Hydrogenation of low molar mass OH‐telechelic polybutadienes catalyzed by homogeneous Ziegler nickel catalysts

Abstract

Two types of low molar mass, medium vinylic polybutadienes containing 2-hydroxypropyl and 2-hydroxyethyl end groups were hydrogenated in the presence of several homogeneous Ziegler Ni catalysts prepared by using Ni(acac) 2 and Ni(2-ethylhexanoate) 2 as metal precursors and BuLi, Li adduct to a diene and Et 3 Al as activators. The catalytic efficiency of these systems determined by rate measurements showed that the best results can be achieved with the Ni(2-hexanoate) 2 ϩ Li-diene (Ni : Li mol ratio ϭ l : 8 -10) catalyst in the solvents commonly used in the synthesis of these polyalkadienes by anionic polymerization of 1,3-butadiene. As found by the kinetic study, the hydrogenation carried out under mild reaction conditions (temperatures of 10 -35°C, hydrogen pressure of 72-178 kPa, Ni concentration of 2.1-10.0 mmol/dm Ϫ3 ) was the first order in the OH-polybutadiene and hydrogen and, over narrow range of catalyst concentrations (4.3-10.0 mmol Ni/dm Ϫ3 ), also in the catalyst. The activation energy of the hydrogenation estimated from the Arrhenius plot was 42 kJ/mol. Changes in the relative proportion of 1,2-, cis-1,4-, and trans-1,4-CAC units of the polymer during hydrogenation indicate the selectivity of the catalyst to the 1,2-hydrogenation. The ease of the addition of hydrogen to the internal CAC unsaturation was found to be opposite to that usually observed (trans Ͼ cis). The present low-pressure hydrogenation of both types of telechelic OH-polybutadienes proceeds with full retention of the average OH functionality and affords the saturated polymers, the residual CAC unsaturation of which (Ͻ1%) has so far been usually achieved by high-pressure hydrogenations.

Homologous Poly(isobutylene)s: Poly(isobutylene)/High-Density Poly(ethylene) Hybrid Polymers

“…[1][2][3][4] Thus, poly(butadiene)s and poly(isoprene)s, easily accessible via radical or anionic polymerization, can serve as starting points for HDPE-and PE-alt-PP type polymers, respectively, after hydrogenation of the olefinic moieties within the chain. [5][6][7][8] With the advent of ring-opening metathesis polymerization (ROMP) [9][10][11] as a controlled polymerization process, the access to regular olefinic polymers has become broader. 12,13 Thus, various three-, 14 four-, 8,10,[15][16][17][18] five- 19,20 and higher membered cycles 19 can be ring-opened and polymerized, yielding the respective substituted unsaturated polymers with controllable chain length and unsaturation.…”

“…With some exceptions, syntheses and investigations of homologous polymers are rarely reported in literature since 1,3-based polymerization reactions are mechanistically relatively scarce reactions. The approach toward this class of polymers is therefore often achieved via hydrogenation strategies of unsaturated polymers, preceded by the synthesis of the appropriate olefinic-polymers. − Thus, poly(butadiene)s and poly(isoprene)s, easily accessible via radical or anionic polymerization, can serve as starting points for HDPE- and PE- alt -PP type polymers, respectively, after hydrogenation of the olefinic moieties within the chain. − With the advent of ring-opening metathesis polymerization (ROMP) − as a controlled polymerization process, the access to regular olefinic polymers has become broader. , Thus, various three-, four-, ,,− five- , and higher membered cycles can be ring-opened and polymerized, yielding the respective substituted unsaturated polymers with controllable chain length and unsaturation. Surprisingly, the strategy to use these unsaturated polymers for the subsequent generation of homologous polymers has not been exploited intensely.…”

Hydrogenated styrene–isoprene–butadiene rubber: optimisation of hydrogenation conditions and performance evaluation as viscosity index improver

“…The SIBR solution was degassed by charging H 2 at 1 MPa, followed by evacuation six times. The homogeneous catalytic hydrogenation of SIBR was performed at 4 MPa H 2 pressure and 60°C for 3 h. Purification was performed through precipitation in ethanol . During the experiment, H 2 pressure was maintained constant using a pressure valve, while the temperature in the reactor increased.…”

Synthesis and characterisation of HSIBR used as viscosity index improver for lubricants

“…After 30 min, the resulting black solution was added to the solution of SIBR immediately, with vigorous stirring. The homogeneous catalytic hydrogenation of SIBR was carried out at 60°C and 4 MPa H 2 pressure for 3 h. The hydrogenated products were purified by dissolving in cyclohexane and reprecipitation in ethanol . Finally, the products were dried under vacuum at 40°C.…”

“…The homogeneous catalytic hydrogenation of SIBR was carried out at 60 C and 4 MPa H 2 pressure for 3 h. The hydrogenated products were purified by dissolving in cyclohexane and reprecipitation in ethanol. [11][12][13] Finally, the products were dried under vacuum at 40 C.…”