Gwan-Su Yi

End-group cross-linkable sulfonated poly(arylene ether) polymer (E-SFQK) was synthesized via direct polymerization of potassium 2,5-dihydroxybenzenesulfonate (SHQ) and decafluorobiphenyl (DFBP), followed by a reaction with ethynylphenol (EP). The cross-linking reaction of the ethynyl end group of E-SFQK was performed at 250 °C. After cross-linking, proton conductivity, water uptake, and swelling ratio of cross-linked membrane decreased from 0.16 (noncross-linked membrane) to 0.13 S/cm, from 86%

High performance of SnP₂O₇-based intermediate temperature fuel cells was obtained with a quaternary ammonium-biphosphate ion-pair coordinated polymer electrolyte.

Due to increased environmental pressures, significant research has focused on finding suitable biodegradable plastics to replace ubiquitous petrochemical-derived polymers. Polyhydroxyalkanoates (PHAs) are a class of polymers that can be synthesized by microorganisms and are biodegradable, making them suitable candidates. The present study looks at the degradation properties of two PHA polymers: polyhydroxybutyrate (PHB) and polyhydroxybutyrate-co-polyhydroxyvalerate (PHBV; 8 wt.% valerate), in t

Ethynyl-terminated fluorinated poly(arylene ether sulfide) (E-FPAESI) was synthesized via nucleophilic aromatic substitution from dihydroxy monomer and pentafluorophenyl sulfide, followed by the reaction with 3-ethynylphenol. Dihydroxy monomer was synthesized in four steps via bromination, Grignard, Suzuki cross-coupling, and demethylation techniques. The number-average molecular weights and polydispersities of the E-FPAESI were in the ranges of 7700−23 000 and 1.53−2.89, respectively. The glass

In order to meet the needs of constantly advancing technologies, fabricating materials with improved properties and predictable behavior has become vital. To that end, we have prepared polydimethylsiloxane (PDMS) polymer samples filled with carbon nanofibers (CFs) at 0, 0.5, 1.0, 2.0, and 4.0 CF loadings (w/w) to investigate and optimize the amount of filler needed for fabrication with improved mechanical properties. Samples were prepared using easy, cost-efficient mechanical mixing to combine t

New series of ethynyl-terminated sulfonated-fluorinated poly(arylene ether)s (ESF-6Fs) were synthesized via nucleophilic aromatic substitution reaction (SNAr) from potassium 2,5-dihydroxybenzenesulfonate (SHQ), 4,4′-(hexafluoroisopropylidene)diphenol (6FBPA), and decafluorobiphenyl (DFBP), followed by the reaction with 3-ethynylphenol. The cross-linked ESF-6F membranes exhibited high glass-transition temperatures in the range of 258−276 °C and good thermal degradation temperatures in the range o

The cross-linkable copolymers (SHQ x -TFV y s) with varying degrees of sulfonation (DS) from 70 to 95% were prepared from potassium-2,5-dihydroxybenzenesulfonate (SHQ), decafluorobiphenyl (DFBP), and 4-(trifluorovinyloxy)-biphenyl-2,5-diol (TFVOH) as a cross-linkable moiety. To develop a highly stable polymer electrolyte membrane (PEM) for application in polymer electrolyte fuel cells (PEFC)s, cross-linked membranes were prepared by chemical cross-linking. The cross-linked membranes were synthes

Cellular silicone reinforced with silica filler prepared using additive manufacturing (AM) have been used widely for vibrational damping and shockwave mitigation. The two most commonly printed cellular silicone structures, simple cubic (SC) and face-centered tetragonal (FCT) display distinctly different static and dynamic mechanical responses dependent upon structure. In this work, the relationship between filler size and composition with mechanical response is investigated using polydimethylsil

ABSTRACT The curing time, surface adhesion, and water absorption characteristics of Sylgard 184 were modified through the addition of catalysts and fillers. Incorporation of small amounts of a platinum‐based Karstedt catalyst greatly decreased curing time at room temperature, whereas the addition of talcum powder (talc), polytetrafluoroethylene (PTFE), and NaY zeolite fillers changed surface adhesion and functionality of Sylgard 184. Fourier‐transform infrared spectroscopy (FT‐IR), rheological a

However, all of these methods invariably suffered from one or more drawbacks such as harsh reaction conditions, long reaction times, difficulty of manipulation, use of exotic reagents, and low reaction yields. Furthermore, in the most of known methods for demethylation of aryl methyl ethers, use of large excess amounts of demethylating agents have been generally required. Thus, it is highly desirable to develop an improved convenient and efficient procedure for demethylation reactions of aryl me