Infrared spectroscopy (IR) and Broadband Dielectric Spectroscopy (BDS) experiments have been performed in poly(trimethylene 2,5-furanoate)(PTF) and poly(trimethylene terephthalate)(PTT) below their ...glass transition temperatures. The BDS experiments reveal a richer inter-molecular dynamic for PTT as characterized by a multimodal β relaxation in contrast with the monomodal one exhibited by PTF. The evolution with temperature of comparable IR absorption bands is very similar for PTF and PTT and shows small shifts in wavenumbers towards lower values, with exception of the band related to the stretching mode of the carbonyl group. In addition, a significant difference appears in the shape of the bands associated with the –CO stretching. While for PTT the absorption feature is comprised of a single component, that for PTF exhibits several components suggesting the presence of hydrogen bonds. This effect may be responsible for the monomodal shape of the β relaxation of PTF since a higher degree of intramolecular coupling between the furan ring and the rest of the monomer is expected. Density Functional Theory (DFT) calculations support the experimental results revealing that as temperature increases an increment of the syn conformations of the 2,5-furandicarboxylic acid (FDCA) moiety is likely to occur in the amorphous state. The energy gain from more stable anti to less stable syn isomers can be compensated by the formation of hydrogen bonds between interchain FDCA moieties in syn conformations. This effect may cause additional hindrance to the intermolecular dynamics of the dielectric β relaxation. It is conceivable that the hindrance exhibited by PTF in both intra and inter-molecular dynamics may play a role in the reduction of gas diffusion and permeability of PTF in comparison with PTT.
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•The molecular dynamics of poly(trimethylene 2,5-furanoate)(PTF) has been investigated by FTIR and BDS.•A hindrance to the intermolecular dynamics of the dielectric β relaxation of PTF is observed.•This fact may play a role on the PTF enhanced gas diffusion and permeability.
This study assesses the impact of Treated Distillate Aromatic Extract (TDAE) oil, at concentrations of 0–20 parts per hundred rubber (phr), on the glass transition temperature (Tg) of High Vinyl/Low ...Styrene Styrene-Butadiene Rubber (HVLSS-SBR), polybutadiene rubber (BR), and their blends with weight ratios of 70/30 and 50/50. Using Dynamic Mechanical Analysis, Broadband Dielectric Spectroscopy, and Positron Annihilation Lifetime Spectroscopy, we found that TDAE modifies Tg and fractional free volume (Fv) differently across materials. In HVLSS-SBR, TDAE reduced Tg by approximately 10 °C and increased Fv by 0.8 %. In BR, TDAE raised Tg by 5–7 °C without altering Fv. The 70/30 blend showed no Tg change but a 0.6 % Fv increase. For the 50/50 blend, one Havriliak-Negami equation indicated a Tg rise of 2–3 °C and a 0.4 % Fv increase. A two-equation analysis revealed a 6 °C Tg increase and 0.9 % Fv boost in the BR-rich phase, versus a 2 °C rise and 0.3 % Fv uptick in the HVLSS-SBR-rich phase. The sequence of compatibility, influenced by TDAE, is crystalline BR > amorphous BR > HVLSS-SBR >70/30 blend >50/50 blend. This study provides valuable insights into the behavior of TDAE oil in rubber blends and can serve as a basis for further research in this field.
