• Polymer(Korea)
• /
• v.37 no.2
• /
• pp.232-239
• /
• 2013

A series of novel imidazole-blocked diisocyanate bioadhesives (IBAs) were synthesized from reaction of toluene 2, 4-diisocyanate (TDI), isophorone diisocyanate (IPDI), hydroxyl-terminated polylactide (HO-PLA-OH), 1,1,1-trimethylolpropane (TMP), and imidazole. Synthesis of IBAs was confirmed by Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). Differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) revealed that the TDI-based IBA had lower thermal dissociation temperature and a faster deblocking rate than IBA based on IPDI. Hydroxyl-terminated polyurethane (HPU) was introduced to study the adhesive effect of the synthesized IBAs. Improvement on elastic modulus, tensile strength and water resistance of IBA-modified HPU in comparison with neat HPU suggested the good adhesive effect of IBA due to the strong chemical reaction between released NCO groups from IBA and hydroxyl groups from HPU.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09a
• /
• pp.489-490
• /
• 2006

Branched sulfonated poly(ether sulfone-ketone) copolymer was prepared with bisphenol A, 4,4-difluorobenzophenone, sulfonated chlorophenyl sulfone (40mole% of bisphenol A) and THPE (1,1,1-tris-p-hydroxyphenylethane). THPE was used 0.4 mol% of bisphenol A to synthesize branched copolymers. Organic-inorganic nano composite membranes were prepared with copolymer and a series of $SiO_2$ nanoparticles (20 nm, 4, 7 and 10 wt%). The composite membranes were cast from dimethylsulfoxide solutions. The films were converted from the salt to acid forms with dilute hydrochloric acid. The membranes were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Sorption experiments were conducted to observe the interaction of sulfonated polymers with water and methanol. Branched copolymer and nano composite membranes exhibit proton conductivities from $1.12{\times}10^{-3}$ to $6.04{\times}10^{-3}\;S/cm^2$, water uptake from 52.9 to 62.4%, IEC from 0.81 to 1.21 meq/g and methanol diffusion coefficients from $1.2{\times}10^{-7}$ to $1.5{\times}10^{-7}\;cm^2/S$.

• Polymer(Korea)
• /
• v.38 no.4
• /
• pp.484-490
• /
• 2014

Reduced graphene oxide (RGO) was fabricated using gelatin as a reductant, and it could be stably dispersed in gelatin solution without aggregation. A series of RGO/gelatin composite films with various RGO contents were prepared by a solution-casting method. The structure and thermal properties of the RGO/gelatin composite films were characterized by UV-vis spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), differential scanning calorimeter (DSC) and thermal gravimetric analysis (TGA). The addition of RGO enhances the degree of crosslinking of gelatin films and decreases the swelling ability of the gelatin films in water, indicating that RGO/gelatin composite films have a better wet stability than gelatin films. The glass transition temperature ($T_g$) of gelatin films is also increased with the incorporation of RGO. The presence of RGO slightly increases the degradation temperature of gelatin films due to the very low content of RGO in the composite films. Since gelatin is a natural and nontoxic biomacromolecule, the RGO/gelatin composite films are expected to have potential applications in the biomedical field.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2002.08a
• /
• pp.336-339
• /
• 2002

Fluorenevinylene-based EL polymers, poly(9,9-dioctylfluorene-2,7-vinylene) (PFV) and poly[(9,9-dioctylfluorene-2,7-vinylene)-co-{2-methoxy-5-(2 ethylhexyloxy)-1,4-phenylenevinylene}] (PFV-co-MEH-PPV), have been synthesized by Gilch polymerization method. The resulting polymers were soluble in common organic solvents and easily spin cast onto the indium-tin oxide (ITO) substrate. The weight average molecular weight and polydispersity of PFV and PFV-co-MEH-PPV were in the range of 22.2 - 43.2 x $10^4$ and 1.9 - 3.0, respectively. Double-layer light-emitting diodes with ITO/PEDOT/Polymer/Al configuration were fabricated. PFV-co-MEH-PPV showed better EL properties than those of PFV and MEH-PPV The turn-on voltage of poly(9,9dialkylfluorene) derivatives were dramatically decreased to the 2.5 V compared to fluorene-based EL polymers. The maximum brightness and luminescence efficiency were up 7 to 1350 cd/$m^2$ and 0.51 Cd/A.

• Bulletin of the Korean Chemical Society
• /
• v.23 no.4
• /
• pp.549-554
• /
• 2002

Thermosensitive poly(organophosphazenes) bearing methoxy-poly(ethylene glycol) (MPEG) and alkylamines as substituents have been synthesized and characterized by elemental analysis, NMR spectroscopy, GPC, and DSC. All the polymers exhibited crystallinity, which was probably induced by the MPEG side chain of the polymers. All the polymers exhibited the lower critical solution temperature (LCSTs) in the range of 28 to $94^{\circ}C$ depending on several factors such as mole ratio of the substituents, kinds of PEG and alkylamines. The higher content of MPEG and shorter chain length of alkylamines of the polymers afforded the higher LCST. The LCSTs of the polymers exhibited almost concentration-independent behavior in the range of 3-30 wt % of the polymers in aqueous solutions. The polymers showed the higher LCSTs in the acidic solutions than in the neutral and basic solutions. The ionic strength of the polymer solution affected the LCST, which decreased with increased NaCl concentration. The polymer bearing almost equimolar substitutuents with the -N-P-N- unit has shown the LCST more sensitive to NaCl and pH than that with the -N-P-O- unit. The polymers were found to degrade in acidic solution but be very stable in alkali solution as well as in the buffer solution of pH 7.4.

