• Bulletin of the Korean Chemical Society
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• v.18 no.1
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• pp.38-43
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• 1997

Poly(ethylene 2, 6-naphthalate-co-tetramethylene 2, 6-naphthalate) (PEN/PBN) copolymers were synthesized and studied by 13C NMR spectroscopy, DSC analysis and X-ray diffraction. A minimum in the melting point vs. composition curve was found at approximately 60 mol% tetramethylene 2, 6-naphthalate. The PEN/PBN copolymers were shown to be statistically random throughout the range of 1, 4-butanediol compositions. The melting point depression behavior of annealed PEN/PBN copolymers depended upon the sequence propagation probability, PS, which is suggested by indivisual crystal formation of two pure comonomers; that is, ethylene-naphthalate-ethylene, EE, and tetramethylene-naphthalate-tetramethylene, BB. However, it can be seen from the X-ray curve that the peaks of PEN/PBN copolymers appear from a crystal lattice which is governed only by the rich component between two different aliphatic units in the copolymer composition.

• Journal of the Korean Chemical Society
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• v.21 no.3
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• pp.219-224
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• 1977

The free radical initiated copolymerization of vinyl acetate (VAc) and bis(${\beta}$-chloroethyl)vinylphosphonate (BCVP) was studied. The monomer reactivity ratios for the monomer pair determined at $50^{\circ{C$ using benzoyl peroxide as an initiator are: $r_1 (VAc) = 0.33,\;r_2 (BCVP) = 0.47$ The values of Alfrey-Price's Q and e for the bis(${\beta}$-chloroethyl)vinylphosphonate were calculated to be 0.06 and 1.1, respectively. The statistical analyses for the monomer sequence distribution and the mean sequence length show that the copolymer formed from these two monomers are of fairly alternating tendency. Differential thermal analysis showed that thermal stability of the copolymers decreases as the content of BCVP in the copolymer increases.

• Journal of Microbiology and Biotechnology
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• v.11 no.6
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• pp.922-927
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• 2001

In an effort to regulate the mammalian cell behavior in entrapment with a gel, we have functionalized hydrogels with the putative cell-binding (-Arg-Gly-Asp-)(RGD) domain. An adhesion molecule of Gly-Arg-Gly-Asp-Ser (GRGDS) peptides, a cell recognition ligand, was induced into thermo-reversible hydrogels, composed of N-isopropylacrylamide with small amounts of acrylic acid (typically 2-5 $mol\%$ in feed), as a biomimetic extracellular matrix (ECM). The GRGDS containing a p(NiPAAm-co-AAc) copolymer gel was studied in vitro for its ability to promote the spreading and viability of cells by introducing a GRGDS sequence. Hydrogel with no adhesion molecule was a poor ECM for adhesion, permiting spreading of only $3\%$ of the seeded cells for 36h. By immobilizing the peptide linkage into the hydrogel, the conjugation of RGD promoted $50\%$ of proliferation for 36h. However, the GREDS sequence, nonadhesive peptide linkage, conjugated hydrogel showed only $5\%$ of the seeded cell for the same time period. In addition, with the serum-free medium, only GRGDS peptides conjugated to hydrogel was able to promotecell spreading, while there was no cell proliferation in the hydrogel without GRGDS. Thus, the GRGDS peptide-conjugated thermo-reversible hydrogel specifically mediated the cell spreading. This result suggests that utilization of peptide sequences conjugating with the cell-adhesive motifs can enhance the degree of cell surface interaction and influence the long-term formation of ECM in vitro.

• Macromolecular Research
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• v.17 no.12
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• pp.1003-1009
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• 2009

Copolymers of N-vinylpyrrolidone (NVP) comonomer with styrene (St), hydroxypropyl methacrylate (HPMA) and carboxyphenyl maleimide (CPMI) were synthesized by free radical polymerization using 2,2'-azobisisobutyronitrile (AIBN) initiator in 1,4-dioxane solvent. The copolymers formed were characterized by FTIR, $^1H$ NMR and $^{13}C$ NMR techniques and their thermal properties were studied by DSC and TGA. Copolymer composition was determined by $^1H$ NMR and/or by elemental analysis and monomer reactivity ratios (MRR) were estimated by the linear methods of Kelen-Tudos (K-T) and extended Kelen-Tudos (EK-T) and the non-linear approach. Copolymers of St and HPMA with NVP formed blocks of one of the monomer units, whereas alternating copolymers were obtained in CPMI-NVP, depending upon the side chain substitution. The MRR values are discussed in terms of monomer structural properties such as electronegativity and electron delocalization. The sequence distribution of monomers in the copolymers was studied by statistical method based on the average reactivity ratios obtained by EK-T method.

