Preventing the Collapse Behavior of Polyurethane Foams with the Addition of Cellulose Nanofiber.

Polyurethane foam manufacturing depends on its materials and processes. A polyol that contains primary alcohol is very reactive with isocyanate. Sometimes, this may cause unexpected problems. In this study, a semi-rigid polyurethane foam was fabricated; however, its collapse occurred. The cellulose nanofiber was fabricated to solve this problem, and a weight ratio of 0.25, 0.5, 1, and 3% (based on total parts per weight of polyols) of the nanofiber was added to the polyurethane foams. The effect of the cellulose nanofiber on the polyurethane foams' rheological, chemical, morphological, thermal, and anti-collapse performances was analyzed. The rheological analysis showed that 3 wt% of the cellulose nanofiber was unsuitable because of the aggregation of the filler. It was observed that the addition of the cellulose nanofiber showed the improved hydrogen bonding of the urethane linkage, even if it was not chemically reacted with the isocyanate groups. Moreover, due to the nucleating effect of the cellulose nanofiber, the average cell area of the produced foams decreased according to the amount of the cellulose nanofiber present, and the average cell area especially was reduced about five times when it contained 1 wt% more of the cellulose nanofiber than the neat foam. Although the thermal stability declined slightly, the glass transition temperature shifted from 25.8 °C to 37.6, 38.2, and 40.1 °C by when the cellulose nanofiber increased. Furthermore, the shrinkage ratio after 14 days from the foaming (%shrinkage) of the polyurethane foams decreased 15.4 times for the 1 wt% cellulose nanofiber polyurethane composite.

Electrochemical Properties According to the Particle Size Effect of Poly(ethylene oxide)-Poly(propylene oxide)-Poly(ethylene oxide) Triblock Copolymer Electrolyte.

The electrolyte of lithium secondary batteries is an important component. Among lithium secondary batteries, the lithium polymer battery, which has similar performance to the lithium secondary battery, is made of a solid polymer electrolyte. Lithium ions in a solid polymer electrolyte exist in the form of a solution by a polar group in a polymer matrix. Lithium ions in the solid polymer electrolyte migrate via the segmental motion of the polymer. That is, the properties of a polymer matrix in a solid polymer electrolyte can affect the conduction of lithium ions. Therefore, this study focused on the electrochemical properties of poly(ethylene oxide)-block-poly(propylene oxide)-blockpoly( ethylene oxide) copolymer-based solid polymer electrolyte. For this, poly(ethylene oxide)-blockpoly( propylene oxide)-block-poly(ethylene oxide) copolymer-based solid polymer electrolytes, which have spherical micelles, and various sizes of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) copolymer micelle, were prepared. Amino acids were added to the poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) copolymer-based solid polymer electrolyte as an ion dissociator to assist in the dissociation of a lithium salt and increase the ionic conductivity of the solid polymer electrolyte. The copolymer-based solid polymer electrolytes was characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, impedance analysis, cyclic voltammetry, and linear sweep voltammetry.

Folic Acid-Polyethyleneimine Functionalized Mesoporous Silica Nanoparticles as a Controlled Release Nanocarrier.

In an effort to develop a biocompatible, cancer-targetable, controllable carrier for use in smart delivery systems, including drug delivery, this study designed a novel polymer-mesoporous silica nanoparticle hybrid material functionalized with dicarboxylic acid-modified MCM-41 (DA-MCM41) and branched polyethylenimine (PEI). First, mesoporous silica nanoparticles (MSNs) were coated with a folic acid (FA)-PEI layer; MCM-41 was prepared by a sol-gel process and diacidfunctionalized MCM-41 was prepared by post-modification. Subsequently, DA-MCM-41 was coated with FA grafted PEI via an electrostatic interaction. The cellular uptake of DA-MCM-41 and the FAPEI layered MSNs by MCF-7 cells was evaluated using dansyl labeled methylene blue (MB). The FA-PEI-functionalized MSNs exhibited higher cellular uptake to MCF-7 cells than DA-MCM-41. This novel nanocarrier was internalized into the targeted tumor cells site-specifically by FA-mediated internalization and the pH-responsive release of guest molecules (here, methylene blue) was realized by an electrostatic interaction between FA-PEI and DA-MCM-41. Overall, FA-PEI-functionalized MSNs may have potential applications in the targeted and controlled delivery of guest molecules for cancer therapy.

Functionalized and Monodispersed Mesoporous Silica Nanospheres with a Schiff-Base for Metal Ion Adsorption.

Mesoporous silica nanospheres (MSNs-AH) with a Schiff-base ligand were synthesized using a snap-top strategy and post-synthetic grafting strategy for metal ion adsorption. The mesoporous MSNs-AH with the Schiff-base ligand were used for the adsorption of metal ions from artificial wastewater and artificial seawater. The adsorption characteristics of the functionalized adsorbents for various metal ions were tested for different adsorption times (1~48 h) in artificial wastewater and artificial seawater. In the case of artificial wastewater, the functionalized adsorbents had no preferential selectivity for metal ions except for Na+ ions, even though the MSNs-AH adsorbent adsorbed most of the metal ions investigated in this work, including Li+, Co2+, Ca2+, Fe3+, Mn2+, Mg2+, Al3+, Zn2+, and Ni2+. In the case of artificial seawater, however, the MSN absorbent showed high selectivity for Li+ ions.

