• Polymer(Korea)
• /
• v.35 no.4
• /
• pp.284-288
• /
• 2011

For the purpose of the pre-industry production of poly(L-lactide) (PLLA) and full understanding of the supercritical polymerization system, large scale polymerization of L-iactide initiated by 1-dodecano/stannous 2-ethyl-hexanoate (DoOH/Sn(Oct)$_2$) was carried out in supercritical chlorodifluoromethane under various reaction conditions (time, temperature and pressure)and reactants (monomer and supercritical solvent) concentrations. A 3 L sized-reactor system was used throughout this study. The monomer conversion increased to 72% on increasing reaction time to 5 h. The molecular weight of PLLA product also increased to 68000 g/moi over the same period. An increase in monomer concentration resulted in a higher molecular weight, up to 144000 g/mol and 97% of monomer conversion. Raising the reaction pressure from 130 to 240 bar also resulted in an increased monomer conversion and molecular weight. To increase heat resistivity of PLLA, methanol treatment and heat-vacuum methods were evaluated. Both of them successfully improved the heat resistivity property of PLLA.

• Composites Research
• /
• v.32 no.1
• /
• pp.71-77
• /
• 2019

In this study, the structural and rheological characterizations of polyacrylonitrile(PAN)/dimethyl sulfoxide(DMSO) solutions for PAN fiber were investigated according to the change of storage times and temperatures. As a result, PAN/DMSO solutions exhibited a very characteristic rheological behavior with variation of temperature. The solutions showed an increase of complex viscosity and a decrease of loss tangent($tan{\delta}$) as temperature was increased over the temperature range of 40 and $70^{\circ}C$ and it could be seen that the viscosity rapidly increased at low frequency. These results indicated that the gel polymer and denser gel structure were formed due to the intermolecular hydrogen bonding of water in the polymer solution depending on the storage time.

• Applied Chemistry for Engineering
• /
• v.22 no.2
• /
• pp.230-234
• /
• 2011

In this work, the primary material for a single layered hardmask which can afford a spin-on process was prepared by the minture of organic and inorganic sources. The preparation of hybrid polymer was attempted by esterification from silanol terminated siloxane compounds and acetonide-2,2-bis(methoxy)propionic acid. The optical, thermal and morphological properties of the test hardmask film was examined in terms of cross-linking agent and additives. In addition, the etch rate of hardmask film and photo resist layer were compared. The hybrid polymer prepared from organic and inorganic materials was found to be useful for hardmask film to form the nano-patterns.

• Journal of the Korean Chemical Society
• /
• v.43 no.1
• /
• pp.28-42
• /
• 1999

Polysilanes with sterically bulky substituents, -[2-( $R^1R^2$-phenyl)propyl]Si[$R^3$]-, such as poly(2-phenylpropyl)(n-hexyl)silane [$R^1=R^2$=H, $R^3$=n-hexyl] were prepared by Wurtz-type coupling reactions with Na using a sonochemical method. The high-intensity ultrasound provided the formation of high quality Na dispersion in toluene and its active surface which was important for the synthesis of polysilanes in Wurtz-type coupling reaction was freshly and continuously regenerated during the process. The polysilanes products were mixtures of high molecular weight polymers with $\={M}_W$ of ∼$10^6$ and low molecular weight polymers with $\={M}_W$ of ∼$10^3$. It was found that the formation of high molecular weight polymerr was greatly influenced by the substituents $R^3$, directly attached to Si. On the contrary, changes on substituents ($R^1, R^2$) gave no influences at all. Overall yields for polysilanes were 75-99% in general but high molecular weight polysilanes were obtained as a major product when substituent $R^3$ is n-hexyl group and low molecular weight polysilanes were obtained as a major product when substituent $R^3$ is cyclohexyl and 2-phenylethyl groups. Effects of reaction conditions to polysilane yields were investigated.

• Weed & Turfgrass Science
• /
• v.3 no.1
• /
• pp.19-28
• /
• 2014

Research was initiated in greenhouse to investigate effects of polymer, calcium, perlite and chitosan on the growth of Kentucky bluegrass (KB). A total of 24 treatment combinations were used in the study. Treatments were made of water-swelling polymer (WSP), calcium, perlite, and chitosan in soil organic amendment (SOA). Significant differences were observed in germination rate, turfgrass coverage, turfgrass density and top growth among treatments. Germination rate, density and plant height varied with time after seeding. A proper mix of WSP is considered to be lower than 3% for turfgrass coverage and density. Regarding survival capability and top growth, however, it was good under 6%. Overall KB growth was more influenced by calcium and perlite than chitosan. Calcium and perlite were the most effective elements for early survival capacity and turfgrass density, respectively. But no effect was found by chitosan. Top growth increased with three elements, being perlite > calcium > chitosan. The chitosan was effective in early germination, but there was no effect on top growth until 3 weeks, when compared with others. A further study is needed for investigating the effect of these materials on the growth characteristics in mixtures of sand and SOA before a field application.

