• Polymer(Korea)
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• v.25 no.3
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• pp.421-426
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• 2001

11-Aminododecanoic acid, to insert the functional group of -COOH reacted with the end group of poly($\varepsilon$-caprolactone) diol, and cetyltrimethylammonium bromide (CTMA), to increase the d-spacing of Montmorillonite (MMT), were intercalated into $Na^+;_-$MMT. The modified MMT was reacted with poly(${varepsilon}-caprolactone$) diol ($M_n{=2000$) in THF solution at $80^{\circ}C$ for 4 hrs. After reaction, poly(${varepsilon}-caprolactone$) ($M_n{=80000$) was mixed into the solution for 12 hrs. To prepare the PCL/clay nanocomposite film this solution was cast into the silicon mold at $60^{\circ}C$ in vacuum oven for 6 hrs. From the results of XRD and TEM, it was found that the exfoliated PCL/clay nanocomposite were prepared. The effects of the amount of MMT on the mechanical properties and thermal properties of PCL/clay nanocomposites have been investigated by tensile tester and DSC. Because the MMT was dispersed homogeneously in PCL matrix, the Young's modulus of the nanocomposite were found to be excellent. However, MMT dispersed in PCL matrix had almost no effect on the tensile strength of the composites. The crystallization temperature of PCL increased in proportion to 3 wt% MMT in the PCL matrix.

• Current Applied Physics
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• v.18 no.11
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• pp.1313-1319
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• 2018

The coil-to-globule behavior of poly{${\gamma}$-2-[2-(2methoxyethoxy)ethoxy]ethoxy-3-caprolactone} (PMEEECL) as a ${\gamma}$-substituted poly (${\varepsilon}$-caprolactone) was investigated via atomistic molecular dynamics (MD) simulation. For this purpose, radius of gyration, end-to-end distance and radial distribution function of the chain in the presence of water were calculated. Consequently, the lower critical solution temperature (LCST) of PMEEECL chain at which the coil-to-globule transition takes place, was determined in each calculated parameter curve. The simulation results indicated that the LCST of PMEEECL was occurred at close to 320 K, which is in a good agreement with previous experimental results. Additionally, the appearance of sudden change in both Flory-Huggins interaction parameter (${\chi}$) and interaction energy between the PMEEECL chain and water molecules at about 320 K confirmed the calculated LCST result. The radial distribution function (RDF) results showed that the affinity of the PMEEECL side chain to water molecules is lower than its backbone.

• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2471-2476
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• 2007

A series of titanium complexes containing terdentate β-ketoiminate ligands were found to be efficient for the ring-opening polymerization of ε-caprolactone (ε-CL), producing poly(ε-caprolactone) (PCL) with bimodal distribution. Steric factors imposed by methyl substituents on the back bone of the alkoxy group affected significantly the polymerization rate and physical properties of the resulting PCL. Intra- and intermolecular transesterifications rather than disproportional rearrangements were responsible for the bimodal behavior and for the change in the molecular weight (Mw). Dilution with toluene reduced yield, and lowered polydispersity (PDI) and Mw of PCL, while the catalytic activities of the dimeric complex, [Ti(Oi-Pr)2(N-alkoxy-β- ketoiminate)]2 and Ti(Oi-Pr)4 were not sensitive to the added solvent. The dimeric complex showed living character, while other catalysts suffered from chain termination reactions.

• Polymer(Korea)
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• v.24 no.3
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• pp.306-313
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• 2000

Polycaprolactone (PCL) macromer containing terminal methacrylate group was synthesized by ring-opening polymerization. The number average molecular weight of PCL macromer was 11600 g/mole and polydispersity index was 1.09. The synthesized PCL macromer was copolymerized with styrene by stable free radical polymerization using 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), benzoyl peroxide, and well-defined poly(styrene-g-caprolactone)s were synthesized. The synthesized copolymers was characterized by $^1$H-NMR and gel permeation chromatography equipped with multiangle laser light scattering detector. Thermal properties of graft copolymers were investigated by DSC.

• Journal of the Korean Applied Science and Technology
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• v.23 no.1
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• pp.85-91
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• 2006

Acrylic resins (HSCs : EA/EMA/2-HEMA/CLA) which contain 80% solid content were synthesized by the copolymerization of monomers (ethyl acrylate, ethyl methacrylate, 2-hydroxyethyl methacrylate) and functional monomer (caprolactone acrylate : CLA) which improves the crosslinking density and physical properties of films. The physical properties of the prepared acrylic resins (HSCs) containing CLA, are as follows: viscosity 1440$^{\sim}$2630 cps ; $M_n$ 1590$^{\sim}$1660 ; and conversions, 81$^{\sim}$86%, respectively. From the correlation of $T_g$ values, viscosities, and $M_n$ of the HSCs, it was found thst viscosity and $M_n$ increased with $T_g$ value.

• Journal of the Korean Applied Science and Technology
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• v.21 no.3
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• pp.197-203
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• 2004

Acrylic resins ($HSC_s$ : EA/EMA/2-HEMA/CLA) which contain 70% solid content were synthesized by the copolymerization of monomers (2-hydroxyethyl methacrylate, ethyl acrylate, and ethyl methacrylate) and functional monomer (caprolactone acrylate : CLA) which improves the crosslinking density and physical properties of films. The physical properties of the prepared acrylic resins (HSCs) containing CLA, are as follows : viscosity 245${\sim}$515 cps ; $M_n$ 2670${\sim}$2840 ; and conversions, 83${\sim}$91%, respectively. From the correlation of $T_g$ values, viscosities, and $M_n$ of the HSCs, it was found that viscosity and $M_n$ increased with $T_g$ value.

