• Title, Summary, Keyword: thermo-reversible

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Thermo-reversible Crosslinking Elastomer through Supramolecular Networks (초분자 네트워크를 이용한 열가역성 가교 탄성체)

  • Bae, Jong-Woo;Oh, Sang-Taek;Kim, Gu-Ni;Baik, Hyen-Jong;Kim, Won-Ho;Choi, Sung-Seen
    • Elastomers and Composites
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    • v.45 no.3
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    • pp.165-169
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    • 2010
  • Recently supramolecular network thermo-reversible crosslinking elastomer having flexibility, various functionality, and advantages of thermoplastic elastomer (TPE) such as recycle and easy processbility is introduced. Although thermo-reversible bonds such as hydrogen bond and ionic cluster is recognized as a common technology since 1990, control technology of bonding and dissociation of crosslink in supramolecular network is a recent technology. In this review, characteristics of thermo-reversible crosslinking elastomer having rheological properties of TPE and reinforcing behaviors of thermoset elastomer are summarized.

Phenotype of Hepartocyte Spheroids in Synthetic Thermo-reversible Extracellular Matrix

  • Park, Keun--Hong;Park, Ju-Young;Bae, You-Han
    • Biotechnology and Bioprocess Engineering:BBE
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    • v.6 no.4
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    • pp.264-268
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    • 2001
  • Aggregates of specific cells are often regarded as better from in artificial organs and mammalian cell bioreactors in terms of cell-specific functionality. In this study, the morphology and liver specific functions of freshly harvested primary rat hepatocytes, which were cultivated as spheroids and entrapped in a synthetic thermo-reversible extracellular matrix, were examined and compared to a control (hepatocytes in single cell form). A copolymer of N-isopropylacrylamide(98 mole % in feed) and acrylic acid (poly (NiPAAm-co-AAC)), a thermo- reversible copolymer gel ma- trix, was used to entrap hepatocytes either in spheroids or single cells. During a 7-day culture pe-riod, the spheroids maintained higher viability and produced albumin and urea at a relatively con-stant rate, while, the single cell culture showed a slight increase in cell numbers and a reduction in albumin secretion Hepatocytes cultrured as spheroids present a potentially useful three-dimensional cell culture system for application in bioartificial liver device.

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Certification of Gibroblase Cell Adhesion and Spreading Mediated by Arg-Gly-Asp (RGD) Sequence on Thermo-Reversible Hydrogel

  • NA, KUN;DONG-WOON KIM;KEUN-HONG PARK
    • Journal of Microbiology and Biotechnology
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    • v.11 no.6
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    • pp.922-927
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    • 2001
  • In an effort to regulate the mammalian cell behavior in entrapment with a gel, we have functionalized hydrogels with the putative cell-binding (-Arg-Gly-Asp-)(RGD) domain. An adhesion molecule of Gly-Arg-Gly-Asp-Ser (GRGDS) peptides, a cell recognition ligand, was induced into thermo-reversible hydrogels, composed of N-isopropylacrylamide with small amounts of acrylic acid (typically 2-5 $mol\%$ in feed), as a biomimetic extracellular matrix (ECM). The GRGDS containing a p(NiPAAm-co-AAc) copolymer gel was studied in vitro for its ability to promote the spreading and viability of cells by introducing a GRGDS sequence. Hydrogel with no adhesion molecule was a poor ECM for adhesion, permiting spreading of only $3\%$ of the seeded cells for 36h. By immobilizing the peptide linkage into the hydrogel, the conjugation of RGD promoted $50\%$ of proliferation for 36h. However, the GREDS sequence, nonadhesive peptide linkage, conjugated hydrogel showed only $5\%$ of the seeded cell for the same time period. In addition, with the serum-free medium, only GRGDS peptides conjugated to hydrogel was able to promotecell spreading, while there was no cell proliferation in the hydrogel without GRGDS. Thus, the GRGDS peptide-conjugated thermo-reversible hydrogel specifically mediated the cell spreading. This result suggests that utilization of peptide sequences conjugating with the cell-adhesive motifs can enhance the degree of cell surface interaction and influence the long-term formation of ECM in vitro.

