Regioregularity-Driven Morphological Transition of Poly(3-hexylthiophene)-Based Block Copolymers

Kim, Jin-Seong,Kim, Yongjoo,Kim, Hyun-Jeong,Kim, Hyeong Jun,Yang, Hyunseung,Jung, Yeon Sik,Stein, Gila E.,Kim, Bumjoon J. American Chemical Society 2017 Macromolecules Vol.50 No.5

<P>Conjugated polymer-based block copolymers (BCPs) offer great potential to provide beneficial nanostructures for efficient organic optoelectronics. However, their complicated self-assembly behavior, which is attributed to the strong crystallization of conjugated blocks, is still not well understood due to the lack of a model BCP system. Herein, we develop a series of novel conjugated polymer-based BCPs, poly(3-hexylthiophene)-block-poly(2-vinylpyridine) (P3HT-b-P2VP), in which the regioregularity (RR) of the P3HT block was varied from 95 to 73%. The tunable RR content allows for precise regulation of P3HT crystallization with minimal influence on the microphase-separation force between the P3HT and P2VP blocks. When RR is high (i.e., 95 or 8S%), structure formation is controlled by crystallization of P3HT, and the ultimate structure is characterized by nanoscale P3HT fibrils in an amorphous matrix. In contrast, as RR decreases to 78 and 73%, P3HT crystallization is suppressed. The self-assembly is controlled by the enthalpic interaction between P3HT and P2VP blocks, much like typical BCPs having two flexible blocks, and thermal annealing drives the formation of well-ordered lamellar or cylindrical phases. This morphological behavior is consistent with a Monte Carlo simulation based on a newly developed coarse-grained model. Significantly, this novel class of RR-controlled P3HT-based BCPs provides a simple method to tune bulk and thin film morphology for a variety of applications in nanostructured organic electronics.</P>

Regioregularity controlled phase behavior for Poly(3-hexylthiophene): A combined study of simple coarse-grained simulation and experiment

Kim, Hyeong Jun,Kim, Jin-Seong,Kim, Youngkwon,Jung, Yeon Sik,Kim, Bumjoon J.,Kim, YongJoo Elsevier 2019 Polymer Vol.178 No.-

<P><B>Abstract</B></P> <P>In this study, we developed a simple coarse-grained simulation model framework to investigate the effect of regioregularity (RR) on the crystallization behavior of poly(3-hexylthiophene) (P3HT). To describe the regio-chemistry of P3HT, two different coarse-grained beads were designed to contain either regio-regularly substituted head-to-tail (HT) orientations or regio-irregularly substituted non-HT orientations, and two beads were randomly incorporated in a single polymer where the total RR was tuned from regio-random (RR = 50%) to regio-regular (RR = 100%). Based on our modeling, the crystallization behaviors in both bulk and solution states were investigated. As the number of irregularly substituted non-HT orientations increased, crystallization temperature in the bulk shifted to a lower temperature. When the RR of P3HT was lower than a critical RR value, which was 72.2% in our study, the crystallization of the P3HT chains was eventually suppressed. In the solution state, most of high RR P3HT chains stacked in parallel to produce nanowire (NW) structure to maximize the number of π-stackings in the system, whereas the P3HTs formed a globule structure when the RR value decreased below critical RR. To experimentally validate our simulation results, we synthesized a series of P3HTs having precisely controlled RRs from 66% to 95% with comparable molecular weights to the simulation. Well-matched experimental results suggested that our simplified model provides efficient computational guidance to describe the RR effect on crystalline feature of P3HTs for the various possible applications in organic optoelectronics.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Simple coarse-grained model is developed to describe the effect of regioregularity (RR) on crystallization of P3HT. </LI> <LI> Experimental validation with a series of P3HTs having a wide range of RR from 66% to 95% is followed. </LI> <LI> Our model predicts critical RR value for crystallization of P3HT in bulk and solution. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

iTILE 프레임워크를 이용한 인터랙티브 타일드 디스플레이 응용프로그램 개발

김석환(Seokhwan Kim),김민영(Minyoung Kim),김수화(Suhwa Kim),김지현(Jihyoun Kim),민철기(Chul-Kee Min),조용주(Yongjoo Cho),박경신(Kyoung Shin Park) 한국HCI학회 2009 한국HCI학회 학술대회 Vol.2009 No.2

