Influence of chain topology on polymer crystallization: poly(ethylene oxide) (PEO) rings vs. linear chains

Abstract

The absence of entanglements, the more compact structure and the faster diffusion in melts of cyclic poly(ethylene oxide) (PEO) chains have consequences on their crystallization behavior at the lamellar and spherulitic length scales. Rings with molecular weight below the entanglement molecular weight (M < M), attain the equilibrium configuration composed from twice-folded chains with a lamellar periodicity that is half of the corresponding linear chains. Rings with M > M undergo distinct step-like conformational changes to a crystalline lamellar with the equilibrium configuration. Rings melt from this configuration in the absence of crystal thickening in sharp contrast to linear chains. In general, rings more easily attain their extended equilibrium configuration due to strained segments and the absence of entanglements. In addition, rings have a higher equilibrium melting temperature. At the level of the spherulitic superstructure, growth rates are much faster for rings reflecting the faster diffusion and more compact structure. With respect to the segmental dynamics in their semi-crystalline state, ring PEOs with a steepness index of ∼34 form some of the "strongest" glasses.

Synthesis of macrocyclic poly(ethylene oxide)s containing a protected thiol group: a strategy for decorating gold surfaces with ring polymers

“…These differences can be probably attributed also to the cyclic topology, since in these two samples, the mass contribution of 3 in the polymer is of only 7 and 4 wt%. The lower T m values (out of equilibrium) found for the rings are in agreement with previous work of Floudas et al 21 on the study of the crystallization behavior of macrocyclic PEO by using standard DSC. It is important to note that our melting/crystallization temperatures are not comparable with their values since the cooling/heating rates used in both studies are different by a factor of 6000.…”

“…In fact, in those studies, the macrocycles were not PEO homopolymers but copolymers where PEO was one of the block components imparting amphiphilicity for generating micelles. [17][18][19] The study of macrocyclic PEO homopolymers has been mainly focused on their physical properties including their crystallization and folding 20,21 and ring dynamics. [22][23][24] Based on the inspiring results obtained by Benetti's group on C-PAOx-grafted surfaces, it is expected that cyclic PEO brushes on gold substrates also promote enhanced surface properties compared to linear PEO brushes.…”

An Ambient Temperature Electrolyte with Superior Lithium Ion Conductivity based on a Self‐Assembled Block Copolymer

“…Wide‐angle X‐ray scattering (WAXS) patterns at room temperature (Figure B) indicated crystalline PEO in the reference material both with and without LiTFSI through typical Bragg reflections at 14.6° (021), 15.1° (110), 19.1° (120), 22.1° (112), and 23.4° (032) . The absence of any reflexes from crystalline LiTFSI in the PEO/LiTFSI reference sample proved complete dissolution of the salt.…”

“…Wide-angle X-ray scattering (WAXS) patterns at room temperature ( Figure 2B)i ndicatedc rystalline PEO in the reference material both with and without LiTFSI through typical Bragg reflections at 14.68 (021), 15.18 (110), 19.18 (120), 22.18 (112), and 23.48 (032). [16] The absence of any reflexes from crystalline LiTFSI in the PEO/LiTFSI reference sample proved complete dissolution of the salt. The resultsf or the ISO-based system with its ultra-small PEO blocks were quite different with only weakr eflections for the neat polymer most likely from nano-crystalline PEO domains.…”

Viscoelastic Properties of Unentangled Multicyclic Polystyrenes

“…In materials science, cyclic polymers can be used as templates for the assembly of nanoparticles [7], building blocks for chemical gels [8] and surface modifiers to prevent nanoparticle aggregation [9,10]. In polymer physics, the absence of chain ends makes cyclic polymers unique in terms of structural (e.g., conformation, crystallization) and dynamic (both segmental and global) properties [11,12,13,14,15]. At the same time, the dynamics of entangled cyclic polymers are greatly influenced by the presence of tiny amounts of unlinked chains (often called contaminants [16,17]).…”