A Pathway to Microdomain Alignment in Block Copolymer/Nanoparticle Thin Films under Electric Field

Bae, Joonwon Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.9

The control over microstructure in block copolymer thin films using external electric fields has become an interesting research topic. In this article, the effect of nanoparticle on the microdomain alignments in block copolymer (polystyrene-b-poly(2-vinylpyridine)/nanoparticle (Au) thin films under electric fields has been examined with transmission electron microscopy. The homogeneous dispersion of Au nanoparticles into the block copolymer matrix was achieved by surface modification of nanoparticles with compatible ligands. Compared with the phenomenon seen in the pristine block copolymer thin films, a peculiar alignment behavior was observed in the block copolymer/nanoparticle hybrid thin films under electric fields. In addition, the different pathways observed in the pristine and nanoparticle incorporated block copolymer thin films were also monitored as a function of exposure time. This work can provide the fundamental information for understanding microdomain alignment in block copolymer/nanoparticle thin films under external electric fields.

Energy efficient capacitors based on graphene/conducting polymer hybrids

Bae, Joonwon,Park, Jeong Yong,Kwon, Oh Seok,Lee, Chang-Soo THE KOREAN SOCIETY OF INDUSTRIAL AND ENGINEERING 2017 JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY -S Vol.51 No.-

<P><B>Abstract</B></P> <P>Graphene (GRP) and conducting polymers (CPs) are interesting classes of emerging materials for various applications. To date, extensive research effort has been devoted to the investigation of diverse properties of graphene and conducting polymers such as polypyrrole (PPy), polyaniline (PAni), and polythiophene (PTh). The combination of these materials can be very advantageous in terms of practical applications in energy storage/conversion systems. Among various those systems, energy efficient electrochemical capacitors (ECs) have become popular due to the recent need for small and portable devices. Therefore, in this article, the application of GRP/CP hybrids for high performance capacitors is described concisely. In particular, an extensive and concise summary on the previous research activities regarding GRP/CP capacitors is covered. Subsequently, recent patents related to the preparation and application of GRP/CP capacitors are also introduced briefly. It is certain that this article can provide essential information for future study.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P> <P>The advantages and synergy of graphene and conducting polymers as electrode candidates for electrochemical capacitors was discussed based on an extensive summary of impressive research activities.</P>

Electrohydrodynamic instabilities of polymer thin films: Filler effect

Joonwon Bae 한국공업화학회 2012 Journal of Industrial and Engineering Chemistry Vol.18 No.1

The influence of various nanoparticles with different dimension, density, dielectric constant, and surface property on electrohydrodynamic (EHD) instabilities of polymer/nanoparticle nanocomposite thin films was examined as a function of nanoparticle concentration. Transmission electron microscopy (TEM)images of polystyrene (PS)/nanoparticles (NPs) thin films demonstrated that all the nanoparticles were uniformly distributed in polymer matrix and the homogeneous dispersions of nanoparticles were not affected by thermal annealing above glass transition temperature. Optical microscopy (OM) observations indicated that thin films of polystyrene containing silica (SiO2), gold (Au), cadmium selenide (CdSe), and titania (TiO2) nanoparticles showed electrohydrodynamic instability patterns similar to those seen in pure polystyrene, up to 3 vol% nanoparticles. The presence of nanoparticles changed the dielectric constant of the thin films, which led to systematic variations in the wavelengths of the surface instabilities, which were consistent with calculated values. Cross-sectional transmission electron microscopy (TEM) images showed that migration or aggregation of the nanoparticles occurred only for silica contrary to other nanoparticles. This work points to a simple route to reduce the scale of final wellordered columnar structures.

The effect of nanoparticle on microdomain alignment in block copolymer thin films under an electric field

Bae, Joonwon,Park, Seon Joo,Kwon, Oh Seok,Jang, Jyongsik Springer-Verlag 2014 JOURNAL OF MATERIALS SCIENCE - Vol.49 No.12

