• 한국고분자학회:학술대회논문집
• /
• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
• /
• pp.71-72
• /
• 2006

We investigated a simultaneous living anionic polymerization process of isoprene (I) and 4styrene-d_8$ (S) in $benzene-d_6$ as a solvent with sec-buthyllithium as an initiator into polyisoprene(PI)-block-poly($styrene-d_8$)(PS) and the polymerization-induced molecular self-assembling process. This process was observed in-situ by time-resolved small-angle neutron scattering (SANS) experiment. The SANS profiles measured exhibited three time regions, where (i) the selective growth of PI chains occurs; (ii) the living chain ends switch from isoprenyllithium to styryllithium, and (iii) the SANS exhibited the polymerization induced disorder-to-order transition and order-to-order transition.

• Current Optics and Photonics
• /
• 제2권3호
• /
• pp.286-290
• /
• 2018

We investigated the dependence of the retardation dispersion on the polarization direction of ultraviolet (UV) light during the photopolymerization of self-organized smectic reactive mesogen (RM) molecules. RM retarder film that was photopolymerized with UV light linearly polarized parallel to the layer plane showed negative dispersion (ND) of retardation for a wide range of UV polymerization temperatures. On the other hand, film that was photopolymerized with unpolarized UV light showed negative dispersion in a narrow range of UV polymerization temperatures. With a certain UV polymerization temperature, the dispersion of retardation was converted from positive to negative, depending on the UV polarization.

• Bulletin of the Korean Chemical Society
• /
• 제31권7호
• /
• pp.1891-1896
• /
• 2010

Submicron-sized polymeric colloidal particles can self assemble into 3-dimensional (3D) opal structure which is a useful template for photonic crystal. Narrowly dispersed polymer microspheres can be synthesized by emulsion polymerization in water using water-soluble radical initiator. In this report, we demonstrate a facile and reproducible emulsion polymerization method to prepare various polymeric microspheres within 200 - 400 nm size ranges which can be utilized as colloidal photonic crystal template. By controlling the amount of monomer and surfactant, monodisperse polymer colloids of polystyrene (PS) and acrylates with various sizes were successfully prepared without complicated synthetic procedures. Such polymer colloids self-assembled into 3D opal structure exhibiting bright colors by reflection of visible light. The colloidal particles and the resulting opal structures were rigorously characterized, and the wavelength of the structural color from the colloidal crystal was confirmed to have quantitative relationship with the size of constituting colloidal particles as predicted by Bragg equation. The tunability of the structural color was achieved not only by varying the particle size but also by infiltration of the colloidal crystal with liquids having different refractive indices.

• International Journal of Safety
• /
• 제9권1호
• /
• pp.6-11
• /
• 2010

Thermal analysis, heating test on gram scale and simulation of exothermic behavior based on kinetic analysis has been conducted in order to evaluate thermal hazards of self-polymerization of MDI. The exothermic reactions of MDI are expected to be the polymerization which forms carbodiimide and carbon dioxide, dimerization and trimerization. When MDI is kept in adiabatic condition during 1 week (10080 hours), the simulated result shows runaway reaction can occur in the case that initial temperature was more than $130^{\circ}C$. The relationship between the initial temperature (T, $^{\circ}C$) and TMR is given in a following equation. TMR=$4.493{\times}10^{-7}$ exp ($9.532{\times}10^3$/(T+273.15)) We propose that the relationship gives important criteria of handling temperature of MDl to prevent a runaway reaction.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
• /
• pp.93-96
• /
• 2001

Structural polymer composites are susceptible to damage in the form of cracks, which form deep within the structure where detection is difficult and repair is almost impossible. A recent methodology for the damage repair of polymer composites using the self-healing technique is reported. The polymerization of the healing agent is triggered by contact with an embedded catalyst, being necessary to damage repair of polymer composites. For this purpose, the self-healing concept is introduced and the manufacturing process of microcapsule with the healing agent is briefly described. The polymerization between the healing agent and the catalyst is verified by the use of ESEM and IR spectroscopy. Finally the efficiency of the self-healing technique is investigated by measuring the critical load of TDCB specimen.

• Macromolecular Research
• /
• 제14권2호
• /
• pp.205-208
• /
• 2006

A polymeric film of a biodegradable poly(1,5-dioxepan-2-one) (PDXO) was formed on a gold surface by a combination of the formation of self-assembled monolayers (SAMs) presenting hydroxyl groups and the surface-initiated, ring-opening polymerization (SI-ROP) of 1,5-dioxepan-2-one (DXO). The SI-ROP of DXO was achieved by heating a mixture of $Sn(Oct)_2$, DXO, and the SAM-coated substrate in anhydrous toluene at $55^{\circ}C$. The resulting PDXO film was quite uniform. The PDXO film was characterized by polarized infrared external reflectance spectroscopy, X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, atomic force microscopy, ellipsometry, and contact angle goniometry.

