Simulation insights on the structure of nanoscopically confined poly(ethylene oxide)

Abstract

ABSTRACT:We employ atomistic computer modeling to investigate the structure and morphology of poly(ethylene oxide) (PEO) chains confined in 1-nm slit pores defined by montmorillonite silicate layers. Molecular dynamics computer simulations reveal the Li ϩ cations to be located in the immediate vicinity of the silicate surfaces and PEO to adopt highly amorphous conformations in a liquidlike bilayer across the slit pores. Despite the orienting influence of the parallel stacked silicate walls, PEO shows no indication of crystallinity or periodic ordering; in fact, for all temperatures simulated, it is less ordered than the most disordered bulk PEO system. These amorphous PEO film configurations are attributed to the combination of severe spatial confinement and the strong coordination of ether oxygens with the alkali cations present in the interlayer gallery. These conclusions challenge the picture traditionally proposed for intercalated PEO, but they agree with a plethora of experimental observations. Indicatively, the simulation predictions are confirmed by wide-angle neutron scattering and differential scanning calorimetry experiments on PEO/montmorillonite intercalates.

Tailored Polyethylene Nanocomposite Sealants: Broad-Range Peelable Heat-Seals Through Designed Filler/Polymer Interfaces

“…Thus, for all the data shown -seal strengths, ATR-FT-IR spectra, ESEM and EDS spectra -the results are consistent only when the interfacial strength increases from weakest between PE and EVA/clay, to weak between PE and clay, to stronger between PE and EVA, in agreement with theoretical and simulation considerations [46,[50][51][52]. Consequently, the origins of the peelable nature of this PE/EVA/clay nanocomposite sealant can be traced to its cohesive failure, mediated by weak interfaces within the nanocomposite, as is schematically illustrated in Fig.…”

Mesoporous silica as nanoreactor for olefin polymerization

“…Okamoto et al argued that it might be difficult for intercalated polypropylene chains in PP/ clay nanocomposites to crystallize because of the limited space between clay layers (2-3 nm) [28]. Manias et al using computer simulations, reported that the intercalated polymer chains in PEO/clay nanocomposite adopt a disordered, liquid-like structure with no crystallinity or periodic ordering of the C-C-O bonds [29]. Although herein we can not give definitive argumentation for the molecular mechanisms behind the disappearance of the PP melting point in our almost-one-dimensional confined polypropylene in Ti-MCM-41 mesopores, we tentatively attribute this behavior to the same confinements as those in pseudo-two-dimensional confinement.…”

Phase behavior of temperature-responsive polymers with tunable LCST: An equation-of-state approach

“…where ω k is the number of configurations available to a r k -mer in the close-packed pure state; ω k is treated as a constant and will cancel out in all applications of interest here (this is not obvious in cases of PEO physisorption on solid surfaces, or in extreme, sub-R g , confinements [22][23][24]). …”