Polymorphism and Stretch-Induced Transformations of Sustainable Polyethylene-Like Materials

Abstract

Herein we demonstrate that polyethylene-like bioderived, biodegradable, and fully recyclable unbranched aliphatic polyesters, such as PE-2,18, develop hexagonal crystal structures upon quenching from the melt to temperatures <∼50 °C and orthorhombic-like packing at higher quenching temperatures or after isothermal crystallization. Both crystal types are layered. While all-trans CH 2 packing characterizes the structure of the orthorhombiclike form, there is significant conformational disorder in the staggered long CH 2 sequences of the hexagonal crystals. On heating, the hexagonal crystals transform to the orthorhombic type at ∼60 °C via melt recrystallization, but no change is apparent during heating samples with the orthorhombic form up to the melting point (∼95 °C). The hexagonal structure is of interest not only because it develops under very rapid quenching from the melt but also because under uniaxial tensile deformation it undergoes a stretch-induced transformation to the orthorhombic structure. Compared to deformation of orthorhombic specimens that maintain the same crystal type, such transformation results in larger strains and enhanced strain hardening, thus representing a desired toughening mechanism for this type of polyethylene-like materials.

Synthesis, Characterization, and Application of High-Molecular-Weight Polyethylene-like Polycarbonates: Toward Sustainable and Recyclable Fibers

“…Introducing low densities of cleavage groups into PE chains to make PE-like polymers can endow them with degradability and recyclability while maintaining thermal and mechanical properties. , Ester, acetal, and carbonate functionalities have been successfully incorporated into the PE backbone via ring-opening polymerization of macrocyclic lactones, − acyclic diene metathesis of dienes or ring-opening metathesis polymerization of cyclic olefins, , and polycondensation of classical A 2 and B 2 monomers (Figure a). , Among these polymerization techniques, polycondensation presents an elegant strategy due to its abundant commercially available and affordable monomers, which grants easy access to tuning polymeric structures and the corresponding properties. , By employing long-chain α,ω-diols derived from vegetable oil derivatives, − Mecking and co-workers prepared corresponding long-chain PE-like polyesters, polyacetals, and polycarbonates with M n over 10 4 g/mol . The long-chain polycarbonates and polyester possess PE-like solid-state structures and, therefore, present good mechanical properties, holding great potential for further applications.…”