Influence of the Degree of Sulfonation on the Structure and Dynamics of Sulfonated Polystyrene Copolymers

Castagna, Alicia; Wang, Wen-Qin; Winey, Karen I.; Runt, James

doi:10.1021/ma102206f

Cited by 50 publications

(74 citation statements)

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“…In our previous work we identified the MaxwellÀWagner Sillars interfacial polarization process in dielectric spectra of SPS9.5 and SPS6.7, both of which were demonstrated to exhibit acid group aggregation. 18 This relaxation arises from space charge accumulation at boundaries between phases in an inhomogeneous media. 32,33 It is also observed for the Zn neutralized ionomers ( Figure 11) and is highly sensitive to the degree of neutralization.…”

Section: Articlementioning

confidence: 99%

“…Atactic polystyrene, purchased from Pressure Chemical (M w = 123 kg/mol, PDI = 1.06), was sulfonated according a previously published procedure. 18 SPS acid copolymers were neutralized by dissolving in a 90/10 v/v mixture of toluene/ methanol. A stoichiometric amount of Zn acetate was dissolved in a 50/50 v/v mixture of toluene/methanol and added slowly into the gently agitated SPS solution to achieve different degrees of neutralization.…”

Section: ' Introductionmentioning

confidence: 99%

“…18 In this publication we will focus on the effect of neutralizing these materials with zinc. In our investigation, morphology was characterized using X-ray scattering and scanning transmission electron microscopy (STEM) while the dynamics were investigated using dielectric relaxation spectroscopy (DRS).…”

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Structure and Dynamics of Zinc-Neutralized Sulfonated Polystyrene Ionomers

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Incorporating small fractions (typically <10 mol %) of ionic groups into polymer chains has been shown to have profound effects on thermal, mechanical, and charge transport properties. 1,2 These ionomers are used in a range of applications including performance coatings, packaging, membranes, and actuators. Ionic species tend to self-assemble into microphase-separated domains due to Coulombic interactions that serve as thermoreversible cross-links.Although ion aggregation and properties of ionomers have been studied extensively using a number of different techniques (including dynamic mechanical analysis (DMA), 3À5 rheology, 6 X-ray and neutron scattering, 2,7À11 and scanning transmission electron microscopy (STEM) 2,11À13 ) little is known about the effect of these ionic clusters on the molecular dynamics of this class of materials. Dielectric relaxation spectroscopy has been used to investigate the dynamics of some ionomers, predominantly on poly(styrene-co-methacrylic acid) and poly(ethyleneco-methacrylic acid) ionomers, 1,14,15 but very little has been done on sulfonated polystyrene. 16,17 We intend to elucidate the connection between aggregate morphology and dynamics by applying an integrated and systematic approach using sulfonated polystyrene (SPS) as a model ionomer.In our previous paper, we demonstrated that sulfonation has an important effect on the structure and dynamics of sulfonated polystyrene acid copolymers (having 3.5, 6.7, and 9.5 mol % sulfonation), the precursors to the ionomers investigated herein. 18 In this publication we will focus on the effect of neutralizing these materials with zinc. In our investigation, morphology was characterized using X-ray scattering and scanning transmission electron microscopy (STEM) while the dynamics were investigated using dielectric relaxation spectroscopy (DRS).' EXPERIMENTAL SECTION Sample Preparation. Atactic polystyrene, purchased from Pressure Chemical (M w = 123 kg/mol, PDI = 1.06), was sulfonated according a previously published procedure. 18 SPS acid copolymers were neutralized by dissolving in a 90/10 v/v mixture of toluene/ methanol. A stoichiometric amount of Zn acetate was dissolved in a 50/50 v/v mixture of toluene/methanol and added slowly into the gently agitated SPS solution to achieve different degrees of neutralization. The reaction was held at 50°C for 2 h. In this publication the ionomers are designated as SPSx-yZn, where x is the mole fraction of sulfonation (3.5, 6.7, or 9.5) and y is the percent neutralization (0, 25, 50, 75, and 100).The neutralized ionomers were solvent cast at ambient conditions, air-dried for 1À2 days, and then dried under vacuum at 120°C for at least 24 h. Ionomers with T g around or above 120°C (SPS6.7-yM and SPS9.5-yM) were further annealed at ∼ T g þ 20°C for another day. The dried ionomer films were then hot pressed at 160°C and used for X-ray scattering, STEM imaging, and dielectric spectroscopy. All materials ABSTRACT: Scanning transmission electron microscopy (STEM), X-ray scattering, and dielectric relaxa...

