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Macromolecular research 11건

  1. [국내논문]   Allyloxy-and Benzyloxy-Substituted Pyridine-bis-imine Iron(II) and Cobalt(II) Complexes for Ethylene Polymerization  

    Kim Il (Department of Polymer Science and Engineering, Pusan National University ) , Han Byeong Heui (Department of Polymer Science and Engineering, Pusan National University ) , Kim Jae Sung (Department of Polymer Science and Engineering, Pusan National University ) , Ha Chang-Sik (Department of Polymer Science and Engineering, Pusan National University)
    Macromolecular research v.13 no.1 ,pp. 2 - 7 , 2005 , 1598-5032 ,

    초록

    A series of ethylene polymerization catalysts based on tridentate bis-imine ligands coordinated to iron and cobalt was reported. The ligands were prepared through the condensation of sterically bulky anilines with allyloxy-and benzyloxy-substituted 2,6-acetylpyridines. The pre-catalyst complexes were penta-coordinate species of the general formula $\{[(ArN=C(Me))_2(4-RO-C_5H_3N)]MCl_2\}$ (Ar=ortho dialkyl-substituted aryl ring; R=allyl, benzyl; M=Fe, Co). In the presence of ethylene and methyl alumoxane cocatalysts, these complexes were active for the polymerization of ethylene, with activities lower than those of metal complexes of the general formula $\{[(2-ArN=C(Me)_2C_5H_3N]MCl_2\}$ (Ar=ortho dialkyl-substituted aryl ring; M=Co, Fe), containing no substituents in 2,6-acetylpyridine ring. The effects of the catalyst structure and temperature on the polymerization activity, thermal properties, and molecular weight were discussed.

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  2. [국내논문]   Synthesis and Characterization of a Novel Silicon-Containing Epoxy Resin   피인용횟수: 2

    Park Soo-Jin (Advanced Materials Division, Korea Research Institute of Chemical Technology ) , Jin Fan-Long (Advanced Materials Division, Korea Research Institute of Chemical Technology ) , Lee Jae-Rock (Advanced Materials Division, Korea Research Institute of Chemical Technology)
    Macromolecular research v.13 no.1 ,pp. 8 - 13 , 2005 , 1598-5032 ,

    초록

    A novel silicon-containing epoxy resin, the diglycidylether of bisphenol A-silicon (DGEBA-Si), was synthesized and characterized. The properties of the DGEBA-Si epoxy resin cured with 4,4-diaminodiphenyl methane (DDM), including its cure behavior, glass transition temperature, thermal stability, and mechanical strength were investigated. The char yield of the DGEBA-Si/DDM system was higher than that of a commercial DGEBA/DDM system, indicating that the DGEBA-Si epoxy resin showed good flame-retardance. The cured DGEBA-Si/DDM specimens possessed lower glass transition temperatures and higher mechanical properties than DGEBA/DDM specimens. These features were attributed to the introduction of siloxane groups into the main chain of the epoxy resin, which resulted in the improved flexibility of the cured DGEBA-Si/DDM system.

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  3. [국내논문]   Using Microwave Irradiation to Prepare New Poly(amide-imide)s Containing Tetrahydropyrimidinone, Tetrahydro-2-thioxopyrimidine, and Trimellitic Rings in Their Main Chains: Synthesis and Characterization   피인용횟수: 1

    Faghihi Khalil (Organic Polymer Chemistry Research Laboratory, Department of Chemistry, Faculty of Science, Arak University, Dept. of Chemical Eng., Faculty of Eng., Azad University of Arak ) , Hagibeygi Mohsen (Dept. of Chemical Eng., Faculty of Eng., Azad University of Arak)
    Macromolecular research v.13 no.1 ,pp. 14 - 18 , 2005 , 1598-5032 ,

