Whangi Kim

Synthesis and characterization of polycarbonates containing terminal and chain interior siloxane

Silicone polycarbonates having polydimethyl siloxane (PDMS) and heptamethyl trisiloxane (HMTS) were synthesized by the interfacial polymerization. Instead of common chain terminator p-tert-butyl phenol (PTBP), eugenol capped HMTS, and PDMS were used. PDMS was also attached into the chain interior of the polymer in different molar ratios. PDMS and HMTS were capped with eugenol through the hydrosilylation reaction using Karstedt’s catalyst. Both monohydroxy and dihydroxy terminated eugenosiloxanes were synthesized in order to use as chain terminator and interior subunit of polymer, respectively. Structural characterization and the study of the properties, such as thermal behavior, thermooxidative stability, surface morphology, wettability of the synthesized polymers were investigated. Flexibility and wettability of the synthesized polymers increases with increasing of silicone content. Polymers showed satisfactory thermo oxidative stability and transparency as good as bisphenol-A-polycarbonate.

Semi‐quantitative HPV viral load in patients with ASC‐US cytology: viral load correlates strongly with the presence of CIN but only weakly with its severity

This study was performed to evaluate the prognostic significance of human papillomavirus (HPV) viral load, expressed in relative light units (RLUs), in patients with atypical squamous cells of undetermined significance (ASC‐US) cytology.

Anion conductive aromatic ionomers containing a 1,2-dibenzoylbenzene moiety for alkaline fuel cell applications

Novel anion-exchange membranes with high conductivities have been prepared for application to alkaline fuel cells. A quaternary ammonium poly(dibenzoylbenzene ether sulfone) membrane was synthesized by chloromethylation, followed by substitution with trimethylamine with an ion-exchange reaction. The quaternary ammonium groups were selectively substituted in the para-position of the pendant phenyl groups of the dibenzoylbenzene unit. The di-quaternary ammonium hydroxide polymers showed an elevated molecular weight and exhibited excellent solubility in polar aprotic solvents. Quaternization and the subsequent ion-exchange reactions were quantitative such that the obtained ionomer membranes had a high ion-exchange capacity (IEC) of up to 1.69 mmolg−1. The resultant polymer membranes were studied by 1H NMR, FT-IR, thermogravimetric analysis (TGA), IEC, water uptake analysis, and ion conductivity analysis.

The Effect of Oligomer Blending on the Flow Properties of Polycarbonate

We successfully prepared high-flow polycarbonate (PC) by blending commercial PC with a low molecular weight PC oligomer. The oligomer was synthesized by the addition of a large quantity of mono functional phenol groups, and the chain end group was reacted withp-tertiary butyl phenol (PTBP) to block the reactivity. The viscosity average molecular weight (Mv) for the oligomer was about 4,000–5,000 g/mol, compared to ∼19,000 g/mol for the PC blend obtained by blending 10 wt% of the prepared oligomer with the commercial grade PC (Mv of 21,000 g/mol). The blended PC had a melt flow index of 45, which is 2.5 times higher, and a processing temperature that was 20 °C lower, than that of commercial grade PC having a similarMv.

Synthesis and Characterization of Polycarbonate Copolymers Containing Benzoyl Groups on the Side Chain for Scratch Resistance

The purpose of this study was to enhance the scratch resistance of polycarbonate copolymer by using 3,3′-dibenzoyl-4,4′-dihydroxybiphenyl (DBHP) monomer, containing benzoyl moieties on the ortho positions. DBHP monomer was synthesized from 4,4′-dihydroxybiphenyl and benzoyl chloride, followed by the Friedel-Craft rearrangement reaction with AlCl3. The polymerizations were conducted following the low-temperature procedure, which is carried out in methylene chloride by using triphosgene, triethylamine, bisphenol-A, and DBHP. The chemical structures of the polycarbonate copolymers were confirmed by 1H-NMR. The thermal properties of copolymers were investigated by thermogravimetric analysis and differential scanning calorimetry, and also surface morphologies were assessed by atomic force microscopy. The scratch resistance of homopolymer film (100 μm) changed from 6B to 1B, and the contact angle of a sessile water drop onto the homopolymer film also increased.

Evaluation of hydrogenation properties on MgHx-transition metal fluoride composites by planetary ball milling

To improve the disadvantages of Mg hydrides, a few studies were conducted for MgHx intermixed with transition metal fluorides. MgF2 formed from the MgHx-transition metal fluoride system can be replaces the initial surface oxide layer and provides a reactive and protective fluorinated surface for for hydrogen uptake. Thus, the absorption/desorption kinetics will be enhanced. In this research, MgHx-transition metal fluoride composites mixture has been prepared by hydrogen induced planetary ball milling. The synthesized powders were characterized by X-ray diffraction analysis, scanning electron microscopy and simultaneous thermogravimetric, differential scanning calorimetric analysis. The hydrogenation behaviors were evaluated by using a sievert’s type automatic pressure-composition-temperature apparatus without any activation treatment. From the characteristics of the absorption kinetics and curves observed, the role of transition metal fluoride was catalyst in hydrogen absorption. The results of Pressure-Composition Isotherm curve, available hydrogen storage amount for MgHx-5 vol% CoF2 composites were 4.85 wt%, for MgHx-5 vol%TiF3 composites were 4.88 wt%. at 623K in the 5th cycle.

