Polymer Hybrid Nanomaterials from Self-Assembly

Ulrich WIESNER 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.2

Block copolymer-nanoparticle hybrid self-assembly

Hoheisel, Tobias N.,Hur, Kahyun,Wiesner, Ulrich B. Elsevier 2015 Progress in polymer science Vol.40 No.-

<P><B>Abstract</B></P> <P>Polymer-inorganic hybrid materials provide exciting opportunities as they may display favorable properties from both constituents that are desired in applications including catalysis and energy conversion and storage. For the preparation of hybrid materials with well-defined morphologies, block copolymer-directed nanoparticle hybrids present a particularly promising approach. As will be described in this review, once the fundamental characteristics for successful nanostructure formation at or close to the thermodynamic equilibrium of these nanocomposites are identified, the approach can be generalized to various materials classes. In addition to the discussion of recent materials developments based on the use of AB diblock copolymers as well as ABC triblock terpolymers, this review will therefore emphasize progress in the fundamental understanding of the underlying formation mechanisms of such hybrid materials. To this end, critical experiments for, as well as theoretical progress in the description of these nanostructured block copolymer-based hybrid materials will be discussed. Rather than providing a comprehensive overview, the review will emphasize work by the Wiesner group at Cornell University, US, on block copolymer-directed nanoparticle assemblies as well as their use in first potential application areas. The results provide powerful design criteria for wet-chemical synthesis methodologies for the generation of functional nanomaterials for applications ranging from microelectronics to catalysis to energy conversion and storage.</P>

Block copolymer directed functional nanoporous materials

이진우,Ulrcih Wiesner 한국고분자학회 2008 한국고분자학회 학술대회 연구논문 초록집 Vol.33 No.2

Estimation of Free-Flow Speed

Joseph Fazio,Brady N. Wiesner,Matthew D. Deardoff 대한토목학회 2014 KSCE JOURNAL OF CIVIL ENGINEERING Vol.18 No.2

In 2010 Highway Capacity Manual, one preferably determines free-flow speed by deriving it from a speed study involving the existing facility or on a comparable facility if the facility is in the planning stage. Many have used a ‘rule of thumb’ by adding 10 km/ h (5 mi/h) above the posted limit to obtain free-flow speed without justification. Two team members using a radar gun and manual tally sheets collected 1668 speed observations at ten sites during several weeks. Each site had a unique posted speed limit sign ranging from 30 km/h (20 mi/h) to 120 km/h (75 mi/h). Five sites were on urban streets. Three sites were on multilane highways, and two on freeways. Goodness-of-fit test results revealed that a Gaussian distribution generally fit the speed distributions at each site at a 5% level of significance. The best-fit model had a correlation coefficient of +0.99. The posted speed limit variable was significant at 5% level of significance. Examining data by highway type revealed that average free-flow speeds are strongly associated with posted speed limits with correlation coefficients of +0.99, +1.00, and +1.00 for urban streets, multilane highways, and freeways, respectively.

Preparation and characterization of fouling-resistant photocatalytic metal membrane embedded with self-organized TiO2 nano tube

Choi, Won-Youl,Park, No-Suk,Wiesner, Mark R.,Kim, Jong-Oh IWA Publishing 2010 Water Science & Technology Vol.62 No.4

<P>A self-organized nano-structured, photocatalytic TiO2 membrane with large surface area of anatase crystallites was successfully fabricated by anodization. The nano-structured anodized TiO2 membrane was characterized using SEM, XRD and TEM techniques and the operational parameters to fabricate such as anodization time and applied anodic potential were also investigated. The anodized TiO2 membrane showed high photocatalytic performance in terms of refractory organics decomposition, bacteria inactivation and membrane permeability, which suggests that problems of conventional photocatalytic treatment and membrane filtration in water and wastewater treatment may be reduced using this combined process.</P>

JMSD 도서관 공원

다니엘 브랜다오(Daniel Bermudez),다이애나 위즈너(Diana Wiesner) 현대건축사 2014 월간 CONCEPT Vol.- No.180

Exploring Periodic Bicontinuous Cubic Network Structures with Complete Phononic Bandgaps

Hur, Kahyun,Hennig, Richard G.,Wiesner, Ulrich American Chemical Society 2017 The Journal of Physical Chemistry Part C Vol.121 No.40

