• Bulletin of the Korean Chemical Society
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• 제31권12호
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• pp.3765-3770
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• 2010

Selective oxidation of olefins has been carried out in water medium with tert-butylhydroperoxide (TBHP, 70% aqueous) as an oxidant using polymer-anchored Ni(II) complex as a catalyst. Several parameters were varied to optimize the reaction conditions. Under the optimized reaction conditions olefins gave selectively allylic oxidation products. The present polymer anchored Ni(II) complex can be recycled five times without any appreciable loss in catalytic activity.

• Bulletin of the Korean Chemical Society
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• 제31권6호
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• pp.1621-1627
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• 2010

The investigation of the catalytic activity of supported rhodium(I) complex [Rh(P-S)$(CO)_2$] (P-S; polymer anchored salicylic acid) toward the reductive carbonylation of nitrobenzene in DMF medium has been reported. Use of basic cocatalysts in the reaction medium enhanced the percentage of more useful phenyl carbamates. Spectroscopic studies indicate that the reaction proceeds through a dimer species [Rh(HS)(CO)(C(O)$OCH_3$)(${\mu}-OCH_3)]_2$ and phenyl isocyanate is formed as an intermediate. A plausible reaction mechanism based on the identification of reactive intermediates from the soluble rhodium variety has been proposed for the carbonylation process.

• Elastomers and Composites
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• 제54권3호
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• pp.182-187
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• 2019

To improve the mechanical properties of glass-fiber-reinforced polypropylene (PP) composites through interfacial adhesion control between the PP matrix and glass fiber, the surface of the glass fiber was modified with PP-graft-maleic anhydride (MAPP). Surface modification of the glass fiber was carried out through the well-known hydrolysis-condensation reaction using 3-aminopropyltriethoxy silane, and then subsequently treated with MAPP to produce the desired MAPP-anchored glass fiber (MAPP-a-GF). The glass-fiber-reinforced PP composites were prepared by typical melt-mixing technique. The effect of chemical modification of the glass fiber surface on the mechanical properties of composites was investigated. The resulting mechanical and morphological properties showed improved interfacial adhesion between the MAPP-a-GF and PP matrix in the composites.

• International Journal of Concrete Structures and Materials
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• 제7권1호
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• pp.3-16
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• 2013

Strengthening concrete structures using FRP composites is a commonly considered technology in many practical situations. The success of the strengthening intervention largely depends on adequate bond between FRP sheets and the concrete substrate. In recent years, techniques to anchor FRP sheets in applications where sheets must develop strength in a short length have been proposed. One of these techniques includes use of FRP anchors embedded into the concrete substrate and forming part of the composite strengthening system. This paper presents the results of studies conducted recently at the University of Massachusetts Amherst to advance the understanding on the behavior of FRP anchored systems.

• 콘크리트학회논문집
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• 제17권6호
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• pp.1085-1090
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• 2005

Rod-type fiber reinforced polymer plastics(FRPs) similar to reinforcing steel bars have rarely been considered. In this study, an experiment was performed using beams strengthened with rod-type CFRPs and high-strength mortar overlay. The test results show that the strengthened beams not only had improved endurance limits but also improved load carrying capacities, stiffness values, and cracking loads as compared to a non-strengthened beam. Strengthened beams anchored with bolts throughout their entire span had more efficient structural behaviors, including composite behavior on the interface between the concrete and mortar, and load carrying capacity, than a strengthened beam anchored only on the end block.

• Biomaterials and Biomechanics in Bioengineering
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• 제2권1호
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• pp.15-22
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• 2015

Poly(ethylene glycol) end-capped with pentafluorophenyl group(s) in ABA (FP-PEG-FP) and AB (mPEG-FP) types were prepared. Even though they were similar in composition, the lower critical solution temperature (LCST) of FP-PEG-FP was observed at $23^{\circ}C$, whereas that of mPEG-FP was observed at $65^{\circ}C$. To understand the large difference in solution behaviour of the two polymers, UV-VIS spectroscopy, microcalorimetry, 1H-NMR spectroscopy, and dynamic light scattering were used. FP-PEG-FP has two hydrophobic pentafluorophenyl groups at the ends of hydrophilic PEG (1000 Daltons), whereas mPEG-PF has a highly dynamic PEG (550 Daltons) block that are anchored to a hydrophobic pentafluorophenyl group. PF-PEG-PF not only has a smaller conformational degree of freedom than mPEG-PF but also can form extensive intermolecular aggregates, therefore, PF-PEG-PF exhibits a significantly lower LCST than mPEG-PF. This paper suggests that topological control is very important in designing a temperature-sensitive polymer.

