Depolymerization of Polyester Fibers with Dimethyl Carbonate-Aided Methanolysis.

Polyester fibers, comprising mostly poly(ethylene terephthalate) with high crystalline content, represent the most commonly produced plastic for ubiquitous textiles, and approximately 60 million tons are manufactured annually worldwide. Considering the social issues of mismanaged waste produced from used textile products, there is an urgent demand for sustainable waste polyester fiber recycling methods. We developed a low-temperature, rapid, and efficient depolymerization method for recycling polyester fibers. By utilizing methanolysis with dimethyl carbonate as a trapping agent for ethylene glycol, depolymerization of polyester fibers from textile products proceeded at 50 °C for 2 h, affording dimethyl terephthalate (DMT) in a >90% yield. This strategy allowed us to depolymerize even practical polyester textiles blended with other fibers to selectively isolate DMT in high yields. This method was also applicable for colored polyester textiles, and analytically pure DMT was isolated via depolymerization and decolorization processes.

Synthesis of Mannosylerythritol Lipid Analogues and their Self-Assembling Properties, Recovery Effects on Damaged Skin Cells, and Antibacterial Activity.

Synthesis of three types of purpose-designed mannosylerythritol lipid (MEL)-D analogues with decanoyl groups, ß-GlcEL-D, α-GlcEL-D, and α-MEL-D, was accomplished utilizing our boron-mediated aglycon delivery (BMAD) methods. Their self-assembling properties, recovery effects on damaged skin cells, and antibacterial activity were evaluated. It was revealed, for the first time, that α-GlcEL-D and α-MEL-D only generated giant vesicles, indicating that slight differences in the steric configuration of an erythritol moiety and fatty acyl chains affect the ability to form vesicles. Analogue α-MEL-D exhibited significant recovery effects on damaged skin cells. Furthermore, α-MEL-D exhibited antibacterial activity as high as that for MEL-D, indicating that α-MEL-D is a promising artificial sugar-based material candidate for enhancing the barrier function of the stratum corneum, superior to a known cosmetic ingredient, and possesses antibacterial activity.

Polyamide (PA) 66 molding defect studied with optical coherence tomography (OCT) and near-infrared (NIR) spectroscopy.

An optical coherence tomography (OCT) system combined with near-infrared spectroscopy (NIRS) was developed to carry out simultaneously the cross-sectional observation and spectral measurement of a specific area inside a polymer sample. This OCT-NIRS system consists of a fiber-optic-based spectrometer combined with an OCT system and enables non-invasive imaging up to a depth of several millimeters and the recording of the NIR spectrum in the observed area. A subsequent analysis of the collected data will provide key information revealing the way in which the microscopic structure of the polymer is affected by the chemical composition around it. A structural defect inside a molded polyamide (PA) 66 sample was examined with the OCT-NIRS system to demonstrate how this technique can be utilized to characterize chemical composition as well as the morphological features inside the sample. A specific void was detected by OCT when the PA sample was molded without any drying treatment. The NIR spectrum collected around the void area of the undried PA was then compared with that of vacuum-dried PA by two-trace two-dimensional (2T2D) correlation analysis to identify a subtle but pertinent difference in the spectral features. The appearance of several correlation peaks in the 2T2D asynchronous correlation spectrum revealed that the OH group represented by the NIR band at 1446 nm is found in relative abundance around the void, which clearly reveals that the development of the void in the molded PA results from inadequate sample pretreatment.

Self-Assembling Properties and Recovery Effects on Damaged Skin Cells of Chemically Synthesized Mannosylerythritol Lipids.

Mannosylerythritol lipids (MELs), which are one of the representative sugar-based biosurfactants (BSs) produced by microorganisms, have attracted much attention in various fields in the sustainable development goals (SDGs) era. However, they are inseparable mixtures with respect to the chain length of the fatty acids. In this study, self-assembling properties and structure-activity relationship (SAR) studies of recovery effects on damaged skin cells using chemically synthesized MELs were investigated. It was revealed, for the first time, that synthetic and homogeneous MELs exhibited significant self-assembling properties to form droplets or giant vesicles. In addition, a small difference in the length of the fatty acid chains of the MELs significantly affected their recovery effects on the damaged skin cells. MELs with medium or longer length alkyl chains exhibited much higher recovery effects than that of C18-ceramide NP.

Microstructure Investigation of Polymer Electrolyte Fuel Cell Catalyst Layers Containing Perfluorosulfonated Ionomer.

