Starting from experimental macro-rheological data, we develop a fitting protocol that succeeded in the separation of the overlapping relaxation phenomena in the dissipative regime for a set of intrinsic healing polymers healing most effectively near their glass transition temperature Tg. To allow for a proper deconvolution, the rheological master curves are converted to a relaxation spectrum (H(τ)) and this is fitted using an optimized mechanical model, e.g. the Maxwell-Weichert model. The deconvolution of overlapping segmental mobility and reversible interactions is successfully demonstrated for a set of polyimide and polyamide polymers containing none, one and two reversible dynamic features near-Tg. Through the fitting parameters, the relaxation timescale of each feature and their apparent process enthalpies are obtained. The quantitative data obtained using the fitting protocol are then compared to macroscopic healing results. As a result, a clear correspondence between the energy stored by the system to accomplish reversible (e.g. H-bonds, π-π) and chain interdiffusion relaxation transitions and the healing efficiency of such polymers are obtained. The implementation of this protocol allows for a clearer identification of the relevant mechanisms in self-healing polymers and paves the way for the development of more efficiently healable polymeric systems.
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http://dx.doi.org/10.1039/c9cp00417c | DOI Listing |
R Soc Open Sci
January 2025
School of Computing and Information Systems, The University of Melbourne, Parkville, Victoria, Australia.
During the COVID-19 pandemic, both government-mandated lockdowns and discretionary changes in behaviour combined to produce dramatic and abrupt changes to human mobility patterns. To understand the socioeconomic determinants of intervention compliance and discretionary behavioural responses to epidemic threats, we investigate whether changes in human mobility showed a systematic variation by socioeconomic status during two distinct periods of the COVID-19 pandemic in Australia. We analyse mobility data from two major urban centres and compare the trends during mandated stay-at-home policies and after the full relaxation of nonpharmaceutical interventions, which coincided with a large surge of COVID-19 cases.
View Article and Find Full Text PDFSoft Matter
January 2025
Department of Chemical & Biomolecular Engineering, University of Houston, Houston, TX 77204, USA.
Microrheology has become an indispensable tool for measuring the dynamics of macromolecular systems. Yet, its ability to characterize polymer dynamics across spatiotemporal scales, which vary among polymers and concentration regimes, is limited by the selection of probe morphologies and sizes. Here, we introduce semiflexible M13 phage as a powerful microrheological probe able to circumvent these constraints to robustly capture the dynamics of polymeric solutions across decades of concentrations, sizes, and ionic conditions.
View Article and Find Full Text PDFJ Phys Chem B
January 2025
Chemical, Biological and Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, J. D. Block, Sec.III, Salt Lake, Kolkata, West Bengal 700 098, India.
We investigated the temperature dependence of the intermolecular dynamics, including intermolecular vibrations and collective orientational relaxation, of one of the most typical deep eutectic solvents, reline, using femtosecond Raman-induced Kerr effect spectroscopy (fs-RIKES), subpicosecond optical Kerr effect spectroscopy (ps-OKES), and molecular dynamics (MD) simulations. According to fs-RIKES results, the temperature-dependent intermolecular vibrational band peak at ∼90 cm exhibited a redshift with increasing temperature. The density-of-state (DOS) spectrum of reline by MD simulations reproduced this fs-RIKES spectral feature.
View Article and Find Full Text PDFPolymers (Basel)
December 2024
Department of Chemistry, Faculty of Food Science and Biotechnology, University of Life Sciences in Lublin, 20-950 Lublin, Poland.
Recovering the relaxation spectrum, a fundamental rheological characteristic of polymers, from experiment data requires special identification methods since it is a difficult ill-posed inverse problem. Recently, a new approach relating the identification index directly with a completely unknown real relaxation spectrum has been proposed. The integral square error of the relaxation spectrum model was applied.
View Article and Find Full Text PDFJ Phys Chem B
January 2025
Nordbayerisches NMR-Zentrum, Universität Bayreuth, 95447 Bayreuth, Germany.
Rubbers prepared from technical poly(butadiene) and natural poly(isoprene) are studied by field-cycling (FC) H NMR relaxometry to elucidate the changes of the relaxation spectrum. Starting with the non-cross-linked polymer successively cross-links are introduced via sulfur or peroxide vulcanization. Applying an advanced home-built relaxometer allows one to probe entanglement dynamics in addition to Rouse dynamics.
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