Thermal and Optical Performance of Glass Cloth Reinforced Organic-Inorganic Hybrid Polymer Composite Film.

Recently there has been considerable interest in flexible display as the next-generation display. The flexible plastic has been recommended as a strong candidate for substrate, but these plastic substrates have many problems to provide the comparable properties of dimensional stability, thermal stability, and solvent resistance to glass in order to apply conventional thin film transistor technology to flexible display. Then in this study, a glass cloth reinforced polymer (GCRP) composite was prepared. To improve the thermal property, glass cloth with an excellent coefficient of thermal expansion (CTE) for reinforcement and organic-inorganic hybrid nanomaterial with polyhedral oligomeric silsesquioxane (POSS) material having excellent heat resistance were introduced to ensure the excellent properties like transmittance, haze, yellow index, thermal stability and chemical resistance. The optical property of GCRP composite was measured by using a spectrophotometer and the CTE of GCRP composite was observed by thermomechanical analysis (TMA).

Disulfide-Containing Crosslinked Polyaniline Cathode for Rechargeable Battery.

Polymer electrodes have had several advantages like being environment friendly, mechanically flexible and more inexpensive than lithium metal which is used as lithium metal oxide-based cathode. But polymer electrodes generally have had lower charge/discharge capacity. Sulfur compounds with organothiol (-SH) or disulfide (S-S) group have advantages about high theoretical capacity but they have poor electronic conductivity. Then in this study, focusing on the enhancement of electrical performance of polymer electrode, disulfide bonds are linked to the side chain of polyaniline (PANI) and conjugated crosslinking between polymer chains is formed. As a result, crosslinked poly(9-amino-5,8-dihydro-1H,4H-2,3,6,7-tetrathia-anthracene) (PADTTAA)-co-PANI electrodes with different ratio of ADTTAA were successfully synthesized. Elemental and compositional analysis on the surface of the polymer sample was measured by using X-ray photoelectron spectroscopy (XPS). And the electrochemical property of disulfide-containing crosslinked PANI based cathode was investigated by confirming cyclic voltammetry and charge-discharge capacity. As the contents of ADTTAA increased, the charge/discharge capacity increased but the conductivity and cycle life decreased.

Polymer Nanocomposite Electrode Consisting of Polyaniline and Modified Multi-Walled Carbon Nanotube for Rechargeable Battery.

In this study, PANI nanocomposite with modified multi-walled carbon nanotube (mMWCNT) was prepared. Herein MWCNT was modified by Friedel-Crafts acylation reaction. The dc conductivity of PANI nanocomposite according to the content of mMWCNT was measured by four-point probe. The highest conductivity of 9.49 S/cm was obtained in case of PANI nanocomposite with 3 wt% of mMWCNT. And it could be known that MWCNT was less damaged by the modification of Friedel-Crafts acylation reaction (mMWCNT) than strong acid treatment (aMWCNT), so the thermal stability of PANI nanocomposite was higher than that of pure PANI. And the morphology and crystallinity of the PANI nanocomposite were investigated by field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM) and X-ray diffraction. Also the electrochemical property of PANI nanocomposite was intensively investigated by cyclic voltammetry (CV) and charge-discharge capacity. From the CV data, it could be known that the charge-discharge capacity of PANI nanocomposite electrode was improved compared to pure PANI and PANI + aMWCNT electrodes.

Poly(hydroxyethyl methacrylate) based networked solid polymer electrolyte.

Solid polymer electrolytes (SPEs) have good safety for lithium battery compared to liquid electrolytes, but they have low ionic conductivity. To solve the problem, the polymer-in-salt system was introduced which has higher ionic conductivity than salt-in-polymer system. However, polymer-in-salt system has disadvantages that are poor mechanical properties with increasing salt concentration. In this study, networked polymer electrolytes consisting of poly(hydroxyethyl methacrylate) (P(HEMA)), lithium triflate (LiCF3SO3, LiTf) and hydrochloric acid (HCl) were prepared. And the electrochemical and mechanical properties of P(HEMA) based SPEs were investigated by using ac impedance analyzer and universal testing machine, respectively.

Antitumor and antiangiogenic active dendrimer/5-fluorouracil conjugates.

