• Journal of dental hygiene science
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• v.8 no.3
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• pp.109-115
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• 2008

Two t-amines, N,N-dimethylaniline (MA), N,N-dimethyl-p-toluidine (MPT), were investigated as new visible light amine initiators for a dental resin composite of UDMA in order to improve photopolymerization effect. Three t-amines mixed with three photosensitizers, camphorquinone(CQ), 1-phenyl-1,2-propane dione(PD) and diacetyl (DA), respectively. And then this mixtures are added to resin monomer, UDMA. Photopolymerization efficiency of UDMA was studied through the use of FT-IR absorption spectroscopy. The photopolymerization effect of amine initiators were compared with that of 4-(dimethylamino)ethyl methacrylate (AEM), the most widely used photoinitiator. The photopolymerization efficiency of UDMA containing the amine initiator increased with irradiation time. The relative polymerization efficiency containing the CQ photosensitizer increase was in the order: AEM < MPT < MA. And the relative polymerization efficiency containing the PD photosensitizer increase was in the order: MPT < AEM < MA. This result shows that MA is most efficient amine initiator with CQ and PD.

• Journal of dental hygiene science
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• v.9 no.2
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• pp.189-195
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• 2009

Two diketones, 1,2-phenylpropanedione (PD) and diacetyl (DA) were investigated as new visible light photosensitizers for dental composite resin of bis-GMA in order to improve the photopolymerization effect. The photopolymerization efficiency of bis-GMA composite resin containing PD and DA was studied by IR absorption spectroscopy. And the results were compared with that of camphorquinone (CQ). Relative photopolymerization efficiency of the photosensitizers increased in the order of DA < CQ < PD. Thus. PO is a new visible light photosensitizer for dental composite resin with higher photopolymerization efficiency than that of CQ.

• The korean journal of orthodontics
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• v.35 no.6 s.113
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• pp.443-450
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• 2005

This study was performed to compare the shear bond strength of orthodontic adhesive to amalgam according to different light sources (halogen-based light and light emitting diode (LED)) and amalgam surface treatments. Ninety extracted human premolars were randomly divided into 6 groups (4 experimental and 2 control groups) of 15 by light sources and surface treatments. Orthodontic brackets were bonded and shear bond strength was measured with an Instron universal testing machine. The findings were as follows: The bond strength of adhesive to amalgam surface was 3-5.5 MPa which was lower than that of acid-etched enamel (19 MPa) control. In the sandblasted amalgam surface, the shear bond strength of the halogen light group was higher than that of the LED group (p < 0.05) but. in the non-treated amalgam surface. there was no significant difference in the shear bond strength according to the light sources (p> 0.05). Within the same light source. sandblasting had no significant effect on the shear bond strength of the adhesive bonded to amalgam surface (p > 0.05). There was no significant difference in shear bond strength according to the light sources in acid-etched enamel control groups. This results suggest that there can be a limit in using light curing adhesives when brackets are bonded to an amalgam surface. Additional clinical studies are necessary before routine use of halogen light and LED light curing units can be recommended in bonding brackets to an amalgam surface.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.10
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• pp.875-880
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• 2016

In this study, we proposed an effective and simple way to directly generate wrinkle patterns on a curved surface. A curved surface was prepared using a 3D printer and an UV (Ultraviolet)-lighting system was utilized to weakly polymerize the UV-curable thin resin layer coated on the surface, resulting in a gradient of material properties in the layer thickness. Subsequently, a thermal curing process was conducted to generate microscale wrinkles by compressive forces that were generated during complete curing. Wrinkle shapes from 5, 15, 25 sec of UV-light exposure were compared. With increasing UV-exposure, the line-width of wrinkles became thicker due to much higher strength of skin zone. The results indicated that the proposed fabrication process could be utilized for surface modification in diverse research fields.

• Polymer(Korea)
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• v.29 no.6
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• pp.613-616
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• 2005

In this word as the first step to develop optical biosensors for a single cell level analysis, the preparation method of nano-scale polymer hydrogel spheres containing an enzyme was set up and the feasibility of the spheres as optical biosensors was investigated. The horseradish peroxidase (HRP) was encapsulated in the PEG hydrogel spheres by suspension photopolymerization, yielding spheres of the average size of 305 nm. After the polymerization, the incorporation and activity of HRP within the spheres were determined by the production of fluorescence resulted from the enzymatic reaction between HRP and $\H_{2}O_{2}$. The fluorescence emission response of the HRP-loaded PEG hydrogel spheres increased by nearly 300$\%$ as hydrogen peroxide concentration was changed from 0 to 11 nM in the presence of Amplex Red. The results suggest that the method to prepare the PEG hydrogel nanospheres containing an enzyme could be used for developing optical biosensors to measure various analytes in the very small samples like a single cell.

