Quantum simulation of molecular problems

==================================================  제  목 : Quantum simulation of molecular problems 연  사 : 허준석 교수님(성균관대학교 화학과) 일  시 : 2017년 3월 9일(목) 오후 4시 30분 장  소 : 화학관 세미나실 (330226호실) ==================================================  Quantum simulation of molecular problems   Joonsuk Huh Department of Chemistry, Sungkyunkwan University   The intrinsic nature of parallelism of quantum states is anticipated to give extraordinary computational power to quantum processors for certain problems. A linear optical network is one of the simplest quantum processors that it could reveal the (computational) quantum supremacy against classical machines. A photon-sampling problem in a linear optical network, so-called Boson Sampling, is a specially designed mathematical problem, which is expected to be intractable for any classical machine. In my talk, I will present what we can do with the photonic quantum simulator (non-universal quantum computer) practically. Boson Sampling is generalized with Gaussian input states to simulate the molecular vibronic spectroscopy [1-5]. [1] J. Huh, G. G. Guerreschi, B. Peropadre, J. R. McClean, and A. Aspuru-Guzik. Boson Sampling for Molecular Vibronic Spectra. Nature Photon. 9 (2015): pp 615-620. [2] J. Huh and M.-H, Yung, Hierarchy in Sampling Gaussian-correlated Bosons, Preprint: arXiv:1608.03731. [3] Y. Shen, J. Huh, Y. Lu, J. Zhang, K. Zhang, S. Zhang and K. Kim, Quantum simulation of molecular spectroscopy in trapped-ion device, Preprint: arXiv:1702.04859 [4] D. G Olivares, B. Peropadre, J. Huh and J. J. García-Ripoll, Quantum emulation of molecular force fields: A blueprint for a superconducting architecture Preprint: arXiv:1611.08101 [5] B. Peropadre, J. Huh and C. Sabin, Dynamical Casimir effect for boson sampling, Preprint: arXiv:1610.07777

• 2017-03-09
• 화학관 330226호

• POSTED DATE : 2017-03-07
• WRITER : 관리자
• HIT : 672

Visible Light-Induced Radical Transformations / Iron Catalysis:from High-valent Lewis Acid Catalyst to Low-valent Redox Catalyst

