Self-assembly of novel lipid-mimicking brush polymers in nanoscale thin films

Jung, Jungwoon,Kim, Heesoo,Ree, Moonhor The Royal Society of Chemistry 2014 SOFT MATTER Vol.10 No.5

<P>A series of well-defined poly(oxy(11-phosphorylcholineundecylthiomethyl)ethylene-<I>ran</I>-oxy(<I>n</I>-dodecylthiomethyl)ethylene) (PECH-PC<I>m</I>: <I>m</I> = 0–100 mol% phosphorylcholine (PC)) polymers were used to prepare nanoscale thin films that were characterized by synchrotron X-ray reflectivity (XR) analysis. The quantitative XR analysis provided structural insights into the PECH-PC<I>m</I> thin films. The PECH-PC0 polymer film formed a well-ordered in-plane oriented molecular multibilayer structure, whose individual layers consisted of two sublayers. One sublayer was composed of the fully extended backbones and inner part of the bristles, exhibiting a relatively low electron density, whereas the other sublayer was composed of a bilayer of the outer parts of the bristles without interdigitation. The PECH-PC100 polymer film also formed a well-ordered in-plane oriented molecular multibilayer structure, the individual layers of which were composed of four sublayers rather than two. The bristles in the layer were interdigitated in part <I>via</I> the zwitterionic interactions of the PC end groups. Surprisingly, regardless of the copolymer composition, the PECH-PC<I>m</I> random copolymer molecules in the thin films self-assembled to form a multilayered structure that resembled the structure formed by the PECH-PC100 polymer. These properties have not been observed in other conventional random brush copolymer films. The remarkable multibilayer structures originated from the zwitterionic PC end groups and their favorable interactions and interdigitated structures, which overcame any negative contributions caused by the heterogeneity of the bristles. The unique self-assembly properties of the PECH-PC<I>m</I> polymers always provide a PC-rich surface. The PECH-PC<I>m</I> random copolymers successfully mimicked the molecular bilayer structures formed by natural lipids.</P> <P>Graphic Abstract</P><P>Well-defined lipid-mimicking brush polymers, which contain phosphorylcholine (PC) moieties, have been demonstrated to favorably self-assemble at a molecular level and form a multibilayer structure in thin films, providing a PC-rich surface. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3sm52263f'> </P>

Molecular Layer-by-Layer Self-Assembly and Mercury Sensing Characteristics of Novel Brush Polymers Bearing Thymine Moieties

Jung, Jungwoon,Kim, Jin Chul,Rho, Yecheol,Kim, Mihee,Kwon, Wonsang,Kim, Heesoo,Ree, Moonhor American Chemical Society 2011 ACS APPLIED MATERIALS & INTERFACES Vol.3 No.7

<P>Two new brush polyoxyethylenes bearing thymine moieties at the bristle ends have been synthesized as model polymers in which the chemical loading of the thymine functional group into the polymer is maximized: poly(oxy(11-thyminoacetyloxyundecylthiomethyl)ethylene) (PECH(S)-T) and poly(oxy(11-thyminoacetyloxyundecylsulfonylmethyl)ethylene) (PECH(SO<SUB>2</SUB>)-T). These brush polymers are thermally stable up to around 225 °C, and their glass transitions occur in the range 23–27 °C, but they have significantly different properties despite the similarity of their chemical structures. In particular, PECH(SO<SUB>2</SUB>)-T films exhibit better performance in sensing mercury ions than PECH(S)-T films. These differences were found to originate in the differences between their morphological structures. The PECH(SO<SUB>2</SUB>)-T film has a multi-bilayer structure without interdigitation, in which the layers stack along the out-of-plane of the film and provide a thymine-rich surface. In contrast, the PECH(S)-T film is amorphous with a relatively low population of thymine moieties at the surface. This study demonstrated that a thymine-rich surface is required for recyclable thymine-based polymers to provide highly improved sensitivity and selectivity as well as full reversibility in the sensing of mercury ions. A thymine-rich surface can be achieved with a brush polymer bearing thymine moieties that can self-assemble into a multi-bilayer structure. Because of the thymine-rich surface, the PECH(SO<SUB>2</SUB>)-T thin films even in only 6 nm thickness demonstrate the detection of mercury ions in aqueous solutions with a detection limit of 10<SUP>–6</SUP> M.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2011/aamick.2011.3.issue-7/am200454x/production/images/medium/am-2011-00454x_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am200454x'>ACS Electronic Supporting Info</A></P>

Well-Defined DNA-Mimic Brush Polymers Bearing Adenine Moieties: Synthesis, Layer-by-Layer Self-Assembly, and Biocompatibility

Kim, Jin Chul,Jung, Jungwoon,Rho, Yecheol,Kim, Mihee,Kwon, Wonsang,Kim, Heesoo,Kim, Ik Jung,Kim, Jung Ran,Ree, Moonhor American Chemical Society 2011 Biomacromolecules Vol.12 No.7