The Sulfonated poly(ether sulfone ketone) ionomers containing partial graphene of mesonaphthobifluorene for PEMFC

Novel sulfonated poly(ether sulfone ketone)s containing mesonaphthobifluorene (MNF) moiety were synthesized and their properties characterized. The prepared polymers had a partial graphene structure due to the MNF group. Poly(ether sulfone ketone)s bearing tetraphenylethylene (TPE) on the polymer backbone were synthesized by polycondensation, after which MNF was formed by the intra-cyclization of TPE by Friedel-Crafts reaction with Lewis acid (FeCl3). The sulfonation was performed selectively on MNF units with concentrated sulfuric acid. The synthesized polymer electrolyte membranes showed better thermal and dimensional stabilities owing to the MNF-induced graphene structure in the polymer backbone. The water uptake of the synthesized membranes ranged from 30%–55%, compared with 32.13% for Nafion 211® at 80°C. The proton conductivity (80°C, RH 90%) ranged from 74.6–101.2 mS/cm, compared with 102.7 mS/cm for Nafion 211®.

Isolation and characterisation of acid- and pepsin-soluble collagen from the skin of Cervus korean TEMMINCK var. mantchuricus Swinhoe

Acid-soluble collagen and pepsin-soluble collagen were extracted from the skin of deer, Cervus korean TEMMINCK var. mantchuricus Swinhoe. The two types of collagen were then characterised using sodium dodecyl sulfate–polyacrylamide gel electrophoresis, amino acid composition analysis, peptide hydrolysis patterns, thermal denaturation temperature, differential scanning calorimetry, Fourier transform infrared spectroscopy, and nuclear magnetic resonance imaging. The yield of pepsin-soluble collagen (9.62%) was greater than that of acid-soluble collagen (2.24%), but both types of collagen showed similar electrophoretic patterns with each other and with calf skin collagen. The peptide hydrolysis pattern results suggested that calf skin collagen and pepsin-soluble collagen from deer skin may be similar in terms of their primary structure. The thermal denaturation temperature of acid-soluble collagen and pepsin-soluble collagen were 36.67°C and 36.44°C, respectively, and their melting temperatures were 110°C and 120°C, respectively, which suggest high thermal stability. Fourier transform infrared showed a triple helical structure and nuclear magnetic resonance confirmed the presence of ‘hydration’ water. These results provide a basis for large-scale production and further application as alternatives to other mammalian collagens.

Studies of Grafted and Sulfonated Spiro Poly(isatin-ethersulfone) Membranes by Super Acid-Catalyzed Reaction

Spiro poly(isatin-ethersulfone) polymers were prepared from isatin and bis-2,6-dimethylphenoxyphenylsulfone by super acid catalyzed polyhydroxyalkylation reactions. We designed and synthesized bis-2,6-dimethylphenoxyphenylsulfone, which is structured at the meta position steric hindrance by two methyl groups, because this structure minimized crosslinking reaction during super acid catalyzed polymerization. In addition, sulfonic acid groups were structured in both side chains and main chains to form better polymer chain morphology and improve proton conductivity. The sulfonation reactions were performed in two steps which are: in 3-bromo-1-propanesulfonic acid potassium salt and in con. sulfuric acid. The membrane morphology was studied by tapping mode atomic force microscope (AFM). The phase difference between the hydrophobic polymer main chain and hydrophilic sulfonated units of the polymer was shown to be the reasonable result of the well phase separated structure. The correlations of proton conductivity, ion exchange capacity (IEC) and single cell performance were clearly described with the membrane morphology.

Preparation and characterization of sulfonated poly (ether sulfone)s containing hexabenzocoronene graphene moiety for PEMF

The novel sulfonated poly(ether sulfone)s containing hexabenzocoronene moiety that is partial graphene structure (SPGHPs) for polymer electrolyte membrane were synthesized and characterized their properties. Graphene is an allotrope of carbon and one-atom-thick planar sheets of sp2-bonded carbon atoms that are densely packed in a honeycomb crystal lattice. Poly(ether sulfone)s containing hexaphenylbenzenes on polymer backbone were synthesized by poly condensation and followed intra-cyclization by friedel-craft reaction with lewis acid (FeCl3) to form partial graphene structure. The sulfonation was taken selectively on hexabenzocoronen units with concentrated sulfuric acid. The structure properties of the sulfonated polymers were investigated by 1H-NMR spectroscopy. The resulted ion exchange capacities (IEC) were 1.09~1.61 meq./g. The water uptakes were 8.84~15.27% at 30 °C and 18.27%~42.38% at 80 °C with changing the ion exchange capacities. The SPGHP membranes exhibit proton conductivities (80 °C, RH 90) of 78.3~105.7 mS/cm compared with 106.2 mS/cm of Nafion 211®.