Circular olefin copolymers made de novo from ethylene and α-olefins.

Ethylene/α-olefin copolymers are produced in huge scale and widely used, but their after-use disposal has caused plastic pollution problems. Their chemical inertness made chemical re/upcycling difficult. Ideally, PE materials should be made de novo to have a circular closed-loop lifecycle. However, synthesis of circular ethylene/α-olefin copolymers, including high-volume, linear low-density PE as well as high-value olefin elastomers and block copolymers, presents a particular challenge due to difficulties in introducing branches while simultaneously installing chemical recyclability and directly using industrial ethylene and α-olefin feedstocks. Here we show that coupling of industrial coordination copolymerization of ethylene and α-olefins with a designed functionalized chain-transfer agent, followed by modular assembly of the resulting AB telechelic polyolefin building blocks by polycondensation, affords a series of ester-linked PE-based copolymers. These new materials not only retain thermomechanical properties of PE-based materials but also exhibit full chemical circularity via simple transesterification and markedly enhanced adhesion to polar surfaces.

Controlling crystal polymorphism of isotactic poly(1-butene) by incorporating long chain branches.

Isotactic poly(1-butene) (iPB-1) is a high performance plastic with outstanding properties, such as flexibility, superior creep, environmental stress cracking and abrasive resistance. However, it exhibits a complex crystal polymorphism and polymorphic transformation behavior, which has limited its commercial development. In this paper, the incorporation of long chain branches (LCBs) causes coil contraction in the melt, which favors the direct melt-crystallization of form III that was generally crystallized from solutions and made of unconventional highly twined lamellae. Consequently, low-to-moderately branched iPB-1 samples as-crystallize from the melt into mixtures of form II and form III by compression-molding and fast cooling of the melt to room temperature, and the fraction of crystals of form III (fIII) increases with increasing concentration of LCBs, whereas highly branched samples can as-crystallize into pure form III with uniform crystal size distribution. The corresponding thermomechanical properties can be modified by controlling fIII.