<P>Two new DNA-mimicking brush polymers were synthesized: poly[oxy(11-(3-(9-adeninyl)propionato)-undecanyl-1-thiomethyl)ethylene] (PECH-AP) and poly[oxy(11-(5-(9-adenylethyloxy)-4-oxopentanoato)undecanyl-1-thiomethyl)ethylene] (PECH-AS). These polymers were found to be thermally stable up to 220 °C and could be applied easily by conventional coating processes to produce good quality films. Interestingly, both brush polymers formed molecular multibilayer structures to provide an adenine-rich surface. Despite the structural similarities, PECH-AS surprisingly exhibited higher hydrophilicity and better water sorption properties than PECH-AP. These differences were attributed to the chemical structures in the bristles of the polymers. The adenine-rich surfaces of the polymer films demonstrated selective protein adsorption, suppressed bacterial adherence, facilitated HEp-2 cell adhesion, and exhibited good biocompatibility in mice. However, the high hydrophilicity and good water sorption characteristics of the PECH-AS film suggest that this brush polymer is better suited to applications requiring good biocompatibility and reduced chance of bacterial infection compared with the PECH-AP film.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/bomaf6/2011/bomaf6.2011.12.issue-7/bm200572t/production/images/medium/bm-2011-00572t_0012.gif'></P>

Novel Brush Polymers with Phosphorylcholine Bristle Ends: Synthesis, Structure, Properties, and Biocompatibility

Kim, Gahee,Park, Samdae,Jung, Jungwoon,Heo, Kyuyoung,Yoon, Jinhwan,Kim, Heesoo,Kim, Ik Jung,Kim, Jung Ran,Lee, Jong Im,Ree, Moonhor WILEY-VCH Verlag 2009 Advanced functional materials Vol.19 No.10

<P>New brush polymers with various numbers of bristle ends incorporating phosphorylcholine (PC) moieties are synthesized. The polymers are thermally stable up to 175 °C and form good-quality films with conventional spin-, roll-, and dip-coating, and subsequent drying processes. Interestingly, all these brush polymers, as a PC-containing polymer, demonstrate a stable molecular multi-bilayer structure in thin films that arise due to the efficient self-assembly of the bristles for temperatures <55 °C and PC-rich surfaces, and therefore successfully mimic natural cell-membrane surfaces. These brush-polymer films exhibit excellent water wettability and water sorption whilst retaining the remarkable molecular multi-bilayer structure, and thus have hydrophilic surfaces. These novel multi-bilayer structured films repel fibrinogen molecules and platelets from their surfaces but also have bactericidal effects on bacteria. Moreover, the brush-polymer films are found to provide comfortable surface environments for the successful anchoring and growth of HEp-2 cells, and to exhibit excellent biocompatibility in mice. These newly developed brush polymers are suitable for use in biomedical applications including medical devices and biosensors that require biocompatibility and the reduced possibility of post-operative infection.</P> <B>Graphic Abstract</B> <P>New brush polymers with various numbers of bristle ends incorporating phosphorylcholine (PC) moieties are synthesized. The new PC-containing brush polymers (see image) form a stable molecular multi-bilayer structure in thin films and successfully mimic natural cell membrane surfaces. The hydrophilic surface of the films repels fibrinogen and platelets and exhibit bactericidal effects. <img src='wiley_img/1616301X-2009-19-10-ADFM200801680-content.gif' alt='wiley_img/1616301X-2009-19-10-ADFM200801680-content'> </P>

자동차 차체에서 빗물의 역류 모사에 관한 연구

이정운(Jungwoon Lee),윤재득(Jeadeuk Yun),박성배(Sungbae Park),정융호(Yoongho Jung) (사)한국CDE학회 2011 한국CDE학회 논문집 Vol.16 No.5

Large number of part design such as for aircraft and automotive development is preceded by functional or sectional design groups for efficiency. With the assembly development of large number of parts, interferences and gaps can be found when the parts and sub-assemblies by those design groups are to be assembled. When rainwater come into the space among parts and is not be drained sufficiently, rainwater within the structure can backflow to gaps or unexpected outlets, which may cause severe problems of part corrosion and electric shock. This research has developed a method and a program to simulate backflow of rainwater within space among parts, which can find unexpected outlets and gaps as in real situation. The developed program can not only simulate up and downstream of liquid, but also the flow with multiple channels of division and joining. The developed method can also be applied to aircraft and ship design process.

