Synthesis of Novel Thermostable Polyamideimides from Bis(2-aminoethyl)terephthalamide and Dianhydrides

Raman spectroscopy study on terephthalamide crystal at high pressures

In this study, we have investigated the structural stability of terephthalamide (TPA) crystal at pressure from ambient to 15 GPa in the diamond anvil cell at room temperature by Raman spectroscopy. Assignment for the Raman vibration modes of TPA crystal at ambient conditions has been performed based on the density functional theory (DFT) calculations. Pressure-induced structural transition was monitored using in-situ Raman spectroscopy. Remarkable changes (including the appearance of new Raman peaks, disappearance of original Raman bands, discontinuous changes in the pressure dependence of some Raman wavenumbers at different pressures) in Raman spectra were observed at approximately 1.3 and 5.2 GPa, provided clear evidences for two pressure-induced phase transitions: phase I to phase II at ∼1.3 GPa, phase II to phase III at ∼5.2 GPa.

Acidolysis of Poly(ethylene terephthalate) Waste Using Succinic Acid under Microwave Irradiation as a New Chemical Upcycling Method

A novel method of chemical upcycling of used poly(ethylene terephthalate) (PET) bottles by acidolysis with succinic acid (SA) was performed under microwave irradiation. The long polyester chain of PET was efficiently fragmented into small molecules and oligomers, such as terephthalic acid and α,ω-dicarboxylic acid oligo(ethylene succinate-co-terephthalate) (OEST). Various input molar ratios of SA/PET from 1.0 to 2.5 were used, and the product mixtures were separated successfully. The recovered terephthalic acid can be reused as a basic chemical. The α,ω-dicarboxylic acid OEST was used as a curing agent for epoxy resin. The recovered SA can be reused for further PET acidolysis. Structures of OEST were identified by Fourier transform infrared (FTIR) spectroscopy, ¹H NMR spectroscopy, and electrospray ionization-mass spectrometry (ESI-MS). The presence of succinic anhydride as a side product was confirmed by FTIR and ESI-MS analyses. The evaporation of SA and the formation of volatile succinic anhydride compete with the acidolysis of PET. The minimum SA/PET ratio of 1.0 was selected so that the acidolysis was effective and without the SA recovery step by MEK treatment. OEST-1.0 was used for curing diglycidyl ether of bisphenol A. The structures and thermal properties of cured adducts were confirmed by FTIR and differential scanning calorimetry (DSC). This chemical upcycling method of PET is eco-friendly without the use of a solvent and a catalyst for the reaction, and all materials were recovered and they could be reused for novel polymer preparation.

Molecular mechanisms of the antibacterial activity of polyimide fibers in a skin-wound model with Gram-positive and Gram-negative bacterial infection in vivo

Recently, the need for antibacterial dressings has amplified because of the increase of traumatic injuries. However, there is still a lack of ideal, natural antibacterial dressings that show an efficient antibacterial property with no toxicity. Polyimide (PI) used as an implantable and flexible material has been recently reported as a mixture of particles showing more desirable antibacterial properties. However, we have identified a novel type of natural polyimide (PI) fiber that revealed antibacterial properties by itself for the first time. The PI fiber material is mainly composed of C, N, and O, and contains a small amount of Ca and Cl; the characteristic peaks of polyimide appear at 1774 cm-1, 1713 cm-1, 1370 cm-1, 1087 cm-1, and 722 cm-1. PI fibers displayed significant antibacterial activities against Escherichia coli (as a Gram-negative bacteria model) and methicillin-resistant Staphylococcus aureus (MRSA, as a Gram-positive bacteria model) according to the time-kill kinetics in vitro, and PI fibers damaged both bacterial cell walls directly. PI fibers efficiently ameliorated a local infection in vivo, inhibited the bacterial burden, decreased infiltrating macrophages, and accelerated wound healing in an E. coli- or MRSA-infected wound model. In conclusion, PI fibers used in the present study may act as potent antibacterial dressings protecting from MRSA or E. coli infections and as promising candidates for antimicrobial materials for trauma and surgical applications.

From Waste to Schiff Base: Upcycling of Aminolysed Poly(ethylene terephthalate) Product

Recycling plastic waste into valuable materials is one of the contemporary challenges. Every year around 50 million tons of polyethylene terephthalate (PET) bottles are used worldwide. The fact that only a part of this amount is being recycled is putting a burden on the environment. Therefore, a technology that can convert PET-based waste materials into useful ones is highly needed. In the present work, attempts have been made to convert PET-based waste materials into a precursor for others. We report an aminolysed product (3) obtained by aminolysis reaction of PET (1) with 1,2 diaminopropane (DAP, 2) under solvent and catalytic free conditions. The highest amount of monomeric product was obtained upon heating the mixture of diamine and PET at 130 °C. The resulting aminolysed product was then converted to a Schiff-base (5) in 25% yield. The chemical structure of the synthesized compounds was confirmed using multi-spectroscopic techniques. The results of this study will be a valuable addition to the growing body of work on plastic recycling.