Abstract
Single-chain polymer nanoparticles (SCNPs) obtained through chain collapse by intramolecular cross-linking are attracting increasing interest as components of all-polymer nanocomposites, among other applications. We present a dielectric relaxation study on the dynamics of mixtures of poly(vinyl methyl ether) (PVME) and polystyrene (PS)-based SCNPs with various compositions. Analogous dielectric measurements on a miscible blend of PVME with the linear precursor chains of the SCNPs are taken as reference for this study. Both systems present completely different behaviors: While the blend with the linear precursor presents dynamics very similar to that reported for PVME/PS miscible blends, in the PVME/SCNP mixtures there are an appreciable amount of PVME segments that are barely affected by the presence of SCNPs, which nearly vanishes only for mixtures with high SCNP content. Interestingly, in the frame of a simple two-phase system, our findings point towards the existence of a SCNP-rich phase with a constant PVME fraction, regardless of the overall concentration of the mixture. Moreover, the dynamics of the PVME segments in this SCNP-rich phase display an extreme dynamic heterogeneity, a signature of constraint effects.
Highlights
Polymer mixing is a convenient method to obtain materials with certain desirable properties, starting from existing materials which do not fit the prescribed requirements
When considering the glass transition phenomenon, an open question is how such mixtures of linear polymers with single-chain polymer nanoparticles (SCNPs) compare with conventional polymer-polymer mixtures; namely, with miscible polymer blends [1]. We have addressed this question by investigating the dynamic behavior around the glass transition of poly(vinyl methyl ether) (PVME) mixtures with PS-based SCNPs by means of band dielectric spectroscopy (BDS), and compared the results with those from a miscible blend of PVME with the linear precursor of the SCNPs
We have investigated the dynamics of the PVME segments in mixtures of PVME and polystyrenebased SCNPs with several concentrations by means of BDS, taking, as reference, a PVME blend with the linear precursor chains of the SCNPs
Summary
Polymer mixing is a convenient method to obtain materials with certain desirable properties, starting from existing materials which do not fit the prescribed requirements Within this broad range of materials, miscible polymer blends have been widely used for easy tuning of the glass transition temperature (Tg ) of the resulting mixture [1]. It is well established that the glass transition of miscible polymer blends extends over a broad temperature range [1] in the interval between the two Tg values of the homopolymers. This occurs as a result of the superposition of disparate contributions from. A prototype of such a miscible polymer blend is the system poly(vinyl methyl ether)/polystyrene (PVME/PS) [6,7], where PVME is basically the only dielectrically active component, as the dielectric relaxation strength at the glass transition temperature of PS is much weaker than that of PVME
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