Synthesis and evaluation of alkoxylated-ether diols of hydroquinone with different chain-lengths as extenders in segmented polyurethanes

Abstract

Two symmetrical alkoxylated-ether diols of hydroquinones (HQ), 1,4-bis(2-hydroxyethoxy)benzene (HQEE) and 1,4-bis(2-hydroxypropoxy)benzene (HQPP), were synthesized from HQ and cyclic carbonates. Another asymmetric alkoxylated-ether diols of HQ, 1-(4-(2-hydroxyethoxy)phenoxy)propan-2-ol (HQEP), was prepared from bisphenol-A through 4-isopropenyl phenol (4-IPP). By taking advantage of the reactivity differences between primary and secondary alcohol in HQEP toward isocyanate group, two more long-chained and low-dispersed extenders, bis(2-(4-(2-hydroxypropoxy)phenoxy)ethyl) hexane-1,6-diyldicarbamate (HQU2) and bis(2-(4-(2-hydroxypropoxy)phenoxy)ethyl) 6,6′-carbonylbis(azanediyl)bis(hexane-6,1-diyl) dicarbamate (HQU3) were prepared by selective reaction between HQEP with 1,6-hexamethylene diisocyanate (HDI). Segmented polyurethanes (PUs) based on HDI, polyethylene-butylene-adipate diol (PEBA-diol), and all five synthesized hard-segment diols as the hard segment ingredients were prepared for comparison. PUs prepared from HQU2 or HQU3 exhibited much balanced properties than those based on HQEE and HQPP. Especially, PU based on HQU3 exhibits highly segregated morphology as well as good physical performances showing good elongation (362 %), high modulus at rubbery plateau regions (115 MPa at E’25°C), high relative tensile strength (7.6 MPa) and thermal stability (306 °C). The result confirms that long-chain extenders with narrow dispersity in molecular weight when used as the hard-segment component can offer substantial advantages in physical properties for PU over those made similarly from discrete and shorter chains counterparts.