Chil-Won Lee

Humidity sensor using epoxy resin containing quaternary ammonium salts

Humidity-sensitive epoxy monomer, glycidyl trimethyl ammonium chloride (GTMAC) was selected as the humidity-sensing resin. Polypropylene glycol diglycidyl ether (PPGDGE) and methyl tetrahydrophthalic anhydride (MTPHA) were used as a comonomer and a curing agent, respectively. The humidity-sensitive membranes were composed of GTMAC, PPGDGE and MTPHA. When impedance characteristics of the epoxy resins containing quaternary ammonium salts were measured, the impedance decreased linearly with an increase in the content of GTMAC in its semi-logarithmic graph. The impedance changed from 10 7 to 10 3 O between 30 and 90%RH, which was required for a common humidity sensor. Temperature dependence, frequency dependence and response time were also measured. The humidity-sensitive characteristics of the sensor did not change even after soaking in water. # 2001 Elsevier Science B.V. All rights reserved.

Humidity sensitive properties of copolymers containing phosphonium salts

Abstract (Vinylbenzyl)triphenylphosphonium chloride (VTPC) was prepared for a humidity-sensitive polyelectrolyte. The humidity-sensitive membranes were composed of cross-linked copolymers with different contents of VTPC, n-butyl acrylate (n-BA) and 2-(N,N-dimethylaminoethyl)methacrylate (VTPC/n-BA/DMAMA=10/35/0, 10/45/0, 10/35/4.5 and 10/35/9). When impedance characteristics of the copolymers were measured, the impedance was decreased with an increase in the content of VTPC. The impedance ranged from 107 Ω to 103 Ω between 50% RH and 95% RH, which was required for a humidity sensor operating at high humidity or a dew point. Temperature dependence, hysteresis and a response time were also measured. The humidity-sensitive characteristics of the cross-linked copolymer of VTPC, n-BA and DAEMA changed little even after soaking in water for 120 min.

Humidity sensitive properties of alkoxysilane-crosslinked polyelectrolyte using sol-gel process

New trialkoxysilyl group-containing copolymers for humidity-sensitive polyelectrolytes were prepared by copolymerization of [2-(methacryloyloxy)ethyl]trimethyl ammonium chloride (METAC), 3-(trimethoxysilyl)propyl methacrylate (TSPM) and 2-ethylhexyl acrylate (2-EHA). They were self-crosslinkable copolymers composed of different contents of METAC/TSPM/2-EHA = 4/1/5 and 4/2/4. The resistance varied from 10(7) to 10(3)[capital Omega] between 20% RH and 95% RH, which was required for a humidity sensor operating at ambient humidity. Temperature dependence, hysteresis, response time, water durability and long-term stability at high temperature and humidity were also measured and estimated.

Preparation of polythiophene LB films and their gas sensitivities by the ouartz crystal microbalance

Abstract The gas sensitivity of polythiophene LB film was investigated. As polythiophene has the conjugated double bond, the potential applications to the various devices using its conducting property have been proposed. The Langmuir-Blodgett(LB) technique has been used to manipulate conducting polymers to multilayer thin films with well defined structures and ordered molecular orientations. In this study, we have synthesized the polythiophene derivatives such as poly(octyl thiophene)(POT), poly(propanoate thiophene)(PEPT) and poly(decanoate thiophene)(PEDT), and observed their behaviors at the air/water interface. For the preparation of polythiophene LB films with good quality, we have used the mixed monolayer with surface active materials like octadecylamine(ODA) and controlled the subphase conditions. Also, for the application to the sensing materials, we have tested the gas sensitivities of polythiophene derivatives LB films to NO 2 gas by the quartz crystal microbalance(QCM).

Humidity-sensitive properties of phosphonium salt-containing polyelectrolytes

New phosphonium salt-containing monomer, (vinylbenzyl) tributyl phosphonium chloride (1), was prepared and polymerized for a humidity-sensing film. The humidity-sensitive membranes were composed of copolymers with different contents of 1 and styrene (2) or n-butyl acrylate (3) (1/2 or 1/3 = 1/0, 4/1, 2/1 and 1/1). When the impedance dependencies on the relative humidity of the copolymers were measured, the impedance increased with an increase in the content of 2 or 3. The impedance ranged from 107 to 104 Ω between 20%RH and 95%RH, which was required for a humidity sensor operating at ambient humidity. Temperature dependence, frequency dependence, hysteresis and response time were also measured and reliability was evaluated.