Perfluorosulfonated ionomers are the most successful ion-exchange membranes at an industrial scale. One recent, cutting-edge application of perfluorosulfonated ionomers is in polymer electrolyte fuel cells (PEFCs). In PEFCs, the ionomers are used as a component of the catalyst layer (CL) in addition to functioning as a proton-exchange membrane. In this study, the microstructures in the CLs of PEFCs were characterized by combined synchrotron X-ray scattering and transmission electron microscopy (TEM) analyses. The CL comprised a catalyst, a support, and an ionomer. Fractal dimensional analysis of the combined ultrasmall- and small-angle X-ray scattering profiles indicated that the carbon-black-supported Pt catalyst (Pt/CB) surface was covered with the ionomer in the CL. Anomalous X-ray scattering revealed that the Pt catalyst nanoparticles on the carbon surfaces were aggregated in the CLs. These findings are consistent with the ionomer/catalyst microstructures and ionomer coverage on the Pt/CB surface obtained from TEM observations.

Rheo-optical Near-infrared (NIR) Analysis of Binary Amorphous Polymer Blend Consisting of Polyvinyl Chloride (PVC) and Polymethyl Methacrylate (PMMA).

A binary amorphous polymer blend consisting of polyvinyl chloride (PVC) and polymethyl methacrylate (PMMA) was studied with a rheo-optical characterization technique based on the combination of a near-infrared (NIR) spectrometer and a tensile testing machine. In rheo-optical NIR spectroscopy, tensile deformations were applied to polymers to induce the displacement of molecular chains while being probed by NIR light. The application of this technique was extended to a partially miscible amorphous polymer blend consisting of PVC and PMMA to demonstrate how it can be utilized to detect subtle but important deformation behavior. A change in the NIR spectral feature revealed that the initial deformation of the blend induces the reorientation of the PVC chains. A part of the PMMA connected to the PVC was tagged during the PVC deformation. Further deformation of the sample eventually resulted in necking propagation to the surrounding area.

Effect of Freeze-Thaw Treatment on the Precipitation of Octyl ß-D-Galactoside Hemihydrate Crystal from the Aqueous Solution.

Cryogenic treatment, like the freeze-thaw process, has been reported to be effective in modifying the physicochemical properties of polymeric hydrogels. However, not much attention has been paid to this process in terms of the precipitation of surfactant-water systems. In this study, two effective cryogenic methodologies were successfully reported to alter the physicochemical properties of a precipitate of an octyl ß-D-galactoside (Oct-Gal)-water system. First, hyperrapid cooling (i.e., cooling at 30°C/min) was found to be an effective type of cryogenic treatment: the phase transition temperature (TK) and enthalpy at the phase transition (∆HK) between the crystal-dispersed phase and the sol (micelle) phase significantly decreased. In addition, cryogenic treatment in the presence of electrolytes, such as NaCl, NaBr, and CsCl, was effective even in the absence of the hyperrapid cooling condition. The hyperrapid cooling or the addition of certain electrolytes was considered to prevent the precipitation of the Oct-Gal hemihydrate crystals prior to the complete freezing of ice and the electrolyte/ice eutectic. Hence, the size of the aggregated crystals prepared by the above-mentioned effective cryogenic treatments seemed to be decreased compared with that of the normal precipitated crystals, thereby changing TK and ∆HK. Thus, two basic methodologies for the modification of the physicochemical properties of the crystal-dispersed phase of surfactant-water systems are discussed.

Oligosaccharide-based Surfactant/Citric Acid Buffer System Stabilizes Lactate Dehydrogenase during Freeze-drying and Storage without the Addition of Natural Sugar.

Experiments were conducted to assess the maintenance effects of oligosaccharide-based surfactants on the enzymatic activity of a model protein, lactate dehydrogenase (LDH), during freeze-drying and room temperature storage using the citric acid buffer system. Oligosaccharide-based surfactants, which exhibit a high glass transition temperature (Tg), promoted the eminent retention of enzymatic activity during these protocols, whereas monosaccharide-based surfactants with a low Tg displayed poor performance at high concentration, albeit much better than that of Tween 80 at middle concentration. The increase in the alkyl chain length did not exert positive effects as observed for the maintenance effect during freeze-thawing, but an amphiphilic nature and a glass forming ability were crucial for the effective stabilization at a low excipient concentration during freeze-drying. Even a low oligosaccharide-based surfactant content (0.1 mg mL(-1)) could maintain LDH activity during freeze-drying, but a high surfactant content (1.0 mg mL(-1)) was required to prevent buffer precipitation and retain high LDH activity on storage. Regarding storage, glass formation restricted molecular mobility in the lyophilized matrix, and LDH activity was effectively retained. The present results describe a strategy based on the glass-forming ability of surfactant-type excipients that affords a natural sugar-free formulation or an alternative use for polysorbate-type surfactants.