============================================================== <세미나1> 제  목 : Visible Light-Induced Radical Transformations 연  사 : 조은진 교수님(중앙대학교) 일  시 : 2016년 12월 8일(목) 오후 4시 장  소 : 화학관 2층 세미나실(330226호실) ============================================================== Visible Light-Induced Radical Transformations Eun Jin Cho Department of Chemistry, Chung-AngUniversity, Seoul 06794, Republic of Korea E-mail:ejcho@cau.ac.kr Recently, visible light photocatalysis has attracted substantial attention due to its environmental compatibility and mechanistic versatility in promoting a large number of synthetically important reactions. We have developed a variety of radical transformations using Ru-, Ir-, and Pt-based photocatalysts under visible light irradiation. Fluoroalkylated organic compounds play significant roles in the pharmaceutical, agrochemical, and material sciences owing to the substantial influence that fluorine substitution has on the physical and chemical properties of substances. Visible light-induced methods allowed access to fluoroalkyl group-containing molecules, such as –CF2R, –CF3,and –CF2SPh groups.1 In the studies, electron deficient carbon-centered fluoroalkyl radicals were successfully generated by the appropriate choice of fluoroalkyl source, photocatalyst, additives, and solvent. Notably, we have observed that additives significantly affect the efficiencies and selectivities of these reactions and can even change the outcome of the reaction by playing additional roles during its course. By understanding the roles of additives, we developed several controlled fluoroalkylation reactions of alkenes and alkynes where different products were formed selectively from the same starting substrates.2-4 Polyheteroaromatic compounds have also attracted much attention due to their unique p-conjugation, which make them suitable functional materials in many applications. The synthesis of carbazole motif has been accomplished using N-substituted amidobiaryls through the merger of photoredox and palladium catalysis.5 The use of 1 mol% of an Ir-photocatalyst obviated the typical high loadings of external chemical additives in the transformation. And recently, we synthesized a new class of polyheteroaromatics from the coupling process between readily accessible 2-heteroaryl substituted aromatic amines and heteroaromatic alkynes by an Ir-catalyzed visible light photocatalysis.6 [References] Chatterjee, T.; Iqbal, N.; You, Y.; Cho, E. J.Acc. Chem. Res. 2016, 49, 2284-2294. Iqbal, N.; Jung, J.; Park, S.; Cho, E. J. Angew. Chem. Int. Ed. 2014, 53, 539-542. Yu, C.; Iqbal, N.; Park, S.; Cho, E. J. Chem. Commun. 2014, 50, 12884-12887. Choi, Y.; Yu, C.; Kim, J. S.; Cho, E. J. Org. Lett. 2016, 18, 3246-3249. Choi, S.; Chatterjee, T.; Choi, W. J.; You, Y.; Cho, E. J. ACS Catalysis, 2015, 5, 4796-4802. Chatterjee, T.; Choi, M. G.; Kim, J.; Chang, S.-K.; Cho, E. J. Chem. Commun. 2016, 52, 4203-4206.   ============================================================== <세미나2> 제  목 : Iron Catalysis:from High-valent Lewis Acid Catalyst to Low-valent Redox Catalyst  연  사 : 강은주 교수님(경희대학교) 일  시 : 2016년 12월 8일(목) 오후 5시 장  소 : 화학관 2층 세미나실(330226호실) ============================================================== Iron Catalysis: from High-valent Lewis Acid Catalyst to Low-valent Redox Catalyst    Eun Joo Kang e-mail: ejkang24@khu.ac.kr   The use of iron compounds as catalysts in organic synthesis is attractive for a number of reasons. It is the most abundant metal in the earth’s crust after aluminum and therefore is much cheaper than the precious metals that are often applied. Regarding the catalytic efficiency and broad applicability, at present iron is still behind palladium as the most versatile catalytic metal, however, the tremendously increasing number of publications demonstrates that iron is catching up. Unlikely palladium, iron can adopt ocidation states from -2 to +5, thus, in low oxidation states it may be operative as an iron-centered nucleophile and catalyze nucleophilic substitutions and additions. In contrast, iron Lewis acid catalyzed reactions have been known for a long time, for example electrophilic aromatic substitutions. Haaving this potential in mind, our lab has been interested in alternative use of iron catalysis in the following organic synthesis. First, we reported Fe catalyzed atom-economical tandem reaction of alkene-iodide in the present of equimolar aryl Grignard reagent. Aryl Grignard reagent is used to generate Fe-Grignard complex and the counter aryl anion is used in the further cross-coupling, thereby affording the tandem cyclization/cross-coupling radical reaction. Also, the nucleophilic cyclization reactions of allenes were catalyzed by Fe(III) to afford the corresponding heterocycle compound. Fe(III) catalysts were applied in the reactions of allenyl amides or allenyl alcohols and cyclized compounds containing O or N heteroatom were produced with moderate to good yields.             

