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Initiating depolymerization at ambient temperature by nonthermal air plasma provides a novel and promising route to convert polymer wastes to valuable small molecules. This study showed that the selectivity of partial oxidation of polyvinyl alcohol (PVA) initiated by nonthermal air plasma can be controlled by the polymer to TiO2 ratio and AC (alternative current) voltage and frequency. Transient responses to applying AC (alternating current) power showed that the CO2 led to the formation of CO, propionaldehyde, and acetaldehyde. Significant formation of propionaldehyde showed that -C-OH in PVA can be directly converted to CH3 in propionaldehyde, unraveling a new reaction pathway in nonthermal plasma chemistry. The selectivity of aldehydes is at the same level as that of CO2. The selectivity of aldehydes was further enhanced by nitrogen plasma while the selectivity toward CO2 was increased in the presence of TiO2. This study demonstrated that ambient nonthermal air plasma could provide a potentially effective approach for the selective conversion of polymers to desired small molecules. 

Solid-state nuclear magnetic resonance (ssNMR) has been playing an indispensable role in revealing the interplay of structure and molecular dynamics in polymers at different states. In this Perspective, we first provide an overview about the fundamental spin interactions in ssNMR and then highlight some recent progress on sensitivity-enhanced ssNMR spectroscopy and in situ NMR. Moreover, we highlight ssNMR applications in the field of polymer crystallization, molecular dynamics, chemical reactions, supramolecular polymers, energy materials, and so on. Finally, our personal perspective is given on the future development at the crossroad of ssNMR and polymer science. 

In the earlier theoretical research, impact of entanglement on folding during crystallization was minimized. The combination of 13C isotope labeling and NMR spectroscopy allows us to quantitatively determine stem to stem distance as well as chain folding distance, hence, we are able to probe chain-level structure. Our recent work indicated that polymer chains are possible to fold prior to crystallization. In this poster, we would like to investigate the folding structure of a semi-crystalline polymer in melt-grown crystals (mgc) by using solid-state NMR spectroscopy and SAXS measurement. First, various 13C enriched poly(L-lactic acid) (PLLA) samples with different molecular weights (Mw = 2.5k – 300k g/mol) across critical entanglement length (Mc = 16k g/mol) were prepared in order to observe the molecular weight dependence of folding structure of PLLA. We revealed that entanglements influence the folding number during crystallization. Second, we attempt to observe the entanglement effect through diluting entanglement density, i.e., blending the PLLA above and below the Mc with different ratio and molecular weight. Based on the experimental results, we would like to highlight the impact of entanglements on folding of semicrystalline polymer in the melt-grown crystal. 

Highly branched polyethylene (PE) thermoplastic elastomer (TPE)s can be synthesized using Brookhart-type α-diimine nickel and palladium catalysts, which show a range of branching number and identity. In this work, we aim at elucidating the structure-property relationship of various PE-TPEs through solution-state and solid-state 13C NMR spectroscopy and mechanical tensile testing. By applying solid-state NMR spectroscopy, DSC, and XRD, it was revealed that small degrees of crystallinity (< 5%) yields polyethylenes that are sufficiently reinforced to exhibit TPE behavior. Across PE samples with similar branching numbers, we relate the effects of branch identity, crystallinity, and molecular weight on the tunable mechanical properties. The structure-property relationship of the PE-TPEs will be discussed. 

Recycling different plastics post-consumers causes downgraded performance due to the physical and chemical property differences conflicting with one another. These properties stem from the incompatibility of the blends to crystallize and blend. As there are millions of tons of waste every year, the ability to effectively blend two plastics such as polyethylene and polypropylene becomes crucial. In this poster, a molecular-level study of polyolefin blend co-crystallization will be explored by utilizing solid-state NMR spectroscopy. It is through NMR spectroscopic techniques and the use of selectively activating various parts of the blend through isotopes that aspects of the arrangement can be made. We will conduct studies into the co-crystallization of the blends utilizing deuterated polymers to access the chain-to-chain interface differences. This will give us the ability to see the relative extent of interaction as well as providing overall system kinetics. From these experiments, a diagram of the co-crystallization structure can be made as well as a defined system to analyze crystallization 

Abstract The evergrowing plastic production and the caused concerns of plastic waste accumulation have stimulated the need for waste plastic chemical recycling/valorization. Current methods suffer from harsh reaction conditions and long reaction time. Herein we demonstrate a non-thermal plasma-assisted method for rapid hydrogenolysis of polystyrene (PS) at ambient temperature and atmospheric pressure, generating high yield (>40 wt%) of C₁–C₃hydrocarbons and ethylene being the dominant gas product (Selectivity of ethylene,S_C2H4 > 70%) within ~10 min. The fast reaction kinetics is attributed to highly active hydrogen plasma, which can effectively break bonds in polymer and initiate hydrogenolysis under mild condition. Efficient hydrogenolysis of post-consumer PS materials using this method is also demonstrated, suggesting a promising approach for fast retrieval of small molecular hydrocarbon modules from plastic materials as well as a good capability to process waste plastics in complicated conditions.