Hydroxyl-functionalized polymers using initiator efficiency

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>). 

By using RCM with the Grubbs catalyst, synthesis of cyclic poly(e-caprolactone) [poly(e-CL)] was reported by Xie et al. [75]. They used 10-undecen-l-ol as initiator to polymerize the e-CL with Sn(Oct)2 as catalyst. The hydroxyl chain end of the poly (e-CL) was further functionalized by the reaction with undecylenic acid chloride to give a divinyl poly(e-CL). The cyclization was carried out in a one-pot reaction at a polymer concentration of 5.0 x 10 " mol/L however, the efficiency of the cyclization was relatively low as their SEC traces showed a large amount of multiblock condensation by-products (Scheme 23). 

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