전기장 하에서의 블록 공중합체와 고분자 블렌드의 미세 구조 변화 거동 비교

배준원 ( Joonwon Bae ) 한국공업화학회 2018 공업화학 Vol.29 No.4

전기장 하에서 유기물은 전기장에 의해 부여된 여러 가지 힘의 영향을 받아서 특이한 거동을 나타낸다. 본 연구에서는, 지금까지 개별적으로 고찰되어 왔던 전기장 하에서의 블록 공중합체와 고분자 블렌드의 미세 거동을 비교 분석하여 특징적인 차이점을 알아보고자 한다. 두 가지 고분자가 공유결합으로 연결된 블록 공중합체와 약한 상호작용으로 혼합된 고분자 블렌드 시스템을 비교대상으로 하였다. 이때, 구성 고분자로는 비슷한 유전상수를 갖는 폴리아크릴로 나이트릴과 폴리메틸메타아크릴레이트를 도입하였다. 유사한 분자량, 같은 농도, 같은 전기장 세기하에서 고분자 블렌드가 전기장에 더욱 민감하게 반응하는 것을 알 수 있었다. 이는 공유결합이 분자의 운동성을 제약하여 전기장에 덜 민감하게 반응하도록 거동하기 때문이다. 본 연구는 고분자 물질의 전기장 하에서의 거동을 이해하는 중요한 정보를 제공할 것이다. In this work, profound microscale behaviors of block copolymer and polymer blend under electric field were investigated using microscopic methods and compared systematically. To this end, both the block copolymer and blend containing polyacrylonitrile (PAN) and poly(methyl methacrylate) (PMMA) were introduced. The two polymers have a similar dielectric constant. Under an identical experimental condition such as temperature, film thickness, field intensity, and exposure time, the polymer blend responded more sensitively than the block copolymer. The presence of covalent bond suppressed the mobility of constituents in block copolymer. This study will be essential for future research activities regarding behaviors of polymeric materials under external fields.

폴리아크릴로나이트릴/리그닌 복합소재로부터 생성된 탄소 필름의 전기적 성질 및 흡착 성능

배준원 ( Joonwon Bae ) 한국공업화학회 2023 공업화학 Vol.34 No.2

리그닌(lignin)은 고분자와 혼합될 수 있고 탄화도 가능하므로 효용성이 크다. 본 실험에서는, 탄화에 유리한 고분자인 폴리아크릴로나이트릴(polyacrylonitrile, PAN)과 리그닌을 혼합하여 탄소 전구체(precursor)로 제조하고, 탄화(carbonization)하여 안정한 탄소 필름이 제어된 탄화 과정을 통해 제조되었다. 얻어진 탄화 소재의 형태적, 전기적 특성들이 분석되었으며, 흡착 성능이 실험적으로 제시되었다. 탄소 전구체 복합소재의 형성은 적외선 분광기(Fourier-transform infrared, FT-IR)를 통해 확인하였고, 생성된 탄소 필름의 외형적 특성은 주사전자현미경(scanning electron microscope, SEM)을 이용하여 고찰하였다. 이를 통해 전구체 필름의 구조적 안정성이 탄화 이후에도 유지됨을 확인하였으며, 필름 내부에 존재하는 리그닌의 흔적도 고찰할 수 있었다. 탄소 필름의 미세 구조는 라만(Raman) 분광기를 통해 분석하였으며, 표면적 및 기공 구조는 BET (Brunauer-Emmett-Teller) 법으로 측정하여, 비교적 균일한 기공이 형성됨을 확인하였다. 탄소 시료의 전기적 특성도 고찰하여, 흡착 소재로서 사용 가능함을 확인하였고, 흡착(adsorption) 테스트를 통해 금속 양이온을 효율적으로 제거할 수 있음을 증명하였다. 본 연구는 해당 분야 향후 연구에 중요한 정보를 제공할 것이다. Lignin is compatible with various polymeric materials and useful as a carbon precursor. In this work, carbon monolith films were produced from polyacrylonitrile (PAN)@lignin precursor films by a controlled carbonization cycle. In addition, their morphological features, electrical properties, and adsorption behavior were analyzed and compared with those of carbonized PAN films. The successful formation of PAN@lignin precursor was confirmed by Fourier-transform infrared (FT-IR) spectroscopy. SEM was used to examine the morphology of precursor and carbonized films, revealing that both precursor and carbonized films retained structural stability following carbonization. A trace of lignin in the carbonized films was also found. The pore structure of the carbonized PAN@lignin film was measured using the BET method, indicating the formation of fairly uniform pores. The electrical properties were also analyzed to obtain the Ohmic relation, which demonstrated that the electrical signal was influenced by incoming materials. Finally, the carbonized PAN@lignin films were useful as adsorbents to remove metal ions. This study provides important information for future initiatives in relevant research fields.