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New generation polydiacetylenes: Thermo-optical properties as active materials of thermally actuated display devices

  • Yarimaga, Oktay;Lee, Su-Mi;Kim, Jong-Man;Choi, Yang-Kyu
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.457-460
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    • 2009
  • The thermo-optical characteristics of new generation fully reversible diacetylene vesicles, DCDDA-mono-mBzA and DCDDA-bis-mCPE, and their solid film composites are utilized as thermochromic display materials. Conspicuous color intensity of their solid films and blue-to-red color shift with non-fluorescent to fluorescent switching at $100^{\circ}C$ make them promising materials for dual color thermally actuated display devices of the near future.

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Preparation and Properties of Modified PHEMA Hydrogels Containing Thermo-responsive Pluronic Component

  • Hong, Kwang-Hyun;Jeon, Young-Sil;Kim, Ji-Heung
    • Macromolecular Research
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    • v.17 no.1
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    • pp.26-30
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    • 2009
  • To modify and strengthen the properties of PHEMA hydrogel, composite hydrogels containing varying amounts of a Pluronic (PEO-PPO-PEO) component were synthesized by bulk polymerization of HEMA in the presence of Pluronic dimethacrylate under mild photo initiating conditions. The effects of the Pluronic component on gel properties were investigated by measuring the degree of swelling with its temperature responsive behavior, the mechanical properties, and the morphology of the composite hydrogels. With increased Pluronic content, the modified PHEMA hydrogels exhibited an increase in the degree of swelling, and the swelling showed an enhanced thermo-responsive behavior that was completely reversible. In addition, improved mechanical strength and the development of a microporous gel morphology were observed in hydrogels containing Pluronic.

Thermo-Sensitive Polyurethane Membrane with Controllable Water Vapor Permeation for Food Packaging

  • Zhou, Hu;Shit, Huanhuan;Fan, Haojun;Zhou, Jian;Yuan, Jixin
    • Macromolecular Research
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    • v.17 no.7
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    • pp.528-532
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    • 2009
  • The size and shape of free volume (FV) holes available in membrane materials control the rate of gas diffusion and its permeability. Based on this principle, a segmented, thermo-sensitive polyurethane (TSPU) membrane with functional gate, i.e., the ability to sense and respond to external thermo-stimuli, was synthesized. This smart membrane exhibited close-open characteristics to the size of the FV hole and water vapor permeation and thus can be used as smart food packaging materials. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), positron annihilation lifetimes (PAL) and water vapor permeability (WVP) were used to evaluate how the morphological structure of TSPU and the temperature influence the FV holes size. In DSC and DMA studies, TSPU with a crystalline transition reversible phase showed an obvious phase-separated structure and a phase transition temperature at $53^{\circ}C$ (defined as the switch temperature and used as a functional gate). Moreover, the switch temperature ($T_s$) and the thermal-sensitivity of TSPU remained available after two or three thermal cyclic processes. The PAL study indicated that the FV hole size of TSPU is closely related to the $T_s$. When the temperature varied cyclically from $T_s-10{\circ}C$ to $T_s+10^{\circ}C$, the average radius (R) of the FV holes of the TSPU membrane also shifted cyclically from 0.23 to 0.467 nm, exhibiting an "open-close" feature. As a result, the WVP of the TSPU membrane also shifted cyclically from 4.30 to $8.58\;kg/m^2{\cdot}d$, which produced an "increase-decrease" response to the thermo-stimuli. This phase transition accompanying significant changes in the FV hole size and WVP can be used to develop "smart materials" with functional gates and controllable water vapor permeation, which support the possible applications of TSPU for food packaging.

Synthesis and Characterization of Biodegradable Thermo- and pH-Sensitive Hydrogels Based on Pluronic F127/Poly($\varepsilon$-caprolactone) Macromer and Acrylic Acid

  • Zhao, Sanping;Cao, Mengjie;Wu, Jun;Xu, Weilin
    • Macromolecular Research
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    • v.17 no.12
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    • pp.1025-1031
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    • 2009
  • Several kinds of biodegradable hydrogels were prepared via in situ photopolymerization of Pluronic F127/poly($\varepsilon$-caprolactone) macromer and acrylic acid (AA) comonomer in aqueous medium. The swelling kinetics measurements showed that the resultant hydrogels exhibited both thermo- and pH-sensitive behaviors, and that this stimuli-responsiveness underwent a fast reversible process. With increasing pH of the local buffer solutions, the pH sensitivity of the hydrogels was increased, while the temperature sensitivity was decreased. In vitro hydrolytic degradation in the buffer solution (pH 7.4, $37^{\circ}C$), the degradation rate of the hydrogels was greatly improved due to the introduction of the AA comonomer. The in vitro release profiles of bovine serum albumin (BSA) in-situ embedded into the hydrogels were also investigated: the release mechanism of BSA based on the Peppas equation was followed Case II diffusion. Such biodegradable dual-sensitive hydrogel materials may have more advantages as a potentially interesting platform for smart drug delivery carriers and tissue engineering scaffolds.