미래에는 생활환경 주변에 다양한 용도의 대형 디스플레이 장치가 설치되고 사용자들에게 편리한 상호작용적인 서비스를 제공할 것으로 예측된다. 그러나 대형 디스플레이는 그 물리적 크기 때문에 기존의 마우스와 키보드와 같은 장치로는 효과적인 사용자 인터랙션이 쉽지 않다. 최근 이런 대형 디스플레이를 위한 인터랙션 방법에 대해 많은 연구가 수행되고 있다. 본 논문에서는 타일드 디스플레이 기반의 인터랙티브 응용프로그램 개발을 지원하는 iTILE 프레임워크와 이를 활용하여 테이프 스위치와 적외선 카메라 텐저블 인터페이스 입력장치를 사용한 응용프로그램에 대해 기술한다. There will be many large displays in common public places, and we expect that these displays will give users many convenient interactive services. However, due to the physical size, typical mouse and keyboard are not suitable for user interactions on large displays. Recently there are many studies investigating on new interaction techniques and input devices developed for user interactions in a large display. In this paper, we describe the iTILE framework designed to help develop the interactive tiled display applications. Then we describe two iTILE applications using the tape switch interface and the tangible interface with infrared camera and markers.

Self-Assembly Behavior of Conjugated Polymer Containing Rod-Coil Block Copolymers: Phase Transition by Structural Modification

Jin-Seong KIM,Yongjoo KIM,Hyeon-Jeong KIM,Hyeong Jun KIM,Hyunseung YANG,Gila E. STEIN,Bumjoon J. KIM 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.2

Calcium Intake is Negatively Associated with Bone Loss During Lactation: A Pilot Study

Cheawon Lee,Seunghee Kim,Hangyeol Jeon,Suyoung Kim,Seolhui Jeong,A Mi Kim,Yoonha Kim,Jongwoon Kim,Clara Yongjoo Park 한국식품영양과학회 2021 한국식품영양과학회 학술대회발표집 Vol.2021 No.10

Calcium (Ca) requirements during lactation are unknown. We investigated the association between Ca intake and bone mineral density (BMD) during lactation. Twenty-one pregnant women with singletons (non-breastfeeding [NBF] n=7; breastfeeding [BF] n=14) were enrolled before delivery. Ca intake during the 3rd trimester and 6 months postpartum was assessed by food frequency questionnaire and interview. Maternal BMD was measured by dual energy X-ray absorptiometry at the lumbar spine, femoral neck, trochanter, intertrochanter (IT), and total hip at delivery and weaning (or 6 months postpartum). The association of Ca intake with % change of BMD (%ㅿBMD) and change of Z-score (ㅿZ) were assessed by linear regression and Spearman’s rank correlation coefficient. No association was observed in NBF women. Similarly, %ㅿBMD and 3rd trimester Ca intake were not associated in BF women. However, Ca intake during lactation was positively associated with IT ㅿZ (β: 0.613, p=0.02). Ca:P ratio during lactation was also positively correlated with IT ㅿ%BMD (β: 0.587, p=0.03). Higher intake of Ca during lactation may prevent lactation-related bone loss at the IT.

Evaluation of Light Intensity and Uniformity of LEDs for Protected Crop Production

Kim, MunJung,Choo, YounKug,Kim, YongJoo,Chung, SunOk Korean Society of Food and Agricultural Informatio 2014 Agribusiness and Information Management Vol.6 No.1

This study was conducted to evaluate light intensity and uniformity of two SMD (surface-mount device) type LEDs for protected crop production. A low-power (0.1 W) and a high-power (1 W) LEDs were selected and the intensity and uniformity was evaluated at different vertical (height) and horizontal (distance) intervals. When the horizontal interval of the LED bar was fixed, the light intensity increased and the uniformity decreased as the height decreased. At the 30~40 cm heights, 20~30% of the area showed $200{\pm}20{\mu}molm^{-2}s^{-1}$. As the horizontal distance of the LED bars increased, while the uniformity increased as well, the light intensity decreased. At the distances of 6~10 cm, 17~23% of the area showed $200{\pm}20{\mu}molm^{-2}s^{-1}$. When the LED bars were added to the sides, the light intensity and uniformity were generally improved. Results showed that the light intensity and uniformity depended on the height and interval of the LED bulbs; therefore, optimum arrangement for the crops interested should be determined through experiments.

