• Macromolecular Research
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• v.9 no.2
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• pp.84-91
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• 2001

Both A-B-A triblock and multiblock copoly(ester-ether)s consisting of poly(L-Lactide) and poly(oxyethylene-co-oxypropylene) were prepared and characterized. The preparation of the triblock copolymer was done by ring-opening copolymerization of L-lactide with a commercially available telechelic copolyether, Pluronic$\^$TM/(PN) by catalysis of stannous octanoate. The molecular weight and unit composition of the produced copolymers were successfully controlled by changing the L-lactide/PN ratio in feed. However, a high molecular weight copolymer incorporating PN in large amount was not obtained because the molecular weight of the resulting copolymer was limited at a high L-lactide/PN composition. The multiblock copolymer was synthesized by the copolycondensation of oligo(L-lactic acid) prepared by thermal dehydration of L-lactic acid, PN, and dodecanedioic acid as carboxyl/hydroxyl adjusting agent. This polycondensation proceeded by catalysis of stannous oxide to give multiblock copolymers with high molecular weight and wide range of compositions.

• Macromolecular Research
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• v.9 no.5
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• pp.259-266
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• 2001

Multiblock copolymer was synthesized by the copolycondensation of oligo(L-lactic acid) prepared by thermal dehydration of L-lactic acid, Pluronic$\^$TM/(PN) and dodecanedioic acid as carboxyl/hydroxyl adjusting agent. This polycondensation proceeded by catalysis of stannous oxide to give the multiblock copolymers with high molecular weight and wide range of compositions. Polymer film was prepared by casting the chloroform solution of the multiblock copolymers having different composition. The multiblock copolymers having relatively high contents of poly(L-lactide) were melt spun into filaments which were subsequently drawn at 60$^{\circ}C$. The copolymer films and the filaments showed an improved flexibility due to the incorporation of the soft segments.

• Macromolecular Research
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• v.16 no.7
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• pp.609-613
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• 2008

Poly($\varepsilon$-caprolactone)-poly(ethylene glycol)-poly($\varepsilon$-caprolactone) (PCL-PEG-PCL) multiblock copolymers at various hydrophobic-hydrophilic ratios were successfully synthesized by the chain extension of triblock copolymers through isocyanate (hexamethylene diisocyanate). Biodegradable films were prepared from the resulting multiblock copolymers using the casting method. The mechanical properties of the films were improved by chain extension of the triblock copolymers, whereas the films prepared by the triblock copolymers were weak and brittle. Atomic force microscopy (AFM) of the multiblock copolymer film showed that the hydrophilic PEG had segregated on the film surface. This is consistent with the observed contact angle of the films.

• Macromolecular Research
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• v.10 no.2
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• pp.67-74
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• 2002

New immunoprotecting membranes were prepared by spin coating the amphiphilic random multiblock copolymers of poly(ethylene glycol) (PEG) and poly(tetramethylene ether glycol) (PTMEG) or poly(dimethyl siloxane) (PDMS) on porous Durapore(R) membrane. The copolymer coating was intended to make a biocompatible, immunoprotecting diffusional barrier and the supporting porous substrate was for mechanical stability and processability. By filling Durapore(R) membrane pores with water, the penetration of coating solution into the pores was minimized during the spin coating process. A single coating process produced a completely covered thin surface layer (~1 ${\mu}{\textrm}{m}$ in thickness) on the porous substrate membrane. The permselectivity of the coated layer was influenced by PEG block length, polymer composition, and thickness of the coating layer. A composite membrane with the coating layer prepared with PEG 2 K/PTMEG 2 K block copolymer showed that its molecular weight cut-of fat any 40 based on dextran was close to the molecular size of IgG (Mw = 150 kDa). However, IgG permeation was detected from protein permeation test, while glucose oxidase (Mw = 186 kDa) was not permeable through the coated membrane.

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

• Macromolecular Research
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• v.15 no.2
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• pp.160-166
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• 2007

Novel multiblock copolymers, based on segmented sulfonated hydrophilic-hydrophobic blocks, were synthesized and investigated for their application as proton exchange membranes. A series of segmented sulfonated poly(arylene ether sulfone)-b-polyimide multiblock copolymers, with various block lengths, were synthesized via the coupling reaction between the terminal amine moieties on the hydrophilic blocks and naphthalene anhydride functionalized hydrophobic blocks. Successful imidization reactions required a mixed solvent system, comprised of NMP and m-cresol, in the presence of catalysts. Proton conductivity measurements revealed that the proton conductivity improved with increasing hydrophilic and hydrophobic block lengths. The morphological structure of the multiblock copolymers was investigated using tapping mode atomic force microscopy (TM-AFM). The AFM images of the copolymers demonstrated well-defined nanophase separated morphologies, with the changes in the block length having a pronounced effect on the phase separated morphologies of the system. The self diffusion coefficient of water, as measured by $^1H$ NMR, provided a better understanding of the transport process. Thus, the block copolymers showed higher values than Nafion, and comparable proton conductivities in liquid water, as well as under partially hydrated conditions at $80^{\circ}C$. The new materials are strong candidates for use in PEM systems.

