Impact of Polymerization Protocol on Structure-Property Relationships of Entirely Lipid-Derived Poly(ester urethane)s

Abstract

The impact of polymerization protocol on phase structure and properties of entirely lipid-derived thermoplastic poly(ester urethane)s (TPEU)s was investigated. The TPEUs were synthesized from 1,7-heptamethylene diisocyanate, polyester diols and 1,9-nonanediol (ND) as chain extender. A two-stage polymerization method was used to prepare two TPEUs; one in which ND was added in the first stage of polymerization as part of the prepolymer and another in the second stage after the prepolymer was formed. Two very different morphologies exhibiting different degrees of phase separation were obtained, driven by the sequence of addition of the chain extender. The incorporation of the chain extender in the prepolymer resulted in a TPEU with a narrow hard segment distribution, enhanced urethane-urethane hydrogen bonding and higher molecular weight. The hydrogen bond density, degree of crystallinity, glass transition temperature and mechanical properties of the TPEUs were directly related to the degree of phase separation and hence polymerization protocol.