• Fibers and Polymers
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• v.4 no.2
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• pp.59-65
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• 2003

PLA/LPCL/HPCL blends composed of poly(lactic acid) (PLA), low molecular weight poly($\varepsilon$-caprolactone) (LPCL), and high molecular weight poly($\varepsilon$-caprolactone) (HPCL) were prepared by melt blending for bioabsorbable fila-ment sutures. The effects of blend composition and blending time on the ester interchange reaction by alcoholysis in the PLA/LPCL/HPCL blends were studied. Their thermal properties and the miscibility due to the ester interchange reaction were investigated by $^1{H-NMR}$, DSC, X-ray, and UTM analyses. The hydroxyl group contents of LPCL in the blends decreafed by the ester interchange reaction due to alcoholysis. Thus, the copolymer was formed by the ester interchange reaction at $200^{\circ}C$ for 30-60 minutes. The thermal properties of PLA/LPCL/HPCL blends such as melting temperature and heat of fusion decreased with increasing ester interchange reaction levels. However, the miscibility among the three poly-mers was improved greatly by ester interchange reaction. Tensile strength and modulus of PLA/LPCL/HPCL blend fibers increased with increasing HPCL content, while the elongation at break of the blend fibers increased with increasing LPCL content.

• Macromolecular Research
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• v.17 no.2
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• pp.72-78
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• 2009

Size control of therapeutic carriers in drug delivery systems has become important due to its relevance to biodistribution in the human body and therapeutic efficacy. To understand the dependence of particle size on the formation condition during nanoprecipitation method, we prepared nanoparticles from biodegradable, amphiphilic block copolymers and investigated the particle size and structure of the resultant nanoparticles according to various process parameters. We synthesized monomethoxy poly(ethylene glycol)-poly($\varepsilon$-caprolactone) block copolymer, MPEG-PCL, with different MPEG/PCL ratios via ring opening polymerization initiated from the hydroxyl end group of MPEG. Using various formulations with systematic change of the block ratio of MPEG and PCL, solvent choice, and concentration of organic phase, MPEG-PCL nanoparticles were prepared through nanoprecipitation technique. The results indicated that (i) the nanoparticles have a dual structure with an MPEG shell and a PCL core, originating from self-assembly of MPEG-PCL copolymer in aqueous condition, and (ii) the size of nanoparticles is dependent upon two sequential processes: diffusion between the organic and aqueous phases and solidification of the polymer.

• Bulletin of the Korean Chemical Society
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• v.22 no.5
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• pp.467-475
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• 2001

A triblock copolymer based on $poly(\varepsilon-caprolactone)$ (PCL) as the hydrophobic part and poly(ethylene glycol) (PEG) as the hydrophilic portion was synthesized by a ring-opening mechanism of ${\varepsilon}-caprolactone$ with PEG containing a hydroxyl group at bot h ends as an initiator. The synthesized block copolymers of PCL/PEG/PCL (CEC) were confirmed and characterized using various analysis equipment such as 1H NMR, DSC, FT-IR, and WAXD. Core-shell type nanoparticles of CEC triblock copolymers were prepared using a dialysis technique to estimate their potential as a colloidal drug carrier using a hydrophobic drug. From the results of particle size analysis and transmission electron microscopy, the particle size of CEC core-shell type nanoparticles was determined to be about 20-60 nm with a spherical shape. Since CEC block copolymer nanoparticles have a core-shell type micellar structure and small particle size similar to polymeric micelles, CEC block copolymer can self-associate at certain concentrations and the critical association concentration (CAC) was able to be determined by fluorescence probe techniques. The CAC values of the CEC block copolymers were dependent on the PCL block length. In addition, drug loading contents were dependent on the PCL block length: the larger the PCL block length, the higher the drug loading content. Drug release from CEC core-shell type nanoparticles showed an initial burst release for the first 12 hrs followed by pseudo-zero order release kinetics for 2 or 3 days. CEC-2 block copolymer core-shell type nanoparticles were degraded very slowly, suggesting that the drug release kinetics were governed by a diffusion mechanism rather than a degradation mechanism irrelevant to the CEC block copolymer composition.

• Journal of the Korean Applied Science and Technology
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• v.24 no.2
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• pp.149-159
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• 2007

In order to prepare high-solid coatings, acrylic resins, HSCs [poly (EA/EMA/2-HEMA/CLA)] that contain 90% solid, were synthesized by copolymerization of ethyl acrylate (EA), ethyl methacrylate (EMA), 2-hydroxyethyl methacrylate (2-HEMA) and caprolactone acrylate (CLA). The high-solid coatings named as CHSCs (HSCs/HDI-trimer) were prepared by the curing reaction between the acrylic resins containing 90% solid contents and the isocyanates (HDI-trimer) curing agent room temperature. The curing behavior and various properties were examined on the film coated with the both high-solid coatings. The glass transition temperatures $(T_g)$ of CHSCs increased proportionally with increasing the predicted $T_g$ value by Fox equation, and had nothing to do with the solid contents. The prepared film showed good properties for $60^{\circ}$ specular gloss, impact resistance, cross-hatch adhesion and heat resistance, and bad properties for pencil hardness, drying time, and pot-life. Among the film properties, the heat resistance was very excellent and could be explained by the introduction of functional monomers of CLA.