Preparation and chemiluminescent properties of perylene-containing polyimides as polymeric red fluorophores

New polyimides containing perylene chromophore were synthesized by imidization reaction of 1,6,7,12-tetrakis(4-tert-butylphenoxy)-3,4,9,10-perylene tetracarboxydianhydride with various alkylenic diamines such as 2,4,8,10-tetraoxaspiro[5,5]undecan-3,9-dipropylamine, polytetrahydrofuran bis(3-aminopropyl) terminate and poly(propylene glycol) bis(2-aminopropylether). The polyimides were characterized by IR, NMR, DSC, UV-Vis and luminescence spectroscopy. All polymers showed an enhanced solubility in common organic solvents such as THF, dibutylphthalate, chloroform and acetone. Chemiluminescent reactions involving hydrogen peroxide and bis(2-carbopentyloxy-3,5,6-trichlorophenyl)oxalate were observed using tetramethyl ammonium salicylate catalyst. The polymeric fluorophores exhibited a strong chemiluminescent red light emission around 620 nm; these are similar to the photoluminescent spectra. The chemiluminescent intensity decayed exponentially, but the glow was maintained more than 24 h and was visible with naked eye.

Synthesis and properties of violet light-emitting polymeric fluorophore

Abstract Chemiluminescent violet light-emitting polymeric fluorophores were synthesized by copolycondensation of N,N ′-dihydroxypropyl-1,6,7,12-tetrakis( p - tert -butylphenoxy)-3,4,910-perylene tetracarboxydiimide and 2-chloro-9,10-di( p -hydroxyphenyl)anthracene with sebacoyl chloride and hexamethylene diisocyanate. The properties of fluorophore polymers were studied by absorption and photoluminescent spectroscopies. The intensities of UV–vis absorbance and photoluminescence spectra appeared at the blue side and the red side of the spectral region. Peroxyoxalate chemiluminescence of polymers provided a strong chemiluminescent violet light emission according to the content of two chromophore units; these were similar to the photoluminescent spectra.

New efficient fused-ring spiro[benzoanthracene-fluorene] dopant materials for blue fluorescent organic light-emitting diodes

New blue fluorescent spirobenzoanthracene-type dopant materials, 3,9-di(di(p-tolyl))aminospiro[benzo[de]anthracene-7,9′-fluorene] (DTSBAF) and 3,9-di(di(4-biphenyl))aminospiro[benzo[de]anthracene-7,9′-fluorene] (DBSBAF), were designed and successfully prepared by an amination reaction of 3-bromo-9-chlorospiro[benzo[de] anthracene-7,9′-fluorene] with di(p-tolyl)amine and di(4-biphenyl)amine, respectively. The EL characteristics of 1,10-dinaphthylspiro[benzo[ij]tetraphene-7,9′-fluorene] (DNSBTF) as the blue host material doped with the above blue dopant materials was evaluated. The electroluminescence spectra of indium tin oxide (150 nm)/N,N′-diphenyl-N,N′-bis[4-(phenyl-m-tolyl-amino)phenyl]-biphenyl-4,4′-diamine (DNTPD, 60 nm)/N,N,N′,N′-tetra(1-biphenyl)-biphenyl-4,4′-diamine (TBB, 30 nm)/SBTF hosts: SBAF dopant (20 nm, 5%)/9,10-di(naphthalene-2-yl)anthracen-2-yl-(4,1-phenylene)(1-phenyl-1H-benzo[d]imidazole) (LG201, 20 nm)/LiF (1 nm)/Al (200 nm) with DNSBTF as a host material show a blue emission band with a full width at half maximum of 50 nm and λmax = 472 nm. The device obtained from DNSBTF doped with DTSBAF showed a good color purity (0.141, 0.254), high luminance efficiency (10.12 cd A−1 at 5 V) and high external quantum efficiency (6.02%).