Small-Angle X-ray Scattering of Polymers

Chu, Benjamin; Hsiao, Benjamin S.

doi:10.1021/cr9900376

Cited by 365 publications

(287 citation statements)

References 322 publications

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“…This is usually based on small angle x-ray scattering data, which however do not provide a real image of the structure [15]. A closed theory about the development of the various morphologies is not available.…”

Section: Introductionmentioning

confidence: 99%

Thermal Analysis of Phase Transitions and Crystallization in Polymeric Fibers

Steinmann¹,

Walter²,

Beckers³

et al. 2013

Applications of Calorimetry in a Wide Context - Differential Scanning Calorimetry, Isothermal Titration Calorimetry and Microca

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Section: Introductionmentioning

confidence: 99%

Thermal Analysis of Phase Transitions and Crystallization in Polymeric Fibers

Steinmann¹,

Walter²,

Beckers³

et al. 2013

Applications of Calorimetry in a Wide Context - Differential Scanning Calorimetry, Isothermal Titration Calorimetry and Microca

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“…[44][45][46] More details related to various aspects of SAXS analysis of polymers are covered in these review articles. 47,48 The morphologies of the pristine SPEEK and SPEEK composite membranes are reflected by the combined SAXS data, which are shown in Figure 2. The desmeared data are plotted on an absolute scale, i.e., the differential scattering cross section d per unit solid angle d , per unit sample volume …”

Section: Resultsmentioning

confidence: 99%

Microstructure-Property Relationships in Sulfonated Polyether Ether Ketone/Silsesquioxane Composite Membranes for Direct Methanol Fuel Cells

Yun

Parrondo

Zhang

et al. 2014

J. Electrochem. Soc.

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The synthesis, structural characterization, and performance evaluation of silsesquioxane -based sulfonated polyether ether ketone (SPEEK) composite membranes for direct methanol fuel cell (DMFC) applications are presented. 3-(trihydroxysilyl)-1-propanesulfonic acid (TPS) was used as a silsesquioxane (SQO) precursor. Two batches of SPEEK membranes with ion exchange capacities (IEC) of 1.06 ± 0.02 meq/g (denoted by SPEEK11) and 1.34 ± 0.05 meq/g (denoted by SPEEK13) were prepared. The SQO loadings in the composite membranes ranged from 5 wt% to 30 wt%. The ionic conductivity of the SPEEK13 membrane (at 60 • C) increased by up to 15 mS/cm (27%) upon incorporation of 15 wt% TPS-derived SQO, while the methanol permeability was at best slightly lowered (5-10%). The morphological changes in the composite membranes resulting from the introduction of SQO was studied by small angle X-ray scattering. The sharp decrease in conductivity with TPS loading was attributed to these changes in the membrane ionic domains. The performance of DMFCs with these SPEEK/SQO composite membranes was governed more by the proton conductivity than the methanol crossover. Compared to pristine SPEEK, the improved DMFC performance (at 60 • C using air and 3M methanol) of SPEEK11+5 wt% TPS and SPEEK13+5 wt% TPS composite membranes (187 mA cm −2 and 240 mA cm −2 at 0.4 V, respectively) was observed. The crossover of methanol from the anode to cathode through the ionic membrane remains one of the challenging obstacles in direct methanol fuel cells (DMFC). Methanol crossover to the cathode leads to a reduction in the operating voltage due to depolarization and mixed potential, and concurrent contamination of the Pt catalyst.1 Perfluorinated membranes such as Nafion have traditionally been used for DMFC systems. However, even though Nafion provides high conductivity and chemical stability, it exhibits large methanol permeability, resulting in relatively poor DMFC performance.2-6 Composite membranes, prepared by adding inorganic materials to an ion conducting polymer matrix, have been proposed and studied in an attempt to reduce methanol crossover.7 Sulfonated polyether ether ketone (SPEEK) is a good choice as a matrix for DMFC applications because it is relatively inexpensive and has lower methanol permeability compared to Nafion. It also exhibits good thermal stability, good mechanical strength and reasonable ionic conductivity.

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“…SAXS experiments were carried out at the beamline X27C of the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory (BNL). In order to obtain high-quality SAXS patterns for the delicate quantitative analysis, a three pinhole collimation system was used to reduce the beam divergence (Chu & Hsiao, 2001) and a vacuum sample chamber was introduced to lower the background scattering from air and Kapton windows. In order to ensure the absence of systematic errors introduced by the detection system, two different types of detector technology (imaging plates and charge-coupled device) with different counting and readout mechanisms were used to record the scattering pattern from the same sampling volume, showing an excellent agreement.…”

Section: Experimental and Data Analysismentioning

confidence: 99%