The self‐diffusion of macromolecules in binary blends of poly(ethylene glycol)

Abstract

The concentration and molecular mass dependencies of the self-diffusion coefficients were obtained for higher molecular mass component in binary blends of the homopolymer poly(ethylene glycol) (PEG) by a nuclear magnetic resonance method with pulsed magnetic field gradient. The shape of the diffusion decay and its dependence on the diffusion observation time in binary PEG blends have been investigated. The experimental results were explained by hypothesizing the existence of cluster formation in polymer melts and polymer blends and the possibility of molecular exchange between clusters. The entanglement time in such systems was evaluated.

Impact of Molecular Weight on Miscibility and Interdiffusion between Poly(N‐vinyl pyrrolidone) and Poly(ethylene glycol)

“…[42][43][44] Diffusion measurements for slightly interacting polymers in the molten state and concentrated polymer solutions have been reported to be approximately consistent with the reptation model, which predicts that b ¼ 2 in Equation (3) for polymers with a MW above a critical value, M e , which is the molecular weight of the polymer chain between entanglements. [6,16,18,45] For short-chain polymers with a MW below M e , diffusion can be modeled successfully by considering a Rouse-like motion of monomer beads connected by entropic springs. Such a model leads to b ¼ 1 in Equation (3).…”

“…[1][2][3][4][5][6][7][8][9] Diffusion in polymer systems is widely recognized to be closely related to the miscibility of diffusing species, [2][3][4][5]7,10] and the diffusion process is appreciably affected by the nature, structure, [11][12][13] and molecular weight of the polymer. [6,[14][15][16] In particular, for only slightly interacting polymers, diffusion of short chains in polymer melts or in concentrated polymer solutions can be successfully modeled by considering a Rouse-like motion of monomer beads connected by ''entropic springs''. [17,18] For longchain polymers diffusing within melts or concentrated solutions, diffusion proceeds by a snake-like motion due to chain entanglements or topological constraints exerted on long chains by their neighbors.…”

Self-diffusion and nuclear magnetic relaxation of dendritic macromolecules in solutions

“…The va[ues D i and Pi of the corresponding components of the system studied are obtained from the analysis of the DD shape [29,30,34]. The use of a relatively high value of PFG (for instance, g,,~x = 30-50 T/m) permits one to measure the diffusion rates of the order of 10-~3-10 -~5 m2/s [38][39][40][41][42][43] characteristic, in particular, for polymers with molecular weights high enough in concentrated solutions and melts.…”

“…In spite of its specific topology, a dendrimer represents a macromofecule composed, s~mi-lar to the typical polymeric chains, of the monomeric units: repeat units and Pulse sequence of the stimulated spin-echo [37] terminal groups. On the basis of this fact, the analysis of experimental data has been made within the frames of basic aspects of de Gennes theory of dynamic scaling [44] and approaches [29,40,42] developed by the examples of analyzing the concentration and molecular-mass (M) dependences of D for various linear polymers.…”

“…It was also observed that the shape of DDs does not depend on the diffusion time t a. This means that there are no reasons to talk about the existence of macromolecular associations, which could existas the analogous formations (clusters) present in solutions of linear flexible chain polymers [38][39][40]42], in the dendrimer solutions studied.…”