• 2016-12-08
• 화학관 330226호

• POSTED DATE : 2016-12-06
• WRITER : 관리자
• HIT : 818

화학작용제 지속도 연구

============================================================== 제  목 : 화학작용제 지속도 연구 연  사 : 임종선 부이사관(국군화학방어연구소) 일  시 : 2016년 11월 24일(목) 오후 3시 장  소 : 화학관 2층 세미나실 (330226호실) ==============================================================      화학작용제 지속도 연구   소형풍동장치를 이용하여 화학작용제의 증발 및 소멸특성의 연구를 통해 야전환경 조건 하 화학작용제의 지속도와 관련 데이터를 축적하고자 본 연구를 수행하였다. 실험에 사용한 화학작용제는 HD와 GD이며, 지표물질로는 비다공성 표면으로 유리, 다공성 표면으로 콘크리트 및 나지표면을 이용하여 실험을 진행하였다. 실험에 적용한 환경조건은 온도, 풍속, 오염량의 세가지 변수이며, 온도는 17℃ ~ 45℃, 풍속은 0.8km/h ~ 13km/h, 오염량은 1g/㎡ ~ 10g/㎡의 범위에서 실시하였다. 실험을 통해 획득한 데이터는 美 ECBC의 실험데이터와 비교하기 위해 ECBC에서 데이터를 처리한 방식대로 데이터를 처리해 비교를 실시하였다. 획득한 ECBC 데이터는 HD와 VX 데이터이다. 미국의 데이터와 비교하기 위해 작용제별 증발속도를 산출해 ECBC에서 제시한 증발속도 계산식을 이용하여 계산된 증발속도 값 및 실제 실험을 통해서 획득된 미국의 증발속도 데이터와 비교하였다. 또한, HD의 STEL(short-term exposure limit), VX의 IDLH(immediately dangerous to life or health) 농도에 해당하는 농도인 0.003mg/㎥에 도달될 때까지의 시간을 측정해 ECBC의 계산식에 의한 지속시간과 실제 데이터를 통해 산출한 지속시간도 같이 비교해 데이터의 신뢰성을 확인하였다. 지속도 데이터와 증기농도 및 흡입량을 기준으로한 위험기준을 토대로 지속시간 기준별 위험수준을 확인했고, 잔류량 분석을 통해 잔류위험을 확인하였다. 분석결과 화학작용제의 증기량이 미미한 시점에서도 잔류위험이 존재하는 것으로 확인되었다.     

• 2016-11-24
• 화학관 330226호

• POSTED DATE : 2016-11-18
• WRITER : 관리자
• HIT : 799

대한화학회 경기지부 추계 심포지엄

  행사명 : 대한화학회 경기지부 추계 심포지엄 행사일자 : 2016년 11월 10일(목) 오후 4시 개최장소 : 성균관대학교 자연과학캠퍼스 화학관 1층 첨단강의실 (330118호) 주최 : 대한화학회 경기지부 발표편수 : 교수 구두발표(3편) 담당자 : 차상원 교수(한국외국어대학교 화학과, swcha@hufs.ac.kr)   내용- 경기도 지역내 신진 연구자 연구분야 소개 및 학술활동 강화- 경기지부 회원 학문교류 및 친목 도모- 일정    4:00~4:30 등록    4:30~4:35 개회사 및 환영사 – 김연규 지부장    4:35~5:00 이안나 교수 (명지대 화학과)                       “Organocatalyzed Asymmetric Reactions”    5:00~5:25 강경태 교수 (경희대 응용화학과)                       “Behaviors of Neurons on Nanotopographies”    5:25~5:50 송창식 교수 (성균관대 화학과)                         “Sustainable Photoactive Polymer Systems Enabled                          by Metal-Terpyridine-based Self-Assembly”    5:50~6:00 폐회사 및 기념촬영    

• 2016-11-10
• 화학관 330118호

• POSTED DATE : 2016-11-08
• WRITER : 관리자
• HIT : 767

Modeling of chemical and physical processes: towards a quantitative engineering approach– practical applications/ Defect creation via synthesis procedure in metal-organic frameworks

