Jie Huan

Bio: Jie Huan is an academic researcher from Soochow University (Suzhou). The author has contributed to research in topics: Adipate & Polymer. The author has an hindex of 1, co-authored 1 publications receiving 3 citations.

The Effect of Trifluoroacetic Acid on Molecular Weight Determination of Polyesters: An in Situ NMR Investigation

Abstract: Due to the poor solubility of aromatic polyesters in common organic solvents, trifluoroacetic acid is usually used as a co-solvent to increase their solubility for characterizations. However, only few works have reported the side reactions induced by it. We present here the application of in situ 1H-NMR techniques to explore its effect on the hydroxyl end-groups, which are usually used for the molecular weight determination of polyesters by end-group estimation method. Using bis(2-hydroxyethyl) terephthalate (BHET) as model compound, 1H quantitative NMR results show the peak integration of hydroxyethyl end-groups decreased with time via a pseudo-first-order kinetics in d-trifluoroacetic acid/d-chloroform mixture solvent (1:10, V:V). This is due to the esterification of hydroxyethyl groups with trifluoroacetic acid, revealed by the 1H-13C gradient-enhanced heteronuclear multiple bond correlation (gHMBC) spectrum. The mixtures of dimethyl terephthalate and BHET with different molar ratio were used to represent poly(ethylene terephthalate) (PET) with different degree of polymerization, and the effect of trifluoroacetic acid on the estimation of hydroxyethyl groups and subsequent molecular weight determination of polyesters was studied. Our results show that if a relative error of 5% is allowed, the NMR measurements must be finished within 1.3 h of solution preparation at 25 °C in the mixture solvent. The results were confirmed in PET sample, while in poly(ethylene adipate), the obtained esterifaction constant is faster that those in aromatic system. The results can be applied to other polymer systems with alcohol functionalized groups, and used as a guideline for the characterization of polyesters and polyethers by end-group estimation method.

Valorization of Polyethylene Terephthalate (PET) Plastic Wastes as Nanofibrous Membranes for Oil Removal: Sustainable Solution for Plastic Waste and Oil Pollution

Abstract: The accumulation of plastic wastes has become a global environmental issue, because of their ever-growing production, slow degradation, and potential environmental hazards. Consequently, reducing their presence in the environment by upcycling has sparked tremendous research interest. Herein, we report the valorization of poly(ethylene terephthalate) (PET) plastic wastes to produce nanofibrous adsorptive membranes for their applications in oil removal. In this study, plastic wastes derived from PET bottles were dissolved in trifluoroacetic acid (TFA) or a TFA/dichloromethane (DCM) binary solvent system and then electrospun into nanofibrous recycled PET (rPET) membranes. The nanofiber morphology was tuned by adjusting the polymer concentration. The nanofibers produced via electrospinning from TFA solutions were more uniform than those produced using TFA/DCM. The influence of acid-mediated recycling on the PET structure was explored via thermogravimetric and X-ray photoelectron spectroscopy analyses. A dynamic mechanical analysis showed that the membranes exhibited high flexibility with effective Young’s moduli. The sorption capacities of the nanofibrous PET membranes for crude oil, diesel, gasoline, and pump oil were 22.9 ± 2, 19.6 ± 1.8, 11.1 ± 1, and 19.3 ± 1.6 g g–1, respectively. The membrane could be recycled by squeezing and reused five times for oil removal while maintaining an sorption capacity of >75%. After the sorption tests, an apparent increase in the fiber diameter was observed due to the oil uptake into the fiber matrix. The present study provides a sustainable solution to plastic and oil pollution management, minimizing the production of new carbon-based materials and lowering carbon emissions. This work aligns with the United Nations’ Sustainable Development Goals, specifically, Goal #12 on responsible consumption and production and #14 on life below water.