• 한국신재생에너지학회:학술대회논문집
• /
• 2005.06a
• /
• pp.235-238
• /
• 2005

Sulfonated poly(ether sulfone) copolymers (PESs) were synthesized using hydroquinone 2-potassium sulfonate (HPS) with other monomers (bisphenol A and 4-fluorophenyl sulfone). PESs with different $mole\%$ of hydrophilic group were prepared by changing the mole ratio of HPS in the polymerization reaction. The chemical structure and the thermal stability of these polymers were characterized by using $^1H-NMR$, FT-IR and TGA techniques. The PES 60 membrane, which has $60 mole\%$ of HPS unit in the polymer backbone, has a proton conductivity of 0.091 S/cm and good insolubility in boiling water. The TGA showed that PES 60 was stable up to $272^{\circ}C$ with a char yield of about $29\%\;at\;900^{\circ}C\;under\;N_2$ atmosphere. To investigate the single cell performance, the catalyst coated PES 60 membrane was used and a single cell test was carried out using $H_2/O_2$ gases as fuel and oxidant at various temperatures. We observed that the cell performance was enhanced by increasing the cell temperature. A current density of $1400 mA/cm^2$ at 0.60 V was obtained at $70^{\circ}C$.

• Journal of the Korean Chemical Society
• /
• v.45 no.3
• /
• pp.230-235
• /
• 2001

Poly(N-isopropylacrylamide) (PNIPAAm) containing polydimethylsiloxane (PDMS) was synthesized using PDMS as crosslinking agent, and characterized by IR and DSC. It seems that the copolymer has separated phases, PNIPAAm and PDMS. The $T_g$ of PNIPAAm was decreased in accordance with the increase of PDMS-contents. The swelling behavior of polymer in water was examined with the function of temperature and PDMS-contents as well. The equilibrium swelling ratio of polymer in water was decreased with increasing PDMS-contents, but lower critical solution temperature (LCST) was not significantly affected by the incorporated PDMS-contents.

• Korean Membrane Journal
• /
• v.6 no.1
• /
• pp.44-54
• /
• 2004

Organic-inorganic composite membranes based on sulfonated poly(phthalazinone ether sulfone) (sPPES)/silica hybrid were prepared using the sol-gel process under acidic conditions. The sulfonation of PPES with concentrated sulfuric acid as sulfonation agent was carried out to prepare proton exchange membrane material. The behaviors of the proton conductivity and methanol permeability are depended on the sulfonation time (5-100 hr). The hybrid membranes composed of highly sulfonated PPES (IEC value: 1.42 meq./g) and silica were fabricated from different silica content (5-20 wt%) in order to achieve desirable proton conductivity and methanol permeability demanded for fuel cell applications. The silica particles within membranes were used for the purpose of blocking excessive methanol cross-over and for forming the path way to transport of the proton due to absorbing water molecules with ≡SiOH on silica. The presence of silica particles in the organic polymer matrix results in hybrid membranes with reduced methanol permeability and improved proton conductivity.

• Macromolecular Research
• /
• v.15 no.1
• /
• pp.59-64
• /
• 2007

Star-shaped, nonlinear optical (NLO) material was synthesized and its optical, thermal, and electro-optic properties were investigated. Three NLO-active dipolar chromophores containing a phenylene ring substituted with a bulky alkyl chain as a conjugation bridge were chemically bonded to the core of 1,1,1-tris(4-hydroxyphenyl)ethane to form a dendritic architecture. The chemical structure and purity of the chromophore were verified by NMR spectroscopy. The chromophore exhibited a broad absorption band centered at around 608 nm tailing up to 760 nm in toluene solution and also showed a discernible solvatochromic shift in more polar solvent. The chloroform solution of the dendrimer produced an absorption band with a red-shifted maximum as large as 28 nm when compared to that of the toluene solution. It was thermally stable up to $275^{\circ}C$ in a nitrogen atmosphere and had a glass transition temperature of $76^{\circ}C$. In a preliminary result, the polymer film containing the dendritic compound exhibited a shift of 19 pm/V taken at $1.55{\mu}$.

• Polymer(Korea)
• /
• v.26 no.2
• /
• pp.253-259
• /
• 2002

The objective of this study is to obtain thermally stable and low optical loss polymers for optical waveguiding materials. The crosslinkable poly (maleimide-co-methacrylate)s were synthesized using a pentafluorophenylmaleimide (an optical loss reducer), two methacrylate derivatives (refractive index controllers), and a glycidylmethacrylate (a crosslinker). These copolymers exhibited good thermal stability and could be thermally crosslinked by heat treatment. The refractive indexes of the copolymers could be precisely controlled by the variation of comonomer feed ratio, which was in the range of 1.45 ~ 1.49. These copolymers had very low birefringence of $6{ imes}10^{-4}$ ~ $1{ imes}10^{-4}$. These copolymers were crosslinked by contact printing and then developed by wet etching to obtain high quality waveguide pattern.