Pharmacological Regulation of Oxidative Stress in Stem Cells

Lee, Jungwoon,Cho, Yee Sook,Jung, Haiyoung,Choi, Inpyo Hindawi 2018 Oxidative medicine and cellular longevity Vol.2018 No.-

<P>Oxidative stress results from an imbalance between reactive oxygen species (ROS) production and antioxidant defense mechanisms. The regulation of stem cell self-renewal and differentiation is crucial for early development and tissue homeostasis. Recent reports have suggested that the balance between self-renewal and differentiation is regulated by the cellular oxidation-reduction (redox) state; therefore, the study of ROS regulation in regenerative medicine has emerged to develop protocols for regulating appropriate stem cell differentiation and maintenance for clinical applications. In this review, we introduce the defined roles of oxidative stress in pluripotent stem cells (PSCs) and hematopoietic stem cells (HSCs) and discuss the potential applications of pharmacological approaches for regulating oxidative stress in regenerative medicine.</P>

Causes and Mechanisms of Hematopoietic Stem Cell Aging

Lee, Jungwoon,Yoon, Suk Ran,Choi, Inpyo,Jung, Haiyoung MDPI 2019 INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES Vol.20 No.6

<P>Many elderly people suffer from hematological diseases known to be highly age-dependent. Hematopoietic stem cells (HSCs) maintain the immune system by producing all blood cells throughout the lifetime of an organism. Recent reports have suggested that HSCs are susceptible to age-related stress and gradually lose their self-renewal and regeneration capacity with aging. HSC aging is driven by cell-intrinsic and -extrinsic factors that result in the disruption of the immune system. Thus, the study of HSC aging is important to our understanding of age-related immune diseases and can also provide potential strategies to improve quality of life in the elderly. In this review, we delineate our understanding of the phenotypes, causes, and molecular mechanisms involved in HSC aging.</P>

자동차 차체에서 빗물의 역류 모사에 관한 연구

이정운(Jungwoon Lee),윤재득(Jeadeuk Yun),박성배(Sungbae Park),정융호(Yoongho Jung) (사)한국CDE학회 2012 한국 CAD/CAM 학회 학술발표회 논문집 Vol.2012 No.2

Large number of part design such as for aircraft and automotive development is preceded by functional or sectional design groups for efficiency. With the assembly development of large number of parts, interferences and gaps can be found when the parts and sub-assemblies by those design groups are to be assembled. When rainwater come into the space among parts and is not be drained sufficiently, rainwater within the structure can backflow to gaps or unexpected outlets, which may cause severe problems of part corrosion and electric shock. This research has developed a method and a program to simulate backflow of rainwater within space among parts, which can find unexpected outlets and gaps as in real situation. The developed program can not only simulate up and downstream of liquid, but also the flow with multiple channels of division and joining. The developed method can also be applied to aircraft and ship design process.

고정형 연료전지 계통연계·독립 운전 전환 안전기술 연구

정재환(JAEHWAN JUNG),유수연(SUYEON YU),이정운(JUNGWOON LEE) 한국가스학회 2023 한국가스학회 학술대회논문집 Vol.2023 No.11

High‐Performance n‐Channel Thin‐Film Field‐Effect Transistors Based on a Nanowire‐Forming Polymer

Hahm, Suk Gyu,Rho, Yecheol,Jung, Jungwoon,Kim, Se Hyun,Sajoto, Tissa,Kim, Felix S.,Barlow, Stephen,Park, Chan Eon,Jenekhe, Samson A.,Marder, Seth R.,Ree, Moonhor WILEY‐VCH Verlag 2013 Advanced functional materials Vol.23 No.16

<P><B>Abstract</B></P><P>A new electrontransport polymer, poly{[<I>N,N′</I>‐dioctylperylene‐3,4,9,10‐bis(dicarboximide)‐1,7(6)‐diyl]‐<I>alt</I>‐[(2,5‐bis(2‐ethyl‐hexyl)‐1,4‐phenylene)bis(ethyn‐2,1‐diyl]} (PDIC8‐EB), is synthesized. In chloroform, the polymer undergoes self‐assembly, forming a nanowire suspension. The nanowire's optical and electrochemical properties, morphological structure, and field‐effect transistor (FET) characteristics are investigated. Thin films fabricated from a PDIC8‐EB nanowire suspension are composed of ordered nanowires and ordered and amorphous non‐nanowire phases, whereas films prepared from a homogeneous PDIC8‐EB solution consist of only the ordered and amorphous non‐nanowire phases. X‐ray scattering experiments suggest that in both nanowires and ordered phases, the PDIC8 units are laterally stacked in an edge‐on manner with respect to the film plane, with full interdigitation of the octyl chains, and with the polymer backbones preferentially oriented within the film plane. The ordering and orientations are significantly enhanced through thermal annealing at 200 °C under inert conditions. The polymer film with high degree of structural ordering and strong orientation yields a high electron mobility (0.10 ± 0.05 cm<SUP>2</SUP> V<SUP>−1</SUP> s<SUP>−1</SUP>), with a high on/off ratio (3.7 × 10<SUP>6</SUP>), a low threshold voltage (8 V), and negligible hysteresis (0.5 V). This study demonstrates that the polymer in the nanowire suspension provides a suitable material for fabricating the active layers of high‐performance n‐channel FET devices via a solution coating process.</P>