• Membrane Journal
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• v.15 no.1
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• pp.8-14
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• 2005

The hyaluronic acid (HA) with excellent biocompatibility can be combined with the monomer polylactide with good biodegradability to produce biocompatible materials which can control the period of degradation in a human body. By freeze drying method, HA and the lactic acid, monomer of polylactide, or lactide, the ester dimer of polylactide, were crosslinked with crosslinking agent, l-ethyl-3-(3-dimethyl aminopropyl) carbodiimide. The analysis of infrared spectroscopy showed that the ester linkage was formed and the analysis of nuclear magnetic resonance (NMR) spectroscopy showed that the ester linkage was due to the reaction of lactic acid and HA. The conversion (6∼32%) and degree of crosslinking (4∼19%) increased but the selectivity was almost constant at 62% as the mole ratio of LA to HA increased from 1 to 10 in the crosslinking reaction. The brittleness became more pronounced and the rate of degradation became faster with more addition of lactic acid resulting from the higher ratio of LA to HA, and the swelling ratio was in the range of 500 to 2000%.

• Textile Coloration and Finishing
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• v.31 no.3
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• pp.177-186
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• 2019

In this study, we investigated for synthetic hydrotalcite in chloroprene rubber foam. Experiments were carried out to find the optimum content ratio by controlling the contents of MgO and Hydrotalcite. Swelling test in toluene immersion was made to measure the crosslinking density of CR foams, and the cure properties were investigated with flat die rheometer and Mooney viscosity. The difference of hardness, tensile strength and elongation at break were observed after immersing in 7% NaCl or 21% NaCl solutions for a day and four days. In addition, the volume change and water content remaining in CR foam were measured after immersing NaCl solution. As content of MgO increased, the value of the cure torque tended to increase, but it was almost constant above 2phr of MgO. However, the Mooney viscosity decreased with increasing MgO content. The crosslinking density, determined by the swelling ratio, showed that the CR compound without MgO showed a higher degree of swelling. When the content of hydrotalcite/MgO was 3:2, it was the lowest volume change of CR form. Also, As the content of hydrotalcite decreased, the difference of mechanical properties before and after immersion NaCl solution increased.

• Polymer(Korea)
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• v.35 no.1
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• pp.66-71
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• 2011

With the synthesis of hyper crosslinked polymer particle (HCPP), having microporous structure with hydroxyl functional group, synthesized via polymerization reaction consists of three stepssuspension polymerization, hyper crosslinking by Friedel-Craft catalysis and hydrolysis reaction, the effects of the ratio of each monomer, hyper crosslinking conditions and $CO_2$ supercritical drying on the variations of surface morphology, pore size & distribution and BET surface area of HCPP have been investigated. It was observed that the formation of surface crack or fracture of HCPP was intimately related with the degree of hyper crosslinking reaction between microphase separated domains. And the value of BET surface area of HCPP increased with the increase of reaction temperature, time and the amounts of solvent used in hyper crosslinking step. Moreover, $CO_2$ supercritical drying was proven to be a very effective method for removing stabilizer, unreacted monomers and oligomers from HCPP but needed to add methanol as a co-solvent for efficient removing of residual catalyst.

• Fibers and Polymers
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• v.5 no.3
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• pp.230-233
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• 2004

The optimum conditions for durable press treatment of cotton fabrics using glyoxal as a nonformaldehyde crosslinking agent were investigated. Crosslinking reaction was conducted in the presence of different catalysts such as aluminum sulfate, magnesium chloride, or magnesium chloride-citric acid mixture at various mole ratios of catalyst to glyoxal. Aluminum sulfate was proven the most effective one among those used. Glycol addition into a glyoxal padding bath increased the wrinkle recovery angle(WRA) and whiteness of treated fabrics. The optimum mole ratio of glycol to glyoxal was 1:1. Diethylene glycol addition produced better overall performance to the glyoxal-crosslinked fabric compared to ethylene glycol addition.

