Polylactide (PLA) has become widely adopted across biomedical, packaging, and manufacturing sectors due to its biodegradability and renewable sourcing. However, the rapid growth in PLA consumption has created urgent challenges related to waste management and the cleaning of processing equipment. This study investigates glycolysis as a promising chemical depolymerization pathway for PLA recycling and in situ reactor cleaning. A systematic analysis of four glycolysis agents (GA) (ethylene glycol, diethylene glycol, propylene glycol, and glycerol) was performed across molar PLA:GA ratios from 1:0.125 to 1:4 at 220 °C, targeting the efficient conversion of high-molecular-weight PLA (Mn ≈ 165 kDa) into low-molecular-weight oligomers. Gel permeation chromatography (GPC) demonstrated that propylene glycol exhibited the highest depolymerization efficiency, yielding oligomers with Mn as low as 200 g·mol⁻¹ even at minimal glycolysis agent ratios, while glycerol produced hydroxyl-rich oligomers optimal for subsequent lactide synthesis. Hydroxyl value (HV) measurements showed excellent agreement with theoretical values (99%) was obtained through thermocatalytic depolymerization and five recrystallization cycles, as confirmed by ¹H nuclear magnetic resonance (¹H NMR) and differential scanning calorimetry (DSC) analyses. The recovered lactide’s high purity renders it suitable for ring-opening polymerization, enabling closed-loop PLA recycling schemes. Overall, glycolysis emerges as a highly promising chemical recycling route complementary to hydrolysis and pyrolysis: propylene glycol maximizes depolymerization efficiency for cleaning applications, while glycerol optimizes oligomer functionality for lactide recovery and advanced material synthesis. Our results provide practical guidelines for selecting glycolysis agents and conditions for cleaning and recycling applications.

Binary and ternary copolymers of acrylonitrile (AN), tert-butyl acrylate (TBA), and n-butyl acrylate (BA) are synthesized through conventional radical polymerization in DMSO in the presence of 2-mercaptoethanol. The thermal behavior of binary and ternary copolymers is studied under argon atmosphere and in air. It is demonstrated that the copolymers of AN contain 1–10 mol.% of TBA split isobutylene upon heating above 160 °C, resulting in the formation of the units of acrylic acid in the chain. The carboxylic groups formed in situ are responsible for the ionic mechanism of cyclization, which starts at lower temperatures compared with pure polyacrylonitrile (PAN) or AN copolymer with BA. The activation energy of cyclization through ionic and radical mechanisms depends on copolymer composition. For the ionic mechanism, the activation energy lies in the range ca. 100–130 kJ/mole, while for the radical mechanism, it lies in the range ca. 150–190 kJ/mole. The increase in the TBA molar part in the copolymer is followed by faster consumption of nitrile groups and the evolution of a ladder structure in both binary and ternary copolymers. Thus, the incorporation of a certain amount of TBA in PAN or its copolymer with BA allows tuning the temperature range of cyclization. This feature seems attractive for applications in the production of melt-spun PAN by choosing the appropriate copolymer composition and heating mode.