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Dive into the research topics where Shih-Fan Wang is active.

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Featured researches published by Shih-Fan Wang.


Journal of the American Society for Mass Spectrometry | 2013

Differentiation of Linear and Cyclic Polymer Architectures by MALDI Tandem Mass Spectrometry (MALDI-MS2)

Aleer M. Yol; David E. Dabney; Shih-Fan Wang; Boyd A. Laurent; Mark D. Foster; Roderic P. Quirk; Scott M. Grayson; Chrys Wesdemiotis

Abstract[M + Ag]+ ions from cyclic and linear polystyrenes and polybutadienes, formed by matrix-assisted laser desorption ionization (MALDI), give rise to significantly different fragmentation patterns in tandem mass spectrometry (MS2) experiments. In both cases, fragmentation starts with homolytic cleavage at the weakest bond, usually a C–C bond, to generate two radicals. From linear structures, the separated radicals depolymerize extensively by monomer losses and backbiting rearrangements, leading to low-mass radical ions and much less abundant medium- and high-mass closed-shell fragments that contain one of the original end groups, along with internal fragments. With cyclic structures, depolymerization is less efficient, as it can readily be terminated by intramolecular H-atom transfer between the still interconnected radical sites (disproportionation). These differences in fragmentation reactivity result in substantially different fragment ion distributions in the MS2 spectra. Simple inspection of the relative intensities of low- versus high-mass fragments permits conclusive determination of the macromolecular architecture, while full spectral interpretation reveals the individual end groups of linear polymers or the identity of the linker used to form the cyclic polymer. FigureMacrocyclic and linear polystyrene and polydiene architectures are conclusively distinguished by the MS2 fragmentation patterns of Ag+-cationized oligomers.


Physical Review Letters | 2017

Evidence and Limits of Universal Topological Surface Segregation of Cyclic Polymers

Qiming He; Shih-Fan Wang; Renfeng Hu; Bulent Akgun; Caleb A. Tormey; Somesh Peri; David T. Wu; Mark D. Foster

If you mix lines and circles, what happens at the edge of the mixture? The problem is simply stated, but the answer is not obvious. Twenty years ago it was proposed that a universal topological driving force would drive cyclic chains to enrich the surface of blends of linear and cyclic chains. Here such behavior is demonstrated experimentally for sufficiently long chains and the limit in molecular weight where packing effects dominate over the topological driving force is identified.


Polymer Chemistry | 2016

Efficient synthesis of well-defined cyclic polystyrenes using anionic polymerization, silicon chloride linking chemistry and metathesis ring closure

Qiming He; Aleer M. Yol; Shih-Fan Wang; Hongwei Ma; Kai Guo; Fan Zhang; Chrys Wesdemiotis; Roderic P. Quirk; Mark D. Foster

An efficient method for the synthesis of well-defined cyclic polystyrenes using anionic polymerization, silicon chloride linking chemistry, and metathesis ring closure has been developed. The macrocycle precursor, α,ω-bis(4-pentenyl)polystyrene, was formed by 4-pentenyllithium-initiated polymerization of styrene, coupling of α-pentenylpoly(styryl)lithium (PLi) with dimethyldichlorosilane to form α,ω-bis(4-pentenyl)polystyrene (Mn = 4600 g mol−1) and reaction of excess PLi with ethylene oxide to facilitate purification. Cyclization of the purified α,ω-bis(4-pentenyl)polystyrene was performed in dichloromethane under mild conditions using a Grubbs catalyst, bis(tricyclohexylphosphine)benzylidine ruthenium(IV) chloride, as a metathesis ring-closure agent. In contrast to prior work, no fractionation is required to obtain the pure product. Both the divinyl precursor and resulting macrocycle were characterized by SEC, MALDI-TOF mass spectrometry (MS) and NMR. The macrocycle was unambiguously distinguished from its precursor using the fragmentation patterns from tandem mass spectrometry (MS2) experiments. The results show that the macrocyclic precursor, α,ω-bis(4-pentenyl)polystyrene, was of high purity and that the cyclization was highly efficient.


Macromolecules | 2011

Synthesis of Cyclic Polystyrenes Using Living Anionic Polymerization and Metathesis Ring-Closure

Roderic P. Quirk; Shih-Fan Wang; Mark D. Foster; Chrys Wesdemiotis; Aleer M. Yol


Physical Review Letters | 2013

Anomalous Surface Relaxations of Branched-Polymer Melts

Shih-Fan Wang; Sewoo Yang; Jaesik Lee; Bulent Akgun; David T. Wu; Mark D. Foster


ACS Macro Letters | 2012

Probing Surface Concentration of Cyclic/Linear Blend Films Using Surface Layer MALDI-TOF Mass Spectrometry

Shih-Fan Wang; Xiaopeng Li; Rebecca L. Agapov; Chrys Wesdemiotis; Mark D. Foster


Macromolecules | 2012

Dynamics of Surface Fluctuations on Macrocyclic Melts

Shih-Fan Wang; Zhang Jiang; Suresh Narayanan; Mark D. Foster


Archive | 2011

Surface Dynamics of Macrocyclic Polystyrene Films

Shih-Fan Wang; Mark D. Foster; Zhang Jiang; Suresh Narayanan


Bulletin of the American Physical Society | 2011

Surface Segregation of Small Macrocyclic

Shih-Fan Wang; Xiaopeng Li; Renfeng Hu; Bulent Akgun; Rebecca L. Agapov; Chrys Wesdemiotis; David T. Wu; Mark D. Foster


Bulletin of the American Physical Society | 2009

Well-defined branched polymers for studying surface segregation

Boxi Liu; Shih-Fan Wang; Roderic P. Quirk; Mark D. Foster

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David T. Wu

Colorado School of Mines

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Suresh Narayanan

Argonne National Laboratory

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Zhang Jiang

Argonne National Laboratory

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Bulent Akgun

National Institute of Standards and Technology

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Rebecca L. Agapov

Oak Ridge National Laboratory

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