    초록

    Under irradiation in a microwave oven, six novel poly(amide-imide)s containing tetrahydropyrimidinone, tetrahydro-2-thioxopyrimidine moieties and trimellitic rings in their main chains were synthesized through the polycondensation reaction of N,N'-(4,4'-diphenylether)bis(trimellitimide) diacid chloride with six different derivatives of tetrahydropyrimidinone and tetrahydro-2-thioxopyrimidine in the presence of a small amount of a polar organic medium, such as o-cresol. The polycondensation proceeded rapidly and completed within 7-9 min, producing a series of new poly(amide-imide)s in high yield that showed inherent viscosities in the range 0.33-0.52 dL/g. These poly(amide-imide)s were characterized by elemental analysis, viscosity measurement, thermal gravimetric analysis, solubility test, and FT-IR spectroscopy. All of the polymers were soluble at room temperature in polar solvents such as N,N-dimethylacetamide, N,N-dimethylformamide, dimethylsulfoxide, tetrahydrofuran, and N-methyl-2-pyrrolidone.

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  4. [국내논문]   Deformation Behavior and Nucleation Activity of a Thermotropic Liquid­Crystalline Polymer in Poly(butylene terephthalate)-Based Composites   피인용횟수: 1

    Kim Jun Young (Department of Fiber and Polymer Engineering, College of Engineering, Hanyang University ) , Kang Seong Wook (Department of Fiber and Polymer Engineering, College of Engineering, Hanyang University ) , Kim Seong Hun (Department of Fiber and Polymer Engineering, College of Engineering, Hanyang University ) , Kim Byoung Chul (Department of Fiber and Polymer Engineering, College of Engineering, Hanyang University ) , Shim Kwang Bo (Department of Ceramic Engineering, CPRC, College of Engineering, Hanyang University ) , Lee Jung Gyu (SKC Film R&D Center)
    Macromolecular research v.13 no.1 ,pp. 19 - 29 , 2005 , 1598-5032 ,

    초록

    Polymer composites based on a thermotropic liquid-crystalline polymer (TLCP) and poly(butylene terephthalate) (PBT) were prepared using a melt blending process. Polymer composites consisting of bulk cheap polyester with a small quantity of expensive TLCP are of interest from a commercial perspective. The interactions between the PBT chains and the flexible poly(ethylene terephthalate) (PET) units in the TLCP phase resulted in an improvement in the compatibility of PBT/TLCP composites. TLCP droplets deformed and fragmented into smaller droplets in the PBT/TLCP composites, which resulted in TLCP fibrillation through the effective deformation of the TLCP droplets. The nucleation activities of the PBT/TLCP composites increased by adding even a small amount of the TLCP component.

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  5. [국내논문]   Recycling Natural Rubber Vulcanizates through Mechanochemical Devulcanization   피인용횟수: 1

    Jang G. K. (Materials Science Centre ) , Das C. K. (Materials Science Centre)
    Macromolecular research v.13 no.1 ,pp. 30 - 38 , 2005 , 1598-5032 ,

    초록

    Sulfur-cured gum natural rubber vulcanizates were devulcanized using two different concentrations of diallyl disulfide. The devulcanization process was performed at $110^{\circ}C$ min in an open two-roll cracker-cum-mixing mill. Natural rubber vulcanizates having various sulfur/accelerator ratios were used to study the cleavage of monosulfide, disulfide, and polysulfide bonds. The properties of devulcanized natural rubber increased upon increasing the disulfide concentration and the mechanical properties of the revulcanized natural rubber increased upon decreasing the sulfur content in the original rubber vulcanizates. The scorch time and the maximum state of cure both increased when the ground vulcanizates were treated with higher amounts of disulfide. TGA and DMA were conducted to study the effects of the devulcanization on the thermal stability and the $T_g$ behavior of the vulcanizates. SEM analysis was conducted to study how the failure mechanism was affected by the devulcanization process. It was possible to recover $70-80\%$ of the original gum rubber properties by using this process. From IR spectroscopic analysis, we observed that the oxidation of the main chains did not occur during high-temperature milling.

