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Practical Synthesis of Alkoxyamine Initiators for Living Radical Polymerization
Moon Bongjin,Kang Minhyuk The Polymer Society of Korea 2005 Macromolecular Research Vol.13 No.3
Various alkoxyamine initiators for nitroxide mediated radical polymerization (NMRP) were prepared in high yields by a simple substitution reaction of nitroxide anions with benzyl bromide. The required nitroxide anions were easily generated by treating either nitroxide free radicals or hydroxy amine with an alkali metal such as sodium or potassium in THF. This method is both practical and efficient, since the ionic conditions prevent other side reactions from occurring, such as the self-coupling or oligomerization reactions that are observed in the case of radical trapping conditions. To demonstrate the utility of the resulting alkoxyamine initiators, end- and telechelic-alkoxyamine PEG macroinitiators derived from the alkoxyamines were synthesized by a simple chemical modification, and used for the preparation of PEG-b-PS and PS-b-PEG-b-PS block copolymers by NMRP.
( Jungeun Bae ),( Hwangbo Song ),( Bongjin Moon ),( Han Bin Oh ) 한국질량분석학회 2016 Mass spectrometry letters Vol.7 No.4
To determine the influence of the cationization agent on the collision activated dissociation (CAD) fragmentation behavior of oligosaccharides, the CAD spectra of the singly protonated, sodiated oligosaccharides and singly sodiated and dibenzo-18-crown-6 ether conjugated oligosaccharides were carefully compared. Each of these three different species showed quite different fragmentation spectra. The comparison of singly protonated and sodiated oligosaccharide CAD spectra revealed that different cationization agents affected the cationization agent adduction sites as well as the fragmentation sites within the oligosaccharides. When the mobility of Na<sup>+</sup> was limited by the dibenzo-18-crown-6 ether encapsulation agent, the examined linear oligosaccharides showed fragmentation patterns quite different from the unmodified ones. For the dibenzo-18-crown-6 ether conjugated oligosaccharides, the charge-remote fragmentation pathways were more likely to be activated than the chargedirected pathways. This work demonstrates that dibenzo-18-crown-6 ether conjugation can potentially provide a route to selectively activate the charge-remote fragmentation pathways, albeit to a limited extent, in tandem mass spectrometry studies.
Bae, Jungeun,Song, Hwangbo,Moon, Bongjin,Oh, Han Bin Korean Society for Mass Spectrometry 2016 Mass spectrometry letters Vol.7 No.4
To determine the influence of the cationization agent on the collision activated dissociation (CAD) fragmentation behavior of oligosaccharides, the CAD spectra of the singly protonated, sodiated oligosaccharides and singly sodiated and dibenzo-18-crown-6 ether conjugated oligosaccharides were carefully compared. Each of these three different species showed quite different fragmentation spectra. The comparison of singly protonated and sodiated oligosaccharide CAD spectra revealed that different cationization agents affected the cationization agent adduction sites as well as the fragmentation sites within the oligosaccharides. When the mobility of $Na^+$ was limited by the dibenzo-18-crown-6 ether encapsulation agent, the examined linear oligosaccharides showed fragmentation patterns quite different from the unmodified ones. For the dibenzo-18-crown-6 ether conjugated oligosaccharides, the charge-remote fragmentation pathways were more likely to be activated than the chargedirected pathways. This work demonstrates that dibenzo-18-crown-6 ether conjugation can potentially provide a route to selectively activate the charge-remote fragmentation pathways, albeit to a limited extent, in tandem mass spectrometry studies.
