English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Zendy Plus

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Zendy Tools

Zendy Open

The mechanism that leads to different fragility values upon approaching the glass transition remains a topic of active discussion. Many researchers are trying to find an answer in the properties of the frozen glassy state. Following this approach, we focus here on a previously proposed relationship between the fragility of glass-formers and their nonergodicity factor, determined by inelastic X-ray scattering (IXS) in the glass. We extend this molecular liquid study to two model polymers; polystyrene (PS) and poly- isobutylene (PIB);for which we change the molecular weight. Polymers offer the opportunity to change the fragilitywithoutalteringthechemicalstructure,justbychangingthechainlength.Thus,wespecificallychose PS and PIB because they exhibit opposite dependences of fragility with molecular weight. Our analysis for thesetwopolymersrevealsnouniquecorrelationbetweenthefragilityandthenonergodicityparameter.Even after a recently suggested correction for a possible contribution of the β relaxation, the correlation is not restored. We discuss possible causes for the failure of the "fragility-nonergodicity factor" correlation, emphasizing the features that are specific to polymers. We speculate that polymers might have specific contributions to fragility related to the chain connectivity that are absent in nonpolymeric systems.

The Role of Chain Length in Nonergodicity Factor and Fragility of Polymers