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  6. [국내논문]   Preparation for Protein Separation of an Ion-Exchange Polymeric Stationary Phase Presenting Amino Acid and Amine Units Through Surface Graft Polymerization  

    Choi Seong-Ho (Department of Chemistry, Hannam University ) , Lee Kwang-Pill (Department of Chemistry Graduate School, Kyungpook National University ) , Shin Chang-Ho (KT&G Central Research Institute)
    Macromolecular research v.13 no.1 ,pp. 39 - 44 , 2005 , 1598-5032 ,

    초록

    Ion-exchange polymeric stationary phases presenting amino acid and amino groups were prepared by the surface grafting of glycidyl methacrylate onto a silica gel surface and subsequent amination. Three kinds of amino acids-L-arginine (Arg), D-lysine (Lys), and D-histine (His)-were used in this study. An ion-exchange polymeric stationary phase presenting ethylene diamine (EDA) was also prepared by surface graft polymerization. Separation of the model proteins bovine serum albumin (BSA), chick egg albumin (CEA), and hemoglobin (Hb) was performed using the amino acid- and amine-derived columns. In separating the CEA/BSA mixture, the resolution time of BSA was longer than that of CEA when using the EDA column, whereas the resolution time of BSA was shorter than that of CEA when using the Arg, Lys, and His columns. In the separation of the Hb/BSA mixture, the resolution time of BSA was longer than that of Hb in the EDA column, whereas the resolution time of BSA was shorter than that of Hb in the amino acid columns (D-Lys, L-Arg, and D-His).

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  7. [국내논문]   Partially Hydrolyzed Crosslinked Alginate-graft-Polymethacrylamide as a Novel Biopolymer-Based Superabsorbent Hydrogel Having pH - Responsive Properties   피인용횟수: 1

    Pourjavadi A. (Polymer Research Laboratory, Department of Chemistry, Sharif University of Technology ) , Amini-Fazi M. S. (Polymer Research Laboratory, Department of Chemistry, Sharif University of Technology ) , Hosseinzadeh H. (Polymer Research Laboratory, Department of Chemistry, Sharif University of Technology)
    Macromolecular research v.13 no.1 ,pp. 45 - 53 , 2005 , 1598-5032 ,

    초록

    In this study, a series of highly swelling hydrogels based on sodium alginate (NaAlg) and polymethacryl­amide (PMAM) was prepared through free radical polymerization. The graft copolymerization reaction was performed in a homogeneous medium and in the presence of ammonium persulfate (APS) as an initiator and N,N'-methylenebis­acrylamide (MBA) as a crosslinker. The crosslinked graft copolymer, alginate-graft-polymethacrylamide (Alg-g­PMAM), was then partially hydrolyzed by NaOH solution to yield a hydrogel, hydrolyzed alginate-graft-poly­methacrylamide (H-Alg-g-PMAM). During alkaline hydrolysis, the carboxamide groups of Alg-g-PMAM were converted into hydrophilic carboxylate anions. Either the Alg-g-PMAM or the H-Alg-g-PMAM was characterized by FTIR spectroscopy. The effects of the grafting variables (i.e., concentration of MBA, MAM, and APS) and the alkaline hydrolysis conditions (i.e., NaOH concentration, hydrolysis time, and temperature) were optimized systematically to achieve a hydrogel having the maximum swelling capacity. Measurements of the absorbency in various aqueous salt solutions indicated that the swelling capacity decreased upon increasing the ionic strength of the swelling medium. This behavior could be attributed to a charge screening effect for monovalent cations, as well as ionic cross-linking for multivalent cations. Because of the high swelling capacity in salt solutions, however, the hydrogels might be considered as anti-salt superabsorbents. The swelling behavior of the superabsorbing hydrogels was also measured in solutions having values of pH ranging from 1 to 13. Furthermore, the pH reversibility and on/off switching behavior, measured at pH 2.0 and 8.0, suggested that the synthesized hydrogels were excellent candidates for the controlled delivery of bioactive agents. Finally, we performed preliminary investigations of the swelling kinetics of the synthesized hydrogels at various particle sizes.

