• Macromolecular Research
• /
• v.10 no.2
• /
• pp.85-90
• /
• 2002

Poly (ethylene oxide)/polylatide/poly(ethylene oxide) (PEO/PL/PEO) tri-block copolymers, which each block is connected by ester bond, were synthesized by coupling reaction of PL with PEO in the presence of pyridine. PL/PEO/PL tri-block copolymer was synthesized by ring opening polymerization of L-lactide initiated by PEO in the presence of stannous octoate. Degradation behavior of the copolymers was investigated in a pH 7.4 phosphate buffer saline (PBS) at 37$\pm$1 $^{\circ}C$. Gel permeation chromatography (GPC) and $^1$H-nuclear magnetic resonance (NMR) were used to monitor the change of mass loss, molecular weight and composition of copolymers. In hydrolytic degradation, the PEO/PL/PEO tri-block copolymer with high PEO contents affected the increase of its mass loss, and resulted in the decrease of its molecular weight as well as PEO composition. However, when PL/PEO/PL and PEO/PL/PEO tri-block copolymers had similar PEO contents, PEO/PL/PEO decreased faster in molecular weight and PEO composition than PL/PEO/PL.

• Proceedings of the Korean Society of Rheology Conference
• /
• 2001.06a
• /
• pp.77-80
• /
• 2001

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2006.05a
• /
• pp.229-232
• /
• 2006

Two novel synthetic route proposed for Hydro-Terminated Poly(EO-ran-THF) and tri-block(PEC-PTHF-PEG) copolymer by cationic ring-opening polymerization of tetrahydrofuran(THF) and ethylene oxide(EO) and just by polymerization of EO on poly-THF, respectively. Polyurethane was synthesized from random and tri-block HTPE using N-100/IPDI mixture as curing agent, and TPB(Triphenylbismuth) as catalyst. The mechanical properties of resultant polyurethane after mixing with various ratio of isocyanate was also investigated. Finally, the post treatment process of HTPE based on amount of catalyst used in the synthesis was studied, to evaluate the optimum curing condition for the polyurethane propellant binder.

• Macromolecular Research
• /
• v.13 no.2
• /
• pp.152-155
• /
• 2005

A dynamic density functional theory is presented for the observation of the phase revolutions of a solution-casting film of di- and tri-block copolymers under solvent evaporation conditions. With the evaporation of the solvent, the inverted phases, the minor part of the component becomes the continuous phase at the higher solvent evaporation rate, as observed in this experiment. Further simulation revealed that these inverted phases are converted into the normal phase and the major part of the component becomes the continuous phase, implying that the inverted phases observed in this experiment are unstable.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.5
• /
• pp.1638-1642
• /
• 2012

A series of poly (lactic acid) (PLA) and poly (ethylene glycol) (PEG) tri and multiblock copolymers with relatively high molecular weights were synthesized through the coupling reaction between the bis(acyl chloride) of carboxylated PLA and mono or dihydroxy PEG. The coupling reaction and the copolymer structures were monitored by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The melting temperature (Tm) of PEG blocks decreased with the presence of PLA sequences attaching to PEG blocks. The CMC values were determined to be 10-145 mg/L depending on the length of PLA and PEG blocks and the structure of the block copolymers.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2005.11a
• /
• pp.417-421
• /
• 2005

Novel two synthetic technics using cationic ring-opening copolymerization of tetrahydrofuran (THF) and ethylene oxide (EO), or just polymerized EO on Poly-THF, could lead to random hydroxyl-terminated poly(EO-ran-THF) or tri-block PEG-PTHF-PEC, respectively. These reactions were carried out using $BF_3O(C_2H_5)_2$ as catalyst, 1,4-butanediol or PTHF as diol initiator. Copolymer structures were controlled by monomer feed ratio, or initial PTHF and EO monomer added amount. The molecular weight of polymer was merely dependant on the ratio of [monomer]/[diol], but not on catalyst. Well-defined random and block hydroxyl-terminated copolyether was found to be as the prepolymer for the propellant binder from the experiment to polyurethane with them.

• Clean Technology
• /
• v.18 no.2
• /
• pp.177-182
• /
• 2012

Mesoporous anatase $TiO_2$ nanoparticles have been synthesized by a hydrothermal method using a tri-block copolymer as a soft template. The resulting $TiO_2$ materials have a high specific surface area of $230\;m^2/g$, a predominant pore size of 6.8 nm and a pore volume of 0.404 mL/g. The electrochemical properties of mesoporous anatase $TiO_2$ for lithium ion battery (LIB) anode materials have been investigated by typical coin cell tests. The initial discharge capacity of these materials is 240 mAh/g, significantly higher than the theoretical capacity (175 mAh/g) of LTO ($Li_4Ti_5O_{12}$). Although the discharge capacity decreases with the C-rate increase, the mesoporous $TiO_2$ is very promising for LIB anode because the surface for the Li insertion is presented significantly with mesopores. Nitrogen doping has a certain effect to control the capacity decrease by improving the electron transport in $TiO_2$ framework.

• Polymer(Korea)
• /
• v.38 no.2
• /
• pp.205-212
• /
• 2014

Polyethersulfone (PES) membranes were modified by various physico-chemical modification methods to enhance the surface hydrophilicity for application as a separation membrane to separate and collect water vapor from the flue gas. Homogeneous PES flat-sheet membranes were prepared and modified by acid treatment, blending and plasma treatment for hydrophilic surface modification. The surface characteristics of the modified PES membranes were evaluated by ATR-FTIR, XPS, SEM and contact angle measurements. No significant change in hydrophilicity was observed for the PES membranes modified by acid treatment with sulfuric acid or blending with various compositions of poloxamer as an amphiphilic PEO-PPO-PEO tri-block copolymer. On the other hand, Ar plasma treatment led to a significant increase in the hydrophilicity of the surface, depending on the plasma treatment time. As a result, the PES membrane could be the most efficiently surface-treated by applying the plasma treatment for enhancing their surface hydrophilicity.