Polybutadiene reaction efficiency

The synthesis of block copolymers with blocks of ultralow cohesion energy densities on the basis of polystyrene-6-polybutadiene via two highly efficient polymer analogous reactions has been presented. 

Initial reports on chemoenzymatic block copolymer synthesis focus on the enzymatic macroinitiation from chemically obtained hydroxy-functional polymers (route A in Fig. 4). The first report on enzymatic macroinitiation was published by Kumar et ah, who used anionically synthesized hydroxy-functional polybutadiene of various molecular weights ranging from 2600 to 19,000Da (Fig. 5) [16]. In a systematic study, the authors investigated the efficiency of the macroinitiation of CL and PDF by Novozym 435 as a function of the polybutadiene macroinitiator. The reaction profile showed that polybutadiene consumption steadily increased with the reaction... 

Although a plethora of divinyl aromatic compounds have been investigated as precursors for hydrocarbon-soluble dihthium initiators (68), the only system which has been demonstrated to produce a hydrocarbon-soluble dihthium initiator is based on l,3-bis(l-phenylethenyl)benzene (60,81—85). The addition reaction of sec-hutylhthium with l,3-bis(l-phenylethenyl)benzene [34241-86-6] (eq. 16) proceeds rapidly and efficiently to produce the corresponding dilithinm species in toluene (86) or in cyclohexane (82). This dihthium initiator is not only soluble in hydrocarbon media such as cyclohexane, benzene, and toluene (even at —20° C) (84), but also functions as an efficient difunctional initiator for the preparation of homopolymers and triblock copolymers with relatively narrow molecular weight distributions (81—83). However, it is necessary to add a small amount of Lewis base or two equivalents of lithium jw-butoxide to produce narrow, monomodal molecular weight distributions. Lithium JW-butoxide is the preferred additive, since high 1,4-polybutadienes are obtained (60). 

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>). 

A gel permeation chromatogram obtained by Heller (13) indicated that Kraton 101 contained 1% polystyrene, 22% polystyrene/1,4-poly-butadiene, and 77% polystyrene/1,4-polybutadiene/polystyrene, apparently because the material is manufactured by coupling of the diblock. The diblock would be present if the coupling reaction is not 100% efficient. Kraton 101 would thus be essentially a blend of ABBA and AB block copolymers. Assuming that Kraton 102 is manufactured in the same way, the molecular weight of the ABBA block copolymer results as about 72,000 from the above data, the polystyrene blocks having a molecular weight of about 12,000, and the polybutadiene center block one of about 48,000. 

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... 

The efficiency of the linking reactions of polychlorosi-lanes with poly(dienyl)lithium compounds has been documented by synthesis of well-defined, narrow molecular weight distribution, 18-armed star-branched polyisoprenes, polybutadienes, and butadiene end-capped polystyrenes by linking reactions with a decaoctachlorosilane [(SiCl)ig] [256, 257]. The linking reactions of poly(butadienyl)lithium (Mjj = 5.3-89.6 x 10 g/mol) with carbosilane dendrimers with up to 128 Si-Cl bonds have been reported to proceed... 

These addition reactions of unsaturated polymers, like liquid polybutadiene, developed into preparations of useful commercial materials. The patent literature describes procedures that use hydrogen peroxide in the presence of organic acids or their heavy metal salts. Reaction conditions place a limitation on the molecular weights of the polymers, because it is easier to handle lower-viscosity solutions. A modification of the procedures is to use peracetic acid in place of hydrogen peroxide. The most efficient methods rely upon formations of organic peracids in situ with cationic exchange resins acting as catalysts. This can be illustrated as follows ... 

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