Iwhan Cho

Synthesis and Morphology of New Discogenic Phthalocyanine Derivatives

Abstract New discogens based on the octasubstituted phthalocyanines (Pc) were synthesized: 2,3,9,10,16,17,23,24-octakis[dodecylthio-1-methyl]-phthalocyanine (1a), 2,3,9,10,16,17,23,24-octakis[4-(dodecylthio)-2-oxa-butyl]-phthalocyanine (1b), 2,3,9,10,16,17,23,24-octakis[dodecyloxy]-phthalocyanine (1c), phthalocyanine 2,3,9,10,16,17,23,24-octa-n-dodecanoate (1d), S-(+)-2,3,9,10,16,17,23,24-octakis[4-(dodecyloxy)-2-oxa-pentyl]-phthalocyanine (1e), as well as their corresponding copper complexes (CuPc) 2a, 2b, 2c and 2e. They were characterized by microanalysis, IR, 1H and 13C NMR spectroscopies, and their mesomorphic behaviors were examined with DSC and optical microscopic methods. The products exhibited the following optical textures and transition temperature ranges: focal conic (1a, 95-267°; 2a, 108-304°), linear default (1b, 52-247°; 2b, 70-255°; 1c, 75-269°; 2c, 78-310°), fan-shaped (1d, 58-303°; 2e, 29-191°). Chiral discogenic PcH2 1e, however, showed a cholestericlike texture (23-151°C) in which the ...

New metal cation-selective ionophores derived from calixarenes: their syntheses and ion-binding properties

Various derivatives (ethoxycarbonylmethyl, carboxymethyl, and ethoxyethyl, etc.) of calix[4]arene, calix[6]arene, and calix[8]arene have been synthesized and their ion-binding properties investigated by solvent extraction, ion-transport through liquid membranes, and u.v. spectroscopy. The extraction of various metal ions (as picrate salts) from the aqueous phase into dichloromethane by the calixarene derivatives showed that the ethoxycarbonylmethyl derivatives exhibited markedly increased extraction efficiency compared with their unsubstituted phenol analogues, and the efficiency was in general comparable to those of crown ethers. The most notable feature was the selectivities exhibited by their ethoxycarbonylmethyl derivatives; calix[4]arene for Na+, calix[6]arene for Cs+, and calix[8]arene for K+. A liquid membrane study with a water–chloroform–water system also indicated that the ion-transport efficiencies exhibited by calixarenes were found to be in accordance with their extraction abilities, confirming the strong participation of the ester carbonyl oxygen in this function. However, the ester derivative of calix[4]arene was an exception in that inefficient carrier activity was observed in spite of high extraction efficiency. The pronounced Cs+ selectivity exhibited by the calix[6]arene ester was further confirmed by the changes in the u.v. spectrum of the ester from 277 and 270 nm to 275 and 267 nm upon interaction with Cs+ ion in methanol.

Synthesis and characterization of di- and triblock copolymers of poly(ethylene oxide) and poly(dl-valine-co-dl-leucine)

Abstract Di- and triblock copolymers of poly(ethylene oxide) (PEO) and poly( dl -valine-co- dl -leucine) were synthesized by ring-opening polymerization of N-carboxyanhydride (NCA)s of dl -valine and dl -leucine initiated by amine-terminated PEOs. The resulting block copolymers were characterized by 1 H NMR , FT-IR, DSC, and wide-angle X-ray diffraction (WAXD). Differential scanning calorimeter revealed that the melting temperature of triblock copolymer was lower than that of diblock copolymer and the study of WAXD patterns of triblock copolymer indicated that PEO segments are stretched during the copolymerization as shown in the formation of complex. The self-assembly behaviors of these di- and triblock copolymers in the aqueous solution showed various forms.

Synthesis and Characterization of Novel Amine-Contained Electroluminescent Polymer

Abstract A new type of processable electroluminescent polymer containing tertiary amine linkage was prepared by typical Wittig reaction between bis(4-formylphenyl) n-butylamine and diphosphonium salt. The resulting polymer was highly soluble in common organic solvents so that it could be spun-cast onto glass plate coated with ITO electrode to give highly transparent homogeneous thin film. The molecular weight of the polymer determined by gel permeation chromatography using polystyrene standards is Mn = 4,500, Mw = 11,600. The structure of the polymer was confirmed by IR, UV-visible, and 1H-and 13C-NMR spectroscopy. We observed successfully the electroluminescence peaked at around 530 nm from the device made of the synthesized polymer. The current-voltage (I-V) curves showed typical rectifying diode characteristic.

Structural analysis of thin films of novel polynorbornene derivatives by grazing incidence X-ray scattering and specular X-ray reflectivity along with ellipsometry

In the present study, structural analyses using synchrotron grazing incidence X-ray scattering, specular reflectivity and ellipsometry were performed on thin films of two novel polynorbornene derivatives, chiral poly(norbornene acid methyl ester) and racemic poly(norbornene acid n-butyl ester), which are potential low dielectric constant materials for advanced microelectronic and display applications. These analyses provided important information on the structure, electron density gradient across the film thickness, chain orientation, refractive index and thermal expansion characteristics of the polymers in substrate-supported thin films. The structural characteristics and properties of the thin films depended on the tacticity of the polymer chain and were further influenced by the film thickness and thermal annealing history.