<P>Controlling the phononic properties of materials provides opportunities for better thermal insulation, reduction of sound noise, and conversion of wasted heat into electricity. Phononic crystals are periodically structured media composed of two or more dissimilar materials offering a unique pathway to control the transmission of phonons, responsible for sound and heat transport. In particular, phononic crystals with cubic network structure possessing complete phononic bandgaps are highly desirable for energy applications but have not been thoroughly investigated, hampering progress in this field. Here we computationally obtained phononic band structures of 16 cubic network structures that could be made by fabrication techniques including block copolymer self-assembly and identified six structures that exhibit complete phononic bandgaps. The champion phononic bandgap structure is the so-called I-WP structure with a bandgap width of 0.41. On the basis of simulation results, design rules to tailor network structures for larger phononic bandgaps are elucidated. We expect that our results will provide guidance to develop novel materials for sonic and thermal devices.</P>

A NEW DIRECTION FOR POWDER INJECTION MOLDING

Martin Bloemacher,Dieter Weinand,H. Wiesner 한국분말야금학회 1996 한국분말야금학회 학술대회논문집 Vol.1996 No.1

Controlling Nanoparticle Location via Confined Assembly in Electrospun Block Copolymer Nanofibers

Kalra, Vibha,Lee, Jinwoo,Lee, Jung Hun,Lee, Seung Goo,Marquez, Manuel,Wiesner, Ulrich,Joo, Yong Lak WILEY-VCH Verlag 2008 Small Vol.4 No.11

<P>Coaxial nanofibers with poly(styrene-block-isoprene) (PS-b-PI)/magnetite nanoparticles as core and silica as shell are fabricated using electrospinning.1–4 Thermally stable silica helps to anneal the fibers above the glass transition temperature of PS-b-PI and form ordered nanocomposite morphologies. Monodisperse magnetite nanoparticles (NPs; 4 nm) are synthesized and surface coated with oleic acid to provide marginal selectivity towards an isoprene domain. When 4 wt% nanoparticles are added to symmetric PS-b-PI, transmission electron microscopy (TEM) images of microtomed electrospun fibers reveal that NPs are uniformly dispersed only in the PI domain, and that the confined lamellar assembly in the form of alternate concentric rings of PS and PI is preserved. For 10 wt% NPs, a morphology transition is seen from concentric rings to a co-continuous phase with NPs again uniformly dispersed in the PI domains. No aggregates or loss of PI selectivity is found in spite of interparticle attraction. Magnetic properties are measured using a superconducting quantum interference device (SQUID) magnetometer and all nanocomposite fiber samples exhibit superparamagnetic behavior.</P> <B>Graphic Abstract</B> <P>The first ever tailored nanofibers with internal confined assembly used as a template to guide nanoparticles are fabricated. The figure shows cross sections of nanofibers with magnetite nanoparticles dispersed in poly(styrene-b-isoprene). The nanoparticles (dark dots) preferentially wet the isoprene domain (dark regions) due to specific surface chemistry. Scale bar is 200 nm. <img src='wiley_img/16136810-2008-4-11-SMLL200800279-content.gif' alt='wiley_img/16136810-2008-4-11-SMLL200800279-content'> </P>

Influence of crystalline peripheral chain length on the solid-state assemblies of amphiphilic dendrons

Chung, Yeon-Wook,Lee, Byung-Ill,Kim, Hyun-Yu,Wiesner, Ulrich,Cho, Byoung-Ki Wiley Subscription Services, Inc., A Wiley Company 2007 Journal of polymer science Part A, Polymer chemist Vol.45 No.21

<P>We prepared third-generation amphiphilic dendrons 3-14 and 3-18 consisting of a hydrophilic aliphatic polyether dendritic core and either tetradecyl or octadecyl peripheries, respectively. Their solid-state self-assembly behavior was investigated by comparison with 3-22 having the same dendritic core and longer docosyl peripheries. In marked contrast to the lamellar assembly of 3-22, small-angle X-ray analysis suggested that 3-14 and 3-18 show oblique columnar structures with presumably elliptical cross sections. The observed results can be rationalized by dendron shape anisotropy, which is strongly associated with the degree of crystallization as a function of alkyl chain length. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4988–4994, 2007</P> <B>Graphic Abstract</B> <P>Solid-state assemblies of amphiphilic dendrons, based on a third-generation aliphatic polyether dendritic core, can be modulated from lamellar to oblique columnar structures as a function of crystalline peripheral chain length. The observed assembly behavior can be explained by variation of dendron shape attributable to the degree of crystallization of alkyl peripheries. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]</P> <img src='wiley_img/0887624X-2007-45-21-POLA22287-gra001.gif' alt='wiley_img/0887624X-2007-45-21-POLA22287-gra001'>