============================================================== <세미나1> 제  목 : Modeling of chemical and physical processes: towards a quantitative engineering approach– practical applications 연  사 : Prof. Phillipe Heynderickx(GHENT UNIVERSITY) <세미나2> 제  목 : Defect creation via synthesis procedure in metal-organic frameworks 연  사 : Prof. Francis.Verpoort(GHENT UNIVERSITY) 일  시 : 2016년 10월 26일(수) 오후 2시 30분 장  소 : 화학관 첨단강의실 (330118호실) ============================================================== <세미나1> Modeling of chemical and physical processes: towards a quantitative engineering approach– practical applications In the early days, researchers were relying on performed experiments to describe reality vialaboratory tests. For example in catalysis (blue triangle in given figure), materials were prepared,characterized in a physical way (e.g. XRD, TEM, BET…) or chemical way (selectivereactions). This practice gained power when computational possibilities were created via theuse of a computer. The next step in this natural process of research was to come up with kineticor physical models describing reality as adequate as possible, giving rise to chemical andphysical descriptors of this reality.Today, the research of Prof. Dr. ir. Philippe M. Heynderickx focuses on the green triangle inthe figure: a combination of catalytic testing of materials (MOFs for e.g. selective adsorptionor fine-chemical reactions or metal oxides catalysts for e.g. selective oxidation reactions), thecorresponding kinetic modeling via fundamental reaction steps using intrinsic data and theupscaling to industrial proportion via reactor simulation.The long-term strategy is the development, construction and implementation of intrinsic kineticmodels describing catalytic reactions for daily relevant applications. Especially environmentalapplications in ‘green chemistry’ conversion, environmental sensors, catalysis andenergy storage applications are envisaged. ------------------------------------------------------------------------------------------- <세미나2> Defect creation via synthesis procedure in metal-organic frameworks Francis Verpoort1,2,3,4, 1 State Key Laboratory of Advanced Technology for Materials Synthesis and Processing; Center for Chemical and Material Engineering, Wuhan University of Technology, Wuhan 430070, P.R. China 2 School of Chemistry, Chemical Engineering and Life Sciences, Wuhan University of Technology, Wuhan 430070, P.R. China. 3 Department of Inorganic and Physical Chemistry, Ghent University, Krijgslaan 281-S3, 9000, Ghent, Belgium 4Ghent University, Global Campus Songdo, 119 Songdomunhwa-Ro, Yeonsu-Gu, Incheon, Korea *E-mail: Francis@whut.edu.cn / Francis.verpoort@ugent.be The variation in synthesis procedure, such as solvothermal, room temperature, microwave and spray drying, for metal-organic frameworks (MOFs) effluences the structure, morphology and properties of the MOF materials such as crystal sizes, particle shape, surface area, defect structures (defects) and gas adsorption properties of N2, CO2, CH4 etc.[1] This work describes procedures to synthesize MOFs exposing dramatically different properties compared with the same MOFs prepared in a conventional manner. These results were deduced and supported from crystal morphologies which are related to the rate of crystallization or crystal growth, from surface and porosity properties evaluation from adsorption measurements, and from temperature decomposition analysis.[2] Furthermore, the crystal framework keeps the same structure as proven from the XRD pattern and coordination functional group analysis (Fig.1). The diversity of defect structures correlates with active sites and thus also with the catalytic performance which is confirmed via example of catalytic reactions. The high catalytic performance of MOFs from this invention is related to the presence of more acid and basic sites occurring on defect structure. Knowledge of the nature and amount of defects is of utmost importance to decide which MOF is suitable for a certain catalytic reaction. Fig1. The synthesis ZIF-8 by different procedure (Spray drying: ZIF-8-SP, Microwave: ZIF-8-MW, Room temperature: ZIF-8-RT, Solvothermal: ZIF-8-SV) and their accompanying XRD patterns (a) The crystal morphology, shape and size investigated by SEM technique (b). The crystal morphology evolution with rate of crystallization effluence of procedure in MOFs synthesis from rapid to slowing growth (top to down direction) present the cube shape to rhombic dodecahedron shape (c). S. Chaemchuen, N.A. Kabir, K. Zhou, F. Verpoort, Chem. Soc. Rev. 42, 9304-9332 (2013). Z. Fang, B. Bueken, D.E. De Vos, R.A. Fischer, Angew. Chem. Int. Ed.54, 7234-7254 (2015)    