• Macromolecular Research
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• v.17 no.11
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• pp.879-885
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• 2009

A macroazoinitiator (MAI) containing a poly(ethylene glycol) (PEG) segment was intercalated in the gallery of sodium montmorillonite (Na-MMT). Acrylic monomers were polymerized using this MAI intercalated in Na-MMT to prepare the acrylic copolymer nanocomposite (AN), which is a multiblock copolymer composed of two segments, an acrylic copolymer and PEG intercalated in Na-MMT (Na-MMT/PEG). When AN was used to modify the reactive hot melt polyurethane adhesive (RHA), the acrylic copolymer segment and Na-MMT/PEG synergistically enhanced the initial bond strength evolution and reduced the set time, even when the amount of Na-MMT in RHA was < 1 wt%. The viscosity of RHA increased and the tensile properties of the cured RHA film decreased due to modification with AN. These variations were more evident as the Na-MMT content in AN was increased.

• Macromolecular Research
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• v.11 no.1
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• pp.42-46
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• 2003

Cell attachment and proliferation on the polymer films of triblock copolymer(ester-ether)s comprising po1y (L-1actide) (PLLA) and poly (oxyethylene-co-oxypropylene)(PN) were investigated using 3T3 fibroblasts. It was found that on the tissue culture polystyrene(TCPS) and the PLLA control film the cells could spread well while on the copolymer films the cells showed a rounded morphology without spreading and proliferated weakly. Especially, little cells proliferated on the films of copolymer having a LN composition of 20 wt%. While the water absorption of the copolymer films increased with increasing PN content, the contact angle against water of copolymer films immersed in aqueous medium was almost identical, being slightly lower than that of the PLLA film. These properties were compatible with the results of cell attachment. The in vitro hydrolysis of the films of triblock and multiblock type copolymers was faster with increasing PN content. The increased hydrolyzability, the flexibility and the decreased cell attachment suggested that these copolymers may have high potential as biodegradable materials for medical use.

• Bulletin of the Korean Chemical Society
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• v.21 no.4
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• pp.383-388
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• 2000

Multiblock copolymers consisting of poly( g-benzyl L-glutamate) (PBLG) as the hydrophobic part and poly(ethylene oxide) (PEO) as the hydrophilic part (GEG) were synthesized and characterized. GEG polymeric micelles were prepared by the dialysis technique. Particle size distributions based on intensity,volume, and number-average were 22.6 $\pm$ 11.9 nm, 23.5 $\pm$ 4.6 nm, and 23.7 $\pm$ 37 nm, respectively. It was observed that par-ticle size and size distribution of GEG polymeric micelles changed significantly with the choice of initial sol-vent. Transmission electron micrographs (TEM) showed the polymeric micelles to be spherically shaped, with sizes ranging from 20 nm to 40 nm in diameter. Fluorescence spectroscopy measurements suggested that GEG block copolymers wereassociated in water to form polymeric micelles, and the critical micelle concentrations (CMC) value of the block copolymers was 0.0094 g/L. Further evidenceof micelle formation of GEG block copolymers and limited mobility of the PBLG chain in the core ohe micelle was obtained with 1 H NMR in D2O.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.370-370
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• 2006

Thermoplastic elastomer gels, which has molecular networks composed of a microphase-separated multiblock copolymer swollen to a large extent by a low volatility mid-block selective solvent such as white oil have various applications. In this particular study, the effect of several network-forming nanoscale fillers such as two different graphite particles and carbon nanotube on the properties of TPE gels prepared from a microphaseordered poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) triblock copolymer with an EB compatible white oil was studied. The linear viscoelastic behavior, sol-gel transition, x-ray diffraction and mechanical properties were discussed. The properties of thermoplastic elastomer gels hybrid with graphite prepared by mixing Poly(styrene-b-ethylene-co-butylene)-b-styrene) with paraffin oil and different amount of expandable graphite were found to increase the mechanical properties at only lower graphite concentration but tends to decrease when paraffin oil/SEBS ratio is lower. The gelation temperature is the same for all TPE gels with different amounts of graphite. Both storage (G') modulus loss (G") modulus of TPE gels slightly increase with addition of graphite.