Thermal properties such as melting temperature can well reflect the microstructure of the polymer material, and have practical implications in the application of nanofibers. In this work, we investigated the melting temperature of individual electrospun poly(vinylidene fluoride) (PVDF) nanofibers with diameters ranging from smaller than 200 nm to greater than 2 µm by the local thermal analysis technique. The PVDF fibers obtained under four different conditions were found to crystallize into α and β phases, and the fiber mats showed typical values in the crystallinity and T_m with no significant difference among the four. However, analyses at single fiber level revealed broad distribution in diameter and T_m for the fibers produced under identical electrospinning condition. The T_m of individual nanofibers was found to remain constant at large diameters and increase quickly when reducing the fiber diameter toward the nanoscale, and T_m values of 220–230 °C were observed for the thinnest nanofibers, much higher than the typical values reported for bulk PVDF. The T_m and molecular orientation at different positions along a beaded fiber were analyzed, showing a similar distribution pattern with a minimum at the bead center and higher values when moving toward both directions. The results indicate that molecular orientation is the driving mechanism for the observed correlation between the T_m and the diameter of the nanofibers.

诸如熔化温度的热性质可以很好地反映聚合物材料的微观结构，并且在纳米纤维的应用中具有实际意义。在这项工作中，我们通过局部热分析技术研究了直径范围从小于200 nm到大于2 µm的单个电纺聚偏二氟乙烯（PVDF）纳米纤维的熔化温度。发现在四种不同条件下获得的PVDF纤维结晶为α和β相，并且纤维毡在结晶度和T _m方面显示典型值，而在这四种之间没有显着差异。但是，单纤维水平的分析表明，直径和T _m分布较广在相同的静电纺丝条件下生产的纤维。发现单个纳米纤维的T _m在大直径时保持恒定，并在朝纳米级减小纤维直径时迅速增加，并且最薄的纳米纤维的T _m值为220–230°C，远高于报告的典型值。用于散装PVDF。分析了沿着串珠纤维的不同位置处的T _m和分子取向，显示了相似的分布模式，当在两个方向上移动时，在串珠中心的最小值和较高的值。结果表明，分子取向是观察到的T _m之间相关性的驱动机制。 和纳米纤维的直径。