• Polymer(Korea)
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• v.28 no.1
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• pp.18-23
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• 2004

Superabsorbent poly(potassium acrylate-co-acrylamide)s were synthesized in particle form using inverse suspension polymerization technique. Mean diameter of the prepared polymer particles decreased from 300 to 50 $\mu\textrm{m}$ with increasing surfactant concentration. The dynamic and equilibrium swelling behaviors during water absorption and drying process were investigated by weight measurement. The swelling ratio of polymer particles in water changed according to not only polymer crosslinking density, but particle size, saline concentration of aqueous medium, and copolymer compositions. Water sorption amount was increased with decreasing particle size, crosslinking agent concentration, and ion concentration in bulk solution. Being different from the water sorption process, the drying process was not significantly affected by particle size, polymer composition, or crosslinking amount.

• Journal of Pharmaceutical Investigation
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• v.35 no.1
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• pp.7-16
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• 2005

Gardeniae Fructus is consisted of geniposide and it's derivatives. For the purpose of treatment of skin disease, geniposide and hydrolyzed products (HP) of Gardeniae Fructus were studied on skin permeation and cross1inking with biological tissue. The hydrolyzed products (HP) and active ingredients of Gardeniae Fructus were identified and investigated about skin permeability. Genipin has provided low cytotoxic cross1inking reagents and formed stable and biocompatible crosslinked products. The permeation enhancing effects of geniposide and genipin under the hydrolyzed products of cream and hydrogel preparations were tested using Franz type diffusion cell and the skin of hairless mouse. The remaining proportions of geniposide and genipin were measured in the hydrolyzed products of cream and hydrogel preparations. The crosslinking of epidermic and endodermic tissue with genipin under the hydrolyzed prodcuts of cream and hydrogel preparation was observed using light microscopy. Increased absorption ratio of the skin of hairless mouse about genipin was higher than that of geniposide. Loads at break, tensile strengths and skin permeation rate of the hydrolyzed products (HP) of cream and hydrogel preparations were higher than the nonhydrolyzed products (NHP). The hydrolyzed products (HP) of cream and hydrogel of Gardeniae Fructus Extracts were proper preparations and crosslinking agents to increase the transdermal absorption with epidermic and endodermic tissue.

• Electrical & Electronic Materials
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• v.10 no.1
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• pp.54-60
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• 1997

The electrical and electromagnetic shielding properties have been investigated in polyaniline free standing films with different degrees of elongation cast from N-methyl 2-pyrrolidone(NMP) solution and camphorsulfonic acid(HCSA) doped polyaniline film. The degree of crystallinity of the crosslinked films increased with increasing the draw ratio. For the case of the oriented films doped with hydrochloric acid, we have the values of conductivities up to 173 S/cm. It is considered that the physical micro-crystalline crosslinking domains act as nucleation sites for the increase of relative crystallinity during stretching. We have obtained the value of conductivity 210 S/cm in the HCSA doped polyaniline film cast from the solvent of m-cresol, which is higher than that of the crosslinking oriented films. The electromagnetic shielding efficiency of HCSA doped polyaniline film obtained 37-41 dB in the frequency range of 10MHz-1GHlz, which is higher than that of the crosslinking oriented films. The higher value of electromagnetic shielding efficiency of HCSA doped polyaniline film suggests strong possibility of electromagnetic shielding material.

