The route used to synthesise the 100% bio-based PHUs, which is based on our previously reported work, is shown in Fig. . In addition to being isocyanate-free, these PHUs provide a high density of polar groups with two hydroxyl and two carbamate functions per repeating unit, which is expected to result in significant dielectric properties. Three different PHUs were synthesised, with various α,ω-diamine alkyl chain lengths, namely n = 6, 8 and 12, referred to as PHU6, PHU8 and PH12, respectively. The chemical structure of the PHUs was confirmed by H NMR (Fig. and Fig ). Full conversion of the cyclic carbonates and amines was assumed since no remaining signals at 5.15 ppm (proton of the methine carbon of EDC) and 2.68 ppm (𝛼𝛼-proton of NH2) were detected. As expected, the ratios of secondary to primary alcohols are of about 85 : 15 for the three polymers. The number average molecular weight, Mn, and the dispersity, Ð, were determined by size exclusion chromatography in DMF (SEC, Fig. ) and found to be Mn = 8.6, 4.4 and 3.4 kg•mol -1 and Ð = 2.2, 3.1 and 2.8, for n = 6, 8 and 12, respectively.