• Macromolecular Research
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• v.10 no.3
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• pp.145-149
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• 2002

Transesterification between poly(trimethylene terephthalate) (PTT) and bisphenol-A-polycarbonate (PC) is studied by differential scanning calorimetry (DSC) and nuclear magnetic resonance (NMR) spectroscopy. When the blend of PTT/PC is annealed at higher temperatures, the samples do not show any melting peak at an initial stage, indicating the samples completely lose their crystallinity due to the formation of random copolymers. However, when the random copolymer is annealed at temperatures lower than the melting temperature of PTT, a melting peak is observed, indicating that the random copolymers are sequentially reordered. The melting point and the heat of fusion of crystals formed from the crystallization-induced sequential reordering depend upon the annealing temperature and time. The average sequence length determined from NMR is increased as the blocks are regenerated.

• Polymer(Korea)
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• v.24 no.1
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• pp.58-64
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• 2000

Poly(butylene terephthalate-co-oxybenzoate) (PBOT ) was synthesized by melt trans-esterification of poly(butylene terephthalate)(PBT) and p-acetoxybensoic acid (ABA) at 250, 260, and 27$0^{\circ}C$ with the compositions of PBT/ABA of 4/6, 5/5, 6/4. The sequence analysis of PBOT with a $^1$H FT-NMR indicated that the number of consecutive oxybenzoate units ranges from 1.2 to 1.5, which is larger than that of the corresponding poly(ethylene terephthalate)(PET)/ABA (PEOT) obtained at the same reaction conditions as the PBOT. The difference in the block length influenced the thermal degradation behavior: Polyoxybezoate (POB), PBT and PEOT showed one-step degradation whereas PBOT exhibited two-step degradation. The results suggested that PBOT consisted of three phases of PBT-rich phase, random phase of PBT and ABA, and ABA-rich phase.

• Journal of the Korean Chemical Society
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• v.55 no.4
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• pp.673-679
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• 2011

Bimodal high-density polyethylenes with different comonomer type and content were synthesized by polymerization of ethylene using Ziegler-Natta catalyst. Their structure and properties were studied using GPC, NMR, DSC and tensile test. It was found that ethylene/1-hexene copolymer exhibits higher tensile strength and elongation at break than that of ethylene/1-butylene copolymer with similar comonomer content. The molecular weight decreases as the comonomer content of the polymer increases. Short chain branching affects the crystallinity and thus the morphology and consequently the mechanical properties of the corresponding bimodal high-density polyethylenes. After SSA treated, the multiple endothermic peaks were observed. Multiple endothermic peaks are mainly attributed to the heterogeneity of ethylene sequence length and lamellar thickness. The difference of broadness index indicates that SCB distribution of polyethylene containing higher comonomer content has improved uniformity.

• Journal of the Korean Vacuum Society
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• v.16 no.1
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• pp.65-73
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• 2007

The control of surface properties and spatial presentation of functional molecules within a microfluidic channel is important for the development of diagnostic assays, microreactors, and for performing fundamental studies of cell biology and fluid mechanics. Here, we present soft lithographic methods to create robust microchannels with patterned microstructures inside the channel. The patterned regions were protected from oxygen plasma by controlling the dimensions of the poly(dimethylsiloxane)(PDMS) mold as well as the sequence of fabrication steps. The approach was used to pattern a non-biofouling polyethylene glycol(PEG)-based copolymer or the polysaccharide hyaluronic acid(HA) within microfluidic channels. These non-biofouling patterns were then used to fabricate arrays of fibronectin(FN) and bovine serum albumin(BSA) as well as mammalian cells.

• Polymer(Korea)
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• v.35 no.1
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• pp.77-86
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• 2011

Polymerization properties of six dinuclear constrained geometry catalysts (DCGC) were investigated. The different length bridges of three catalysts were para-phenyl (Catalyst 1), para-xylyl (Catalyst 2), and para-diethylene phenyl (Catalyst 6). The other three DCGC have the same para-xylyl bridge with the different substituents at the phenyl ring of the bridge. The selected substituents were isopropyl (Catalyst 3), n-hexyl (Cataylst 4), and n-octyl (Catalyst 5), It was found that the longer catalyst not only exhibited a greater activity but also prepared a higher molecular weight copolymer. The catalyst 3 having a bulky isopropyl substituent revealed the lower activity but formed the highest molecular weight polymer comparing with the other alkyl substituted DCGCs. These results were able to be understood on the basis of the electronic and steric characteristics of the bridge. This study confirms that the control of the bridge structure of DCGC may contribute to control the microstructure of polymers.

• Polymer(Korea)
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• v.28 no.6
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• pp.468-477
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• 2004

The polymer blends of waste poly(vinyl chloride) (RPVC) and waste polyethylene (RPE) were prepared by melt mixing. Various ethylene-vinyl acetate copolymers (EVA) and ethylene-methacrylic acid Na salt copolymer (ionomer) were used as compatibilizer. Their morphologies and mechanical properties were evaluated as a funtion of mixing sequence and time. EVA with high vinyl acetate contents showed a rapid increment of tensile properties when small amount was added. Tensile properties of the blends were gradually increased with the addition of ionomer. Morphologies of RPVC/RPE blends were analyzed by scanning electron microscopy. FT-IR data showed that EVA was a good compatibilizer in RPVC/RPE blend compared to ionomer. Mechanical properties of the blends were highly enhanced when RPVC and compatibilizer were mixed and first RPE was added later.