolymers

SummaryA new initiation system is described, allowing bulk polymerizations of isobutylene to be carried out at about-78°C, in the absence of a polar chlorinated solvent. The initiation system consists of two components, the first of which is boron trichloride (BCl3) used as co-initiator, and the other component is a polymer insoluble in the monomer and containing chloroallyl structures or structures with a chlorine atom bound at the tertiary carbon atom in their chains. Bulk polymerizations of isobutylene proceed at the boundary between the solid and the liquid phase for many hours, and the polymeric initiator used is grafted by isobutylene. Dichloromethane raises reactivity of the initiation system.

Thermal Degradation of Vinylchloride/α-Olefin Copolymers

Abstract The preliminary results obtained for the thermal degradation of vinylchloride/α-olefin copolymers are, in part, unexpected. Decrease of the initial polyene length with the increase of comonomer content is a reasonable consequence of the shorter viny chloride sequence lengths, but the constancy of these lower values in the course of further degradation indicates, that some secondary reactions of the polyenes (e.g. cyclization) must be absent here. The decrease of the HCl elimination rate in case of copolymers differs from the dependence given by the weak sites model. Formally, the rate is proportional to a netative power of conversion, the value of the exponent depending on the composition. These results indicate the necessity of further research for clearing up the unknown details of PVC degradation mechanism.

Isobutylene polymerization in the presence of t-BuCl/SnCl4

SummaryThe effect of tert-butyl chloride in the polymerizations of isobutylene carried out in the presence of SnCl4 in dichloromethane at temperatures-20°C and-78°C was investigated. Synthesized polyisobutylene samples showed a bimodal molecular weight distribution (MWD) and it was found that the weight content of the lowermolecular weight (LMW) fraction increased with increasing t-BuCl concentration in the polymerization mixture. The effect of ageing of the initiation mixture t-BuCl/SnCl4 in CH2Cl2 prepared in advance on MWD of the PIB samples was also studied. Ageing of the initiation system supports the formation of the LMW fraction and this oily PIB is the only product of the polymerization at-20°C,

Polymerization of isobutylene initiated with the system 2,5-dichloro-2,5-dimethylhexane/SnCl4

\bar M_n \sim 500,\bar M_w /\bar M_n \leqslant 1.4

The structure and stability of poly(vinyl chloride)

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Structure of chlorinated poly(vinyl chloride). X. Conclusions on the chlorination mechanism

SummaryIt has been surprisingly discovered that an initiator system based on PVC/SUCl4 produces bulk polymerization of isobutylene even under conditions, when a mixture of isobutylene and SnCl4, in the absence of a polar medium, does not polymerize. The PVC polymers used were the powders of the commercial suspension PVC Neralit S-652, lower-molecular-weight PVC prepared by extraction of Neralit S-652 with acetone (PVC-AE) and the copolymer of vinyl chloride with 2-chloropropene (VC/2CP). The kinetics of polymerizations were studied dilatometrically at −78°C. It was found that the bulk polymerization of isobutylene proceeds at the boundary between the solid (PVC) and liquid (isobutylene) phase over an unusually long period of time which, depending on the type of PVC used, can last more than 7 days. It followed from the determination of the initial polymerization rate that the activity of the studied types of PVC decreases in the order PVC-AE > VC/2CP ≫ PVC.

Structure and stability of poly(vinyl chloride), 2 Initiation of hydrogen chloride chain elimination†

SummaryThe polymerizations of isobutylene in dichloromethane at-20°C initiated with the system 2,5-dichloro-2,5-dimethylhexane (DDH)/SnCl4 were investigated. The polyisobutylene (PIB) samples obtained were examined by GPC and their molecular weight distribution curves were determined. It was found that PIB products obtained by the conventional procedure have a bimodal MWD and the weight content of the lower-molecular weight fraction increases with increasing concentration of DDH in the polymerization feed. The effect of ageing of DDH/SnCl4 mixtures prepared in advance on MWD of the PIB samples was also proved. The results achieved lead to a conclusion that the ageing of the initiation system consists probably in the formation of the complex DDH-SnCl4-H2O, which protogenically again initiates the oligomerization of isobutylene, giving rise to oils with a narrow MWD, the polydispersity index