ABSTRACT
Polymers often face a trade-off between stiffness and extensibility-for example, toughening rigid polymers by incorporating plasticizers or flexible polymers leads to strikingly decreased stiffness. Herein, we circumvent this long-standing tricky dilemma in materials science via constructing soft-hard dual nanophases in polymers. As-fabricated dual-nanophase PLA shows a high yield strength of 69.1 ± 4.4 MPa, a large extensibility of 279.1 ± 25.5%, and a super toughness of 115.2 ± 10.3 MJ m-3, which are 1.2, 48 and 82 times, respectively, those of neat PLA. Combined high stiffness, large ductility, and super toughness are unprecedented for PLA and enable bio-sourced PLA to replace petroleum-based resins such as PP, PET and PC. Besides, soft-hard dual nanophases in polymers are rarely reported due to significant constraints in terms of modifier dispersion/aggregation, interfacial regulation, and processing difficulties. The construction strategy described herein, combining controlled annealing and a well-designed plasticizer, can efficiently construct soft-hard dual nanophases in polymers, which will greatly advance the nanostructure design of polymers. More importantly, the proposed strategy for materials design will be widely applicable to industrial manufacturing in terms of nanophase construction and interfacial optimization due to the simplicity and availability at a large scale. We envision that this work offers an innovative and facile strategy to circumvent the trade-off between stiffness and extensibility and to advance the nanostructure design of high-performance polymers in a manner applicable to industrial manufacturing.
ABSTRACT
The realization of high stiffness, high extensibility, and multi-functions for polylactic acid (PLA) is a vital issue for its practical applications. Herein, hydroxyalkylated tannin acid (mTA), a phenolic compound-based modifier with plentiful flat aromatic structures and flexible isopropanol oligomers, is designed and fabricated to act as the multifunctional modifier for PLA. The mTA exhibits the capability of emitting fluorescence and blocking UV light due to the combination of flat aromatic structures and plentiful flexible chains. Besides, mTA with high grafting degree (h-mTA) shows an excellent compatibility to PLA due to the hydrogen bonding interface and the high affinity of grafted isopropanol oligomers to PLA. As a result, the as-prepared PLA/h-mTA20 composite exhibits a strikingly improved extensibility by 61.2 times while maintaining the high yield strength of PLA. Moreover, PLA/h-mTA can serve as a fluorescent material with multi-mode responsiveness as well as a UV-shielding material with high transparency. We envision that this work opens a novel yet facile way to prepare a strong, tough, and multifunctional PLA material with expanded application scopes and will promote the practical applications of phenolic compounds in polymers.
