Ionic aggregates in Zn‐ and Na‐neutralized poly(ethylene‐<i>ran</i>‐methacrylic acid) blown films

Benetatos, Nicholas M.; Winey, Karen I.

doi:10.1002/polb.20623

Cited by 19 publications

(19 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In a paper that describes STEM and SAXS studies of Na-EMAA; a featureless micrograph is the result even though the SAXS spectra shows a clear peak; in fact, the SAXS pattern is identical to a sample that shows clear aggregation [59]. No explanation was given for the inconsistency.…”

Section: Ionomer Synthesismentioning

confidence: 99%

Review and critical analysis of the morphology of random ionomers across many length scales

Grady

2008

Polymer Engineering & Sci

101

View full text Add to dashboard Cite

This review presents a description of what is known about ionomer morphology. All papers on ionomer morphology are not included in this review; but all relevant questions about ionomer morphology are posed and answered as completely as possible. The review is critical; that is, reasons are given for morphologies that are deemed to be more or less likely. The review is organized along three length scales: sub-nanometer, nanometer to 10 nm, and greater than 10 nm. Within each length scale, all three phases are considered: crystalline, amorphous, and ionic aggregate. The purity of the three phases, the arrangement of atoms in the three phases, the size and shape of the three phases, and their arrangements in space relative to each other are explored in this review. A model for the shape of aggregates in ionomers that have well-ordered internal environments is presented. This model proposes that aggregates are fundamentally planar, but will ''roll up'' into tubes or other related structures in order to reduce the number of atoms at aggregate edges. This model was developed primarily based on the varied morphologies ionomers have shown in electron micrographs, but is consistent with other indirect measurements of ionomer morphology.

show abstract

Section: Ionomer Synthesismentioning

confidence: 99%

Review and critical analysis of the morphology of random ionomers across many length scales

Grady

2008

Polymer Engineering & Sci

101

View full text Add to dashboard Cite

show abstract

“…The most common model used to interpret ionomer morphologies is the modified hard-sphere (MHS) model, which assumes monodisperse spherical ionic aggregates with liquid-like order and a separation of closest approach that is greater than the aggregate diameter. − To implement the MHS model, it is advisible to validate its assumptions through direct visualization of aggregates. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) has been successfully implemented for direct imaging of ionic aggregates in some ionomer systems. − This technique captures micrographs that are two-dimensional projections of ionic aggregates (∼1 nm) densely arranged in 3-D, and the images possess considerable overlap between the aggregates, which complicates interpretation. Thus, compact aggregates may be indistinguishable from elongated ones in the transmission images, especially because the microtomed samples for electron microscopy are typically ≥50 nm in thickness.…”

Section: Introductionmentioning

confidence: 99%

Direct Comparisons of X-ray Scattering and Atomistic Molecular Dynamics Simulations for Precise Acid Copolymers and Ionomers

Buitrago¹,

Bolintineanu

Seitz³

et al. 2015

Macromolecules

Self Cite

118

View full text Add to dashboard Cite

Designing acid-and ion-containing polymers for optimal proton, ion, or water transport would benefit profoundly from predictive models or theories that relate polymer structures with ionomer morphologies. Recently, atomistic molecular dynamics (MD) simulations were performed to study the morphologies of precise poly-(ethylene-co-acrylic acid) copolymer and ionomer melts.Here, we present the first direct comparisons between scattering profiles, I(q), calculated from these atomistic MD simulations and experimental X-ray data for 11 materials. This set of precise polymers has spacers of exactly 9, 15, or 21 carbons between acid groups and has been partially neutralized with Li, Na, Cs, or Zn. In these polymers, the simulations at 120 °C reveal ionic aggregates with a range of morphologies, from compact, isolated aggregates (type 1) to branched, stringy aggregates (type 2) to branched, stringy aggregates that percolate through the simulation box (type 3). Excellent agreement is found between the simulated and experimental scattering peak positions across all polymer types and aggregate morphologies. The shape of the amorphous halo in the simulated I(q) profile is in excellent agreement with experimental I(q). The modified hard-sphere scattering model fits both the simulation and experimental I(q) data for type 1 aggregate morphologies, and the aggregate sizes and separations are in agreement. Given the stringy structure in types 2 and 3, we develop a scattering model based on cylindrical aggregates. Both the spherical and cylindrical scattering models fit I(q) data from the polymers with type 2 and 3 aggregates equally well, and the extracted aggregate radii and inter-and intra-aggregate spacings are in agreement between simulation and experiment. Furthermore, these dimensions are consistent with real-space analyses of the atomistic MD simulations. By combining simulations and experiments, the ionomer scattering peak can be associated with the average distance between branches of type 2 or 3 aggregates. This direct comparison of X-ray scattering data to the atomistic MD simulations is a substantive step toward providing a comprehensive, predictive model for ionomer morphology, gives substantial support for this atomistic MD model, and provides new credibility to the presence of stringy, branched, and percolated ionic aggregates in precise ionomer melts.

show abstract

“…Ionomers derived from copolymers of ethylene and methacrylic acid (MAA) have been well-known since the 1960s, principally due to their versatile mechanical properties and chemical stability. − , Since these materials have relatively low MAA content and MAA units are randomly placed in the highly branched polyethylene (PE) chains, long PE sequences exist and are capable of crystallization. The microstructure–property–processing relationships of these traditional ionomers have been the subject of many previous publications. − …”

Section: Introductionmentioning

confidence: 99%

Dynamics of Precise Ethylene Ionomers Containing Ionic Liquid Functionality

Choi

Middleton²,

Soccio

et al. 2015

Macromolecules

Self Cite

View full text Add to dashboard Cite

This paper presents the first findings on the molecular dynamics of the remarkable new class of linear and precisely functionalized ethylene copolymers. Specifically, we utilize broadband dielectric relaxation spectroscopy to investigate the molecular dynamics of linear polyethylene (PE)-based ionomers containing 1-methylimidazolium bromide (ImBr) pendants on exactly every 9th, 15th, or 21st carbon atom, along with one pseudorandom analogue. We also employed FTIR spectroscopy to provide insight into local ionic interactions and the nature of the ordering of the ethylene spacers between pendants. Prior X-ray scattering experiments revealed that the polar ionic groups in these ionomers self-assemble into microphase-separated aggregates dispersed throughout the nonpolar PE matrix. We focus primarily on the dynamics of the segmental relaxations, which are significantly slowed down compared to linear PE due to ion aggregation. Relaxation times depend on composition, the presence of crystallinity, and microphase-separated morphologies. Segmental relaxation strengths are much lower than predicted by the Onsager theory for mobile isolated dipoles but much higher than linear PE, demonstrating that at least some ImBr pendants participate in the segmental process. Analysis of the relaxation strengths using the Kirkwood g correlation factor demonstrates that ca. 10−40% of the ImBr ion dipoles (depending on copolymer composition and temperature) participate in the segmental motions of the precise ionomers under study, with the remainder immobilized or having net antiparallel arrangements in ion aggregates.

show abstract

Ionic aggregates in Zn‐ and Na‐neutralized poly(ethylene‐ran‐methacrylic acid) blown films

Cited by 19 publications

References 12 publications

Review and critical analysis of the morphology of random ionomers across many length scales

Review and critical analysis of the morphology of random ionomers across many length scales

Direct Comparisons of X-ray Scattering and Atomistic Molecular Dynamics Simulations for Precise Acid Copolymers and Ionomers

Dynamics of Precise Ethylene Ionomers Containing Ionic Liquid Functionality

Contact Info

Product

Resources

About