Béla Iván

New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer agents (inifers) V. synthesis of α-tert-butyl-ω-isopropenylpolyisobutylene and α, ω-di(isopropenyl)polyisobutylene

SummaryPolyisobutylenes carrying one or two terminal isopropenyl unsaturations have been obtained by complete dehydrochlorination of α-tert. -butyl-ω-tert. chloropolyisobutylene and α, ω-di(tert.-chloro) polyisobutylene, respectively. By the use of t-BuOK in refluxing THF only 1-olefin formed leading to a new macromer and a symmetrical telechelic diolefin. According to H1 NMR spectroscopy the structure of this new telechelic polymer is:

New telechelic polymers and sequential copolymers by polyfunctional initiator‐transfer agents (inifers). VII. Synthesis and characterization of α,ω‐di(hydroxy)polyisobutylene

A new telechelic polyisobutylene diol, HOCH2PIBCH2OH, carrying two terminal primary hydroxyl end groups has been prepared from α,ω-di(isobutenyl)polyisobutylene, CH2C(CH3)- CH2PIBCH2C(CH3)CH2, by regioselective hydroboration followed by alkaline hydrogen peroxide oxidation. Infrared (IR) spectra, 1H-NMR analysis of the pure and silylated products, and ultraviolet (UV) spectra of phenylisocyanate-treated diols indicate quantitative yields and two CH2OH termini per polyisobutylene chain. The viscosity of HOCH2PIBCH2OH is higher than that of the starting α,ω-diolefin. The telechelic diol prepolymer opens new avenues to the synthesis of many new materials, e.g., polyurethanes.

New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer agents (inifers)

SummaryLinear and three-arm star tosyl-telechelic polyisobutylenes (i.e., PIBs carrying two and three p-toluene-sulfonic acid ester end groups, respectively) have been synthesized and characterized by a variety of techniques. Subsequently these prepolymers were used as macroinitiators for the ring opening polymerization of 2-methyl-2-oxazoline leading to linear poly(N-acetylethyleneimine-b-isobutylene-b-N-acetylethyleneimine) and three-arm star poly(N-acetylethyleneimine-b-isobutylene). High yields (78–98%) and blocking efficiencies (70–80%) have been obtained. The absence of free polyisobutylene in the product indicates highly efficient initiation of 2-methyl-2-oxazoline polymerization by the tosyl-telechelic polyisobutylene. The less than 100% blocking efficiencies are probably due to chain transfer to 2-methyl-2-oxazoline. Hydrolysis of these block copolymers yielded poly(ethyleneimine-b-isobutylenes).

Synthesis of isobutenyl-telechelic polyisobutylene by functionalization with isobutenyltrimethylsilane

Abstract Isobutenyl-telechelic polyisobutylenes (PIBs) were synthesized by reacting tert-chlorine-telechelic and living PIBs with isobutenyltrimethylsilane (IBTMS) in the presence of TiCl4 in CH2Cl2/hexane (40/60 v/v) solvent mixtures at −78°C. In order to obtain PIB oligomers, living polymerization of isobutylene was induced by the di-(2-hydroxy-2-propyl)-5-tert-butylbenzene (tBuDiCumOH)/BCl3 combination in CH2Cl2 followed by addition of required amounts of hexane and TiCl4 to avoid polymer precipitation and permanent termination. Although quantitative end-quenching of living PIB was achieved with IBTMS, chain coupling between the living PIB chains and isobutenyl-ended polymers also occurred. This side reaction was avoided by isobutenylation of tert-chlorine-telechelic PIB with IBTMS in the presence of TiCl4. The resulting isobutenyl-telechelic PIB contains exclusively exoCH2C(CH3)CH2 endgroups, and is free from CHC(CH3)2 endo olefins usually obtained in small quantities (∼3–8% of total double bonds) as a side product of other methods used in the past.

Reversible crosslinking during thermal degradation of PVC

SummaryPVC undergoes rapid crosslinking during thermal degradation. Diels-Alder addition of conjugated polyenes was proposed as a possible crosslinking mechanism by earlier authors. By the use of conditions favoring retro Diels-Alder reaction of crosslinks (treatment with maleic anhydride at elevated temperature) it was proved that crosslinks are largely reversible. Evidently Diels-Alder addition of the conjugated polyenes plays an important role in crosslinking during thermal degradation of PVC.

