• Polymer(Korea)
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• v.32 no.4
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• pp.385-389
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• 2008

Chain propagation and chain transfer in anionic polymerization of hexafluoropropylene oxide were investigated under various reaction conditions such as the stabilization of reaction temperature, the amount of hexafluoropropylene solvent, and the feeding rate of hexafluoropropylene oxide monomer. Anionic initiator for the polymerization was synthesized from cesium fluoride and hexafluoropropylene oxide in tetraethyleneglycol dimethylether. It was possible to obtain a high molecular weight poly(HFPO) ($M_w$ 14800) using the anionic initiator in conditions of stabilized reaction temperature, and optimized addition of solvent and monomer feeding (HFP/initiator mole ratio=31.5 and HFPO feeding rate=11.67 g/hr). Otherwise, chain transfer reaction in anionic polymerization was increased. From the results of molecular weight in various reaction conditions, it was found that chain propagation and chain transfer in anionic polymerization of HFPO were very sensitive to reaction conditions.

• Polymer(Korea)
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• v.37 no.1
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• pp.80-85
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• 2013

Anionic polymerization of hexafluoropropylene oxide (HFPO) was investigated under various reaction conditions such as various hexafluoropropylene (HFP) oligomers composed of dimer and trimer, reaction temperatures, and feeding rates of hexafluoropropylene oxide monomer. HFP oligomer was synthesized from cesium fluoride (CsF) and HFP in tetraethyleneglycol dimethylether (TG). Under 5 g of CsF, 200 g of HFP, 10 g of TG, and reaction temperature $30^{\circ}C$, HFP dimer content in oligomer was relatively increased. HFPO oligomer with a high molecular weight ($M_w$ 3600) was synthesized in conditions of reaction temperature $0^{\circ}C$, HFP oligomer with 35.1% of dimer, and 1.85 g/min of HFPO feeding rate. Otherwise, chain transfer was increased under unoptimized reaction conditions. Consequently, it was found that reaction conditions impact chain propagation and chain transfer in the anionic polymerization of HFPO.

• Applied Chemistry for Engineering
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• v.21 no.6
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• pp.621-626
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• 2010

Anion exchange membranes can be used for reverse electrodialysis for electric energy generation, and capacitive deionization for water purification, as well as electrodialysis for desalination. In this study, anion exchange membranes of poly((vinylbenzyl) trimethylammonium chloride-2-hydroxyethyl methacrylate)/poly(vinyl alcohol) were prepared through the polymerization of (vinylbenzyl)trimethylammonium chloride and 2-hydroxyethyl methacrylate in aqueous poly(vinyl alcohol) solutions, esterification with glutaric acid, and cross-linking reaction with glutaraldehyde. We investigated electrochemical properties for the anion exchange membranes prepared according to experimental conditions. Ion exchange capacity and electrical resistance for the membranes were changed with a variation in the monomer ratio in polymerization. Water uptake and conductivity for the membranes decreased with an increase in the content of glutaric acid in esterification. The change in the time of crosslinking reaction with the formed film and glutaraldehyde affected electrochemical properties such as water uptake, conductivity, or transport number for the membranes. Chronopotentiometry and limiting current density for the anion exchange membranes prepared were measured.

• Journal of the Korean Chemical Society
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• v.23 no.6
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• pp.402-411
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• 1979

The synthesis of pyrrolidone-N-sulfonyl chloride has been carried out by the reaction of pyrrolidone with sulfuryl chloride in benzene. It was attempted to study the catalytic effect of pyrroldone-N-sulfonyl chloride as an initiator for anionic polymerization of pyrrolidone. It was found that as a concentration of initiator decreased, inherent viscosity of the resulting polymer increased up to 1.8 dl/g. The highest rate of polymerization and equilibrium conversion was observed when mole ratio of PNSC to KOH was 0.25. In general, the observed value of polymerization and equilibrium conversion in circumstances using PNSC/KOH catalysis system were higher than using $CO_2$/KOH catalysis system.