고분자/그래핀 복합재료의 센서 응용 및 그래핀 함량이 센서 거동에 미치는 영향

배준원 ( Joonwon Bae ) 한국공업화학회 2020 공업화학 Vol.31 No.1

본 연구에서는 롤 공정으로 제작된 고분자(polydimethylsiloxane, PDMS)/그래핀(graphene) 복합재료를 기판으로 하여 간단한 표면처리 공정을 통해 센서를 구현하였고, 이 센서의 성능과 거동에 대한 고찰을 실시하였다. 고분자와 그래핀파우더를 혼합한 전구체를 3-롤 공정으로 제조하였고, 이를 2-롤 공정에 도입하여 고분자/그래핀 기판 소재를 제조하였다. 나아가, 간단한 표면처리 공정을 통하여 센서의 요체가 되는 환형 다당류(cyclodextrin, CD)를 도입하였다. 표면처리의 유효성의 적외선 분광기를 통해서 확인하였고, 전기 신호 전달의 가능성을 옴의 법칙을 통하여 분석하였다. 간단한 형태의 센서를 구현하여, 분석 물질(methyl paraben, MePRB)을 도입하였을 때, 아주 낮은 농도 수준(10 nM)까지 감지 신호를 얻을 수 있었다. 특히, 그래핀의 함량이 낮을 경우 센서 측정이 어려움을 확인할 수 있었다. 이는, 높은 그래핀 함량에서 보여주는 그래핀 입자의 배향이 다소 억제되어 발생하였을 것으로 사료된다. 이는 첨가제의 물리적인 배향이 센서의 성능에 영향을 미칠 수 있다는 것을 의미한다. 이 정보는 향후 유사한 시스템의 센서를 구현하는 연구에 도움이 될 것으로 기대된다. In this study, a polymer/graphene hybrid composite was prepared by a simple roll-method and a simple sensor was produced by a convenient surface engineering procedure. The sensor performance was examined and the effect of graphene content on the sensing behavior was monitored. A polymer (polydimethylsiloxane, PDMS) paste containing graphene powder was prepared by a three-roll apparatus and polymer/graphene hybrid composite was produced by a two-roll technique. The sensing medium, cyclodextrin (CD) was introduced by a convenient bio-conjugation method. The efficacy of surface modification was confirmed by FT-IR spectroscopy and the ohmic relation was observed on composite surfaces. An analyte (e.g., methyl paraben, MePRB) at a 10 nM concnetration could be detected. When the graphene loading was low, the sensor performance was relatively poor. This was attributed to the absence of graphene alignments, which were observed for the composites having a high graphene loading. This indicates that the sensor performance was influenced by physical alignments of the filler. This article can provide important information for future research on developing sensing devices.

폴리피롤-사이클로덱스트린 혼성체를 이용한 유해화합물질의 검출

배준원 ( Joonwon Bae ) 한국공업화학회 2019 공업화학 Vol.30 No.2

폴리피롤(polypyrrole)은 전기를 전도하는 고분자로 뛰어난 전기적 신호 전달을 지니며, 사이클로덱스트린(cyclodextrin)은 환형다당류(cyclic oligosaccharide) 분자들로서 저분자량 물질을 포획할 수 있는 친환경 물질로 널리 활용되고 있다. 따라서 이들 두 가지 물질을 혼합하여 혼성체를 제조할 수 있다면 사이클로덱스트린이 host가 되어 guest 물질을 포획하였을 때 발생하는 전기 신호를 폴리피롤이 민감하게 전달할 수 있게 되어 우수한 감지 능력을 갖게 된다. 따라서 본 연구에서는 폴리피롤/사이클로덱스트린 혼성체를 간단한 수용액 방식으로 제조하여, 제조된 혼성체를 하이드로젤(hydrogel)에 도입하여 건조한 후 금 전극 위에 적용하여 대표적인 유해성 분자인 메틸파라벤(methyl paraben)을 검출할 수 있는지에 대해서 살펴보았다. 그리고 폴리피롤만으로 이루어진 물질과 비교해 봤을 때, 사이클로덱스트린의 도입 효과는 존재하는 것으로 나타났다. 이 연구는 전도성 고분자와 친환경 분자 혼성체를 유해물질 감지에 활용할 수 있는 가능성을 제시하고 있다. Polypyrrole is a typical electrical conducting polymer, which has an excellent charge transport property. Cyclodextrins are a group of toxic-free and cyclic oligosaccharide molecules, capable of capturing low molecular weight chemicals. Considering these advantages, hybrid materials of polypyrrole and cyclodextrin can be used to detect hazardous compounds. Cyclodextrin molecules can accommodate toxic chemicals by the formation of host-guest complexes and generate electric signals, which are effectively delivered by polypyrrole backbone. In this study, the polypyrrole/cyclodextrin hybrid material was prepared using a facile wet method and included into a hydrogel. Subsequently, it was applied to a simple sensor system with a gold-patterned electrode for the detection of potentially hazardous material, methyl paraben. Compared with pristine polypyrrole, it was found that the polypyrrole/cyclodextrin hybrid showed an improved performance. This study can be an example of using environmentally benign conducting polymer/cyclodextrin hybrids as sensing media.

