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المؤلفون: Byoung Chul Chun, Yong-Chan Chung, Seul Bee Lee
المصدر: Journal of Applied Polymer Science. 128:3446-3454
مصطلحات موضوعية: Materials science, Flexibility (anatomy), Polymers and Plastics, Linear polymer, General Chemistry, Grafting, Surfaces, Coatings and Films, chemistry.chemical_compound, medicine.anatomical_structure, chemistry, Polymer chemistry, Materials Chemistry, Copolymer, medicine, Pendant group, Phenylisocyanate, Polyurethane
الوصف: Polyurethane (PU) with a diphenylamino side group is tested for low temperature flexibility at −30°C and compared with a linear PU without the diphenylamino side group. The PU is composed of 4,4′-methylenebis(phenylisocyanate) (MDI), poly(tetramethyleneglycol) (PTMG), 1,4-butanediol (BD), and the diphenylamino group that is grafted to PU chains by a second MDI. The mechanical and shape memory properties of these two types of PU, which differ in the PTMG and the diphenylamino group content, are compared. In the best case, a 306% increase in the maximum stress compared with the linear polymer is attained with a little decrease in the strain. Shape recovery at 45°C increases to 94% and remains ∼90% after four cyclic tests. Low temperature flexibility can be improved by increasing the diphenylamino content. The PU with a diphenylamino side group demonstrates the low temperature flexibility at −30°C, whereas the linear PU must be warmed to room temperature to attain the same degree of flexibility. The exceptional low temperature flexibility is analyzed and is discussed together with the experimental data. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
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المؤلفون: Byoung Chul Chun, Sung Jae Shin, Yong-Chan Chung, Jae Won Choi
المصدر: Fibers and Polymers. 13:815-822
مصطلحات موضوعية: Materials science, Polymers and Plastics, General Chemical Engineering, Relative viscosity, Soft segment, Infrared spectroscopy, General Chemistry, Shape-memory alloy, chemistry.chemical_compound, chemistry, visual_art, Ultimate tensile strength, visual_art.visual_art_medium, Copolymer, Composite material, Polycarbonate, Polyurethane
الوصف: The polyurethane (PU) copolymer was laterally crosslinked with an extra MDI, in which a more rigid polycarbonatediol replaced the conventional poly(tetramethyleneglycol) as a soft segment. What is the impact of the possible molecular interaction between polycarbonate soft segments and lateral crosslinking. The structural change after crosslinking and the impact of new soft segment were followed by infrared spectra, crosslink density, UV-VIS spectra, and relative viscosity. The tensile stress could improve as much as 554 % by selecting the polycarbonate soft segment and the lateral crosslinking. Shape recovery was over 90 % for the entire series and reproducible for four test cycles. The adoption of polycarbonate soft segment and lateral crosslinking significantly could improve the tensile strength and shape recovery compared to PU with polyetherdiol or polyesterdiol soft segment.
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63
المؤلفون: Yong-Chan Chung, Byung Hee Lee, Kyung Hoon Chung, Byoung Chul Chun
المصدر: Journal of Applied Polymer Science. 133
مصطلحات موضوعية: Materials science, Diglycidyl ether, Polymers and Plastics, 02 engineering and technology, General Chemistry, 010402 general chemistry, 021001 nanoscience & nanotechnology, Grafting, 01 natural sciences, 0104 chemical sciences, Surfaces, Coatings and Films, chemistry.chemical_compound, chemistry, Ultimate tensile strength, Thermal, Materials Chemistry, Composite material, 0210 nano-technology, Polyurethane
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64
المؤلفون: Ha Youn Kim, Yong-Chan Chung, Jae Won Choi, Byoung Chul Chun
المصدر: Journal of Elastomers & Plastics. 45:333-349
مصطلحات موضوعية: Materials science, Polymers and Plastics, Intrinsic viscosity, Shape-memory alloy, Grafting, chemistry.chemical_compound, Differential scanning calorimetry, chemistry, Reagent, Ultimate tensile strength, Polymer chemistry, Materials Chemistry, Copolymer, Polyurethane
الوصف: The effect of the pendant tertiary butyl group on the shape recovery and tensile properties of a polyurethane (PU) block copolymer was investigated. The pendant tertiary butyl group was designed to interrupt molecular interactions and to disturb the close contact between PU chains through its bulky structure and, thus, to improve the shape recovery at subzero temperatures, while maintaining high and reproducible tensile properties and the shape recovery at ambient temperature. The attachment of the tertiary butyl group did make a difference in the phase separation of the hard and soft segments in the PU structure, as determined from the results of infrared and differential scanning calorimetry. The crosslink density and the intrinsic viscosity experienced an unusual increase with the tertiary butyl content due to partial crosslinking by the grafting reagent. Shape recovery and retention were reproducible after performing repeated shape memory tests. Finally, the effect of the tertiary butyl group on the shape recovery at −10°C was compared with that of linear PU, and the reason for the remarkable flexibility is discussed.