• Korean Journal of Food Science and Technology
• /
• v.31 no.3
• /
• pp.600-605
• /
• 1999

Methyl linoleate was oxidized at 60, 90, 120 and $150^{\circ}C$, respectively, with sparging oxygen for different periods of time. On the basis of the peroxide values determined at four temperatures, four heating times were chosen for the analysis of physicochemical parameters, such as peroxide value, total oxidation products, polymer content, viscosity, refractive index and characteristics of thermal degradation by DSC (Differential Scanning Calorimeter). The content of peroxide linkage (C-O-O-C) polymer and ether or carbon to carbon linkage (C-O-C/C-C) polymer were analyzed by High Performance Size Exclusion Chromatography (HPSEC). The polymer formed at four temperatures was qualitatively identified as dimer. The polymer with peroxide linkage (C-O-O-C) were detected from methyl linoleate oxidized at $60^{\circ}C\;and\;90^{\circ}C$, but they were not detected from methyl linoleate oxidized at $120^{\circ}C\;and\;150^{\circ}C$. The enthalpy changes increased as peroxide value increased whereas maximum degradation temperature decreased. The highest correlation coefficients were obtained between maximum degradation temperature $(T_m)$, exothermic enthalpy changes and peroxide value, peroxide linkage (C-O-O-C) polymer content.

• Applied Chemistry for Engineering
• /
• v.23 no.5
• /
• pp.462-466
• /
• 2012

$\beta$-cyclodextrin ($\beta$-CD) polymers were prepared in a strong alkali condition solution (NaOH solution 30% (w/v)) using epichlorohydrin (EPI) as a cross-linker, and the molar ratio of EPI to $\beta$-CD was 10 : 1. The $\beta$-CD content in $\beta$-CD polymers is about 52%. In order to get the photo-responsible and pH-responsible, cinnamic acid was added to be inserted into the cavities of $\beta$-CD due to the hydrophobic interaction. The complex formation was confirmed using transmission electron microscope. The dimerization degree of complexes increased under UV irradiation at $\lambda$ = 365 nm but decreased under the UV irradiation at $\lambda$ = 254 nm. Dynamic light scattering analysis of particle sizes showed that the sizes of complexes did not change with different UV wavelength. Moreover, the complexes were pH-responsible because of the carboxyl group of cinnamic acid, but the size and zeta potential of the complex did not change in strong acid and alkali conditions.

• Proceedings of the Korean Fiber Society Conference
• /
• 2001.04b
• /
• pp.59-62
• /
• 2001

• Applied Chemistry for Engineering
• /
• v.2 no.1
• /
• pp.56-63
• /
• 1991

The monomer, 1-(2-carbomethoxyacryloyl)-5-fluorouracil(CMAFU) was synthesized from trans-${\beta}$-carbomethoxyacryl chloride and 2, 4-bis(trimethylsilyloxy)-5-fluoropyrimidine. A copolymer of CMAFU with methyl methacrylate (MMA)[poly(CMAFU-co-MMA)] was also prepared with 2, 2'-azobisisobutyronitrile in cyclohexanone at $60^{\circ}C$. Physiological genetic effects of 5-fluorouracil(5-FU), CMAFU and poly(CMAFU-co-MMA) on Drosophila melanogaster were investigated by the adult feeding method of Lewis and Bacher. It was found that a physiological genetic effect on the Drosophila melanogaster was considerably weaker for CMAFU and its copolymer than 5-FU.

• Journal of the Korean Chemical Society
• /
• v.26 no.3
• /
• pp.179-187
• /
• 1982

The copolymerization of N-acryloylpyrrolidone and acrylonitrile was performed in N,N'-dimethylformamide at 50$^{\circ}$C and monomer reactivity ratio was obtained by using IR working curve and Fineman and Ross equation. ($r_1$ = 0.43, $r_2$ = 1.56) It is found that resulting copolymer is good polymeric initiator for anionic graft copolymerization of 2-pyrrolidone. Graft copolymers with polybutylamide (nylon-4) grafts onto poly(NAP-Co-AN) backbone were synthesized and the various effects on the graft copolymerization of 2-pyrrolidone were examined. The rate constants ($K_p$) of graft anionic polymerization at 40 and 50$^{\circ}$C were 2.82${\times}$10 and 2.93${\times}$10(l/mole, min), respectively.