• 2016-10-26
• 화학관 330118호

• POSTED DATE : 2016-10-25
• WRITER : 관리자
• HIT : 804

Interfaces in Science and Technology

============================================================== 제  목 : Interfaces in Science and Technology 연  사 : Prof.Per Claesson(KTH Royal Institute of Technolog) 일  시 : 2016년 10월 18일(화) 오후 4시 30분 장  소 : 화학관 첨단강의실 (330118호실) ==============================================================                    Interfaces in Science and Technology Per Claesson, percl@kth.se KTH Royal Institute of Technology, School of Chemical Science and Engineering, Department of Chemistry, Division of Surface and Corrosion Science, Drottning Kristinas väg 51, SE-100 44 Stockholm, Sweden   Abstract   Interfaces are becoming key to development in a range of areas, including development of nanomeaterials and nanocomposities, green corrosion protection systems, bisurfaces and biomaterials, anti-icing technologies, and aqueous lubrication technologies. This presentation will provide an overview of some activities at the Surface and Corrosion Science Division at the Royal Institute of Technologyin Stockholm. The presentation will introduce and discuss the following topics:   The quest for green corrosion protective coatings, where we have achived promising results with several different systems including i) UV-cured polymer films (≈ 10 µm thick) incorporating small amount of conducting polymer, ii) superhydrophobic coating layers, and iii) thin films (≈ 100 nm) of mussel adhesive polymers and ceria nanoparticles.   Nanomechanical properties of the interphase, i.e. the region next to a particle embedded in a polymer matrix. Such studies are performed using scanning probe methods and provide direct measurements of nanomechanical properties with a high spatial resolution.   Molecular lubrication synergies underlying the outstanding lubrication properties of synovial joints, and the development of biomimetic lubricants providing low friction and high load bearing capacity in aqueous media, where we have achieved results that are comparable to that found in synovial joints.     The surface chemical approach to anti-icing and de-icing surfaces, where modification of surface properties are utilized for achieving low ice adhesion. At present it seems that such approaches could provide benefit for relatively small surfaces as found in heat exchangers and windscreens.       

• 2016-10-18
• 화학관 330118호

• POSTED DATE : 2016-10-17
• WRITER : 관리자
• HIT : 658

Development of Metal-Catalyzed Direct C-H Amination Reactions

  ============================================================ 제  목 :  Development of Metal-Catalyzed Direct C-H Amination Reactions 연  사 :  장석복 교수(KAIST) 일  시 :  2016년 12월 1일(목) 오후 4시 15분    장  소 :  화학관 첨단강의실(330118호) -----------------------------------------------------------  Development of Metal-Catalyzed Direct C-H Amination Reactions Sukbok Chang  Institute for Basic Science (IBS), Daejeon 305-701, Korea Department of Chemistry, Korea Advanced Institute of Science & Technology (KAIST), Daejeon 305-701, South Korea E-mail: sbchang@kaist.ac.kr   The mechanism of the Ir(III) and Rh(III)-mediated C–N coupling reaction, which is the key step of catalytic C-H amidation, was investigated in an integrated experimental and computational study. Novel amidating agents containing a 1,4,2-dioxazole moiety allowed for designing a stoichiometric version of the catalytic C–N coupling reaction and giving access to reaction intermediates that reveal details about each step of the reaction. Both DFT and kinetic studies strongly point to a mechanism where the M(III) complex engages the amidating agent via oxidative coupling to form a M(V)-imido intermediate, which then undergoes migratory insertion to afford the final C–N coupled product. For the first time, the stoichiometric versions of the Ir and Rh-mediated amidation reaction were compared systematically to each other. Iridium reacts much faster than rhodium (~ 1100 times at 6.7 oC) with the oxidative coupling being so fast that the activation of the initial Ir(III)-complex becomes rate-limiting. In the case of Rh, the Rh-imido formation step is rate-limiting. These qualitative difference stems from a unique bonding feature of the dioxazole moiety and the relativistic contraction of the Ir(V), which affords much more favorable energetics for the reaction. For the first time, a full molecular orbital analysis is presented to rationalize and explain the electronic features that govern this behavior. [1] S. H. Cho, J. Kim, J. Kwak, Sukbok Chang, Chem. Soc. Rev.2011, 40, 5068-5083 [2] K. Shin, H. Kim, S. Chang, Acc. Chem. Res. 2015, 48, 1040-1052 [3]Y. Park, K. T. Park, J. G. Kim, S. Chang, J. Am. Chem. Soc. 2015, 137, 4534-4542 [4] W. Xie, J. H. Yoon, S. Chang, J. Am. Chem. Soc. 2016, 138, 12605-12614 [5] Y. Park, J. Heo, M.-H. Baik, S. Chang, J. Am. Chem. Soc. 2016, 13      