• Polymer(Korea)
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• v.33 no.5
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• pp.458-462
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• 2009

We have synthesized ABC linear triblock copolymers, i.e., polystyrene-b-poly(ethylene oxide)-b-polylactide, via sequential anionic and ring-opening polymerizations. In the first anionic polymerization step, styrene was polymerized in cyclohexane using sec-butyllithium as the initiator. Poly (styryl) lithium was hydroxylated by the addition of ethylene oxide, and the subsequent protonation with methanolic HCl. In the second anionic polymerization step, potassium naphthalenide was used to deprotonate the hydroxyl group of the PS to generate the macroinitiator of PS-$O^-K^+$. Polymerization of ethylene oxide was performed in THF and terminated with methanolic HCl. In the ring-opening polymerization step, the PS-b-PEO-$AlEt_2$ macroinitiator was prepared from an $AlEt_3$/pyridine system in THF, and the polymerization of lactide was performed at $90^{\circ}C$. The resulting block copolymers showed well-defined molecular weights and narrow molecular weight distributions as revealed by $^1H$- NMR spectroscopy and gel permeation chromatography (GPC).

• Applied Chemistry for Engineering
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• v.9 no.7
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• pp.1018-1022
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• 1998

Characteristics and catalytic activities of 12-molybdophosphoricacid catalysts modified by ring opening polymerization of tetrahydrofuran (THF) were studied in this work. 12-Molybdophosphoricacid catalysts modified by THF showed higher conversions and product yields than the mother acid in the vapor-phase ethanol conversion. It was believed that the enhanced catalytic activities of modified 12-molybdophosphoricacids were due to structural flexibility of heteropolyanions and weakened hydrogen bond around heteropolyanions. THF interacted with protons and crystalline water molecules of heteropolyacids. The interaction between THF and heteropolyanoins, which crystalline water molecules act as intermediary, was the dominant factor deciding the catalytic activities of modified 12-molybophosphoricacids.

• Polymer(Korea)
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• v.25 no.1
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• pp.1-5
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• 2001

Monomer casting nylons were synthesized by casting anionic polymerization of ${\varepsilon}$-caprolactam. Polymerization rates, molecular weights of the products and the conversions were determined while varying the content of catalysts in the range of 0.2~0.6 mol% and 0.1~1.0 mol% for initiator. The polymerization rates were enhanced as the ratio of catalysts to initiator increased. The maximum molecular weight was observed when the ratio of catalysts to initiator was 0.8, and as the ratio increased the molecular weight decreased. On the other hand, when the ratio of catalysts to initiator was below 0.8, the conversions and the molecular weights were abruptly diminished due to the termination of growing chains.

• Elastomers and Composites
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• v.33 no.4
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• pp.255-266
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• 1998

One-step continuous reactive blend with EPDM is investigated using a modular intermeshing corotating twin screw extruder This was performed via anionic polymerization mechanism. Mechanical properties were characterized and compared with mechanical blends.

• Polymer Science and Technology
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• v.8 no.4
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• pp.421-426
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• 1997

• Applied Chemistry for Engineering
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• v.17 no.3
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• pp.303-309
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• 2006

In this study, functional anion-exchange membranes have been prepared and characterized to improve the permeation fluxes of the anion and urea for peritoneum dialysis. They were prepared by UV and radiation graft polymerization methods. The separation-membrane prepared by UV graft polymerization showed the highest grafting degree when HEMA and VBTAC were mixed by 1:2 ratio. However, the grafting degree decreased slightly at compositions above the 1:2 ratio because of the disruption of UV penetration caused by build-up of homopolymer. In the case of photo-initiator, the grafting degree increased up to 0.2 wt%, above which it decreased to a small extent. For the two membranes prepared by radiation graft polymerization, the VBTAC/HEMA membrane showed 96% grafting degree for 6 h reaction time and the GMA membrane showed over 100% grafting degree for 2 h reaction time. Anion-exchange membranes were prepared with 113% grafting degree and with DEA and TEA exchange groups. The DEA membrane showed the conversion degree of 70% in 4 h reaction time while the TEA membrane showed 30% in 2 h reaction time. The prepared anion-exchange membranes were permeable to only anions and urea, but not cations.