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Carbon dioxide (CO2) has long been recognized as an ideal C1 feedstock comonomer for producing sustainable materials because it is renewable, abundant, and cost-effective. However, activating CO2 presents a significant challenge because it is highly oxidized and stable. A CO2/butadiene-derived δ-valerolactone (EVP), generated via palladium-catalyzed telomerization between CO2 and butadiene, has emerged as an attractive intermediate for producing sustainable copolymers from CO2 and butadiene. Owing to the presence of two active carbon–carbon double bonds and a lactone unit, EVP serves as a versatile intermediate for creating sustainable copolymers with a CO2 content of up to 29 wt % (33 mol %). In this Review, advances in the synthesis of copolymers from CO2 and butadiene with divergent structures through various polymerization protocols have been summarized. Achievements made in homo- and copolymerization of EVP or its derivatives are comprehensively reviewed, while the postmodification of the obtained copolymers to access new polymers are also discussed. Meanwhile, potential applications of the obtained copolymers are also discussed. The literature references were sorted into sections based on polymerization strategies and mechanisms, facilitating readers in gaining a comprehensive view of the present chemistry landscape and inspiring innovative approaches to synthesizing novel CO2-derived copolymers. 

ABSTRACT This work investigated the effect of isophthalate (iso) content in poly(ethylene terephthalate) (PET) materials on its degree of crystallinity (χ%) and mechanical properties. Melt blends were prepared from virgin (0 iso-wt.%) and bottle-grade (1.7 iso-wt.%) PET and subsequently spun into fibers. The mechanical and crystallinity properties were determined using differential scanning calorimetry (DSC), X-ray diffraction (XRD), and uniaxial tensile testing. The crystallinity results determined from DSC and XRD quantified the relationship between iso-content and χ% in the materials. It was found that melt-mixing of different isophthalate grades had a lesser effect on melting temperature (Tm) and χ% than chemically recycled random copolymers of terephthalate and isophthalate. It was further shown that random copolymers of <0.25 iso-wt.% had comparable crystallinity to the virgin high-modulus low-shrink (HMLS) materials. 

We report the design and synthesis of an α-diimine PdII catalyst that copolymerizes functionalized and long chain α-olefins to produce semicrystalline polyethylene materials. Through a chain-straightening polymerization mechanism, the catalyst afforded high-melting point polymers with Tm values of up to 120 °C. The chain-straightening polymerization operates with high [ω,1]-insertion selectivity at high alkene concentrations and with varying α-olefin chain lengths, including propylene. The Pd catalyst can copolymerize 1-decene and methyl decenoate into semicrystalline ester-functionalized polymers with incorporation percentages proportional to the comonomer ratio (up to 13 mol %). 13C nuclear magnetic resonance and isotope labeling studies revealed that the improved selectivity relative to those of other systems arises from a high selectivity for [2,1]-insertion (96%) coupled with rapid chain-walking for a total of 90 mol % of 1-decene undergoing net [10,1]-insertion. 

Stereoregularity significantly influences the crystallization, mechanical, and thermal properties of polymers. In this work, we investigate crystallization behaviors and molecular dynamics of atactic (a)-, isotactic (i)-, and syndiotactic (s)-hydrogenated poly(norbornene) (hPNB)s by using small-angle X-ray scattering and solid-state (ss) NMR. a-hPNB exhibits a much higher crystallinity (Φc) (82%) and long period (L) (80 nm) than i- and s-hPNB (50–55% and 17–21 nm). Moreover, in the s-hPNB crystalline region, chain dynamics is not thermally activated up to the melting temperature (Tm), while in the crystalline regions of i- and a-hPNB, small amplitude motions occur in a slow dynamic regime of 10–2–102 s. The molecular dynamics follows Arrhenius behavior in a-hPNB up to the crystal–crystal transition temperature (Tcc), while these dynamics are surprisingly saturated in i-hPNB under these conditions. Temperature dependence of the molecular dynamics leads to different crystal–crystal transitions between i- and a-hPNBs: i-hPNB changes the trans conformation to the gauche one due to the localized bond rotations where chain dynamics is restricted, whereas a-hPNB keeps a nearly trans conformation and conducts fast chain dynamics due to the amplified C–C bond rotations in the high-temperature phase. Such fast chain dynamics leads to unique crystallization behaviors of hPNB, specifically in the atactic configuration due to configurational disorder coupled with conformational flexibility.