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  8. [국내논문]   Release of Calcein from Temperature-Sensitive Liposomes in a Poly(N-isopropylacrylamide) Hydrogel  

    Han Hee Dong (Advanced Materials Division, Korea Research Institute of Chemical Technology ) , Kim Tae Woo (Advanced Materials Division, Korea Research Institute of Chemical Technology ) , Shin Byung Cheol (Advanced Materials Division, Korea Research Institute of Chemical Technology ) , Choi Ho Suk (Department of Chemical Engineering, Chungnam National University)
    Macromolecular research v.13 no.1 ,pp. 54 - 61 , 2005 , 1598-5032 ,

    초록

    We prepared temperature-sensitive liposomes (TS-liposomes) modified with a thermo sensitive polymer, such as poly(N-isopropylacrylamide) (PNIPAAm), to increase the degree of drug release from liposomes at the hyperthermic temperature. A PNIPAAm hydrogel containing TS-Iiposomes was also prepared to obtain a hydrogel complex at body temperature. In addition, a depot system for local drug delivery using the polymer hydrogel was developed to enhance therapeutic efficacy and prevent severe side effects in the whole body. The PNIPAAm-mod­ified TS-liposome was fixed into the PNIPAAm hydrogel having a high temperature-sensitivity. The release behavior of calcein, a model drug, from TS-liposomes in the PNIPAAm hydrogel was then initiated by external hyperthermia; the results indicated that sustained release as a function of temperature and time was caused by the thermosensitivity of the liposome surface and diffusion of the drug into the PNIPAAm hydrogel. Our results indicated that TS-liposomes in a PNIPAAm hydrogel represented a plausible system for local drug delivery.

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  9. [국내논문]   Preparation of Electrospun Oxidized Cellulose Mats and Their in vitro Degradation Behavior   피인용횟수: 1

    Khil Myung Seob (Department of Textile Engineering, Chonbuk National University ) , Kim Hak Yong (Department of Textile Engineering, Chonbuk National University ) , Kang Young Sic (Department of Textile Engineering, Chonbuk National University ) , Bang Ho Ju (Department of Textile Engineering, Chonbuk National University ) , Lee Douk Rae (Department of Textile Engineering, Chonbuk National University ) , Doo Jae Kyun (Department of General Gynecology and Obstetrics med. School, Chonbuk National University)
    Macromolecular research v.13 no.1 ,pp. 62 - 67 , 2005 , 1598-5032 ,

    초록

    This paper investigated the effect of biodegradation behavior on the oxidation of cellulose nanofiber mats. The cellulose mats were produced through electro spinning. The diameter of an electrospun fiber varied from 90 to 240 nm depending on the electrospinning parameters, such as the solution concentration, needle diameter, and rotation speed of a grounded collector. Oxidized cellulose (OC).mats containing different carboxyl contents were prepared using $NO_2$ as an oxidant. The total carboxyl content of the cellulose nanofiber mats obtained after oxidation for 20 h was $20.6\%$ . The corresponding carboxyl content was important from a commercial point of view because OC containing $16-24\%$ carboxyl content are used widely in the medical field as a form of powder or knitted fabric. Degradation tests of the OC mats were performed at $37^{\circ}C$ in phosphate-buffered saline (pH 7.4). Microscopy techniques were introduced to study the morphological properties and the degradation behavior of the OC mats. Morphological changes of the mats were visualized using optical microscopy. Within 4 days of exposure to PBS, the weight loss of the OC mats was $>90\%$ .

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  10. [국내논문]   Reaction Kinetics for the Synthesis of Oligomeric Poly (lactic acid)   피인용횟수: 1

    Yoo Dong Keun (Department of Chemical Engineering, Polymer Technology Institute, Sungkyunkwan University ) , Kim Dukjoon (Department of Chemical Engineering, Polymer Technology Institute, Sungkyunkwan University ) , Lee Doo Sung (Department of Polymer Engineering, Polymer Technology Institute, Sungkyunkwan University)
    Macromolecular research v.13 no.1 ,pp. 68 - 72 , 2005 , 1598-5032 ,

    초록

    A low-molecular-weight poly(lactic acid) was synthesized through the condensation reaction of L-lactic acid. The effects that the catalyst and temperature have on the reaction rate were studied to determine the optimum reaction conditions. The reaction kinetics increased with temperature up to $210^{\circ}C$ , but no further increase was observed above this temperature. Among a few selective catalysts, sulfuric acid was the most effective because it maximized the polymerization reaction rate. Reduction of the pressure was another important factor that enhanced this reactions kinetics.

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