Highly Enhanced Crystallization Kinetics of Poly(l-lactic acid) by Poly(ethylene glycol) Grafted Graphene Oxide Simultaneously as Heterogeneous Nucleation Agent and Chain Mobility Promoter

Abstract

Nanofillers can act as effective heterogeneous nucleation agents for semicrystalline polymers; however, it never facilitates the crystal growth. In the current work, we proposed a facile strategy to enhance the crystallization kinetics of poly(Llactic acid) (PLLA) by simultaneously accelerating the crystal nucleation and growth. Herein, we synthesized poly(ethylene glycol) (PEG) grafted graphene oxide (GO) (PEGgGO). Pronounced effects of PEGgGO on the crystalline morphology and crystallization rate of PLLA were explicitly clarified by direct morphological observation and quantitative crystallization kinetics analysis. The results manifested that, in contrast to the unmodified GO, PEGgGO desirably dispersed in PLLA and also preserved the high nucleation ability. More importantly, the flexible PEG chains on GO served as a chain mobility promoter and boosted the crystal growth rate of PLLA. Compared to the PLLA/GO nanocomposite containing 0.5 wt % GO, the nucleation density and crystal growth rate of the PLLA/PEGgGO one were increased by 110% and 14.3% at the crystallization temperature of 130°C, respectively, leading to 52.2% relative augment in the final crystallinity. Our proposed methodology offers the flexibility of fabricating the polymer nanocomposits with well-dispersed nanofillers and also high crystallinity, by which the step toward the high-performance nanocomposites will be further.

Structural evolution of poly(l-lactide) block upon heating of the glassy ABA triblock copolymers containing poly(l-lactide) A blocks

“…The acceleration of chain mobility was also found to facilitate the crystallization kinetics of the semicrystalline polymers [29,44,45]. It has been reported that the mesophase can be formed by the addition of other components to PLLA such as polyethylene glycol and carbon dioxide (CO 2 ), which are known to reduce the T g of PLLA [27,29,46].…”

Simultaneously improving stiffness, toughness, and heat deflection resistance of polylactide using the strategy of orientation crystallization amplified by interfacial interactions

“…So conventional injection molded parts are almost amorphous. For sheared samples, our previous work manifests that intense shear flow can remarkably enhance oriented chain segments along the flow direction (so‐called precursor) . In the case of the cooling temperature of the melt in the mold is above the T g , in which the molecular chains of PLA still have good mobility, shear heating with long duration may accelerate relaxation of oriented crystals, after all, the orientation and chain relaxation of molecular chains exist simultaneously and competitively under intense shear flow.…”

“…However, only increasing matrix crystallinity usually change the distribution and phase domain size of elastomer particle aggregates, ultimately affect toughness of the blends . In our previous work, we utilized a modified injection molding technology‐oscillation shear injection molding (OSIM) to impose a strong shear on the melt during actual melt processing, uncovering that shear flow can promote the formation of orientated morphology, enhance nucleation, and crystallinity of PLA, which is helpful in the improvement of strength . Moreover, we have qualitatively revealed the relationship between distribution of crystalline morphology (thickness and averaged crystallinity of skin layer) and the thermomechanical performance of injection‐molded pure PLA parts .…”

Interfacial effects on crystallization behavior of polymer nanocomposites with polymer‐grafted nanoparticles

“…The grafted chains can not only impart nanoparticles with desirable dispersion but also act as nucleation sites in semicrystalline polymers . As compared to bare NPs, the PGNPs act as the more effective heterogeneous nucleating agents.…”