Gas-phase peptide sequencing by TEMPO-mediated radical generation
Lee, Minhee,Kang, Minhyuck,Moon, Bongjin,Oh, Han Bin Royal Society of Chemistry 2009 The Analyst Vol.134 No.8
<P>Collisional activation of 2-[(2,2,6,6-tetramethylpiperidin-1-yloxy)methyl]benzoic acid (TEMPO-Bz)-conjugated peptide cations, prepared by attaching a TEMPO-derived precursor <B>1</B> to an <I>N</I>-terminal amino group or a lysine side chain, resulted in the formation of radical species. The subsequent tandem mass spectrometry on the radical cations exhibited odd-electron peptide backbone dissociations in the same manner as that observed by electron capture dissociation (ECD) or electron transfer dissociation (ETD). For example, <I>a</I>-, <I>x</I>-, or <I>z</I>-types of ions were major fragments and the disulfide bond was readily cleaved. The TEMPO-FRIPS (free radical initiated peptide sequencing) was also applicable to characterizing even singly protonated peptides, in contrast to ECD or ETD in which only doubly or highly protonated cations are responsive. The TEMPO-FRIPS approach also has universality in that it can be used in any type of a tandem mass spectrometer.</P> <P>Graphic Abstract</P><P>A new peptide mass spectrometry sequencing method using a TEMPO-free radical initiator tag provides ECD/ETD-like peptide backbone dissociation fragments. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b904115j'> </P>
Cyclodextrin-based reactive porogen for nanoporous ultra-low dielectrics
Min, Sung-Kyu,Moon, Bongjin,Kim, Hyunjung,Rhee, Hee-Woo Elsevier 2011 Current Applied Physics Vol.11 No.1
<P><B>Abstract</B></P><P>We prepared ultralow dielectrics with remarkably high mechanical strengths (E ∼ 8.1 GPa and H ∼ 1.2 GPa). The reactivity of porogens was critical to enhanced mechanical properties of ULK. In the case of non-reactive porogens the mechanical properties of nanoporous ultralow dielectrics dramatically decreased with reduction in dielectric constant. However, reactive CD was very effective in the preparation of ULK for the next generation semiconductors.</P> <P><B>Highlights</B></P><P>► We examined the effect of porogen reactivity on the properties of dielectrics. ► Cyclodextrin was functionalized as a reactive porogen with alkoxy silane groups. ► Reactivity of porogens was critical to the enhanced mechanical properties. ► But the reactivity did not affect the dielectrical properties. ► Reactive CD produced the utmost modulus and hardness of nanoporous dielectrics.</P>
Structures of ionic liquid–water mixtures investigated by IR and NMR spectroscopy
Cha, Seoncheol,Ao, Mingqi,Sung, Woongmo,Moon, Bongjin,Ahlströ,m, Bodil,Johansson, Patrik,Ouchi, Yukio,Kim, Doseok The Royal Society of Chemistry 2014 Physical chemistry chemical physics Vol.16 No.20
<P>Imidazolium-based ionic liquids having different anions 1-butyl-3-methylimidazolium ([BMIM]X: X = Cl<SUP>−</SUP>, Br<SUP>−</SUP>, I<SUP>−</SUP>, and BF<SUB>4</SUB><SUP>−</SUP>) and their aqueous mixtures were investigated by IR absorption and proton NMR spectroscopy. The IR spectra of these ionic liquids in the CH<SUB><I>x</I></SUB> stretching region differed substantially, especially for C–H bonds in the imidazolium ring, and the NMR chemical shifts of protons in the imidazolium ring also varied markedly for ILs having different anions. Upon the introduction of water to screen the electrostatic forces and separate the ions, both IR and NMR spectra of [BMIM]X (X = Cl<SUP>−</SUP>, Br<SUP>−</SUP>, I<SUP>−</SUP>) showed significant changes, while those of [BMIM]BF<SUB>4</SUB> did not change appreciably. H–D isotopic exchange rates of C(2)–H in [BMIM]X–D<SUB>2</SUB>O mixtures exhibited an order: C(2)–H⋯Cl > C(2)–H⋯Br > C(2)–H⋯I, while the C(2)–H of [BMIM]BF<SUB>4</SUB> was not deuterated at all. These experimental findings, supported by DFT calculations, lead to the microscopic bulk configurations in which the anions and the protons of the cations in the halide ionic liquids have specific, hydrogen-bond type of interaction, while the BF<SUB>4</SUB><SUP>−</SUP> anion does not participate in the specific interaction, but interacts less specifically by positioning itself more above the ring plane of the imidazolium cation. This structural change dictated by the anion type will work as a key element to build the structure–property relationship of ionic liquids.</P> <P>Graphic Abstract</P><P>Imidazolium-based ionic liquids having different anions 1-butyl-3-methylimidazolium ([BMIM]X: X = Cl<SUP>−</SUP>, Br<SUP>−</SUP>, I<SUP>−</SUP>, and BF<SUB>4</SUB><SUP>−</SUP>) and their aqueous mixtures were investigated by IR absorption and proton NMR spectroscopy. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4cp00589a'> </P>