Crystallization behavior of polyethylene oxide/para‐nitroaniline microdispersed composites
TL;DR: In this paper, the crystallization behavior of polyethylene oxide (PEO) containing microdispersed nonlinear optical chromophores such as para-nitroaniline (PNA) has been investigated with respect to composition and different methods of film preparation techniques.
Abstract: The crystallization behavior of polyethylene oxide (PEO) containing microdispersed nonlinear optical chromophores such as para-nitroaniline (PNA) has been investigated with respect to composition and different methods of film preparation techniques viz. solvent casting, melt casting, and powder molding. Large variations in the intensities of major reflections, 012 and 101, from PNA crystallites were observed depending on the composition as well as the method of preparation. The morphology of the samples examined under cross-polarizing conditions revealed highly birefringent crystallites dispersed in the spherulitic morphology of the PEO matrix in contrast to weakly birefringent crystals of the additive by itself. At high concentrations exceeding 45 wt % the PNA crystals act as substrates for the growth of polymer crystals. These results have been explained on the basis of intermolecular interaction as well as good lattice match between the crystalizing components, leading to preferential growth of the crystals along a certain direction. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1127–1137, 1997
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TL;DR: In this paper, a series of poly(ethylene oxide)/sodium montmorillonite hybrids were synthesized utilizing melt intercalation with compositions covering the complete range from pure polymer to pure clay.
Abstract: The polymer chain conformation under confinement and the morphology of the nanohybrid materials are investigated in hydrophilic polymer/layered silicate nanocomposites. A series of poly(ethylene oxide)/sodium montmorillonite hybrids were synthesized utilizing melt intercalation with compositions covering the complete range from pure polymer to pure clay. Intercalated nanocomposites with mono- and bilayers of PEO chains are obtained in all cases. The intercalated chains as well as the ones adsorbed on the outer surface of the clay particles remain purely amorphous; their conformation, however, exhibits different characteristics from those of the amorphous neat polymer melt. It is only for compositions where a large amount of excess polymer exists outside the completely full galleries that the polymer crystallinity is recovered.
105 citations
TL;DR: This article provides a review of research activities mainly in the laboratory on polymer dynamics under severe confinement utilizing different polymer systems: polar and non-polar polymers were mixed with hydrophilic or organophilic silicates, respectively, whereas hyperbranchedpolymers were studied in an attempt to probe the effect of polymer-surface interactions.
Abstract: The static and dynamic behavior of polymers in confinement close to interfaces can be very different from that in the bulk. Among the various geometries, intercalated nanocomposites, in which polymer films of ∼1 nm thickness reside between the parallel inorganic surfaces of layered silicates in a well-ordered multilayer, offer a unique avenue for the investigation of the effects of nanoconfinement on polymer structure and dynamics by utilizing conventional analytical techniques and macroscopic specimens. In this article, we provide a review of research activities mainly in our laboratory on polymer dynamics under severe confinement utilizing different polymer systems: polar and non-polar polymers were mixed with hydrophilic or organophilic silicates, respectively, whereas hyperbranched polymers were studied in an attempt to probe the effect of polymer–surface interactions by altering the number and the kinds of functional groups in the periphery of the branched polymers. The polymer dynamics was probed by quasielastic neutron scattering and dielectric relaxation spectroscopy and was compared with that of the polymers in the bulk. In all cases, very local sub-Tg processes related to the motion of side and/or end groups as well as the segmental α-relaxation were identified with distinct differences recorded between the bulk and the confined systems. Confinement was found not to affect the very local motion in the case of the linear chains whereas it made it easier for hyperbranched polymers due to modifications of the hydrogen bond network. The segmental relaxation in confinement becomes faster than that in the bulk, exhibits Arrhenius temperature dependence and is observed even below the bulk Tg due to reduced cooperativity in the confined systems.
47 citations
TL;DR: In this article, the structure of polymeric composite based on spontaneous precipitation of sodium [3-cobalt(III) bis(1,2-dicarbollide)], NaCoD, with poly(ethylene oxide), PEO, in salted aqueous solutions was studied.
Abstract: We studied a structure of polymeric composite based on spontaneous precipitation of sodium [3-cobalt(III) bis(1,2-dicarbollide)], NaCoD, with poly(ethylene oxide), PEO, in salted aqueous solutions. Although the solid nanocomposite, which can be considered as a homogeneous matter, cannot form monocrystals due to the high flexibility of PEO chains, we can characterize the PEO/NaCoD structure by means of solid state NMR spectroscopy, from WAXS reflections and with help of already published structures of related systems. It indicates that the layered structure of solid NaCoD and the helical crystalline structure of PEO have disappeared after their mutual interaction. The NMR results clearly show that CoD– anions are regularly dispersed within the PEO matrix, which consists of two distinct types of polymeric chains: one part interacting with dicarbollide clusters and the second one acting as a ligand of sodium counterions that also form regular pattern within the composite.
37 citations
Journal Article•
TL;DR: In this article, a series of poly(ethylene oxide)/sodium montmorillonite hybrids were synthesized utilizing melt intercalation with compositions covering the complete range from pure polymer to pure clay.
Abstract: The polymer chain conformation under confinement and the morphology of the nanohybrid materials are investigated in hydrophilic polymer/layered silicate nanocomposites. A series of poly(ethylene oxide)/sodium montmorillonite hybrids were synthesized utilizing melt intercalation with compositions covering the complete range from pure polymer to pure clay. Intercalated nanocomposites with mono- and bilayers of PEO chains are obtained in all cases. The intercalated chains as well as the ones adsorbed on the outer surface of the clay particles remain purely amorphous; their conformation, however, exhibits different characteristics from those of the amorphous neat polymer melt. It is only for compositions where a large amount of excess polymer exists outside the completely full galleries that the polymer crystallinity is recovered.
23 citations
TL;DR: In this article, the authors showed that the glass transition temperature can be controlled by varying the poly(ethylene oxide) (PEO) content and the length of the PEO side chain.
17 citations