Hydrogenated PBD

This paper is a discussion of the main results we have on the thermoreversible gelation of block copolymers of the MXM type in o-xylene, where M is syndiotactic poly(methyl methacrylate) (sPMMA) and X is either polybutadiene (PBD), hydrogenated PBD (PEB), poly(styrene-b-butadiene-b-styrene) (SBS) triblock or the hydrogenated version of this triblock (SEBS) (25-28). 

Ngai and Plazekl O fjnd g strong correlation between in the Arrhenius region and barriers to internal rotation. The only polymer data reported are for PE and hydrogenated PBD. This work supports our assignment of Tip as occurring when the polymer chain first overcomes intramolecular barriers to rotation. 

When using decaline as solvenL a macroinitiator based on a hydrogenated PBD was used as a starting substance for block copolymer preparation which was functionalized by bis(carbamoyllactams) under the catalysis of NaH [64]. 

Hydroformylation and subsequent hydrogenation of C=C and -CHO groups of PBD appear to be an appropriate means whereby a pendent hydroxy group can be introduced onto the polymer backbone. A variety of partially hydroformyl ated (2-20%) and hydroxymethy-lated polymers have been synthesized by a two-step catalytic reaction and characterized by I.R. and 1H N.M.R. spectroscopy. As expected, the hydrophilic group, OH, in the polymer resulted in a greater decrease in the intrinsic viscosity as compared to the HPBD. 

Dilute Solution Viscometry - The hydrogenated and hydroformyl ated (10%) PBD were completely soluble in toluene. Intrinsic viscosity measurements were carried out in toluene at 30°C using a Cannon-Ubbelohde viscometer. 

Hydroxymethyl ati on of Polybutadiene - The hydroformyl ated PBD reaction solution obtained above was subsequently hydrogenated directly using the following reaction conditions Hydroformyl ated PBD solution = 75 ml, RuC1H(C0)(P(CcHc)3)3 = 1.05 mol/m3, Hydrogen pressure = 600 psig, Temperature = 1 0 C. 

The overall catalytic reactions involved in the two step synthesis of hydroxymethyl ated PBD are given by Equations 1-6. It can be seen from reactions (1-6) that the addition of -CHO functional group can occur in three ways resulting in the formation of three types of hydroformyl ated PBD repeating units as shown by species A, B or C. Subsequent hydrogenation of units A, B and C result in the formation of hydroxymethylated PBD repeating units A, ... 

The efficiency of Crabtree s catalyst as a catalyst for small molecule hydrogenation has been known for many years. Unlike many homogeneous hydrogenation catalysts, Crabtree s catalyst is able to reduce hindered olefins at favourable rates.7 It has never been reported as a catalyst for the hydrogenation of rubber except for its use in the hydrogenation of bulk PBD.8 This paper describes the first use of Crabtree s catalyst in the hydrogenation NBR. Kinetic data are presented and analyzed to understand the underlying chemistry. 

The hydrogenation in a liquid-liquid system with ionic liquids as the catalyst phase was also applied to the hydrogenation of polymers. The first studies were presented by the group of Rosso et al. [91], who investigated the rhodium-catalyzed hydrogenation of polybutadiene (PBD), nitrile-butadiene rubber (NBR) and styrene-butadiene rubber (SBR) in a [BMIM][BF4]/toluene and a [BMIM][BF4]/tolu-ene/water system. The activity of the catalyst followed the trend PBD>NBR> SBR, which is the same order as the solubility of the polymers in the ionic liquid. The values in percentage total hydrogenation after 4 h reaction time were 94% for PBD and 43% for NBR, and after a reaction time of 3 h was 19% for SBR. 

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