• Applied Chemistry for Engineering
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• v.18 no.6
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• pp.607-611
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• 2007

To improve transfection efficiency, we prepared histidine-low molecular weight water-soluble chitosan (LMWSC) having the potential to form complex with DNA as a cationic polymer. Histidine-LMWSC was synthesized by the esterification reaction and removing phthaloyl group. The histidine-LMWSC was characterized using FT-IR, $^1H$ NMR spectra. Histidine-LMWSC was complexed with plasmid DNA (pDNA) in various polymer/DNA (N/P) weight ratios, and the complex was identified using gel retardation assay. The particle sizes of the hisitidine-LMWSC/DNA complexes were measured on a DLS instrument by fixing the histidine-LMWSC/DNA weight ratio of 10/1. Owing to the utilization of a large excess amount of cationic LMWSC against anionic DNA, the particle size of histidine-LMWSC/DNA complexes was in the range of 100~200 nm. Therefore, histidine-LMWSC will be useful in the development of gene carriers.

• Membrane and Water Treatment
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• v.7 no.6
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• pp.521-537
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• 2016

Laboratory-scale experiments were carried out to investigate the adsorption equilibrium, the adsorption kinetics and facilitated transport of two cationic dyes (Methylene Blue (MB) and Rhodamine B (RB)) on Polymer Inclusion Membrane (D2EHPA-PIM). Different adsorption isotherms (Freundlich, Langmuir and Temkin models) as well as kinetics models indicated that the adsorption process is spontaneous and exothermic. Under the optimal conditions, the adsorption removal efficiencies reach about 93% and 97% for MB and RB respectively. Different extraction values by D2EHPA-PIM were obtained for the two cationic dyes: MB is weakly extracted at pH 2.0 (E% = 18.7%) whilst E% = 82.4% was observed for RB at the same pH. This difference was exploited in a mixture containg both the 2 cationic dyes for the selective extraction of RB at pH 2. Desorption of both dyes was achieved from the membrane by using acidic aqueous solutions and desorption ratio up to 90% was obtained. The formulas of the extracted complexes by the PIMs were, determined by the method of slopes. The dyes transport was elucidated using mass transfer analysis where in it found relatively high values of the initial flux ($J_0$) as 41.57 and $18.74{\mu}mol.m^2.s^{-1}$ for MB and RB respectively.

• Polymer(Korea)
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• v.25 no.2
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• pp.168-176
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• 2001

The effect of novel N-crotyl-N,N-dimethyl-4-methylanilinium hexafluoroantimonate (CMH) curing agent as a thermal latent initiator on thermal behaviors, rheological properties, and thermal stability of diglycidylether of bisphenol A (DGEBA) epoxy cationic system was investigated. From DSC measurements of DGEBA/CMH system, it was shown that this system exhibits an excellent thermal latent characteristic at a given temperature. The conversion and conversion rate of DGEBA/CMH system increased with increasing the concentration of initiator, due to high activity of CMH. Rheological properties of the system were investigated under isothermal condition using a rheometer The gelation time was obtained from the analysis of storage modulus (G'), loss modulus (G"), and damping factor (tan $\delta$). As a result, the reduction of gelation time was affected by high curing temperature and concentration of CMH, resulting in high degree of network formation in cationic polymerization, due to difference of activity. The thermal stability of the cured epoxy resin was discussed in terms of the activation energy for decomposition and thermal factors determined from TGA measurements.ents.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2006.06b
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• pp.271-278
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• 2006

We used polymers of alternating cationic and anionic nature to build up shells on fiber surfaces, strengthen the worn-out fibers and improve paper properties made from such fibers. OCC and ONP pulps were either dipped or salted out in the cationic polyallylamine, polyacrylamide and starch solutions. After centrifugal drying, these were followed by treatments in anionic polyacrylic acid, poly-acrylamide, and starch solutions, respectively. The shell-enhanced fibers were formed into handsheets and their physical properties evaluated. The results show that building multiple shells on worn-out fiber surfaces can strengthen the fibers and paper. The simpler and more practical impregnation-centrifuging treatment provided the desired effects, whereas salting out the polymers produced somewhat superior fibers. The latter process, were impractical, however. The first pair of polymeric shells imparted marked strength improvement, whereas later layers had diminishing efficacies. Overall, the methods can improve fiber quality, attaining paper strength requirements without resorting to expensive measures. Alternate cationic polymer and filler powders were also deposited on fiber surface based on the micriparticle system in an anticipation of stiffness gains. Platy minerals, such as montmorillonite, bentonite, sericite, clay and talc were added following cationic PAM. After dewatering of polymer-pigment shelled fiber of one to 3 pairs of layers, handsheets either calendered or uncalendered were evaluated. The results indicate that regardless of calendaring, stiffness of the handsheets did not improve appreciably while certain other strength properties showed gains. We also attempted the novel starch gel filler addition method wherein tapioca starch and filers (PCC, sericite or clay) were mixed at high solids content of 50% and cooked until gelatinized. The filled handsheets were dried under various conditions and then tested for their properties. Improvements in strengths of modified filled paper were observed.

• Elastomers and Composites
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• v.39 no.3
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• pp.209-216
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• 2004

Two types of polyurethane-acrylate polymer were synthesized by reaction of 2-hydroxyethyl methacrylate(HEMA), acrylamide(AA), and polyurethane prepolymer. Water-soluble cationic polyurethane/acrylate retention aids were prepared by using polyurethane-acrylate, benzyl chloride and distilled water. The retention, drainage and strength properties of the retention aids were investigated. The retention of cationic polyurethane/acrylate type retention aids maintained around 70 % regardless of nm. COD value of white water was much reduced by adding the retention aids to it. Drainage property was also improved by addition of the retention aids. In addition, specific compression strength of the paper was improved a little by addition of the retention aids. PU-HEMA type showed better performance than PU-AA in terms of compression strength of the paper.

