• Macromolecular Research
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• v.11 no.4
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• pp.291-295
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• 2003

Dextran as a candidate material for colon-specific drug delivery has been studied. Crosslinked dextran hydrogels were prepared by mixing dextran, $MgCl_2$, glutaraldehyde (GA) and polyethyleneglycol (PEG 400) in water. The dextran hydrogels were characterized by measuring equilibrium swelling ratios and mechanical strengths. Response surface methodology (Central Composite Design) was used to evaluate the swelling behaviors and mechanical strengths as functions of concentrations of $MgCl_2$, GA, and PEG 400, which was found to be useful for the evaluation. It showed that the swelling behavior and mechanical strengths were influenced significantly by PEG 400 and $MgCl_2$ concentrations.

• Journal of the Korean Graphic Arts Communication Society
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• v.21 no.1
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• pp.11-20
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• 2003

Equilibrium swelling curves of N-isopropyl acrylamide(NIPA) gel and its ionized copolymer gels were obtained as a function of temperature. Discontinuous volume changes of the gels were observed. Phase transition temperature was increased with the ionized counter parts of the gels. Equilibrium swelling of ionized copolymer gel cylinder was found to depend strongly on their diameters. Crosslinking density of NIPA gel was adjusted by increasing N,N'-methylenebisacrylamide(BIS). Phase transition temperature was increased with the crosslinking density.

• Polymer(Korea)
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• v.37 no.4
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• pp.478-485
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• 2013

In this study, hydrogels with fast swelling and high absorbent properties were prepared using biopolymers approved as a food additive and their swelling properties were characterized. To improve the swelling properties of conventional hydrogels, we formed gas bubbles using a foaming agent in the process of preparing hydrogels and characterized in terms of equilibrium swelling ratio, swelling kinetics and cytotoxicity. In particular, alginate hydrogels observed by a digital microscope have an open-pore channels structure with the sizes of hundreds micrometers. Also, the cell viability of all hydrogels were found to be much higher than that of poly(acrylic acid).

• Journal of Korean Society of Forest Science
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• v.4 no.1
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• pp.30-32
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• 1965

Many kind tree species are growing in Korea. However most of them are inferior in wood qualities and production for commercial utilization except several species. Among the useful several species Red Pine (Pinus densiflora S. et. Z.) is growing in main tree species and most generally utilizing wood in korean forest. It is used widely as mine timbers, cross ties, boxes, floorings, pulpwoods, constructions and engineerings. Although this species is most useful and economical in this country, the basical properties on relation between wood and relative humidities were not studied certainly. This study was performed by need of inspection the hygroscopic and swelling properties to be apllied for physical manufacturing. According to the results the Equilibrium Moisture Contents of each relative humidity conditions are as table (3), and the swelling values of sap and heartwood are as table (4) and (5) in text. In this study sapwood moisture contents are higher than heartwood in each relative humidities conditions. Tangential and radial ratios of average swelling values are 1:1.971 in sapwood and 1:2.178 in heartwood.

• Journal of Pharmaceutical Investigation
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• v.21 no.2
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• pp.91-95
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• 1991

Polyethylene glycol, polypropylene glycol and block copolymer of ethylene glycol and propylene glycol were crosslinked by triisocyanate to form water swellable, rubbery polymer. The equilibrium swelling of the hydrogels ranged from 3% to 60% according to the hydrophobic-hydrophilic properties of the prepolymers. Model drugs, sodium salicylate and prednisolone were incorporated in the polymer matrices by swelling loading. Physical properties of the drugs affected the drug release mechanisms due to the change in the swelling behaviors of the polymeric devices. Zero order release was observed in the case of relatively hydrophobic polymer matrices.

• Macromolecular Research
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• v.14 no.2
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• pp.132-139
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• 2006

The dispersion of organoclay in ethylene propylene diene terpolymer (EPDM) matrix was correlated with the rheological and swelling properties of nanocomposites. X-ray diffraction pattern (XRD) and transmission electron microscopic (TEM) analysis exhibited the disordered-intercalated structure of EPDM/organoclay nanocomposite. The extent of the disordered phase increased with increasing organoclay content up to a limiting value of 3 wt% after which equilibrium tended towards intercalation. The dispersion effect of organoclay in EPDM matrix was clarified by the physicochemical properties like rheological response and swelling thermodynamics in toluene. The increase in viscoelastic properties of EPDM nanocomposite with increasing organoclay content up to 3 wt%, followed by a subsequent decrease up to 4 wt%, was correlated in terms of the disordered and ordered states of the dispersed nano-clay sheets. Swelling measurements revealed that the change in entropy of the swelling increased with the increase in disorder level but decreased with the increase in intercalation level of organoclay in the disordered-intercalated nanocomposite. The increase in solvent uptake was comparable with the free volume in EPDM matrix upon inclusion of silicate particles, whereas the inhibition in solvent uptake for higher organoclay loading was described by bridging flocculation.

