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Chiaki Nishiura,Valerie Williams,Krzysztof Matyjaszewski 한국고분자학회 2017 Macromolecular Research Vol.25 No.6
Iron and copper complexes with anionic phenolate-bis(pyridyl)amine ligands were synthesized and examined as catalysts for atom transfer radical polymerization (ATRP) of methyl (meth)acrylate and styrene. With copper complexes, polymers with narrow molecular weight distributions, M w/M n ~1.2, were prepared. The catalytic performance of copper catalysts was affected by nature of halogen species and by the steric and electronic effects. In iron-mediated ATRP procedures, the number-average molecular weights of the polymers increased with monomer conversion, however, the molecular weight distributions of the resulting polymers were relatively broad M w/M n~1.7, due to slow deactivation processes.
Aftabuzzaman, M.,Kim, Chang Ki,Kowalewski, Tomasz,Matyjaszewski, Krzysztof,Kim, Hwan Kyu Royal Society of Chemistry 2019 Journal of Materials Chemistry A Vol.7 No.35
<P>To date, the facile preparation of ruthenium nanoparticles homogeneously dispersed in mesoporous carbons remains a big challenge. Here, a poly(butyl acrylate)-<I>b</I>-polyacrylonitrile block copolymer was dissolved in dimethyl sulfoxide with ruthenium(iii) acetylacetonate (Ru(acac)3) and then pyrolyzed after electrospinning. Ru(acac)3 was confined in the polymer network and converted to RuO2, which was further reduced to Ru nanoparticles (Ru-NPs) at high temperature, eventually producing well-dispersed Ru-NPs embedded in STMCs (Ru-NPs@STMCs). The as-prepared Ru-NPs@STMCs show many attractive features, such as spherical shape with a high surface area, numerous active species (Ru and N), and an interconnected structure with meso/micropores, resulting in fast mass transport and ion diffusion pathways. The synergetic effect of Ru-NPs and STMCs gives rise to excellent electrochemical performance, with a very high specific gravimetric capacitance of 656.25 F g<SUP>−1</SUP> at a scan rate of 10 mV s<SUP>−1</SUP>, good rate capability, and excellent long-term cycling stability (almost 100% retention after 5000 cycles). To our knowledge, this performance is one of the best results reported for Ru/carbon-based materials and is comparable to that of other RuO2/carbon-based materials. This study not only gives insights into the design and construction of novel nanocomposites for high-performance supercapacitors but also provides a new approach to engineering metal/carbon composites applicable to energy storage and energy conversion devices.</P>
Kim, Chang Ki,Zhou, Haoran,Kowalewski, Tomasz,Matyjaszewski, Krzysztof,Kim, Hwan Kyu American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.2
<P>Among various photovoltaic devices, dye-sensitized solar cells (DSSCs) are one of the most potentially clean and renewable energy conversion devices because of their low fabrication cost, environmentally friendly nature, and high power conversion efficiency. However, the use of rare metals such as Pt counter electrodes (CEs) is one of the major drawbacks of DSSC devices for broad real-life applications. In this regard, alternative materials to Pt CEs have been long sought for DSSCs employing both cobalt and iodine redox couples. Therefore, in this study, soft-templated tellurium-doped mesoporous carbons (<B>Te-SMC</B>s) were synthesized for the first time by the simple pyrolysis of PAN-<I>b</I>-PBA block copolymer in the presence of a tellurium precursor for replacing the Pt CE. To confirm the chemical composition and porosity, the as-prepared <B>Te-SMC</B> materials were evaluated by elemental analysis (XPS and EDS) and nitrogen sorption isotherms measurement. The as-prepared <B>Te-SMC</B> materials contained mainly mesopores and retained the three-dimensional hierarchical graphite-like structure with many defect sites. They displayed doping levels with nitrogen of 9.15 atom % and tellurium of 0.15 atom % and had a specific surface area of 540 m<SUP>2</SUP> g<SUP>-1</SUP>. Therefore, these characteristics enabled the development of a high-performance CE in DSSCs with cobalt and iodine redox couples. As a result of its catalytic performance, <B>Te-SMC</B> exhibited outstanding electrocatalytic activity as well as a significantly improved electrochemical stability than those of Pt CE for both redox couples even after 1000 potential cycles. The results show that a maximum conversion efficiency of 11.64 and 9.67% could be achieved under one sun illumination (AM 1.5G) for <B>SGT-021</B>/Co(bpy)<SUB>3</SUB><SUP>2+/3+</SUP>- and <B>N719</B>/I<SUP>-</SUP>/I<SUB>3</SUB><SUP>-</SUP>-based devices with <B>Te-SMC</B> CEs, and their power conversion efficiency is superior to the corresponding device with Pt CEs.</P> [FIG OMISSION]</BR>
Park, Sangwoo,Zhong, Mingjiang,Lee, Taeheon,Paik, Hyun-jong,Matyjaszewski, Krzysztof American Chemical Society 2012 ACS APPLIED MATERIALS & INTERFACES Vol.4 No.11
<P>Temperature-responsive photo-cross-linkable poly[oligo(ethylene oxide) monomethyl ether methacrylate] (POEOMA)-based star polymers were synthesized by atom transfer radical polymerization (ATRP), for the modification of silicon (Si) wafer surfaces. The polymers showed a lower critical solution temperature (LCST) behavior in aqueous media. The polymers were modified with benzophenone (Bzp) functional groups that were utilized in UV-triggered (λ = 365 nm) cross-linking reactions for the preparation of polymer networks. The star polymers were deposited onto the surfaces of Si wafers by spin coating, and stable polymer films were formed by simple UV irradiation. The stability of thermoresponsive cross-linked polymer films deposited on the Si wafer was confirmed by changing their hydrophilicity by changing the temperature of the environment. In addition, the POEOMA-based star polymers could be utilized for the preparation of photolithography-patterned surfaces. The successful formation of uniform stable polymeric films indicates that Bzp-functionalized POEOMA star polymers can be used for a simple Si surface modification.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2012/aamick.2012.4.issue-11/am301597b/production/images/medium/am-2012-01597b_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am301597b'>ACS Electronic Supporting Info</A></P>
Schmitt, Michael,Choi, Jihoon,Min Hui, Chin,Chen, Beibei,Korkmaz, Emrullah,Yan, Jiajun,Margel, Shlomo,Burak Ozdoganlar, O.,Matyjaszewski, Krzysztof,Bockstaller, Michael R. The Royal Society of Chemistry 2016 SOFT MATTER Vol.12 No.15
<P>The effect of polymer modification on the deformation characteristics and processibility of particle assembly structures is analyzed as a function of particle size and degree of polymerization of surface-tethered chains. A pronounced increase of the fracture toughness (by approximately one order of magnitude) is observed as the degree of polymerization exceeds a threshold value that increases with particle size. The threshold value is interpreted as being related to the transition of tethered chains from stretched-to-relaxed conformation (and the associated entanglement of tethered chains) and agrees with predictions from scaling theory. The increase in toughness is reduced with increasing particle size - this effect is rationalized as a consequence of the decrease of entanglement density with increasing dimension of interstitial (void) space in particle array structures. The increased fracture toughness of particle brush materials (with sufficient degree of polymerization of tethered chains) enables the fabrication of ordered colloidal films and even complex 3D shapes by scalable polymer processing techniques, such as spin coating and micromolding. The results, therefore, suggest new opportunities for the processing of colloidal material systems that could find application in the economical fabrication of functional components or systems compromised of colloidal materials.</P>