• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.321-321
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• 2006

Aromatic diacetylenes form stable oligomeric diradicals when irradiated with UV light or heated at temperatures above their melting points. In this paper, the formation of stable diradicals is discussed, and the mechanism of polymerization in the presence of peroxide in solution, is discussed. The diphenyldiacetylene undergoes polymerization through coupling of diradicals, and not by the successive addition of radical species.

• Journal of Technologic Dentistry
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• v.44 no.3
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• pp.76-80
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• 2022

Purpose: The purpose of this study is to analyze the depth according to curing using photocurable resin for dental three-dimensional printing. Methods: A stainless mold with a height of 4 mm was prepared. Ultraviolet (UV) polymerization resin was injected into the mold. Photocuring was then performed for 5 minutes using a photopolymerizer, and the height was measured using a digital measuring instrument (first group). Second, light polymerization was also performed outside the mold for 5 minutes, and the height was measured using a digital measuring instrument. Third, light polymerization was further performed for 5 minutes, and the height was measured using a digital measuring instrument. Statistical analysis was performed with the Kruskal-Wallis test, which is a nonparametric test (α=0.05). Results: The third group had the largest measurement length, whereas the first group had the smallest. However, the difference between groups was not statistically significant (p>0.05). The color of the first group was different from that of the second and third groups. Conclusion: All of the 4-mm-thick photocured specimens had a curing reaction, but the part that was not directly irradiated with UV did not show its original color.

• Journal of Korean Ophthalmic Optics Society
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• v.8 no.2
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• pp.129-134
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• 2003

A wide variety of unsaturated vinyl derivatives can be induced to undergo free-radical chain polymerization. The capability to carry out a thermodynamically feasible polymerization relies on its kinetic feasibility on whether the proceeds at a reasonable rate under a given set of reaction conditions. Initiator or promoter is often required to achieve the kinetic feasibility. Only a few unsaturated monomers including methyl methacrylate(MMA) are known to absorb light between 250 and 500 nm which is the most convenient wavelength range. Also, the polysilanes with unusual optical and electronic properties have been used as ceramic precursors, deep UV photoresists, photoconductors. The hydrosilation has been used to make many interesting types of silicon containing polymers such as copolymer, dendrimers. Bulk polymerization of monomers with different molar radio of hydrosilanes(9:1 through 1:9) were performed. A quartz test tube charged with monomer and hydrosilane was degassed and irradiated with 250 nm UV for 6 hours. The polymer was taken in toluene, precipitated in hexane, filtered off, and dried. It was found that the initiators appeared to competitively and concurrently function as both chain initiation and transfer agents in the polymerization of vinyl monomers.

• Membrane and Water Treatment
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• v.1 no.2
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• pp.103-120
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• 2010

Surface modification of microfiltration and ultrafiltration membranes has been widely used to improve the protein adsorption resistance and permeation properties of hydrophobic membranes. Several surface modification methods for converting conventional membranes into low-protein-binding membranes are reviewed. They are categorized as either physical modification or chemical modification of the membrane surface. Physical modification of the membrane surface can be achieved by coating it with hydrophilic polymers, hydrophilic-hydrophobic copolymers, surfactants or proteins. Another method of physical modification is plasma treatment with gases. A hydrophilic membrane surface can be also generated during phase-inverted micro-separation during membrane formation, by blending hydrophilic or hydrophilic-hydrophobic polymers with a hydrophobic base membrane polymer. The most widely used method of chemical modification is surface grafting of a hydrophilic polymer by UV polymerization because it is the easiest method; the membranes are dipped into monomers with and without photo-initiators, then irradiated with UV. Plasma-induced polymerization of hydrophilic monomers on the surface is another popular method, and surface chemical reactions have also been developed by several researchers. Several important examples of physical and chemical modifications of membrane surfaces for low-protein-binding are summarized in this article.

• Bulletin of the Korean Chemical Society
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• v.23 no.1
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• pp.35-40
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• 2002

Photoreaction of guest organic anions in layered organic-inorganic hybrid materials was investigated. The layered hybrids were synthesized by an anion-exchange reaction of $[LiAl_2(OH)_6]Cl{\cdot}yH_2O$ layered double hydroxide with aqueous (Z,Z)- and (E,E)-muconates under inert atmospheric condition, to give new organicinorganic hybrids of $[LiAl_2(OH)_6]_2[(Z,Z)-C_6H_4O_4]{\cdot}zH_2O$ and $[LiAl_2(OH)_6]_2[(E,E)-C_6H_4O_4]{\cdot}H_2O$, respectively. The basal spacings calculated by XRPD of intercalates indicate that muconate anions have almost vertical arrangements against the host $[LiAl_2(OH)_6]^+$ lattices in the interlayer of organic-inorganic hybrid materials. When UV light was irradiated on the suspension of $[LiAl_2(OH)_6]_2[(Z,Z)-C_6H_4O_4]{\cdot}zH_2O$, the (Z,Z)-muconate anions of the gallery space of hybrids were polymerized in the aqueous media while it was isomerized into more stable (E,E)-muconate in the methanollic suspension in the presence of catalytic amount of molecular iodine. All the products were characterized using elemental analysis, TGA, XRPD, FT-IR, $^1H$ NMR and $^{13}C$ CP-MAS NMR.