• Computers and Concrete
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• 제18권5호
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• pp.951-968
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• 2016

In this study, pullout capacities of post-installed deformed bars anchored in low strength concrete using different bonding materials are investigated experimentally. The experimental study was conducted under outdoor and indoor conditions; on the beams of an actual reinforced concrete building and on concrete bases constructed at Istanbul Technical University (ITU). Ready-mixed cement based anchorage mortar with modified polymers (M1), ordinary cement with modified polymer admixture (M2), and epoxy based anchorage mortar with two components (E) were used as bonding material. Furthermore, test results are compared with the predictions of current analytical models. Findings of the study showed that properly designed cement based mortars can be efficiently used for anchoring deformed bars in low quality concrete. It is important to note that the cost of cement based mortar is much lower with respect to conventional epoxy based anchorage materials.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.635-638
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• 2004

External bonding of steel plates has been used to strengthen deficient reinforced-concrete structures since the 1960s. In recent years, fiber-reinforcde polymer(FRP) plates have been increasingly used to replace steel plates due to their superior properties. This paper is concerned with anchorage failure due to crack propagation parallel to the boned plated near or along the adhesive/concrete interface, staring from the critically stressed position toward the anchored end of the plates. Factor of bond-slip interface model is average bond stress, effective length, slip volume and fracture energy. The aim of the present paper is to provide a comprehensive assessment of bond-slip interface model with concrete and CFRP plates.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 추계학술발표대회
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• pp.12.1-12.1
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• 2009

Nano-hydroxyapatite (N-HAp)has shown the pivotal role in producing bone-regenerative materials since it has similarity to natural bone minerals in terms of size, morphology, and the composition. Currently, the combination of biopolymers and N-HAp is recognizedas an attractive approach in generating hybrid scaffolds for bone tissueengineering. Surface engineering is an important issue since it determines whether cells can effectively adhere and proliferate on porous scaffolds. We aim to develop a synthetic approach to porous 3D scaffolds by immobilizing N-HAp on pore surfaces. The discrete nano-level anchoring of N-HAp on the scaffold pore surface is achieved using surface-repellent stable colloidal N-HAp with surface phosphate functionality. This rational surface engineering enables surface-anchored N-HAp to express its overall intrinsic bioactivity,since N-HAp is not phase-mixed with the polymers. The porous polymer scaffolds with surface-immobilized N-HAp provide more favorable environments thanconventional bulk phase-mixed polymer/N-HAp scaffolds in terms of cellular interaction and growth. In vitro biological evaluation using alkalinephosphatase activity assay supports that immobilized N-HAp on pore surfaces of polymer scaffolds contributed to the more enhanced in vitro osteogenicpotential. Besides, the scaffolds with surface-exposed N-HAp provide favorable environments for enhanced in vivo bone tissue growth, estimated by characteristic biomarkers of bone formation such as collagen. The results suggest that newly developed hybrid scaffolds with surface-immobilized N-HApmay serve as a useful 3D substrate with pore surfaces featuring excellent bonetissue-regenerative properties. Acknowledgement. This research was supported by a grant (code #: 2009K000430) from 'Center for Nanostructured Materials Technology' under '21st Century Frontier R&D Programs' of the Ministry of Education, Science and Technology, Korea.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.86-88
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• 2006

The novel linear- (V-LUM) and cross-type macromonomers (C-VUM) of vinyl-terminated bifunctional polyurethane were synthesized and applied to the dispersion polymerization of styrene and MMA in ethanol. The existence of the vinyl terminal groups and the grafted macromonomer with styrene and PMMA was verified using 1H NMR and 13C NMR. Monodisperse polystyrene (PS) microspheres were successfully obtained above 15 wt % of macromonomer relative to styrene. The macromonomer can efficiently stabilize higher surface area of the particles compared to a conventional stabilizer, PVP. The grafting ratio of the PS calculated from 1H NMR linearly increased up to 0.048 with 20 wt % of the macromonomer and the high molecular weights (501,300 g/mol) of PS with increased glass transition and enhanced thermal stability were obtained. Furthermore, the stable and monodisperse PMMA microspheres having a weight-average diameter of $5.09{\mu}m$ and a good uniformity of 1.01 were obtained with 20 wt% L-VUM. The molecular weight increased, but the size of the PMMA particles decreased with the macromonomer concentration due to the increased stabilizing effect. The molecular weight of the PMMA was approximately two fold higher than that by a conventional PVP. The L-VUM acts as a reactive stabilizer, which gives polyurethane-grafted PS or PMMA with a high molecular weight. In addition, the XPS result showed that the C-PS (PS using the C-VUM) was anchored with a larger amount of PEG than that of the L-PS (PS using the L-VUM) on the particle surface. Thus, the reaction and stabilizing mechanism of the macromonomers for the formation of PS particles is proposed.