Biobased Linear and Crystallizable Polyhydroxy(amide-urethane)s from Diglycerol Bis(cyclic carbonate) and the Polyamides of Dimer Fatty Acids

Abstract

Diglycerol and dimer acid (DA) are used as precursors for the solvent- and catalyst-free synthesis of fully biobased non-isocyanate polyurethanes to replace toxic isocyanates and petroleum-based reactants. Linear polyhydroxy(amide-urethane)s (L-NIPHAUs) were synthesized via the melt aminolysis copolymerization between diglycerol dicarbonate (DGDC) and diamino-telechelicoligoamides (DAPAhs) from DA and hexamethylenediamine (HDA). By changing the DA/HDA molar ratios, the structures of DAPAhs and L-NIPHAUs were regulated in a simple and straightforward manner. Atomic force microscopy (AFM) and dynamic mechanical analysis (DMA) of the L-NIPHAUs reveal that the huge polarity difference between the hard segments (HSs) and soft segments (SSs) leads to nanophase separation. The N-amidohexylene-diglycerolbis(hydroxyurethane)-N′-amidohexylene and N-amido-hexylene-N′-amido segments form double HSs, while the bulky nonpolar DA residues serve as SSs. L-NIPHAUs also exhibit semicrystalline structures with good thermal stability evidenced by wide-angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), and thermogravimetry analysis (TGA). They possess Tm ranging from 94 to 110 °C and tunable mechanical properties with a tensile strength of 7.3–12.1 MPa and strain at break of 311–858%. Introducing DA segments increases the hydrophobicity of L-NIPHAUs and the water contact angle and decreases the surface energy. L-NIPHAUs also show excellent solvent resistance in organic solvents, thanks to their intramolecular hydroxyurethane hydrogen bonding, three-dimensional inherent intermolecular hydrogen bonding networks, and the modification of bulky nonpolar DA SSs.