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The conversion of biobased fatty acids and waste cooking oil (WCO) into chemically recyclable polyesters provides a promising strategy for designing sustainable polyethylene-like materials. We use coarse-grained modeling to elucidate how branching architecture influences crystallization and melting in polyesters composed of WCO-derived branching diols, linear diols, and diesters. We identify the effects of branching on crystallization and melting temperatures and ordering of both the backbone and the side chains during cooling. We quantify the disruption in backbone ordering due to increasing branching content and ordering of the longer side chains. We find that branching content modulates the net effect of the branch length. At lower branching content the backbone ordering dominates, yielding similar behavior for different branch lengths, while at higher branching content, polyesters with longer branches exhibit higher crystallinity and increased melting and crystallization temperatures. These results provide a predictive framework for designing sustainable polyesters with tunable crystallization behavior. 

Saturated fatty acids (SFAs) are abundant resources from both nature and waste streams (i.e., waste cooking oil (WCO)). However, it remains a significant challenge for transformation into difunctional derivatives as useful monomers. Here we report a formaldehyde-mediated strategy to upcycle saturated fatty methyl esters (sat-FAMEs) into 1,n-diester monomers. This two-step process involves (i) formaldehyde-enabled α-methylenation via aldol condensation and (ii) Pd-catalyzed distal alkoxycarbonylation via a chain-walking mechanism. Demonstrated on C16, C18 esters and WCO-derived mixtures, the strategy yields highly pure α-methyl diester monomers, which can be polymerized into high-molecular-weight polyesters that largely mimic low-density polyethylene in mechanical properties. The materials exhibit exceptional extensibility (340-930%) and yield stress (7-10 MPa). This approach enables valorization of fatty acids into fully recyclable high-performance materials. 

The growing burden of plastics on the environment represents an urgent global challenge. We report a robust strategy to convert waste cooking oil (WCO), an abundant biomass waste, into chemically recyclable polyesters that mimic polyethylene in performance but offer degradability and excellent adhesion. Through catalytical transformation, both the fatty acid and glycerol components of WCO are valorized into monomers, which are then polymerized into long-chain linear and branched aliphatic polyesters with tunable crystallinity and mechanical properties. These materials, especially branched polyesters with long aliphatic side chains, rival low-density polyethylene (LDPE) in flexibility and strength and notably outperform commercial adhesives in shear strength by creating robust yet temporary bonds with multiple substrates, offering safety, ease of handling, and removability. These mimics can be depolymerized and repolymerized under mild conditions, even in mixed plastic streams. Simulations and experiments reveal that the strikingly increased crystallinity in polyesters with longer side chains is driven by side-chain alignment, offering new molecular insights for materials design. This work illustrates a powerful waste-to-materials approach that aligns with circular economy principles and elevates the potential of biomass in sustainable plastics’ innovation. 

Incorporating degradable linkages into polyolefin backbones offers a promising route toward sustainable alternatives. For semicrystalline degradable polyolefins, understanding the impact of such linkages on their crystallization behaviors is important, since the crystallization process governs their morphology formation and thus dictates mechanical and thermal performance. Here, we studied the crystallization behaviors of degradable polyethylene (PE) mimics containing sparsely inserted ester linkages along the polymer backbone, which exhibit comparable mechanical and thermal properties to conventional PE. Two systems, HDPE-DM and LLDPE-DM, were investigated and compared with their commercial, non-degradable counterparts under isothermal and non-isothermal conditions. We found that ester incorporation does not alter the thermodynamics of the perfect crystal. However, relative to the non-degradable PE mimics (HDPE-M), the presence of ester linkages accelerates crystallization kinetics by reducing the overall crystallization activation energy and promoting chain folding. The crystallization activation energy of HDPE-DM was comparable to that of commercial HDPE, indicating that ester linkages can be introduced in polymer backbones without significantly impacting their crystallization behaviors and thus relevant industrial manufacturing processes. These findings provide new insights into how degradable linkages influence crystallization in degradable PE materials, which may inform the design and process of sustainable polyolefin materials with a balanced performance and recyclability. 

Poly(lactic acid) (PLA) offers a renewable and degradable alternative to petroleum-based plastic, but its mechanical properties are not ideal for many applications. Herein, we describe the synthesis and polymerization of oxo-3,8-dioxabicyclo[3.2.1]octane (ODO), a bio-derived bicyclic lactone, and show that copolymers of L-lactide (LA) with small amounts of ODO have improved mechanical properties over PLA. Homopolymerization of ODO to poly(oxo-3,8-dioxabicyclo[3.2.1]octane) (PODO) is optimized for both solution-phase, organocatalytic and melt-phase, metal-catalyzed conditions. In comparison to the monocyclic analog, ε-caprolactone (CL), ODO has a lower enthalpy of polymerization and faster rate of polymerization. PODO is an amorphous, elastomeric polyester that has a 90 °C higher Tg than poly(ε-caprolactone) (PCL). Statistical copolymerization of LA with small fractions of ODO yields tough and transparent thermoplastics that have over 12× elongation at break compared to native PLA, while maintaining Tg, Young’s modulus (E), and yield strength. Together, these results describe how the incorporation of the tetrahydrofuran ring alters polymerizability and the thermomechanical properties of the homopolymer and copolymer materials.