Online monitoring of Silicone Network Formation by Means of In-Situ Mid-Infrared Spectroscopy

The ReactIR™ reaction analysis system was used to monitor the crosslinking copolymerization of trimethylsilyl methacrylate with α,ω-methacryloyl-terminated oligo(dimethylsiloxane). Characteristic infrared bands proved useful to determine the total methacrylate concentration. After less than 12 h at 60 °C using 0.14% 2,2′-azoisobutyronitrile (AIBN), the methacrylate conversion during the crosslinking reaction exceeded 98%. The comparison of the crosslinking reaction with a methacrylate homopolymerization showed that significant autoacceleration occurred during network formation. Time-dependent monomer conversion [M]/[M]0 for TMSMA homopolymerization (run H in Table 1) and the corresponding crosslinking polymerization (run N) as revealed by the peak at 1 326 cm−1.

Crosslinking, scission and benzene formation during PVC degradation under various conditions

SummaryThe kinetics and mechanism of crosslinking and chain scission has been studied on several PVC samples during thermal thermooxidative, dynamic, and HCl catalyzed degradation. During pure thermal degradation crosslinking at a constant rate without scission occurs, while in the presence of oxygen and/or shear scission is not negligible. In the dynamic test, under shear both processes are fast, compared to static tests. The mechanism of benzene formation without main chain scission is discussed.

Structural defects in poly (vinyl chloride). IV: Thermal degradation of vinyl chloride/acetylene copolymers

Abstract Vinyl chloride/acetylene copolymers have been prepared under subsaturation conditions. Copolymerization rates and molecular weights of the copolymers decrease with increasing concentration of acetylene in the monomer feed, indicating that acetylene is a retarder in vinyl chloride polymerization. The concentration of internal double bonds in the copolymers determined by ozonolysis increases with increasing amount of acetylene in the feed. Thermal degradation has been performed at 110 with solid samples and at 170° in solution under inert atmosphere. The extent of HCl loss as a function of time shows a rapid initial phase followed by a slower steady rate The initial dehydrochlorination rates are higher for copolymer samples containing higher concentrations of internal double bonds. Quantitative analysis of the u.v. and visible spectra of degraded copolymers shows that the sum of the concentration of polyenes with 4–12 conjugated double bonds increases rapidly in the first phase of degradation, but then decreases slowly, due to secondary reactions of polyene sequences.

Living carbocationic polymerization. XXXVIII, On the nature of the active species in isobutylene and vinyl ether polymerization

Abstract The nature of the species that gives rise to living carbocationic polymerization (LP+Pzn) of isobutylene (IB) coinitiated by Friedel-Crafts acids (FCA) in the presence of electron pair donors (ED) has been investigated. It is proposed that the key species responsible for mediating LC+Pzn of IB are FCA·ED complexes, formed by Lewis acid-Lewis base interaction, where FCA = BCl3 TiCl4, and ED = ethyl acetate, tetrahydrofuran, etc. Free EDs are inhibitors of IB polymerization. These findings are in sharp contrast to those of LC+Pzn of vinyl ethers coinitiated by EtAlCl2 in which excess (i.e., free) EDs are required for the living polymerizations to occur. Comparison of IB polymerizations induced by the 2-chloro-2,4,4-trimethylpentane/BCl3 and 2-acetyl-2,4,4-trimethylpentane/BCl3 systems shows that these reactions do not proceed by the same intermediate (i.e., by tert-chlorides) and that the mechanisms of BC13- and TiC14-coinitiated living polymerizations are different. Experiments with the proton tra...

The effect of reaction conditions on the chain end structure and functionality during dehydrochlorination of tert‐chlorinetelechelic polyisobutylene by potassium tert‐butoxide

Dehydrochlorination of tert-chlorine-telechelic polyisobutylene with potassium tert-butoxide in refluxing tetrahydrofuran is quantitative after 22 h, but results in ca. 3% endo olefin chain ends which are not reactive in some subsequent functionalization reactions. The formation of these undesired structures is most likely due to simultaneous thermally induced HCl loss. Lower temperatures and longer reaction times led to exclusive formation of external double bonds in some cases but to incomplete dehydrochlorination.