Multilayer
structures are not only applied to manipulate properties
of synthetic polymer materials such as rainbow films and barrier films
but also widely discovered in natural materials like nacre. In this
work, in situ formation of an interconnected multi-nanolayer (IMN)
structure in poly(butylene adipate-co-terephthalate) (PBAT)/poly(butylene
succinate) (PBS) cocontinuous blends is designed by an extensional
flow field during a “casting–thermal stretching”
process, combining the properties of two components to a large extent.
Hierarchical structures including phase morphology, crystal structure,
and lamellar crystals in IMN films have been revealed, which clearly
identifies the crucial role of extensional flow. The oriented PBAT
phase in the IMN structure can be beneficial to the epitaxial growth
of PBS crystals onto the PBAT nanolayers, thus improving interfacial
adhesions. Furthermore, intense extensional stress can also promote
crystallinity and thicken the lamellar structure. Given such distinct
features in the fully biodegradable films, a simultaneous enhancement
in tear strength, tensile strength, and puncture resistance has been
achieved. To the best of our knowledge, the tear strength of IMN films
about 285.9 kN/m is the highest level in the previous works of this
system. Moreover, the proposed fabrication way of the IMN structure
is facile and scalable, which is highly expected to be an efficient
strategy for development of structured biodegradable polymers with
excellent comprehensive properties.