Toughening of syndiotactic polystyrene and poly(2,6-dimethyl-1,4-diphenylene oxide) blends. I. Influence of mixing protocol and blend conditions

It is well known that brittle polymers can be considerably toughened by the incorporation of miscible amorphous polymers or a thermoplastic elastomer. The effect of rubber toughening was studied via reactive extrusion to investigate the fracture mechanism and morphology controls of syndiotactic polystyrene (SPS)/poly(2,6-dimethyl-1,4-diphenylene oxide) (PPO) blends. Successful rubber toughening was achieved in compatibilization using reactive extrusion. The reactive polystyrene (RPS) as a compatibilizer and styrene–ethylene/butylene–styrene block copolymer (SEBS) as an impact modifier were used in an extrusion experiment. The impact strength was highly dependent on the blending condition and the composition. The best result was obtained by 2-step mixing; the first mixing of PPO with RPS (1.0 phr oxazoline content) and functionalized SEBS (f-SEBS, 0.4 phr maleic anhydride content) then followed with SPS mixing. Increase in RPS level gave rubber particle size reduction due to the reactions at the interfaces among polymer phases, as demonstrated by the decreased tan δ value. The storage modulus (E′) of SPS/PPO blends was decreased with increasing PPO content.

SYNTHESIS AND ELECTRONIC EFFECT OF THE SUBSTITUENTS ON ANIONIC RING-OPENING POLYMERIZATION OF PARA-SUBSTITUTED PHENYL CYCLOPROPANES

Abstract As an extension of studies in the anionic polymerization of activated cyclopropanes with electronically push-pull substituents, p-substituted phenylcyclopropane-l,l-dicarbonitriles having MeO, Me, H, Cl, and NO2 as substituents were prepared. The electronic effects of substituents upon the ring-opening reaction during anionic polymerizations were examined by determining the rate constants of polymerizations, conversions and molecular weights of the resulting polymers. The rate constants of polymerization(kp) in DMSO by 2 mole% cyanide ion at 35°C were p-MeO=0.45, p-Me=0.14, p-H=0.07, p-Cl=0.06 and p-NO2=0.011 liter/mole.sec, and the rate constants of polymerization in DMSO by 5 mole% pyridine at 35°C were p-Me0=0.048, p-Cl=7.6 × 10−3 and p-NO 2 =1.64 × 10 − 3 liter/mole.sec. , respectively. The electronic effect exerted by substituents were well consistent with the Hammett relationship(log k/ko = σ ϱ) when Browns σ+ constants were used. The reaction sensitivity constants(ϱ) obtained from cyanide ion initiator were −1.0 and −0.94 for pyridine initiation. These results indicate that the anionic ring-opening polymerization of p-substituted phenylcyclopropanes is carried out via highly conjugated zwitterionic transition state in the ring opening reaction. Furthermore, in the case of the polymerization initiated by pyridine or triethylamine, the formation of macrozwitterion during polymerization is a feasible mechanism. As an extension of studies in the anionic polymerization of activated cyclopropanes with electronically push-pull substituents, p-substituted phenylcyclopropane-1,1-dicarbonitriles having MeO, Me, H, Cl, and NO2 as substitutents were prepared. The electronic effects of substituents upon the ring-opening reaction during anionic polymerizations were examined. The rate constants of polymerization (kp) in DMSO by 2 mole% cyanide ion at 35°C were p-MeO=0.45, p-Me=0.14, p-H=0.07, p-Cl=0.06 and p-NO2=0.011 liter/mole.sec., and the rate constants of polymerization in DMSO by 5 mole% pyridine at 35°C were p-MeO=0.048, p-Cl=7.6 × 10−3 and p-NO2=1.64 × 10−3 liter/mole.sec. The electronic effect exerted by substituents were well consistent with the Hammett relationship (log k/ko=σ ϱ) when Browns σ+ constants were used. The reaction sensitivity constants (ϱ) obtained from cyanide ion initiator were −1.0 and −0.94 for pyridine initiation. These results indicate that the anionic ring-opening polymerization of p-substituted phenylcyclopropanes is carried out via highly conjugated zwitterionic transition state in the ring opening reaction.

The first synthesis of a transition metal-catalyzed homopolymer having pendentt-boc-protected quinizarin for patterned fluorescence images

A homopolymer having pendentt-Boc-protected quinizarin moieties has been prepared for patterned fluorescence images. The homopolymer P{t-BQN (2-norbornenylmethyl di-tert-butoxycarbonylquinizarin)}5 was prepared by palladium-catalyzed addition polymerization. Thet-Boc-protecting groups of the polymer were efficiently removed during chemical amplification process and revealed original properties of quinizarin, allowing patterned fluorescence images in the polymer film.

Extraction of cholesterol by non-ionic cholesterol-based polymeric vesicles

SummaryIn the search for the potential method to extract the free cholesterol from certain biological systems, a nonionic polymeric amphiphile was prepared from cholesterol-based monomer and acrylamide. This copolymer dispersed well forming vesicles when sonicated and was found to be effective for the extraction of cholesterol in water as the experiment with [14C]cholesterol indicated. Extraction became more effective as temperature was raised.

Vesicle formation by non-ionic polymerizable cholesterol-based amphiphiles

Abstract Sonication of a non-ionic polymerizable chlosterol-based amphiphile, 1-ethenyl-3-(8-(cholest-5-en-3β-yloxy)- 3,6-dioxaoctyl)-2-pyrrolidone, in water resulted in the formation of bilayer vesicles. The vesicle formation was evidenced by transmission electron microscopy and[ 14 C] sucrose entrapment. Polymeric vesicles, prepared by polymerization in the bilayer, showed increased stability.