고분자/베타-사이클로덱스트린 포접 화합물로 이루어진 고분자 혼성체 필름의 물성 및 구조에 미치는 게스트 분자의 영향

배준원 ( Joonwon Bae ) 한국공업화학회 2021 공업화학 Vol.32 No.5

본 연구에서는 게스트 분자(guest molecule)의 특성이 고분자/베타-사이클로덱스트린(beta-cyclodextrin) 포접화합물(inclusion compound)로 이루어진 고분자 필름의 구조 및 물성에 미치는 영향에 대해서 고찰하고자 한다. 본 연구에서 사용된 게스트 분자는 미백 효과를 지니는 것으로 알려진 3가지로 하이드로퀴논(hydroquinone, HQ), 알부틴(arbutin, AB), 그리고 트랜액사믹 애시드(tranexamic acid, TA)이다. 먼저, 베타-사이클로덱스트린과 게스트 분자 간의 포접화합물의 성공적인 형성과 이를 포함하는 고분자 필름의 제조여부를 라만(Raman) 분광학으로 확인하였다. 포접화합물을 포함하는 고분자 필름의 구조 및 물성은 엑스선 회절법(X-ray diffraction)과 주사열용량법 및 열중량추적법 같은 열분석법으로 고찰하였다. 그 결과, 트랜액사믹 애시드의 영향이 다른 분자의 영향과 비교하여 상당히 상이하였음을 관찰할 수 있었다. 이러한 경향은 간단한 분자 시뮬레이션 기법으로 재검증하였다. 본 연구는 포접화합물을 형성하는 게스트 분자들의 상이한 영향에 대한 체계적인 접근을 통한 실험적 검증의 사례로 향후 관련 연구에 중요한 정보를 제공할 것으로 기대된다. In this study, the effect of molecular features of guest molecules on the structure, property, and formation of poly(vinyl alcohol) (PVA)/beta-cyclodextrin (bCD) inclusion compound hybrid films was investigated using three types of guest molecules such as hydroquinone (HQ), arbutin (AB), and tranexamic acid (TA). First, the successful formation of inclusion compounds between bCD and the guest molecules, and polymer/inclusion compound hybrid were proved using Raman spectroscopy. The effect of bCD-based inclusion compounds on the structure and property of PVA matrix composites containing inclusion compounds was also studied using X-ray diffraction (XRD) and thermal analyses such as differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). It was notable that the effect of TA to the crystalline structure of the PVA was significantly different from that of using other guest molecules including HQ and AB. It was also supported by a simple molecular simulation result. This article will be a good example for demonstrating the effect of molecular characteristics on the inclusion compound formation in polymer films, which can provide important information for relevant future research.

타이타니아 나노막대가 포함된 블록 공중합체 박막 표면의 전기장하에서의 불안정성 거동 연구

배준원 ( Joonwon Bae ) 한국공업화학회 2016 공업화학 Vol.27 No.2

The influence of titania nanorods with an average diameter of 10 nm and an average length of 30 nm on the electrohydrodynamic instability of block copolymer (polystyrene-b-poly(2-vinylpyridine)) thin film was investigated in this article. The presence of titania nanorods increased the dielectric constant of the film, which resulted in a systematic reduction in the wavelength of the surface instability. Cross-sectional transmission electron microscopy analysis indicated that the migration/ aggregation of titania nanorods did not occur as a result of the applied electric field. This work can provide a simple route to the pattern formation using electrohydrodynamic instability with an aid of nanoparticles.