Cellulose nanocrystal dispersion-ability in polylactides with various molecular weights prepared in dichloromethane/dimethyl sulfoxide solvents for electrospinning applications

Abstract

In this study, effects of polylactide molecular weight, i.e., high (HPLA), medium (MPLA), low (LPLA), and dichloromethane (DCM)/dimethyl sulfoxide (DMSO) blend ratio on cellulose nanocrystal (CNC) dispersion quality in solution casted PLA/CNC nanocomposites were investigated via small amplitude oscillatory shear rheological analysis, while crystallization behavior, thermal degradation, morphological structure of the nanocomposites were also reported. Due to its low dielectric constant, none of the nanocomposites with 100DCM indicated a change in their complex viscosity as a result of poor CNC dispersion. This is while the increase in DMSO content (50%vv-1) improved CNC dispersion. The superior CNC dispersion-ability in PLAs with lower molecular weight was confirmed. The poorer CNC dispersion in HPLA attributes to hindering effect of higher molecular weight on solvent and nanoparticle diffusion. The better dispersed CNCs influenced crystal nucleation behavior of PLAs and increased crystallinity degree. In addition, the impact of well-dispersed CNCs on fiber formation quality of nanocomposites was reported. Introducing finely dispersed CNCs (1 wt%) in LPLA refined fiber diameters around 1200 nm with more homogenous structure. Besides, the use of 100DCM and the use of DMSO at high contents (50%vv-1) deteriorated fiber formation, respectively, due to low conductivity of DCM and high boiling temperature of DMSO.