1,721,054 research outputs found
고분자의 유리 전이 온도 측정 방법 및 유리 전이 온도 측정 장치
No full textProvided are a method of and a device for measuring a glass transition temperature and a degree of crystallinity of a polymer. According to the measurement method and the device of one exemplary embodiment of the present invention, a glass transition temperature and a degree of crystallinity may be measured easily, rapidly, and accurately in a field other than a laboratory, and fast and accurate conversion is possible for various measurement conditions such as temperature, frequency, etc
Tailored mechanical properties of soybean oil-based non-isocyanate polyurethanes by copolymer integration
No full textStiff thermoset polyurethane (PU) plays a crucial role in high-performance applications, particularly in industries requiring exceptional mechanical integrity, chemical resistance, and thermal stability. To reduce the environmental impact of PU production, (i) soybean oil has emerged as a renewable and abundant alternative to petroleum-based feedstocks, offering biodegradability and a reduced carbon footprint, while (ii) non-isocyanate polyurethane (NIPU) provides a greener approach by eliminating hazardous isocyanate compounds and avoiding isocyanate-functionalized chemicals. However, the development of soybean oil-based NIPU faces challenges in achieving the desired stiffness and resistance against fracture due to the large molecular size and inconsistent structure of soybean oil, which result in low crosslinking density and a lack of short-range ordering. To address the limitations of soybean oil-based NIPU, we developed a method that restricts polymer network relaxation by incorporating short-range ordered polymer segments using a copolymer with ethyl methacrylate (EMA) segments. Surpassing the highest mechanical properties reported for soybean oil-based NIPU to date, co-NIPU-x derived from copolymers with higher EMA content exhibits improved mechanical properties, demonstrating a four-fold increase in Young's modulus and a two-fold increase in tensile stress. The adjustable poly(2-aminoethylmethacrylate-ran-ethylmethacryate) (poly(AEMA-ran-EMA)) composition ratio allows for a wide range of mechanical properties, with Young's modulus ranging from 60 to 1030 MPa and tensile stress from 2.1 to 25 MPa. Furthermore, these NIPU samples exhibited enhanced adhesion properties with lap shear strength exceeding 7 MPa, significantly higher than those of traditional formulations. The thermal stability was improved with the NIPU samples resisting structural degradation, and chemical resistance was confirmed by sufficient swelling ratios in both hydrophilic and hydrophobic solvents, underscoring their suitability for a broader range of industrial applications.
Sphingomyelinase‐Mediated Multitimescale Clustering of Ganglioside GM1 in Heterogeneous Lipid Membranes
No full textAbstract Several signaling processes in the plasma membrane are intensified by ceramides that are formed by sphingomyelinase‐mediated hydrolysis of sphingomyelin. These ceramides trigger clustering of signaling‐related biomolecules, but how they concentrate such biomolecules remains unclear. Here, the spatiotemporal localization of ganglioside GM1, a glycolipid receptor involved in signaling, during sphingomyelinase‐mediated hydrolysis is described. Real‐time visualization of the dynamic remodeling of the heterogeneous lipid membrane that occurs due to sphingomyelinase action is used to examine GM1 clustering, and unexpectedly, it is found that it is more complex than previously thought. Specifically, lipid membranes generate two distinct types of condensed GM1: 1) rapidly formed but short‐lived GM1 clusters that are formed in ceramide‐rich domains nucleated from the liquid‐disordered phase; and 2) late‐onset yet long‐lasting, high‐density GM1 clusters that are formed in the liquid‐ordered phase. These findings suggest that multiple pathways exist in a plasma membrane to synergistically facilitate the rapid amplification and persistence of signals
Interfacial shear rheology of perfluorosulfonic acid ionomer monolayers at the air/water interface
No full textWe report a systematic rheological analysis of perfluorosulfonic acid (PFSA) ionomer monolayers at the air/water interface. Equipped with a custom-designed double wall knife-edge interfacial rheometer, we measure both the linear and nonlinear viscoelasticity of various PFSA ionomer monolayers. Based on rheological measurements along with other static measurements, we find that the rheological properties of the PFSA ionomer monolayers mainly originate from the electrostatic interaction of negatively charged groups (SO3−) rather than direct interactions between backbones, as is typical of other polymeric monolayers. Although the rheological properties mainly come from the SO3− groups, equivalent weight (EW) and length of the side chain affect the rheological properties as well: (1) surface activity increases with EW, thereby a larger EW tends to have stiffer interfaces; (2) PFSA ionomer with longer side chains also has larger shear moduli at the same surface pressure (Π), presumably because the longer side chain has larger configurational entropy, thus leading to better closed packing. Moreover, it is found from Π dependent measurements that both the elastic and viscous moduli exhibit unusually weak dependence on Π compared with typical polymeric and surfactant monolayers. The weak Π dependence can be explained in terms of charged colloids with long-range repulsive interactions, as they are susceptible to shear stress but resistive to compressional stress. This rheology of ionomers and their underlying morphology at the interface are expected to provide useful information for various membrane applications where ultrathin membranes can be helpful, such as ion exchange membranes and fuel cell/flow battery membranes.