• 2016-12-01
• 화학관 330118호

• POSTED DATE : 2016-11-28
• WRITER : 관리자
• HIT : 682

“Postsynthetic Modifications of Metal-Organic Frameworks“

========================================================== 제  목 :  Postsynthetic transmetalation of metal-organic frameworks 연  사 :  나명수 교수(UNIST) 일  시 :  2016년 11월 17일(목) 오후 4시 15분    장  소 :  화학관 첨단강의실(330118호) ===========================================================                               Postsynthetic transmetalation of metal-organic frameworks   Myoung Soo Lah   Department of Chemistry, Ulsan National Institute of Science & Technology (UNIST)   50 Unist-gil, Ulju-gun, Ulsan, Korea 44919 Fax: +82-(52)-217-2019 E-mail address: mslah@unist.ac.kr   The replacements of framework metal ions and ligands were investigated in metal–organic frameworks (MOFs). The transmetalated MOFs could be obtained by soaking an MOF in the solution of a new replacing metal ion. By simply controlling the soaking time, not only fully transmetalated isostructural framework structure but also selectively transmetalated core-shell bimetallic structure could be prepared. The ligand exchanged MOFs could also be obtained via soaking an MOF in the solution of a new replacing ligand. By controlling the concentration of the replacing ligand, not only an entropically favorable MOF with completely exchanged ligand but also enthalpically favorable MOF with selectively exchanged ligand in the alternating layers could be obtained. While there is no significant structural rearrangement of the framework during the replacement of the framework metal ion, the replacement of the framework ligand led to the significant structural reorganization of the framework.            

                            

   

• 2016-11-17
• 화학관 330118호

• POSTED DATE : 2016-11-17
• WRITER : 관리자
• HIT : 612

Living Supramolecular Polymerization

============================================================= 제  목 : Living Supramolecular Polymerization 연  사 : Dr Kazunori Sugiyasu(NIMS) 일  시 : 2016년 10월 6일(목) 오후 4시 30분 장  소 : 화학관 세미나실 (330226호실) ============================================================== Living Supramolecular Polymerization   Kazunori Sugiyasu Molecular Design & Function Group, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan E-mail: SUGIYASU.Kazunori@nims.go.jp      Supramolecular polymers are a new type of polymer in which monomeric units are brought together by reversible and highly directional non-covalent bonds, such as hydrogen bonding, coordination bonding, and p-p stacking. Therefore, supramolecular polymers are endowed with intriguing functionalities and properties that originate from the dynamic behavior of the non-covalent bonds. However, the “dynamic” reversible polymerization process in turn implies that controlling the length of supramolecular polymers is entropically unlikely. As such, in contrast to conventional polymer chemistry, an important challenge in realizing living polymerization technique has still remained in the supramolecular polymer chemistry1. In this presentation, I would like to show the first example of living supramolecular polymerization reported by us recently2. Our supramolecular polymerization was very unique in that the polymerization pathway was coupled with a competing aggregation pathway3. This pathway complexity dictated the spontaneous supramolecular polymerization to be kinetically controlled, and the addition of “seeds” of the supramolecular polymer initiated the supramolecular polymerization. We have investigated this polymerization process in a similar way to analyze the living polymerization: (1) the polymerization kinetics was the first order to the concentration of the seeds, (2) polymerization can be repeated many times, and (3) polydispersity indices (PDI) of the obtained polymers were around 1.1. All these results demonstrated that we succeeded for the first time in realizing living supramolecular polymerization.   Scheme 1. Pathway complexity of supramolecular polymerization2.     References (a) de Greef, T. F. A.; Smulders, M. M. J.; Wolffs, M. ; Schenning, A. P. H. J.; Sijbesma, R. P.; Meijer, E. W. Chem. Rev. 2009, 109, 5687; (b) van der Zwaag, D.; de Greef, T. F. A.; Meijer, E. W. Angew. Chem. Int. Ed. 2015, 54, 8334; (c) Ogi, S.; Stepanenko, V.; Sugiyasu, K.; Takeuchi, M.; Würthner, F. J. Am. Chem. Soc. 2015,137, 3300; (d) Kang, J.; Miyajima, D.; Mori, T.; Inoue, Y.; Aida, T. Science2015, 347, 646. Ogi, S.; Sugiyasu, K.; Manna, S.; Samitsu, S.; Takeuchi, M. Nat. Chem. 2014, 6, 188. Ogi, S.; Fukui, T.; Melinda, L. J.; Takeuchi, M.; Sugiyasu, K. Angew. Chem. Int. Ed. 2014, 53, 14363.