• Bulletin of the Korean Chemical Society
• /
• 제23권2호
• /
• pp.325-329
• /
• 2002

In this study, the dependency of the behavior of propagating front on the reaction condition in frontal polymerization reaction has been studied. We have used some multifunctional acrylates as a monomer and ammonium persulfate as an initiator for the polymerization reactions. In frontal polymerization, a method of producing polymeric materials via a thermal front that propagates through the unreacted monomer/initiator solution, the behavior of self propagating front shows various dynamic patterns depending on the reaction condition. We have obtained some spin modes of propagating front in the number of 'hot spots' or 'spin heads' by changing the reaction condition. The effect of the reactor tube diameter on the mode of propagating front has also been studied by using some reactor tubes with different size of tube diameter and it has been examined in some detail by adopting an experimental method of two-tubes system.

• Macromolecular Research
• /
• 제15권7호
• /
• pp.633-639
• /
• 2007

A variety of NMR techniques were applied to the micro-chemical structural characterization of polyanilines prepared via an efficient synthetic method in a self-stabilized dispersion medium in which the polymerization was conducted in a heterogeneous organic/aqueous biphasic system without any stabilizers. Here, the monomer and growing polymer chain were shown to function simultaneously as a stabilizer, imparting compatibility for the dispersion of the organic phase, and as a form of flexible template in an aqueous reaction medium. Polymerizations predicated on this concept generated polyanilines with a low defect content: solution state $^{13}C-NMR$ and solid $^{13}CDD/CP/MAS$ spectroscopy indicated that the synthesized HCPANi and its soluble derivative, HCPANi-t-BOC, evidenced distinctly different NMR spectra with fewer side peaks, as compared to conventionally prepared PANis, and the complete structural assignments of the observed NMR peaks could be determined via the combination of both 1D and 2D techniques. Ortho-linked defects in HCPANi were estimated to be as low as 7%, as shown by a comparison of the integration of the carbonyl carbon resonance peaks.

• 폴리머
• /
• 제38권6호
• /
• pp.791-800
• /
• 2014

Friedel-Crafts 직접 아실화 반응을 이용하여 $P_2O_5$/폴리인산 매질에서 다중벽 탄소나노튜브(MWNT)와 4-클로로벤조산(CBA)을 반응시켜 클로로벤조일(CB)기가 도입된 MWNT(c-MWNT)를 제조하였다. 이때 반응시키는 CBA양을 조절하여 염소원자 함량이 최대 5.3 wt%(CB기 함량 20.86 wt%)인 c-MWNT를 얻었다. 한편, 열가소성 엔지니어링 플라스틱 소재인 폴리(페닐렌 설파이드) (PPS)와 MWNT의 계면접착력을 증가시키기 위하여, 4-클로로벤젠티올(CBT)의 자기축합에 의한 PPS 중합시 c-MWNT를 함께 넣고 중합시킨 후 호모 PPS를 제거하여 MWNT-g-PPS를 얻었다. 이 MWNT-g-PPS의 열 및 표면 특성들을 분석하였으며, c-MWNT와 CBT가 반응하여 c-MWNT 표면에 PPS가 생성되었음을 확인하였다.

• Restorative Dentistry and Endodontics
• /
• 제31권5호
• /
• pp.352-358
• /
• 2006

본 연구는 코어용 이중 중합 레진의 중합도에 미치는 두께의 영향과 빛이 감소된 깊은 와동에서 자가 중합에 의한 영향을 조사하고자 하였다. Luxacore Dual과 Luxacore Self (DMG Inc, Hamburg, Germany) 두 종류의 코어용 레진 수복재를 지름 10 mm, 두께가 2, 4, 6, 8 mm 의 Teflon mold에 주입하고 자가중합 시키거나 혹은 $500 mW/cm^2$의 광도로 제조자의 지시에 따라 중합 후 $37^{\circ}C$ 증류수에 24시간동안 저장하였다. 각 시편의 윗면과 아랫면에서 Knoop's hardness를 측정하였다. 결과는 ANOVA로 통계 분석 하였고 Tukey's test로 사후 검정하였다. Luxacore Self와 Luxacore Dual을 자가중합 시킨 군의 중합도는 두께에 따른 영향을 받지 않았다. Luxacore dual을 광중합한 경우 중합은 2 mm, 4 mm와 6 (적층충전) mm군에서는 밑면의 효과적인 중합이 일어났으나 8 (적층충전) mm군, 6, 8 (단일충전) mm군은 밑면에서 불완전한 중합을 보였다 (p < 0.05). 따라서 이 실험 결과에 의하면 4 mm를 초과하는 경우 단일충전보다 적층충전이 더 좋은 것으로 나타났다.