One-pot synthesis of fully biobased polyureas with excellent mechanical properties from epoxidized soybean oil

Abstract

Owing to their highly flexible structure, polymers based on epoxidized soybean oil (ESO) usually exhibit poor mechanical properties. This work was aimed at improving their mechanical properties by incorporating a ureido bond into the backbone of such polymers. Polyureas (PUrs) were successfully designed and prepared from urea, 1,10-decanediamine (DDA) and ESO via a one-pot strategy. Urea first reacted with DDA to form an oligourea, which was then polymerized with ESO. The content of ureido function could be adjusted by simply changing the feeding ratio of urea/DDA and epoxy/ureido to tune the mechanical properties of the obtained PUrs. The one-pot PUrs exhibited comparable thermal and mechanical properties to those obtained via the two-pot synthetic method, in which ESO was polymerized with 1,10-decylene bisurea (DBU). By maintaining an equal amount of ureido and epoxy groups and changing the feeding ratio of urea/DDA from 2 : 1 to 3 : 2 and even to 4 : 3, the glass transition temperature of PUrs increased from 26.9 to 56.4 °C, as detected by the dynamic mechanical thermal analysis. Furthermore, the tensile strength increased from 8.2 to 17.7 MPa, while the elongation at break declined from 430% to 180%. The one-pot synthetic strategy for PUrs developed in this work is promising for the construction of high-performance vegetable oil-based sustainable polymers.