• Polymer(Korea)
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• v.35 no.2
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• pp.171-175
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• 2011

Isophorone diisocyanate(IPDI), polytetramethylene glycol 1000 (PTMG1000), and N-methyl diethanol amine (MDEA) were applied to prepare cationic polyurethane water dispersions (PUD). Various neutralizers and chain extenders were introduced in order to investigate property changes, such as particle size, viscosity, $T_g$, tensile strength, and water swellability, depending on chemical structure of those chemicals. While the PUDs neutralized by acetic acid showed a typical elastomeric behavior, the others used with hydrochloride presented crystalline behavior. Among chain extenders isophorone diamine (IPDA) provided the best mechanical property. The particle size of the PUD neutralized with HCl was smaller than that with acetic acid. It is believed that this is attributed to the size difference of counter ions. The PUD chain-extended with hydrazine had the smallest particle size.

• Macromolecular Research
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• v.10 no.1
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• pp.34-39
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• 2002

Cure behavior of an epoxy resin was investigated at different cure temperatures (110, 120, 130, 140, and 150 $^{\circ}C$) and cure times in the presence of 2 wt% of an N-benzylpyrazinium hexafluoroantimonate (BPH) cationic catalyst by means of differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The glass transition temperature ( $T_{g}$) and chemical conversion (x) at the different temperatures were determined from DSC thermograms. The $T_{g}$ and x vs. In time data were superposed up to $T_{g}$ = 10$0^{\circ}C$ and x = 0.70 by shifting horizontally at a reference temperature of $T_{g}$ = 13$0^{\circ}C$. It is interesting that the $T_{g}$ and x of the superposed data increase rather slowly in the early stage of cure and rapidly thereafter. Therefore, the increase of the $T_{g}$ and x can be divided into two regions; $R_{I}$= -18.4(= $T_{go}$ ) ~5$^{\circ}C$ and $R_{II}$ = 5 ~ 10$0^{\circ}C$ in $T_{g}$, and $R_{I}$ : 0~0.24 and $R_{II}$ : 0.24~0.70 in x. The $R_{I}$ is closely related to the initiation reactions between BPH and epoxy and between hydroxy group and epoxy in this epoxy/catalyst system. From the kinetic analysis of the $T_{g}$-shift, activation energy was 12.5 kcal/mol. The relationship between $T_{g}$ and x was also considered. The gelation and vitrification times for different cure temperatures were obtained from DMA curves.urves. DMA curves.urves.

• Macromolecular Research
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• v.17 no.4
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• pp.221-226
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• 2009

The present study firstly describes the synthesis of novel, thermo-latent initiators based on xanthenyl phosphonium salts with different counter anions and phosphine moieties and secondly examines their efficiency in the bulk polymerization of glycidyl phenyl ether(GPE). The polymerization was performed with phosphonium salt initiators($I_{SbF6}$, $I_{PF6}$, $I_{AsF6}$ and $I_{BF4}$) at ambient temperature to $200^{\circ}C$ for 1 h. The order of initiator activity was $I_{SbF6}>I_{PF6}>I_{AsF6}>I_{BF4}$. To examine the effect of the phosphine moiety on the initiator activity, polymerization was carried out with $I_{SbF6}(Ph_{3}P)$ and $II_{SbF6}(Bu_{3}P)$ at ambient temperature to $170^{\circ}C$ for 1 h. The order of reactivity was $I_{SbF6}>II_{SbF6}$. In general, the conversion percentage increased with increasing polymerization temperature. The thermal stability of these salts was measured by thermo gravimetric analysis(TGA). The solubility of phosphonium salts in various organic solvents and epoxy monomers was also investigated.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.6
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• pp.709-715
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• 2007

The dewaterability of a sludge can be characterized by two ways: the residual moisture content in the sludge cake after dewatering process, and the filtration of the sludge. Time to filter (TTF) represents filtration processes that are special cases of the flow through a solid matrix concept. TTF characterizes a resistance to filtration. The sludge resistance, in turn, can be subdivided into resistances associated with the solid phase and the liquid phase to evaluate the effect of each of the two phases on sludge dewaterability. In order to determine the dewatering characteristics of the water sludge samples, TTF and zeta potential were measured. For these studies cationic polymer was chosen for water sludge dewatering experiments. The zeta potential of thickener sludges neared from minus values to zero values till 4 days after sampling. The dewaterability of thickener sludges using cationic polymer was deteriorated according to the increase of detention time. As the detention time was increased from 4 to 10 days, the optimal dose of the polymer was increased from 4 to 8mg/L. Therefore, the optimal detention time plays an important part for the dewaterability of a sludge.

• Journal of the Korean Ceramic Society
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• v.51 no.4
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• pp.324-331
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• 2014

The dispersion characteristics of AlN-4.5 wt% $Y_2O_3$ powder mixture by various dispersants were investigated in ethanol and methyethly-ketone (MEK) solvents. In general, the cationic polymer dispersants demonstrated superior dispersion of the powder as compared to the non-ionic ester-type dispersants or anionic phosphate-ester-based ones. The dispersion performance of the cationic polymer dispersants was sensitive to the type of solvent. An anhydric maleic-acid-based graft copolymer dispersant, AFB-1521, demonstrated a very good dispersion capability in ethanol but exhibited a much inferior dispersion in MEK. On the other hand, the dispersion of the powder mixture was very good with a phosphate-ester-based block polymer dispersant, BYK-111, in MEK solvent, while dispersionwas much degraded in ethanol.