• Bulletin of the Korean Chemical Society
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• v.4 no.4
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• pp.162-169
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• 1983

The swelling and stress-elongation experiments have been performed for two kinds of gels of tactic poly (2-hydroxyethyl methacrylate) (P-HEMA) with varying crosslinker concentrations. The gels of isotactic and syndiotactic P-HEMA were swollen in aqueous salt solutions upon varying molal concentrations. The solute used were NaCl, $MgCl_2$, $Na_2SO_4$, $MgSO_4$ and urea. The water content at equilibrium swelling and the salt partition coefficient were determined, and stress-elongation curves of the gels were obtained. From these results, the effective number of chain (${\nu}_e$) and the Flory-Huggins interaction parameter (${\chi}_1$) were also obtained. The swelling experiment was also performed under varying solvents, and the degree of swelling was determined. The solubility parameter of P-HEMA was obtained as 13.4 (cal/mole)$^{l/2}$ using the correlation between the degree of swelling and the solubility parameter (${\delta}_1$) of solvents. The mechanical properties of syndiotactic P-HEMA is stronger than that of isotactic P-HEMA, and the water content of both gels become smaller when the crosslinking increases. Isotactic P-HEMA contains more water content than syndiotactic P-HEMA does.

• YAKHAK HOEJI
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• v.41 no.1
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• pp.22-29
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• 1997

Poloxamer-poly (acrylic acid) (PAA) interpenetrating polymer networks (IPNs) were prepared via matrix polymerization of acrylic acid with poloxamer prepolymer. The equilibrium s welling of poloxamer/PAA IPNs was determined in various pH medium. The swelling of poloxamer/PAA IPNs was more affected by pH difference compared with the swelling of homo PAA gel due to protonation and deprotonation of the PAA network, followed by reversible formation and dissociation of the interpolymer complex due to hydrogen bonding between acidic hydrogens and ether oxygens. Nonionic/anionic/cationic drugs were incorporated into IPN matriceds as a model drug and their release behavior was studied. Nonionic, drug revealed release patterns depending solely on pH dependent swelling kinetics. In contrast, the release of ionic drugs was significantly affected by ionic drug-polymer interaction as well as the swelling kinetics.

• Journal of Applied Biological Chemistry
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• v.48 no.4
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• pp.213-217
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• 2005

Microbial hydrogel was prepared with poly(${\gamma}$-glutamic acid) produced from Bacillus subtilis BS62 using crosslinking reagent, ethylene glycol diglycidyl ether (EGDE), and its physico-chemical characteristics were examined. Hydrogel which prepared from 10 grams of 10% PGA solution with $600\;{\mu}l$ of EGDE at $50^{\circ}C$ for 17 h swelled 4,320 times its dry weight, and time to reach swelling equilibrium in deionized water at 4 to $45^{\circ}C$ range was about 20 h. Swollen hydrogel shrunk in ionic solutions, and rate of shrinkage was higher in calcium chloride solution than sodium chloride solution. Swelling rate of hydrogel increased 1.3-fold of initial swelling rate for 30 min at $80^{\circ}C$.

• Journal of Pharmaceutical Investigation
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• v.24 no.3
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• pp.155-165
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• 1994

Some mucoadhesive polymers such as hydroxypropylcelluose (HPC) and carbopol-934 (CP) have been employed for the preparation of mucoadhesive polymeric systems, and their physical properties including mucoadhesion, swelling, and drug release were evaluated. A new simple experimental technique that can quantitatively measure the bioadhesive properties of various polymeric systems has been developed by the methods of detachment force test. As the polymeric systems, the discs of freeze-dried HPC/CP solid dispersions were prepared. The mucosa used in these tests were upper, middle, and lower parts of small intestine of male rats weighing $300{\sim}350\;g$. Detachment forces were increased as the mole fraction of CP increased in discs of HPC/CP solid dispersions. In the points of intestinal site dependence of mucoadhesion, the solid dispersions revealed non-specific mucoadhesion to the intestine. Swelling and drug release characteristics of mucoadhesive polymeric systems were studied extensively to find out the feasibility for the oral controlled delivery systems. Swelling ratio, expressed as the final height/initial height, has been determined in various pH buffer solutions. Hydrochlorothiazide (HCT) was employed as a model drug for release study. Apparent swelling and drug release rate constants, $K_s$ and $K_r$ respectively, were obtained from the square-root time plot of either swelling ratio or released amount of drug, particularly for the time periods before reaching the equilibrium. As a result, the swelling ratio of HPC/CP solid dispersions was increased as the weight percentage of CP increased. Similarly, the release of HCT from the solid dispersions was dependent on pH changes and CP contents, resulted in the slower release of HCT with the increases of pH and CP contents.