Sorbic Acid–Tung\nOil–Sulfur Terpolymer\nPrepared via Inverse Vulcanization and Its Application as Antibacterial\nand Toughness Modifier for Polylactide

Biopolymers as abundant, sustainable, and environment-friendly\nrenewable material have been regarded as the best alternative to nondegradable\nfossil products. However, these biopolymers are often confronted with\nproblems such as high prices, poor mechanical properties, and susceptibility\nto bacterial erosion. In the current study, inverse vulcanization\nwas adopted to synthesize polymers with multisulfur segments cross-linked\nby plant-based sorbic acid and non-edible tung oil. The synthesized\ncopolymer exhibited tailorable glass transition temperatures (0.3–24.8\n°C) and rheological behaviors with modulus alterable within an\norder of magnitude. The addition of transesterification catalyst Zn(acac)<sub>2</sub> lowered the activation energy of stress relaxation by ∼20\nkJ/mol. Thanks to the dynamic reversible S–S bonds, this networked\npolymer also exhibited regulatable thermal self-healing behaviors.\nMoreover, in the blending with polylactide (PLA), the reversible dissociation\nof S–S bonds at high temperature facilitates the dispersion\nof polysulfides in the PLA matrix, which can be further improved by\nadding catalyst, adjusting monomer ratios, etc. As a result, the polysulfides\nnot only toughen the PLA but also endow the blends with excellent\nantibacterial activities attributed to the intrinsic bacteriostatic\nsorbic acid and sulfur. Used as a modifer for bioplastics to adjust\ntheir mechanical properties and functions, polysulfides are expected\nto have potential applications in medical materials or food packaging\nfields.