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Section: Articlementioning

confidence: 99%

Section: ' Introductionmentioning

confidence: 99%

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Structure and Dynamics of Zinc-Neutralized Sulfonated Polystyrene Ionomers

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“…37,60,61 Based on this consideration, the precise positioning of acid groups has recently been attempted, and the resultant PEMs having controlled ionic sequencing revealed well-defined ionic aggregates with a higher degree of organization in comparison to the conventional systems having a statistical distribution of acid groups. 16,[62][63][64] Although such issues in diverse sulfonated PEMs have clearly been elucidated, no consensus has thus far been reached concerning the role of the phase separation between the hydrophilic phases and hydrophobic domains in determining the membrane transport properties. The issue of phase separation should be fundamentally important in unraveling the structure-property relationship of sulfonated PEMs; however, the ill-defined, process-dependent, heterogeneous structures of many sulfonated PEMs have hampered the acquisition of quantitative information on them.…”

Section: Introductionmentioning

confidence: 99%

Ion transport in sulfonated polymers

Park

Kim

2013

J Polym Sci B Polym Phys

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As the focus on proton exchange fuel cells continues to escalate in the era of alternative energy systems, the rational design of sulfonated polymers has emerged as a key technique for enhancing device efficiency. Although the synthesis and characterization of a wide variety of sulfonated polymers have been extensively reported over the last decade, quantitative understanding of the factors governing the ion transport properties of these materials is in its infancy. In this article, we describe the current understanding of the thermodynamics and ion transport in sulfonated polymers. Various strategies for accessing improved transport properties of sulfonated polymers are presented by focusing on their structure-property relationship. The major accomplishment of obtaining well-defined morphologies for these sulfonated polymers is highlighted as a novel means of controlling the transport properties. Recent studies on the thermodynamics, morphologies, and anhydrous transport properties of sulfonated block copolymers comprising ionic liquids, geared towards high temperature polymer electrolyte membranes as a prospective technology, are also expounded.

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“…The "conduction free" dielectric loss was determined using the derivative method described in our previous papers. 12,13 ' RESULTS AND DISCUSSION Morphology. Spherical bright regions corresponding to Csrich ionic aggregates within a PS matrix of lower average atomic number are observed in HAADF STEM images of the Csneutralized SPS ionomers ( Figure 1).…”

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Influence of Cation Type on Structure and Dynamics in Sulfonated Polystyrene Ionomers

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Ionomers, polymers containing ionic functionality, have been a significant research focus over the past 5 decades. 1 Their enhanced properties, such as toughness and moduli, over their non-ionic counterparts make these materials attractive for a breadth of applications including performance coatings, films, adhesives, and tough thermoplastic parts. 1 This property enhancement arises from the microphase separation of ionic species into aggregates due to strong electrostatic interactions, which behave as thermoreversible cross-links. 1 Extensive investigation of the morphology of these ionic rich domains and resulting mechanical and dynamic mechanical properties of these materials has been performed. 1À11 However, the fundamental connection between aggregate structure and molecular dynamics is not well-defined. Dielectric relaxation spectroscopy (DRS) is a powerful tool for probing molecular dynamics and can reveal information about segmental chain motion, ion motion and polarization processes.In an effort to elucidate the correlation between ionic aggregate structure and dynamics, we systematically investigated a model ionomer, sulfonated polystyrene (SPS), with varying degrees of sulfonation and neutralization as well as neutralizing ion types, utilizing X-ray scattering, scanning transmission electron microscopy, and DRS. In two previous publications, we discussed the effect of sulfonation on the structure and dynamics of SPS acid copolymers and the influence of neutralizing these copolymers with zinc. 12,13 In the current paper we examine the role of neutralizing ion type (Na, Cs, and Zn) and discuss the effects of sulfonation and neutralization on structure and dynamics of Cs-and Na-neutralized SPS.' EXPERIMENTAL SECTION Sample Preparation. Atactic polystyrene, purchased from Pressure Chemical (M w = 123 kg/mol, PDI = 1.06), was sulfonated according to a previously published procedure. 12 SPS acid copolymers were neutralized by dissolving in a 90/10 v/v mixture of toluene/methanol. A stoichiometric amount of metal acetate (Na, Cs, and Zn) was dissolved in a 50/50 v/v mixture of toluene/methanol and added slowly into the gently agitated SPS solution to achieve different percentages of neutralization. The reaction was held at 50°C for 2 h. In this publication, the ionomers are designated as SPSxÀyM, where x is the mole percent of sulfonation (3.5, 6.7, or 9.5), y is the percent neutralization (0, 25, 50, 75, and 100), and M is the neutralizing ion (Na, Cs, or Zn). In total, 23 polymers were studied and are listed in Table 1.The neutralized ionomers were solvent cast at ambient conditions, air-dried for 1À2 days, and then dried under vacuum at 120°C for at least 24 h. Ionomers with T g around or above 120°C (SPS6.7ÀyM and SPS9.5ÀyM) were further annealed at ∼T g þ 20°C for another day. The dried ionomer films were then hot pressed at 160°C and used for X-ray scattering, STEM imaging, and dielectric spectroscopy. All materials were stored in vacuum desiccators prior to characterization. Selected samples were sent ...

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Influence of the Degree of Sulfonation on the Structure and Dynamics of Sulfonated Polystyrene Copolymers

Cited by 50 publications

References 34 publications

Structure and Dynamics of Zinc-Neutralized Sulfonated Polystyrene Ionomers

Structure and Dynamics of Zinc-Neutralized Sulfonated Polystyrene Ionomers

Ion transport in sulfonated polymers

Influence of Cation Type on Structure and Dynamics in Sulfonated Polystyrene Ionomers

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