Bio-oil derived polyesteramides as water-degradable replacements for polyethylene†

Abstract

The seed oil from Brassica carinata is a promising source for biobased aviation fuel. Interestingly, the seeds contain considerable sinapic acid and erucic acid, both of which can be utilized for bioplastic synthesis. From the latter, we report herein the synthesis of biobased and water-degradable polyesteramides (PEAs) via N,N′-bis(2-hydroxyethyl)brassylamide (BHEBA). This diol was prepared from ethanolamine and brassylic acid, a C13 oxidation product of the C22 erucic acid, which makes up 42% of the fatty acids present in this non-GMO (non-genetically modified) Ethiopian mustard seed oil. After optimization of conditions, BHEBA was polymerized with aliphatic diacids to obtain the designed PEAs with high purified yields (77–88%) and good molecular weights (M_n = 7000–10 700 Da). The melting temperatures of these PEAs ranged from 130–139 °C, values comparable to those of several grades of polyethylene. Compared to shorter diacids, the brassylic acid incorporated into PEA structures improves hydrophobicity, and mechanical performance was not compromised after a daylong exposure to water. Furthermore, a 12-month PEA degradation study revealed significant hydrolytic degradation (at least 37% loss in M_n) under all the conditions studied: pH 2, pH 5, seawater, and deionized water. Their degradability was further evaluated under high-temperature conditions compared to several commercial plastics, establishing their superior degradability in seawater and deionized water. Chemical recyclability of PEA was demonstrated through facile aminolysis with ethanolamine to regenerate the BHEBA monomer in 84% yield. While further mechanical property improvement would be ideal, the results substantiate the high potential of brassylic acid-based polyesteramides to be eco-friendly replacements for some petroleum-derived commodity plastics, especially polyethylene.