URL الوصول: https://explore.openaire.eu/search/publication?articleId=doi_________::26082eede6eabdb0aef738baf354ca1f
https://doi.org/10.1177/0095244312452272 -
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المؤلفون: Hyang Mi Chung, Byoung Chul Chun, Jae Won Choi, Yong-Chan Chung
المصدر: High Performance Polymers. 24:295-304
مصطلحات موضوعية: Materials science, Polymers and Plastics, Organic Chemistry, Aromaticity, Grafting, chemistry.chemical_compound, chemistry, Reagent, Polymer chemistry, Ultimate tensile strength, Materials Chemistry, Copolymer, Pendant group, Spectroscopy, Polyurethane
الوصف: The impact of the pendant anthryl group on the low temperature flexibility and tensile properties of a polyurethane block copolymer was investigated. The pendant anthryl group was designed to interrupt molecular interactions and to disturb the close contact between polyurethane (PU) chains through its rigid aromatic rings; thus, to improve the flexibility at extremely low temperatures, while maintaining high and reproducible tensile properties and the shape recovery at ambient temperatures. The attachment of the anthryl group was confirmed using the infrared (IR), nuclear magnetic resonance (NMR), and ultraviolet-visible (UV-VIS) spectroscopy. Increasing the anthryl content led to an unusual increase in the crosslink density due to partial crosslinking by the grafting reagent. The shape recovery and retention results were reproducible after performing repeated shape memory tests. Finally, the effect of the anthryl group on the shape recovery at −30 °C was compared with that of linear PU, and the reason for the remarkable flexibility at low temperature is discussed.
URL الوصول: https://explore.openaire.eu/search/publication?articleId=doi_________::72352401e14f1a8f29dc157786e2f828
https://doi.org/10.1177/0954008312439318 -
66
المؤلفون: Yong-Chan Chung, Byoung Chul Chun, Duy Nguyen, Jae Won Choi
المصدر: Macromolecular Research. 20:883-886
مصطلحات موضوعية: Materials science, Polymers and Plastics, Biocompatibility, General Chemical Engineering, Organic Chemistry, Grafting, chemistry.chemical_compound, chemistry, Polymer chemistry, Ultimate tensile strength, Materials Chemistry, Copolymer, Reactivity (chemistry), Pendant group, Ethylene glycol, Polyurethane
الوصف: Polyurethane (PU) has undergone an extensive study and can be functionalized by the grafted pendant groups. Actually, poly(ethylene glycol) (PEG) has been grafted to polyurethane to improve the biocompatibility in biomedical applications, and low temperature shape recovery was improved by the grafted pendant group. The tensile strength and the shape recovery were raised by the terminal and the lateral crosslinking. The carbamate unit in PU was frequently employed as the grafting point due to advantages such as ample linking sites, high reactivity, and mild coupling conditions. Shape memory PU with propionic acid side group was already reported for the control of mechanical strength. Meanwhile, the neutralization pairing between dimethylamino and carboxyl head groups was applied for the vesicle formation from single chain surfactants. In this investigation, the PUs grafted with a dimethylamino or a carboxyl pendant group were ionically crosslinked by neutralization to increase their molecular interaction and the impact on tensile strength and shape memory is examined.
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المؤلفون: Byoung Chul Chun, Hyun Shik Park, Yong-Chan Chung, Jae Won Choi
المصدر: High Performance Polymers. 24:200-209
مصطلحات موضوعية: chemistry.chemical_compound, Materials science, Polymers and Plastics, chemistry, Organic Chemistry, Materials Chemistry, Copolymer, Shape-memory alloy, Composite material, Polyurethane, Characterization (materials science)
الوصف: Shape memory polyurethane (SMPU) flexibly crosslinked by a hydrophobic poly(dimethylsiloxane) (PDMS) spacer at its side through allophanate bonding was tested for shape recovery at −30 °C and compared to a linear SMPU. The SMPU was composed of 4,4′-methylenebis(phenylisocyanate) (MDI), poly(tetramethyleneglycol) (PTMG), 1,4-butanediol (BD), and PDMS that was connected to SMPU chains by a second MDI. The mechanical and shape memory properties of two types of SMPU, differing in PTMG and PDMS content, were compared. In the best case, a 283% increase in maximum stress compared to the linear polymer was attained without any sacrifice of strain. Shape recovery at 45 °C increased to 91% and remained at more than 80% after four cyclic tests. Shape recovery at 0 °C could be improved by increasing PDMS content, and the critical shape recovery temperature decreased with increasing PDMS content. The PDMS-crosslinked SMPU demonstrated instant shape recovery at −30 °C in comparison with the linear SMPU that must be warmed to room temperature for complete shape recovery. The extraordinary shape memory results were analyzed and are discussed together with differential scanning calorimetry and infrared data.