Catalytic co-pyrolysis of keyboard plastic and sawdust toward petrochemical-grade hydrocarbons over niobium-loaded zeolite catalyst
No full textThis study examines for the first-time the in-situ co-pyrolysis of e-waste plastic, keyboards (KB) and sawdust (SD) in different blending ratios (2/1, 1/1, and 1/2) using a tandem microreactor-gas chromatography/mass spectrometry system at 600 degrees C. The blend with SD/KB = 2/1 exhibited a positive synergistic effect in the fractionation of the components and production of valuable aromatics, such as benzene, toluene, ethylbenzene, xylene (BTEX), with a significant lowering of oxygenates. For the catalytic co-pyrolysis, H beta(25) exhibited prominent results toward the BTEX production compared to HZSM-5(30) and H beta(38). Among the metal-loaded (Nb, Zn, and Fe) H beta(25), the maximum amount of BTEX was determined over Nb/H beta(25) with catalyst/feedstock = 3/1. The results of the ex-situ micropyrolyzer configuration highlighted the prominent significance of the in-situ mode toward the activation in breaking the KB polymeric structure. Moreover, the lab-scale co-pyrolysis results exhibited a maximum positive synergistic effect (21.54 %) in the quantified yield of BTEX over the Nb/H beta(25) catalyst. Furthermore, the Nb/H beta(25) catalyst was also subjected to the three lab-scale catalytic co-pyrolysis cycles to evaluate its structural stability and durability.
One-step Synthesis of Viscoelasticity Controlled Ultrathin Film PSA via initiated Chemical Vapor Deposition
No full textControllable one-step double emulsion formation <i>via</i> phase inversion
No full textWe propose a simple yet universal/controllable strategy to form double emulsions by phase inversion.</p
Processable, reversible, and reusable 100 % bio-based pressure sensitive adhesives using nanostarch
No full textWe developed a 100 % bio-based pressure sensitive adhesive (PSA) possessing strong adhesion, as well as reusability, recyclability, and on-demand removability. The adhesive formulation is based on a colloidal mixture of starch (specifically amylopectin) nanoparticles and cellulose nanofibrils, combined with an aqueous solution of sorbitol and glycerol. Optimization of water supply and substitution of water with hygroscopic glycerol were implemented to address the challenges caused by the use of high water contents in hydrogels. By leveraging physical crosslinking through hydrogen bonding, we achieved high adhesion strength, reversibility, and reusability with 100 % bio-based materials. The optimal formulation demonstrates excellent rheological and adhesion properties, which are comparable to petrochemical-based adhesives in terms of tack, peel strength, and shear strength. While there are areas for further optimization, this work provides a foundational step towards a more sustainable adhesive industry.
Structural Determinants of Chirally Selective Transport of Amino Acids through the α-Hemolysin Protein Nanopores of Free-Standing Planar Lipid Membranes
No full textDespite the importance of the enantioselective transport of amino acids through transmembrane protein nanopores from fundamental and practical perspectives, little has been explored to date. Here, we study the transport of amino acids through alpha-hemolysin (alpha HL) protein pores incorporated into a free-standing lipid membrane. By measuring the transport of 13 different amino acids through the alpha HL pores, we discover that the molecular size of the amino acids and their capability to form hydrogen bonds with the pore surface determine the chiral selectivity. Molecular dynamics simulations corroborate our findings by revealing the enantioselective molecular-level interactions between the amino acid enantiomers and the alpha HL pore. Our work is the first to present the determinants for chiral selectivity using alpha HL protein as a molecular filter.
P‐132: A Sticky, Thermo‐curable Nano‐Adhesive for Future Flexible Display Applications: Ultrathin, Soft, and Fast‐acting
No full textWe suggest a thermally curable, “sticky” nano-adhesive for future flexible display applications. Due to the low glass transition temperature (Tg), nano-adhesive is readily attachable to various substrates. The adhesive was thermos-curable via an ionic cross-linking reaction within 5 min at 120 ℃. The thickness of the nano-adhesive can be reduced down to 50 nm and formed a uniform, conformal adhesion in a large area
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