A Study on Thermodynamic Efficiency for HTSE Hydrogen and Synthesis Gas Production System using Nuclear Plant (원자력 이용 고체산화물 고온전기분해 수소 및 합성가스 생산시스템의 열역학적 효율 분석 연구)

  • Yoon, Duk-Joo;Koh, Jae-Hwa
    • Transactions of the Korean hydrogen and new energy society
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    • v.20 no.5
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    • pp.416-423
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    • 2009
  • High-temperature steam electrolysis (HTSE) using solid oxide cell is a challenging method for highly efficient large-scale hydrogen production as a reversible process of solid oxide fuel cell (SOFC). The overall efficiency of the HTSE hydrogen and synthesis gas production system was analyzed thermo-electrochemically. A thermo-electrochemical model for the hydrogen and synthesis gas production system with solid oxide electrolysis cell (SOEC) and very high temperature gas-cooled reactor (VHTR) was established. Sensitivity analyses with regard to the system were performed to investigate the quantitative effects of key parameters on the overall efficiency of the production system. The overall efficiency with SOEC and VHTR was expected to reach a maximum of 58% for the hydrogen production system and to 62% for synthesis gas production system by improving electrical efficiency, steam utilization rate, waste heat recovery rate, electrolysis efficiency, and thermal efficiency. Therefore, overall efficiency of the synthesis production system has higher efficiency than that of the hydrogen production system.

Thermo- and Acid/base-induced Spectral Switching of a Poly(N-isopropylacrylamide) Copolymer Containing Benzopyran-based D-π-A type Dye Units

  • Lee, Eun-Mi;Gwon, Seon-Yeong;Ji, Byung-Chul;Kim, Sung-Hoon
    • Textile Coloration and Finishing
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    • v.22 no.3
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    • pp.181-186
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    • 2010
  • A thermoresponsive poly(NIPAM-co-dye) labeled with benzopyran-based D-$\pi$-A type dye was prepared by typical radical copolymerization. It can be also constructed a acid/base-induced molecular switch by modulation of intramolecular charge transfer with protonation/deprotonation. The lower critical solution temperature behavior was investigated by means of UV-vis spectroscopy which allows the measurement of the phase transition from $25^{\circ}C$ to $45^{\circ}C$ in aqueous DMSO solution. The morphology of the internal microstructure of the poly(NIPAM-co-dye) hydrogel was observed by scanning electron microscopy. The reversible switch could be obtained by thermal and acid/base stimuli.

Synthesis and Swelling Characteristics of Poly(N-isopropylacrylamide) Containing Polydimethylsiloxane and Nano Clay (Nano Clay와 Polydimethylsiloxane을 포함하는 Poly(N-isopropylacrylamide) 공중합체의 합성과 팽윤거동)

  • Nho, Hui-Cheol;Lee, Chan-Woo;Park, Sang-Youn;Yoon, Koo-Sik
    • Polymer(Korea)
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    • v.34 no.2
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    • pp.166-171
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    • 2010
  • Poly(N-isopropylacrylamide)(PNIPAAm) containing polydimethylsiloxane(PDMS) block and nano clay was obtained by the polymerization of NIPAAm and [3-(methacryloylamino)propyl]trimethyl ammonium montmorillonite(MAPTAC-MMT) with PDMS-macroinitiator. The polymer was characterized with FT-IR, XRD and DSC. The addition of PDMS in the polymers did not affect the value of the lower critical solution temperature(LCST) and the glass transition temperature($T_g$) of the PNIPAAm. However, the swelling ratio decreased with increasing PDMS contents. In the case of PNIPAAm containing nano clay, the content of MAPTAC-MMT did not affect swellability, but the $T_g$ of the PNIPAAm decreased with increasing nano clay contents.