N¹, N⁶-bis (4-aminobutyl) adipamide (BABA) diamine and sebacic acid (SA), also called BABA/SA polyamide salt, were used in a typical melt polymerization processes of polyamide 6 (PA6) to form a series of PA6-BABA/SA copolyamides. The effects of BABA/SA on the isothermal crystallization kinetics of PA6-BABA/SA were studied for the first time. An isothermal crystallization analysis demonstrates that the PA6-BABA/SA matrix provided a higher crystallization rate and shorter half-crystallization time than virgin PA6 did. The degree of crystallization of the PA6-BABA/SA₃₀ matrix was also the lowest among all of the samples considered herein. This result is attributed to the high nucleation efficacy of a small amount of BABA/SA in the crystallization of PA6. Values of the Avrami exponent (n) from 1.84 to 3.91 were observed for all of the polyamide samples, suggesting that the crystallization was involved via a two- to three-dimensional growth mechanism. These findings deepen our understanding of the structure–property relationship of PA6-BABA/SA copolyamides, favoring their practical application.

In this work, a new family of fully biobased thermoplastic polyurethanes (TPUs) with thermo-induced shape memory is developed. First, a series of TPUs were successfully synthesized by the one-shot solvent-free bulk polymerization of bio-poly(1,3-propylene succinate) glycol (PPS) with various molecular weights (M_n = 1000, 2000, 3000, and 4000), 1,4-butanediol (BDO), and 4,4′-methylene diphenyl diisocyanate (MDI). These polyurethanes (PUs) are denoted as PPS-x-TPUs (x = 1000, 2000, 3000, and 4000), where x represents the M_n of PPS in the polymers. To determine the effect of the molecular weight of the soft segment of PU, all PPS–TPUs were formed with the same hard segment content (32.5 wt %). The soft segment with high molecular weight in PPS-4000-TPU caused a high degree of soft segment entanglement and formed many secondary bonds. PPS-4000-TPU exhibited better mechanical (tensile strength: 64.13 MPa and hardness: 90A) and thermomechanical properties (maximum loading: 2.95 MPa and maximum strain: 144%) than PPS-1000-TPU. At an appropriate shape memory programming temperature, all synthesized PPS-x-TPUs exhibited excellent shape memory behaviors with a fixed shape rate of >99% and a shape recovery rate of >86% in the first round and 95% in the following rounds. Therefore, these bio-TPUs with shape memory have potential for use in smart fabrics.