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Dielectric spectroscopy is employed to study the relaxation phenomena in natural polyhydroxyalkanoates (PHAs) upon temperature and frequency variations. Effects of PHAs molecular structure on the relaxation, arising from the differences in monomeric composition, are investigated under identical conditions in a frequency range of 10−2–106 Hz, and at different temperatures. All PHA samples showed different dielectric response at different temperature. Primary α -relaxation signals are observed at temperature corresponding to the glass transition temperature. On the other hand, secondary β - and γ -relaxations are detected at low temperatures, and attributed to local motions of polar groups and small segments of the polymer chain. The dielectric properties of representative PHA samples are compared and discussed. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators (TENGs) have long been considered as a promising solution to meet the increasing energy demands caused by technological advancements. A notable recent approach to improve the output power of TENGs is by utilizing solid polymer electrolytes (SPEs) as the contact layers. However, the enhancement mechanism brought by the ionic species doped in SPEs was not clearly explained. Herein, polyvinyl alcohol (PVA) was subsequently doped with different ionic species to form PVA-SPEs, which were then paired with silicone rubber (SR) in contact-separation mode TENGs. The effect of different ionic species was investigated using two general classes of PVA-SPEs, i.e. cation-SPEs and anion-SPEs. Among the various PVA-SPEs, PVA-CaCl 2 and PVA-NaNO 3 provided the largest enhancements in electrical outputs for cation- and anion-SPEs respectively, recording averages of 95% and 90% increments. The addition of ionic species creates an internal ionic polarization within the PVA-SPEs, thus increasing their dielectric constants and ultimately the electrical outputs. Upon contact electrification (CE), the surface charges and electrostatically induced charges on the electrode generates an external electric field across the PVA-SPEs, hence inducing an internal ionic polarization field due to ionic migration. Due to the presence of the internal ionic polarization field, the difference in the highest electrons' energies (Δ E) between PVA-SPE and SR increases, which consequently enhances the electron transfer during CE. The enhancement mechanism is elucidated by a modified overlapped electron cloud (OEC) model. This model is supported by Kelvin Probe Force Microscopy (KPFM) study in which the potential differences after CE of PVA-SPEs are much higher compared to pristine PVA. A maximum power density of 11.3 W/m2 was recorded for PVA-CaCl 2 /SR, which is a 180% increase over that of pristine PVA/SR. This work demonstrates a reliable and straightforward method to enhance the electrical power output of TENGs. Moreover, an in-depth understanding on the enhancement mechanism by an internal ionic polarization field is provided, hence unfolding a new paradigm for polymer-based TENGs. [Display omitted] ● Ionic doping in PVA is shown to be a reliable and straightforward method to enhance the electrical outputs of TENGs. ● PVA-SPEs demonstrate significant enhancements of triboelectric electrical outputs and dielectric properties. ● These enhancements are due to the contact electrification-induced internal ionic polarization. ● A modified OEC model and KPFM measurements are used to elucidate the enhancement mechanism of electrical outputs. ● The TENG of PVA-CaCl 2 / SR generates a power output of 11.3 W/m2, which is a 180% increase over that of PVA/ SR. [ABSTRACT FROM AUTHOR]

Abstract The sugar anomeric effect on the thermotropic phase transition of stearyl glucoside was investigated. Standard analysis to study the phase transition through differential scanning calorimetry (DSC), and optical polarizing microscopy (OPM) was applied. In addition, small- and wide-angle X-ray scattering (SWAXS) and impedance spectroscopy (IS) were used to elucidate the phase structural information and the dielectric response of the glycolipid self-assembly system, respectively. A distinctive solid-to-liquid crystal phase transition of α - and β -stearyl glucoside was observed. At ambient temperature we observed semi-crystalline structure for the former and gel phase for the latter. α -Stearyl glucoside showed only one-step transition from semi-crystal to lamellar liquid crystal phase. In contrast, the gel phase of β -stearyl glucoside showed several distinct transition states prior to lamellar liquid crystal phase. Here the underlying reason for the observed β -stearyl glucoside polymorphism possibly involved strong intermolecular interaction originating from the combination of interlayer H-bonding and intralayer van der Waals forces. Graphical abstract Unlabelled Image Highlights • Sugar stereochemistry affects the lipid packing and hydrogen bond of the glycolipid. • Both glycolipid anomers form different solid phase structure at ambient temperature. • α -Anomer shows one step of semi-crystalline–to–liquid crystalline phase transition. • β -Anomer shows multiple steps of gel–to–liquid crystalline phase transition. [ABSTRACT FROM AUTHOR]

• Synthesis of new side-chain liquid crystalline copolymers containing polarisable groups. • Azobenzene groups confer light-responsive character to the electrolytes. • Electro-donating and electro-withdrawing groups tailor molecular structure. • High conductivity values are reached (10–2.9 S·cm−1) under anhydrous conditions. • Ion conductivity occurs through nematic and smectic phases, decoupled from the polymer backbone. We have prepared and characterised a series of side-chain liquid crystalline homopolymers and terpolymers containing different azobenzene derivatives (R AzB), sulfonic groups (2-acrylamido-2-methyl-1-propanesulfonic acid, AMPS), and methyl(methacrylate) groups (MMA), as monomeric units. We have evaluated the effect of different para-substitutes of 6-(4-azobenzene -4′-oxy)hexyl methacrylate, at the side chains, OCH 3 , NO 2 and H, on the phase behaviour and conductivity of the new polymers. The copolymers can form smectic and nematic phases, depending on their composition, and have light responsiveness, conferred by the azobenzene chromophores. The terpolymer with methoxy terminations, MeOAzB/AMPS/MMA, exhibits the highest conductivity values of the series (10−2/10−3 S·cm−1 range) through liquid crystalline phases and with signs of decoupling from polymeric segmental motions. These materials are promising candidates to develop new light-responsive polymeric electrolytes for electrochemical conversion devices in which ionic conductivity under anhydrous conditions can be controlled by their nanostructure. [ABSTRACT FROM AUTHOR]