Antitumor and antiangiogenic active dendritic compounds conjugated with 5-fluorouracil (5-FU) were synthesized and characterized. First, the core structure based on ascorbic acid and dicarboxylic acid was synthesized, amidated with ethylenediamine. For the synthesis of higher generated dendrimer, it was reacted further with methyl acrylate to increase molecular weight through Michael addition reaction, followed by the continuous repeating amidation reaction, finally, used to synthesize covalently bound dendrimer/5-FU conjugates. The in vitro cytotoxicities of the conjugates was evaluated with mouse mammary carcinoma, mouse leukemia, and human histiocytic lymphoma as cancer cell lines and mouse liver cells as a normal cell line, and showed lower values than 5-FU. The in vivo antitumor activities of the conjugates against mice bearing sarcoma 180 tumor cell line were better than 5-FU. Especially, Second generated dendrimer (G-2)/5-FU conjugates showed excellent in vivo antitumor as well as antiangiogenic activities evaluated by the embryo chorioallantoic membrane assay due to slow hydrolysis rate and the amount of 5-FU released.

Electrochemical properties of solid polymer electrolytes prepared by the hard/soft acid base principle.

In order to improve the electrochemical properties including ionic conductivity of SPEs (solid polymer electrolytes), understanding of the interaction between the polymer and salt in the SPE is important. In this study, four types of polymer matrices and four types of salts were used according to the hard/soft acid base (HSAB) principle. The results of impedance measurement reveal that the ionic conductivities are affected by the HSAB principle at low salt concentration. With increasing salt content, however, the SPEs are influenced by the ion hopping property of salt rather than by the solubility of the polymer with salt. In contrast, the PPS-based SPE shows different characteristics because it is prepared as a slurry phase at high salt content.

Electrochemical performance of poly(vinyl alcohol)-based solid polymer electrolyte for lithium polymer batteries.

Solid polymer electrolytes (SPEs) are an excellent alternative to liquid electrolytes due to their non-volatility, low toxicity, and high energy density. In this study, a SPE having the ion transport mechanism decoupled from segmental motion of a polymer based on poly(vinyl alcohol) (PVA) containing the salt lithium trifluoromethane sulfonate (LiCF3SO3, LiTf) has been prepared to overcome the low ionic conductivity of traditional SPEs at room temperature. PVA has a high glass transition temperature (358 K) and good mechanical properties, and despite being atactic, it can crystallize, especially if highly hydrolyzed. From an ac impedance analysis, it was found that the ionic conductivity of the PVA-based SPE increased with increasing salt concentration. In particular, a dramatic increase was observed between 40 and 50 wt% of salt. The ionic conduction mechanism of the PVA-based SPE is proposed based on intensive study using FT-IR spectroscopic measurements, XRD and AFM. Through measurements of linear sweep voltammetry (LSV) and cyclic voltammetry (CV), it is also found that the SPE with PVA and LiCF3SO3 has good electrochemical stability.

Polystyrene-Al2O3 composite solid polymer electrolyte for lithium secondary battery.

In a common salt-in-polymer electrolyte, a polymer which has polar groups in the molecular chain is necessary because the polar groups dissolve lithium salt and coordinate cations. Based on the above point of view, polystyrene [PS] that has nonpolar groups is not suitable for the polymer matrix. However, in this PS-based composite polymer-in-salt system, the transport of cations is not by segmental motion but by ion-hopping through a lithium percolation path made of high content lithium salt. Moreover, Al2O3 can dissolve salt, instead of polar groups of polymer matrix, by the Lewis acid-base interactions between the surface group of Al2O3 and salt. Notably, the maximum enhancement of ionic conductivity is found in acidic Al2O3 compared with neutral and basic Al2O3 arising from the increase of free ion fraction by dissociation of salt. It was revealed that PS-Al2O3 composite solid polymer electrolyte containing 70 wt.% salt and 10 wt.% acidic Al2O3 showed the highest ionic conductivity of 9.78 × 10-5 Scm-1 at room temperature.

Optical and electrochemical detection of saccharides with poly(aniline-co-3-aminobenzeneboronic acid) prepared from enzymatic polymerization.

Boronic acid-based sensors for saccharides have been developed via biocatalysis. The self-doped copolymer of poly(aniline-co-3-aminobenzeneboronic acid) [poly(aniline-co-AB)], with various mole ratios of two components, was synthesized by oxidative enzymatic polymerization using a natural biocatalyst such as horseradish peroxidase together with an anionic polyelectrolyte template (sulfonated polystyrene) under mild conditions (pH 4.5). Poly(aniline-co-AB), having an aniline boronic acid-to-aniline ratio of 1:2 on average, gave rise to a green doped polymer with absorption maxima at 745 nm. The potentiometric detection of saccharides using poly(aniline-co-AB) is presented. Characteristics of both transient and steady-state response associated with the complex formation of poly(aniline-co-AB) with various saccharides were monitored by UV-vis spectroscopy and cyclic voltammetry (CV). The results obtained from UV-vis spectroscopy and CV show that the sensitivity of enzymatically synthesized water-soluble poly(aniline-co-AB) for various saccharides was improved significantly compared to the chemically synthesized counterpart. A possible mechanism for the sensitive detection of sugar molecules by boronic acid is proposed on the basis of UV-vis and IR spectrophotometry, and four-point probe conductivity measurements.