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Polymers have become indispensable across fields of application, and understanding their structure–property relationships and dynamic behaviour is essential for performance optimization. Polymer ...membranes, particularly ion exchange membranes, play a crucial role in renewable energy conversion technologies, fuel cells, solar energy conversion, and energy storage. In this context, broadband dielectric spectroscopy (BDS) offers a powerful, non-destructive approach to investigate the electrical response and relaxation dynamics of polymers. These properties are investigated by parametrizing the system’s impedance response in terms of a network of circuit elements, i.e. the electrical equivalent circuit (EEC), whose impedance resembles the one of the system under investigation. However, the determination of the EEC from BDS data is challenging due to system complexity, interdependencies of circuit elements, and researcher biases. In this work, we propose a novel approach that incorporates a convolutional neural network (CNN) model to predict the EEC topology. By reducing user bias and enhancing data analysis, this approach aims to make BDS accessible to both experienced users and those with limited expertise. We show that the combination of machine learning and BDS provides valuable insights into the dynamic behaviour of polymer membranes, thus facilitating the design and characterization of tailored polymers for various applications. We also show that our model outperforms state-of-the-art machine learning methods with a top-5 accuracy of around 80% for predicting the circuit topology and a parameter fitting error as low as 0.05%.
This work aims at better understanding the interactions existing between the liquid electrolyte and the solid composite electrode in a Li-ion battery. We substituted the common active material (e.g. ...LiNi1/3Mn1/3Co1/3O2 or LiFePO4) by an insulating (inactive) γ-Al2O3 compound in order to detect and evidence the interaction between the carbon black electronic additive and the liquid electrolyte. Our study presents the characterization of charge (electrons and ions) transport at different scales by combining a high-frequency analysis performed by broadband dielectric spectroscopy (BDS, up to 1010 Hz), along with a low-frequency analysis performed by electrochemical impedance spectroscopy (EIS, down to 10−3 Hz). Two carbon black materials with two different specific surface areas (80 m2.g−1 and 65 m2.g−1, respectively) were studied. The electronic percolation threshold and the kinetics of impregnation of the hierarchical composite electrode by the liquid electrolyte have been determined with respect to the carbon black content. The significant influence of the adsorbtion of ions at the carbon black surface on the electrons transport is particularly highlighted and explained.
Polyelectrolyte-based conductive hydrogels are being extensively explored for applications in energy storage and as electrode materials for batteries. We synthesized ionically crosslinked sodium ...carboxymethyl cellulose (NaCMC), esterified NaCMC, and Ca2+ doped esterified NaCMC hydrogels. This work aims to understand the effect of Ca2+ ions on the NaCMC and esterified NaCMC. FTIR, SEM, Rheology and EIS studies were performed to understand the structure and dynamics of hydrogels. Results confirmed that Ca2+ ions have an important role in determining the rheological and dielectric response of hydrogels. Power law behavior was observed in their rheological response with exponent (n) of 0.81 for G′ and 0.76 for G″ of ionically crosslinked NaCMC, 5.38 for G′ and 4.70 for G″ of esterified NaCMC, whereas, negative exponents −1.44 for G′ and −1.10 for G″ of Ca2+ ion doped esterified NaCMC. Ionically crosslinked NaCMC hydrogels have relaxation times (τ) in the range of 8.9 × 10−5 s–2.8 × 10−5 s may be due to the formation of temporary dipoles by electrostatic bridge formations with dc conductivity of (0.1 S/cm–5 S/cm), whereas, esterified NaCMC showed relaxation times (10−3 s–8.9 × 10−5 s) with increasing ester crosslinks and dc conductivity of (0.05 S/cm–0.8 S/cm). Interestingly, Ca2+ ion doped esterified hydrogels showed multiple dielectric relaxations on Ca2+ ion addition with different relaxation times may be due to change in ionic environment. The understanding obtained from this work may be useful for designing tuneable hydrogels with optimum electrical and mechanical properties.
•Addition of Ca2+ in esterified NaCMC showed decrease in mechanical properties and multiple dielectric relaxation processes•Storage modulus increased for ionically crosslinked (Metal ligand coordination) and esterified NaCMC, however, decreasing trend was observed for Ca2+ doped esterified NaCMC hydrogels•Dielectric relaxation times decreased with Ca2+ ion addition for ionically crosslinked NaCMC hydrogels•Decrease in dielectric relaxation time observed with increasing ester crosslinks in esterified NaCMC hydrogels
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