Myrcene anionic polymerization

Myrcene is, to our knowledge, the only monoterpene which has been the object of living anionic polymerization (LAP) and copolymerization studies [91]. These systems involved A -butyl lithium as the initiator, and either benzene or THF as solvent. When the reaction was carried out in the former, 1,4-addition was favoured (85-90 per cent). 

One of the limitations of anionic polymerization is the types of monomers which can be polymerized without termination and chain transfer. The most well-behaved systems are the vinyl monomers based on styrene and butadiene which are available primarily from petroleum feedstocks. Several years ago we began a search for anionically polymerizable monomers which would be available from renewable natural resources. One of the monomers uncovered (rediscovered) in this search was myrcene (4) 7-methyl-3-methylene-1,6-octadiene,... 

Myrcene is an interesting diene (actually triene) monomer since it has an isolated double bond in its alkyl side chain. Thus, this monomer provides a unique opportunity to study the effects of internal ir-bond interactions in living anionic polymerizations and also to examine the effects of this functionality on the physical properties of poly(myrcene) and various block copolymers as reported herein. 

ABA triblock copolymers have been prepared by sequential anionic polymerization of styrene (A), myrcene (B), and again styrene. Polymerizations were initiated by sec-butyllithium at room temperature using benzene as the solvent. The resulting thermoplastic elastomeric copolymers had average MWs in the range of 2-100 kg/mol the PDl and microstracture of the polymyrcene block were not provided [39]. 

The acylic monoterpenes myrcene (7-methyl-3-methylene-l,6-octadiene) and ocimenes (a-ocimene 3,7-dimefliyl-l,3,7-octatriene, alloocimene 2,6-dimethyl-2,4,6-octatriene) (Fig. la-c) represent unsaturated hydrocarbons bearing conjugated double bonds, which in principle can be polymerized by radical, anionic, and cationic procedures as well as by coordination polymerization processes. 

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