• Journal of Pharmaceutical Investigation
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• v.26 no.4
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• pp.273-280
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• 1996

Chondroitin sulfate/gelatin microspheres containing dexamethasone 21-acetate were prepared by complex coacervation method and their release patterns were examined in vitro. Microspheres prepared with a small amount of crosslinking agent had smooth surface and few pores, but those with a large amount of crosslinking agent were more porous and less spherical. In vitro release patterns were varied by changing polymer/drug weight ratio and amount of crosslinking agent. The release rate of dexamethasone 21-acetate in the presence of collagenase was faster than that in the absence of collagenase. Anti-inflammatory effect of dexamethasone 21-acetate microspheres was more efficient than that of dexamethasone 21-acetate solution in carrageenan-induced arthritis in the rat. On the basis of the above results, we might expect the degradation and drug release rate of these microspheres to be regulated by the degree of crosslinking and the level of enzymes. In patients with severe rheumatoid arthritis who have high concentration of collagenase, more drug would be released from the microspheres. An intra-articular injection therapy of rheumatoid arthritis with desired release kinetics could be developed to enhance patient compliance and therapeutic index.

• Korea Journal of Cosmetic Science
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• v.2 no.1
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• pp.11-19
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• 2020

The aim of this study is to investigate the effect of various pentapeptides on hair repair depending on the characteristics of comprising amino acids using crosslinking agents in hair. Total ten peptides were synthesized with two kinds of amino acids respectively, of which were previously categorized according to R group of the amino acids contributing to the characteristic of each peptide: STTSS (Ser-Thr-Thr-Ser-Ser), LIILL (Leu-Ile-Ile-Leu-Leu), CMMCC (Cys-Met-Met-Cys-Cys), DEEDD (Asp-Glu-Glu-Asp-Asp), RKKRR (Arg-Lys-Lys-Arg-Arg), TAMRA-STTSS, TAMRA-LIILL, TAMRA-CMMCC, TAMRA-DEEDD, and TAMRA-RKKRR. Pentapeptide alone, or pentapeptides with crosslinking agents such as polymeric carbodiimide (PCI) and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) were treated to chemically damaged hair. Hair diameter and break strength (N = 40/case) were measured to calculate tensile strength of hair for computing hair repair ratio, and fluorescence yields (N = 20/case) were collected for hair treated with TAMRA-peptides. The tensile strength of hair treated with pentapeptides alone, or pentapeptides with cross-linking agents is consistent with the fluorescence yield from the microscope images of the cross-sectioned hair in vision and in numerical values. Pentapeptides consisting of hydrophobic amino acids (LIILL), amino acids with sulfur (CMMCC), and basic amino acids (RKKRR) increased the tensile strength in perm-damaged hair. Pentapeptides with no extra carboxyl/amine groups in R group of amino acids resulted in no significant differences in hair strength and fluorescence yield among hairs treated with alone and with crosslinkers. Pentapeptides with extra carboxyl groups or amine groups enabled further strengthening of hair due to increased bonds within the hair after carbodiimide coupling reaction. The hair repairs of pentapeptides with various amino acid sequences were studied using crosslinking. Depending on the physical characteristics of comprising amino acids, the restoration of damaged hair was observed with tensile strength of hair and fluorescence signals upon cross-sectioned hair in parallel to possibly understand the binding tendency of each pentapeptide within the hair.

• Journal of Biomedical Engineering Research
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• v.34 no.3
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• pp.117-122
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• 2013

Hyaluronic acid(HA) microbeads were synthesized by dropping the sodium hyaluronate(Streptococcus) solutions in NaOH into a solution mixture of divinyl sulfone(DVS) in 2-methyl-1-propanol, followed by stirring, cleaning and drying process at room temperature. The initial experimental conditions are crosslinking time(CLTi) of 5 h, crosslinking temperature(CLTe) of room temperature, injection air pressure(IAPr) of 5 psi, and DVS concentration( DVSc) of 0.2 vol%, respectively. Then, parametric studies were performed by varying the parameters to investigate the morphology, the porosity, the swelling ratio and the size of the beads. The microbead size pattern was not regular to function of the degree of crosslink. It was observed that the swelling ratio, the degree of crosslink, and the pore size can be controlled by adjusting the CLTi, CLTe and DVSc. Among the parameters investigated, the smallest bead size can be achieved by varying the CLTi parameter. The lowest swelling ratio, as an indication of the highest degree of crosslink, can be obtained by varying CLTe.