• Proceedings of the Membrane Society of Korea Conference
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• 1998.04a
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• pp.99-101
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• 1998

1. Introduction : The conventional grafting polymerization technique requires chemically reactive groups on the surface as well as on the polymer chains. For this reason, a series of prefunctionalization steps are necessary for covalent grafting. The surface prefunctionalizational technique for grafting can be used to ionization radiation, UV, plasma, ion beam or chemical initiators. Of these techniques, radiation method is one of the useful methods because of uniform and rapid creation of active radical sites without catalytic contamination in grafted samples. If the diffusion of monomer into polymer is large enough to come to the inside of polymer substrate, a homogeneous and uniform grafting reaction can be carried out throughout the whole polymer substrate. Radiation-induced grafting method may attach specific functional moieties to a polymeric substrate, such as preirradiation and simultaneous irradiation. The former is irradiated at backbone polymer in vacuum or nitrogen gas and air, and then subsequent monomer grafting by trapped or peroxy radicals, while the latter is irradiated at backbone polymer in the presence of the monomer. Therefore, radiation-induced polymerization can be used to modification of the chemical and physical properties of the polymeric materials and has attracted considerable interest because it imparts desirable properties such as blood compatibility. membrane quality, ion excahnge, dyeability, protein adsorption, and immobilization of bioactive materials. Synthesizing biocompatible materials by radiation method such as preirradiation or simultaneous irradiation has often used $\gamma$-rays to graft hydrophilic monomers onto hydrophobic polymer substrates. In this work, in attempt to produce surfaces that show low levels of anti-fouling of bovine serum albumin(BSA) solutions, hydroxyethyl methacrylate(HEMA) was grafted polypropylene membrane surfaces by preirradiation technique. The anti-fouling effect of the polypropylene membrane after grafting was examined by permeation BSA solution.

• Macromolecular Research
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• v.15 no.1
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• pp.74-81
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• 2007

A series of photoreactive mesogens based on chalcone were prepared and their morphological behavior and reactivity were studied according to a variable number of alkyloxy tail carbons. The linear ester compounds 3a-h comprised two chalcone units connected to a benzene ring through ester linkages. All linear ester compounds showed enantiotropic liquid crystalline phases. The X-ray diffractograms for the mesophases of compounds 3a-h showed a set of reflections in the small-angle region which consisted of more than three sharp diffraction peaks with d spacings in the ratio of 1:1/2:1/3, confirming the well defined smectic A structures of the compounds. Compounds 3a-h were considered to be bifunctional monomers due to the presence of two photoreactive chalcone groups. Upon UV irradiation, its polymerization proceeded through the [2+2] addition reaction between chalcone units in a stepwise manner. An image pattern was obtained by the photopolymerization of the liquid crystal of the compound (3h) with decyloxy tails through a photomask. The irradiated part became dark while the masked part remained birefringent under polarized optical microscopy, which was ascribed to the production via the UV irradiation of a polymer or a dimer having cyclobutane rings by [2+2] addition, which thereby disrupted the alignment of the molecules.

• Journal of Photoscience
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• v.7 no.4
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• pp.131-133
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• 2000

A Styrene-derived polymer having pendent phenoxyanthraquinones for photochromism was prepared by AIBN-initiated radical polymerization. Syntgesus of the monomers was straightforward and the polymer was obtained in 65% yield. Photoinduced rearrangement from the “trans” quinone forms to the “ana” quinone forms readily occurred both in solution and in film when the polymer was irradiated with UV light.

• Elastomers and Composites
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• v.49 no.3
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• pp.199-203
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• 2014

Terpolymer syrups were photopolymerized from 2-ethylhexyl acrylate, 2-hydroxylethyl acrylate and isobornyl acrylate to prepare acrylic pressure sensitive adhesives (PSAs). After polymerization, various crosslinkers as 1,6-hexanediol diacrylate (HDDA), poly (ethylene glycol) diacrylate (PEGDA, Mn = 250, 575, and 700) were added and then UV-irradiated to prepare the semi-IPN type PSAs. Their adhesion performance and storage modulus (G') were strongly dependent on their chemical structure and molecular weight of the crosslinkers. Optical properties such as transmittance (> 92.5 %), haze (< 1.0 %) and color-difference (< 0.3) of PSAs samples were not affected by crosslinker types used in this study.

• Polymer(Korea)
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• v.32 no.1
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• pp.70-76
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• 2008

The PES-g-BTCA membrane was synthesized by UV irradiation method and then used to be modified into the PES anion exchange membrane by the amination reaction. Their chemical structures and adsorption properties were investigated. The degree of grafting and amination were increased with increasing the reaction time and had the maximum values of 138% and 1.20 mmol/g at 80 min, respectively. The initial thermal degradation temperature of PES membrane was $400^{\circ}C$. Which was reduced as the surface modification reaction had proceeded. The values of contact angle for PES membrane were decreased from 68.1 to $40.2^{\circ}$ with increasing the extent of amination, the water up-take and ion exchange capacity were also increased with increasing UV irradiation time until 80 min. The average pore size and BET surface area were decreased in order of PES, PES-g-BTCA, and aminated PES ion exchange membrane. Their average pore sizes were 624.8, 359.7, and 138.5 ${\AA}$, and their surface areas were 10.1,9.7 and 1.7 $m^2/g$, respectively.