URL الوصول: https://explore.openaire.eu/search/publication?articleId=doi_________::20c5933d217ad9c9992206e92db95742
https://doi.org/10.1177/0954008311435799 -
68
المؤلفون: Joon Young Lee, Yong-Chan Chung, Byoung Chul Chun, Jae Won Choi
المصدر: Journal of Applied Polymer Science. 126:E225-E232
مصطلحات موضوعية: chemistry.chemical_classification, Materials science, Polymers and Plastics, General Chemistry, Polymer, Surfaces, Coatings and Films, chemistry.chemical_compound, Differential scanning calorimetry, chemistry, Covalent bond, Polymer chemistry, Ultimate tensile strength, Materials Chemistry, Copolymer, Molecule, Carboxylate, Polyurethane
الوصف: Malic acid, a molecule containing two carboxyl groups per molecule, was grafted to polyurethane (PU) through a carbamate group. The polymer was transformed to the anionic carboxylate form to observe the impact on the tensile strength and shape recovery of the PU. The electrostatic repulsion of the carboxylate reduced the molecular interactions between PUs, a result that was designed to improve the shape recovery at sub-zero temperatures while maintaining high and reproducible tensile strength and shape recovery at ambient temperatures. The grafted carboxyl group was quantitatively determined by acid–base titration, and the change in the molecular interactions was confirmed via IR spectroscopy and differential scanning calorimetry. The viscosity experienced an unusual increase with increasing carboxylate content due to the covalent crosslinking caused by the grafting reagent. Shape recovery and retention were reproducible over repeated shape memory tests. Finally, the shape recovery behavior of each PU was compared at temperatures between −30 and 10°C. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
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المؤلفون: Yong-Chan Chung, Duy Nguyen, Byoung Chul Chun, Jae Won Choi
المصدر: Bulletin of the Korean Chemical Society. 33:707-710
مصطلحات موضوعية: chemistry.chemical_classification, Materials science, General Chemistry, Polymer, Grafting, chemistry.chemical_compound, chemistry, Functional group, Polymer chemistry, Copolymer, Phenyl group, Functional polymers, Pendant group, Polyurethane
الوصف: Polyurethane (PU) has been known for shape memory, ease of synthesis, and versatile applications, and the crosslinking improved the tensile and shape memory properties. The grafting of functional groups to polymers has been extensively researched for the development of new functional polymers without harming their basic structure. Actually, the pendant naphthalene kept PU flexible at low temperature by hindering the molecular interactions between PU chains. PU was made water-compatible by incorporating a pendant carboxylate-ammonium salt group. The previous pendant groups were all attached to the PU through a diol-containing pendant group. Here, allophanate bonding was employed as a method for grafting a functional group to PU due to the advantages of having more available linking sites, higher reactivity, and simple reaction conditions. The pendant group can change the molecular interaction between PU chains, and the impact of this on the tensile and shape memory properties is very intriguing. The rigid aromatic ring as a pendant group may reduce molecular interactions and contribute to low temperature flexibility. In this investigation, the impact of the grafted phenyl group on the tensile properties and low temperature flexibility is examined.
URL الوصول: https://explore.openaire.eu/search/publication?articleId=doi_________::e79435576a9828ed0aff85cc99179a1d
https://doi.org/10.5012/bkcs.2012.33.2.707 -
70
المؤلفون: Yong-Chan Chung, Dong Hyung Lee, Byoung Chul Chun, Jae Won Choi
المصدر: Journal of Intelligent Material Systems and Structures. 23:505-513
مصطلحات موضوعية: Materials science, Mechanical Engineering, chemistry.chemical_compound, Viscosity, chemistry, Reagent, Ultimate tensile strength, Tartaric acid, Copolymer, General Materials Science, Titration, Composite material, Pendant group, Polyurethane
الوصف: The tartaric acid was laterally attached to polyurethane through the carbamate of polyurethane, and the impact on the shape-memory and tensile properties of polyurethane was investigated. The electrostatic repulsion of the tartarate could reduce the molecular interactions between polyurethanes, a result that was designed to improve low-temperature flexibility while maintaining high and reproducible tensile strength and shape recovery above room temperature. The attachment of the tartaric acid was quantitatively determined by acid–base titration, and the change in the molecular interaction between hard segments was confirmed via infrared spectroscopy. Both cross-linking density and viscosity experienced an unusual increase with increasing tartarate content due to partial cross-linking caused by the grafting reagent. Shape recovery and retention were reproducible over repeated shape-memory tests. Finally, the low-temperature flexibility was determined at −10°C, and the reason for the difference was discussed.
URL الوصول: https://explore.openaire.eu/search/publication?articleId=doi_________::03f26f6b74b269343a404dc4e78eb121
https://doi.org/10.1177/1045389x12436737
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