Ethylene oxide reaction with polybutadiene

Other monomers, such as butadiene (164) and isoprene (165), have been polymerized and hydroxylated hy the reaction of the corresponding hving polymers with ethylene oxide. Bifunctional living polybutadiene has been generated in hexane using living oligomeric isoprene or 2,3-dimethylbutadiene as initiator (166). The hydroxyl functionality varies between 1.7 and 2.0. 

It has been shown recently (10) that such block structures could be tailored precisely by the general method summarized hereabove. It is indeed possible to convert the hydroxyl end-group of a vinyl polymer PA (f.i. polystyrene, or polybutadiene obtained by anionic polymerization terminated with ethylene oxide),into an aluminum alcoholate structure since it is well known that CL polymerizes in a perfectly "living" manner by ring-opening insertion into the Al-0 bond (11), the following reaction sequence provides a direct access to the desired copolymers, with an accurate control of the molecular parameters of the two blocks ... 

Reed 332) has reported that reaction of ethylene oxide with the a,(a-dilithiumpoly-butadiene in predominantly hydrocarbon media (some residual ether from the dilithium initiator preparation was present) produced telechelic polybutadienes with hydroxyl functionalities (determined by infrared spectroscopy) of 2.0 + 0.1 in most cases. A recent report by Morton, et al.146) confirms the efficiency of the ethylene oxide termination reaction for a,ta-dilithiumpolyisoprene functionalities of 1.99, 1.92 and 2.0j were reported (determined by titration using Method B of ASTM method E222-66). It should be noted, however, that term of a, co-dilithium-polymers with ethylene oxide resulted in gel formation which required 1-4 days for completion. In general, epoxides are not polymerized by lithium bases 333,334), presumably because of the unreactivity of the strongly associated lithium alkoxides641 which are formed. With counter ions such as sodium or potassium, reaction of the polymeric anions with ethylene oxide will effect polymerization to form block copolymers (Eq. (80) 334 336>). 

Reaction with acid then yields carboxyl-terminated polybutadiene (CTPB). Hydroxyl end groups are provided by termination with ethylene oxide ... 

The transformation of the anionic chain end in hydroxyl groups is made by the reaction of living anionic polybutadiene with propylene oxide or ethylene oxide, followed by hydrolysis or by neutralisation of the resulting alcoholate groups (reactions 9.10 and 9.11) [21-24]. 

In addition to being a synthetic route to unusual graft copolymers, the metalation technique offers a way to add functional groups to the chain by reactions characteristic of organolithium compounds. Hydroxyl or carboxyl groups, for instance, can be added by treating the metalated polyisoprene or polybutadiene (22) solution with ethylene oxide or C02, respectively. The lithium alkoxide and carboxylic salt obtained (23) in... 

Reed has reported that reaction of ethylene oxide with the a,(a-dilithiumpoly-butadiene in predominantly hydrocarbon media (some residual ether from the dilithium initiator preparation was present) produced telechelic polybutadienes with hydroxyl functionalities (determined by infrared spectroscopy) of 2.0 + 0.1 in most cases. A recent report by Morton, et al. confirms the efficiency of the ethylene oxide termination reaction for a,ta-dilithiumpolyisoprene functionalities of 1.9, 1.92 - i reported (determined by titration using Method B of ASTM... 

Glycosylated block copolymers, prepared by a thiol-ene radical photoaddition reaction of 2,3,4,6-fefra-O-acetyl-l-thio-fc-D-glucopyranose onto l,2-polybutadiene-( -poly(ethylene oxide), have been demonstrated to self-assemble in dilute aqueous solution and spontaneously form vesicles (glycosomes) with sugar-coated asymmetric membranes (Fig. 5.20) [45]. 

In addition to free radical intermediates, grafting reactions can be achieved through anionic intermediates. For example, the treatment of 1,4-polybutadiene with t-butyllithium (Reaction 15) (51) or a polyamide with sodium (Reaction 16) (51-53)yields polymeric anions which can initiate the graft polymerization of styrene, formaldehyde, acrylonitrile, and ethylene oxide. 

Synthetic rubbers are produced as commodities. Polybutadiene, polybutylene, polychloroprene and polyepichlorohydrin are examples of elastomeric homopolymers. Copolymeric rubbers comprise poly-(butadiene-co-styrene), poly(butadiene-co-acryloni-trile), poly(ethylene-co-propylene-co-diene), and poly-(epichlorohydrin-co-ethylene oxide). The unsaturated group in the comonomer provides reactive sites for the crosslinking reactions. Copolymers combine resilience with resistance to chemical attack, or resilience in a larger temperature range, and thermoplastic-like properties. There are several studies in the literature describing the preparation of blends and composites of elastomers and conductive polymers. A description of some significant examples is given in this section. 

However, the reaction of growing active centers with a deactivating molecule, serving as precursor of the functional group to be introduced, is the most commonly used method. The preparation of co-hydroxy polybutadiene by deactivation of living polybutadiene carbanions by ethylene oxide is an illustration of this strategy ... 

Two reactions can occur during wear oxidative degradation as a result of frictional heating in the contact zone and mechanochemical degradation initiated by shear-induced rupture of chemical bonds. Present evidence favors the latter process. For example, in the absence of oxygen, the wear of cis-polyisoprene changes to resemble that of c/x-polybutadiene, whereas the wear of poly(ethylene-co-propylene) is unaltered (Gent and Pulford, 1983). These results are in accord with the response of these materials to free radical reactions. 

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