Partial Miscibility-Driven Nucleation of Poly(3-hydroxybutyrate- co -3-hydroxyhexanoate) with Indigo Dye

High Resolution Image Download MS PowerPoint Slide Melt-miscible nucleating agents for poly(3-hydroxybutyrate- co -3-hydroxyhexanoate) (PHB- co -HHx) can enhance the processability of the polymer for thin film and fiber applications. However, most melt-miscible nucleators have poor nucleation efficacy compared to nonmiscible nucleating agents such as orotic acid. In this work, indigo was blended into PHB- co -HHx, and its performance as a melt-miscible nucleating agent was evaluated. Indigo was found to dye the polymer at all loadings, but it was observed that indigo nucleates the polymer at loadings >0.075% w/w, with a 0.1% indigo sample having a T c and % X c of 92.2 °C and 37.8%, respectively. These values were found to be comparable to 1% orotic acid ( T c – 94.9 °C, % X c – 36.7%), despite the substantially lower indigo loading. Subsequent analysis by polarized optical microscopy (POM) revealed that at low loadings, indigo was melt-miscible with PHB- co -HHx, which contributed to better nucleating agent dispersion throughout the polymer matrix. Additionally, the 1/ t 1/2,Theo. value of 0.1% indigo was observed to be 0.03 min –1 lower than 1% orotic acid at 100 °C, exhibiting nearly identical crystallization kinetics. Interestingly, the lattice parameter matching and potential H-bond interactions between indigo and PHB- co -HHx were found to be much worse than the matching between orotic acid and PHB- co -HHx. Instead, the excellent nucleation performance of indigo was attributed to partial miscibility at 0.1% loading, which allowed for thorough dispersion and even self-assembly of the nucleating agent in the polymer.