Modulating Barrier Properties of Stereocomplex Polylactide: The Polymorphism Mechanism and Its Relationship with Rigid Amorphous Fraction

Qi Chen, Rafael Auras, Jacob Judas Kain Kirkensgaard, Ilke Uysal-Unalan*

*Corresponding author for this work

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review

Abstract

The barrier properties of semicrystalline polymers are crucial for their performance and their use as packaging materials. This work uncovers the mechanism of polymorphism modification (α, α' and stereocomplex-crystals) and its combined effect on the oxygen and water vapor barrier properties of semicrystalline stereocomplex polylactide (SCPLA). A polymorphic selective filler-type nucleator was employed to eliminate the temperature effect on the development of polymorphism and rigid amorphous fraction (RAF), allowing correlations of barrier properties with different crystal forms and RAF combinations under the same amorphous composition (SCPLA). The oxygen and water vapor barrier performances strongly correlated with crystallinity and crystal form but were not monotonically related to the RAF quantity. The study proposes that the chain conformation of intermediate phases between the crystalline and amorphous phases differs with the associated crystal forms, thereby leading to different RAF "qualities" and contributing to different gas diffusion and solubility coefficients of the amorphous regions. RAF's per unit excess free volume may be varied with crystal forms, for instance: α' ≫ SC > α. Therefore, SCPLA with α' crystals exhibited high oxygen and water vapor permeabilities. Those with high SC and α crystals showed similar barrier behaviors governed by Henry's law dissolution and followed a linear "two-phase" relationship with total crystallinity.

Original languageEnglish
JournalACS Applied Materials & Interfaces
Volume15
Issue42
Pages (from-to)49678-49688
Number of pages11
ISSN1944-8244
DOIs
Publication statusPublished - Oct 2023

Keywords

  • biodegradable polymer
  • gas barrier
  • semicrystalline polymer
  • structure–property relation
  • three-phase crystalline model

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