The details of poly(butylene fumarate) (PBF) as highly effective nucleating agent for poly(butylene succinate) (PBS) were systematically studied via X-ray diffraction, differential scanning calorimeter, polarized optical microscopy, and atom force microscopy. All results show that PBF can significantly improve the melt-crystallization temperature and the degree of crystallinity of PBS during the nonisothermal crystallization process. Both crystallization time span and spherulitic size of PBS decrease drastically with the addition of a small amount of PBF, which shows that PBF not only enhances the primary nucleation of PBS by epitaxial mechanism, but also greatly accelerates the secondary nucleation during spherulite growth. The secondary nucleation parameters of PBS, K g and G 0, are notably improved just with a small amount of PBF. Furthermore, the appearance of wrinkles on PBF-nucleated PBS ultrathin film visually suggests that PBF indeed affects the subsequent growth behavior, besides the primary nucleation.

Hexagonal boron nitride nanosheets (BNNSs) were prepared by a facile chemical exfoliation method. Then cosolution film casting method was used to obtain poly(butylene adipate) (PBA)/BNNSs nanocomposites. The incorporated BNNSs changed the formation condition of the polymorphic crystals of PBA. The results of differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) showed that BNNSs significantly facilitated the formation of α-form crystals for isothermal and nonisothermal crystallization. Compared to pure PBA at 28°C, the α-form crystals would not disappear until the temperature decreased to 13°C with the addition of 0.5 wt % BNNSs. In addition, the excellent heterogeneous nucleation ability of BNNSs was identified by the nonisothermal and isothermal crystallization process. The enzymatic degradation experiments exhibited that PBA/BNNSs nanocomposites possessed a considerably lower degradation rate than neat PBA. This work demonstrates that BNNSs is an efficient material to regulate the formation of polymorphic crystals and the degradation behavior of PBA.

We have studied melting of poly­(butylene succinate), isothermally crystallized over a wide temperature range, employing a combination of the Hoffman–Weeks plot and the Gibbs–Thomson crystallization line, determined by small-angle X-ray scattering measurements. A change in the slope α of the Hoffman–Weeks (H–W) line, accompanied by a change of the slope of the crystallization line, was observed for crystallization temperatures higher than 110 °C. α was reaching a value of 1, implying that no intersection point between the H–W line and the T m = T c line could be obtained. (T m is the measured melting temperature and T c is the temperature at which the sample was crystallized). This observation was corroborated by the crystallization line, which was found to be parallel to the melting line for T c > 110 °C. We relate these changes in slope to different stabilization mechanisms of the secondary nuclei at the growth front of polymer lamellar crystals. For T c > 110 °C, secondary nuclei are proposed to be stabilized by coalescence of neighboring nuclei, all having a small width. By contrast, for T c > 110 °C, the number density of secondary nuclei is low and thus their coalescence is rare. Accordingly, nuclei are stabilized by growing in size, mainly increasing their width.

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Hydroxyl-functional hexagonal boron nitride nanosheets (OH-BNNSs) were prepared successfully by ultrasonic treatment, and then homogeneous dispersions of OH-BNNSs in 1,4-butanediol (BDO) were obtained. Various techniques were applied to characterize the OH-BNNSs and their hydroxyl functional groupd. Furthermore, biodegradable poly(butylene succinate) (PBS)/OH-BNNS nanocomposites were prepared by in situ polymerization of succinate acid (SA) and BDO containing well-dispersed OH-BNNS. The nucleating effect of low OH-BNNS loadings on PBS in the PBS/OH-BNNS nanocomposites was investigated. It is found that OH-BNNSs significantly improve the melt-crystallization temperature and degree of crystallinity of PBS during the nonisothermal crystallization process without changing the crystal structure of PBS. Moreover, the Avrami exponent n calculated for isothermal crystallization increased from 2 to 3 after the addition of 0.05 wt % OH-BNNSs. The nucleation density of PBS spherulites in the nanocomposites increased dramatically. These results demonstrate that OH-BNNSs function as an outstanding nucleating agent of PBS.