High Throughput Data Mapping for Coarse-Grained Reconfigurable Architectures

Yongjoo Kim,Jongeun Lee,Shrivastava, A.,Yoon, J. W.,Doosan Cho,Yunheung Paek IEEE 2011 IEEE transactions on computer-aided design of inte Vol.30 No.11

<P>Coarse-grained reconfigurable arrays (CGRAs) are a very promising platform, providing both up to 10-100 MOps/mW of power efficiency and software programmability. However, this promise of CGRAs critically hinges on the effectiveness of application mapping onto CGRA platforms. While previous solutions have greatly improved the computation speed, they have largely ignored the impact of the local memory architecture on the achievable power and performance. This paper motivates the need for memory-aware application mapping for CGRAs, and proposes an effective solution for application mapping that considers the effects of various memory architecture parameters including the number of banks, local memory size, and the communication bandwidth between the local memory and the external main memory. Further we propose efficient methods to handle dependent data on a double-buffering local memory, which is necessary for recurrent loops. Our proposed solution achieves 59% reduction in the energy-delay product, which factors into about 47% and 22% reduction in the energy consumption and runtime, respectively, as compared to memory-unaware mapping for realistic local memory architectures. We also show that our scheme scales across a range of applications and memory parameters, and the runtime overhead of handling recurrent loops by our proposed methods can be less than 1%.</P>

Physical and Rheological Properties of Indonesian Natural Rock Asphalt

Yongjoo Kim 한국도로학회 2018 한국도로학회 학술대회 발표논문 초록집 Vol.2018 No.05

In 1924, natural roack asphalt, which is called Asbuton, was found in South East Sulawesi, Buton Island, Indonesia. Since 2006, Asbuton has been widely applied on national road, provincial road and district roads not only for low volume traffic roads but also for the medium and heavy traffic roads. The use of Asbuton in Indonesian road infrastructure development is increasing because the deposits are estimated to be 677 million tons while current annual production is only approximately 20,000 tons. Asbuton mainly consist of asphalt and mineral like a Trinidad Lake Asphalt. The asphalt content of Asbuton is about 35% or less. Many researchers agreed that pure asphalt binder should be separated from its minerals of Asbuton in order for the conventional asphalt binder to be used widely and economically. Asbuton could replace the conventional asphalt binder. In this study, fundamental and reheological properties of pure asphalt binder extrcted from Asbuton are evauluated to find a possiblity to repalce it as the conventional asphalt binder. The first, pure asphalt binder extrcted from Asbuton through extraction process. Second, penetration test, softening point test, ductility test, and flash point test are conducted to measure physical properties of pure asphalt binder extrcted from Asbuton. Third, dynami shear rheometer (DSR) test, rolling thin film ovens(RTFO) test, pressure aging vessel(PAV) test, and bending beam rheometer(BBR) test are conducted to determine perfoemance grade as a reheological properties. Based on the limited laboratory test results, pure asphalt binder extrcted from would be possibly used as modified additive to improve physical properties and the performance grade at high tempertaure.

Crystallization Behavior of Polyvinylidene Fluorine (PVDF) in NMP/DMF Solvents

YongJoo Kim(김용주) 한국고분자학회 2023 한국고분자학회 학술대회 연구논문 초록집 Vol.48 No.1

Behaviour Analysis of Unpaved Roads by Surface Treatment Materials

Yongjoo Kim,Hae-Won Park,Kyungnam Kang,Kanghun Lee,Hongjun Kwon 한국도로학회 2022 한국도로학회 학술대회 발표논문 초록집 Vol.2022 No.10