• 2016-10-06
• 화학관 330226호

• POSTED DATE : 2016-10-04
• WRITER : 관리자
• HIT : 634

[Plenary Seminar] 9월 29일(목)

====================================== 제  목 :  Control of molecular orientation, thermal stability, and photochemical stability in vapor-deposited organic glasses 연  사 :  Mark D. Ediger 교수(University of Wisconsin-Madison) 일  시 :  2016년 9월 29일(목) 오후 4시 15분    장  소 :  화학관 첨단강의실(330118호) --------------------------------------                                                         

Control of molecular orientation, thermal stability, and photochemical stability in vapor-deposited organic glasses Mark Ediger University of Wisconsin-Madison   We have used physical vapor deposition and the mobility of glassy surfaces to prepare what are likely the most stable glasses on the planet.(1) These materials have the properties expected for “million-year-old” glasses, including high density and high mechanical moduli.(2) Surprisingly, these glasses “melt” like crystals, with a constant velocity transformation front.(3) In addition, they resist photochemical degradation better than liquid-cooled glasses. Molecular orientation in vapordeposited glasses can be highly anisotropic.(4) These properties all depend systematically on the substrate temperature during deposition and can be measured efficiently with high throughput spectroscopic ellipsometry.(5)   The interesting properties of vapor-deposited glasses arise from the high mobility of glass surfaces. During deposition, molecules near the free surface have the opportunity to sample many different packing arrangements. This mechanism allows the molecular orientation in vapor-deposited glasses to be predicted from molecular dynamics computer simulations(4, 6) and could be useful for optimizing the performance of organic light emitting diodes (OLEDs). 1. Swallen SF, et al. (2007) Organic glasses with exceptional thermodynamic and kinetic stability. Science 315(5810):353-356. 2. Kearns KL, Still T, Fytas G, & Ediger MD (2010) High-Modulus Organic Glasses Prepared by Physical Vapor Deposition. Adv. Mater. 22(1):39-+. 3. Swallen SF, Traynor K, McMahon RJ, Ediger MD, & Mates TE (2009) Stable Glass Transformation to Supercooled Liquid via Surface-Initiated Growth Front. Phys. Rev. Lett. 102(6):065503. 4. Dalal SS, Walters DM, Lyubimov I, de Pablo JJ, & Ediger MD (2015) Tunable molecular orientation and elevated thermal stability of vapor-deposited organic semiconductors. P Natl Acad Sci USA 112(14):4227-4232. 5. Dalal SS, Fakhraai Z, & Ediger MD (2013) High-Throughput Ellipsometric Characterization of Vapor-Deposited Indomethacin Glasses. J. Phys. Chem. B 117(49):15415-15425. 6. Singh S, Ediger MD, & de Pablo JJ (2013) Ultrastable glasses from in silico vapour deposition. Nature Materials 12(2):139-144.

                      

• 2016-09-29
• 330118호실

• POSTED DATE : 2016-09-29
• WRITER : 관리자
• HIT : 610