• Polymer(Korea)
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• v.39 no.3
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• pp.461-467
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• 2015

This paper reports the combined effects of the triblock copolymer surfactant poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol) (PEG-PPG-PEG) and imidazole on the opto-electrical and mechanical properties of poly(3,4-ethylenedioxythiophene) (PEDOT)-based thin films prepared via vapor phase polymerization (VPP) using ferric p-toluenesulfonate as a catalyst. Various PEDOT-based thin films were synthesized using PEG-PPG-PEG and imidazole alone and in combination to compare and correlate their effects on film properties. The improved conductivity of the PEDOT films was higher than $1300S{\cdot}cm^{-1}$ when the surfactant and imidazole were used together. The PEG-PPG-PEG chain length was also varied to identify the best conditions for the VPP-based preparation of PEDOT thin films.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.1
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• pp.102-109
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• 2003

The purpose of this study was to evaluate the linear polymerization shrinkage(%) and microhardness of composite resin(Z-100, 3M, USA) according to 2-step light curing method. Conventional light curing unit(Curing Light 2500, 3M USA) and 2-step light curing unit(Elipar Highlight, ESPE, Germany) were used as light source. The strain gauge method was used for determination of polymerization shrinkage(%). Samples were divided by 3 groups according to light curing methods (Group I : $450mW/cm^2$, 40sec, Group II : $650mW/cm^2$, 40sec, Group III : $150mW/cm^2$, 10sec & $650mW/cm^2$, 30sec). Preparations of acrylic molds were followed by filling and curing. Strain gauges attached to each sample were connected to a strainmeter. Measurements were recorded at each second for the total of 10 minutes including the periods of light application. And microhardness of each group after 24hours from light irradiation were measured. Obtained data were analyzed statistically using Ore-way ANOVA and/or Scheffe test. The results of the present study can be summarized as follows: 1. Composite resin in acrylic molds showed the initial expansion at the early phase of polymerization. This was followed by the contraction with the rapid increase in volume during the first 60 seconds and gradually diminished as curing process continued. 2. The lowest linear polymerization shrinkage(%) was found in group III followed by group I, II during the measuring periods. 3. Group III using 2-step curing method showed statistically significant reduction of linear polymerization shrinkage(%) compared with group I, II at 1 minute and 10 minutes from light irradiation(p<0.05). 4. The microhardness values of each group not revealed significant difference.

• Journal of the korean academy of Pediatric Dentistry
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• v.29 no.1
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• pp.19-29
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• 2002

The purpose of this study was to compare the polymerization shrinkage and the compressive strength of composite and compomer cured with two different light sources ; conventional halogen-light curing unit and recently-developed plasma arc curing unit. The 'strain gauge method' was used for determination of polymerization shrinkage and the compressive strength was measured by universal testing machine. The results of the present study can be summarized as follows: 1. Filling materials in polyethylene molds showed the initial expansion in the early phase of polymerization. This was followed by the rapid contraction in volume during the first 60 seconds and gradually diminished as curing process continued. 2. The polymerization shrinkage in tooth samples was generally lower than in the mold samples. 3. The generally lower amount of linear polymerization shrinkage was observed in compomer and plasma arc curing unit group when compared to composite and conventional curing unit. 4. The higher compressive strength values was found in composite groups regardless curing methods. The results of this study strongly support the application of plasma arc system and fluoride-containing compomer in the field of clinical pediatric dentistry claiming its effectiveness in curing the esthetic dental materials and the anticariogenic capacity.

• Proceedings of the Korean Fiber Society Conference
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• 2002.04a
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• pp.344-346
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• 2002

그라프트중합법은 고분자막이나 직포, 부직포, 합성지 등에 기존 소재의 특성을 손상하지 않고 여러 가지 기능을 가진 관능기를 부여할 수 있다는 점에서 각종 섬유 및 범용성 고분자 소재의 개질 및 특성부여 방법으로 이용되고 있다[1,2,3]. 광조사에 의한 그라프트 중합법은 빛의 침투가 약하고 활성점이 균일하게 형성되지 못한다는 단점이 있으나 그 취급의 용이성 및 안전성, 설비의 경제성 및 실용성이 높을 뿐만 아니라 원재료의 물성을 크게 손상시키지 않으면서 특정 단량체를 그 표면에 도입시킬수 있어 섬유 및 고분자 재료의 표면성질이나 친수성 개선뿐만 아니라 역삼투성 및 이온선택투과성과 같은 기능성의 부여 등에도 적용 가능함이 확인되었다[4]. (중략)

• Journal of Korean Ophthalmic Optics Society
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• v.17 no.2
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• pp.135-141
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• 2012

Purpose: Polymerization of HEMA(2-hydroxyethyl methacrylate) which can be used in the soft contact lens has been performed by using electron beam(EB) irradiation, and examined the best condition for the polymerization. Comparing the physical properties of the contact lenses to the one fabricated by thermal polymerization method, we check the use possibility of the EB irradiation to the fabrication of the soft contact lens. Methods: We investigated the degree of polymerization of the HEMA according to the composition of the monomer, the additive ratio and the dose of electron beam (0~120 kGy). The degree of polymerization was measured depending on the EB dose to research the best synthetic condition under the EB irradiation. The physical properties of the contact lens such as water content(%), oxygen transmissibility(Dk/t) and optical transmittance were analysed by using the FT-IR results with comparing the two different polymerization method (thermal and electron beam polymerization) with same additive ratio. Results: When the dose of electron beam was above 100 kGy, the degree of polymerization of HEMA was above 99% with regardless using cross-linker and initiator. The water content of the lens fabricated by EB method showed 10% higher than the one by the thermal method which was 40%. The lens fabricated by EB method also showed higher oxygen transmissibility(Dk/t) as same with the water content, and showed twice higher value in the lens fabricated by pure HEMA. According to the FT-IR results, hydrophilic property of the lens fabricated by EB method was increased due to increasing the intermolecular hydrogen bonding. It showed above 90% optical transmittance in the visible range of wavelength on the contact lenses fabricated by the both of two different polymerization method. Conclusions: The polymerization of HEMA without cross-linker and initiator was successful above 100 kGy of EB irradiation. Moreover the lens fabricated from the polymer synthesized by pure HEMA with 100 kGy of EB showed the highest water content and oxygen transmissibility. Therefore EB irradiation is another possible method to synthesize the polymer which can be used for the soft contact lens.