Modified magnetite (Fe 3 O 4 ) was easily mixed in a matrix of a polynorbornene-based copolymer to realize a nanocomposite of organic polymer and inorganic metal oxide nanoparticles. The crystalline structure and the diameter of the modified Fe 3 O 4 were evaluated with X-ray diffraction and atomic force microscopy, revealing the crystalline Fe 3 O 4 nanoparticles in the nanometer size range with an average diameter of 55 nm, a value close to that indicated by dynamic light scattering (68 nm). The transition temperature of the composite of 51 • C was determined using differential scanning calorimetry and the thermal stability and dynamic mechanical properties of the easily formed composite were investigated using thermogravimetry and dynamic mechanical analysis. The shape memory effect was evaluated in terms of shape recovery rate and speed, while thermally and electromagnetically triggered shape memory properties were documented. The recovery time triggered by Fe 3 O 4 is 186 s.
Two conjugated polymers, with different side chains of alkoxysubstituted difluorobenzene and alkyl-substituted difluorobenzene based on quinoxaline (Qx) as the electron acceptor unit and benzodithiophene as the electron donor unit, named HFQx-T and HFAQx-T, were used as electron donor polymers to fabricate all-polymer solar cells (all-PSCs) with a naphthalenediimide−bithiophene n-type semiconducting polymer (N2200). Usually, halogenated solvents are harmful to natural environment and human beings, and solvent additives were disadvantageous in the process of roll-toroll technology. The Qx-based polymers are successfully used to fabricate high-performance all-PSCs, which processed with the nonhalogenated solvent tetrahydrofuran (THF) at room temperature. With THF as the processing solvent, the active layer showed a higher absorption coefficient, better phase separation, exciton dissociation, and charge carrier mobilities than that processed with CHCl 3 . Moreover, the photovoltaic properties have been dramatically improved with THF. The optimized device of HFAQx-T:N2200 processed with THF delivered an efficient power conversion efficiency (PCE) of 7.45%, which is the highest PCE for all-PSCs from Qx-based polymers processed by a nonhalogenated solvent.
Dry solvent-free and gel polymer electrolytes were analyzed based on poly[bis(2-(2-methoxyethoxy) ethoxy) phosphazene] (= MEEP) with the salts LiBOB, LiPF6, and LiTFSI with regard to stability versus lithium deposition at lithium metal electrodes under dc current flow. Symmetrical cells were used with two lithium metal electrodes. The interfaces were monitored using direct optical microscopy and accompanying intermediate impedance measurements. The results were compared with measurements on a dry polymer electrolyte of dissolved LiTFSI in PEO (Li : EO = 1 : 10). The PEO-based electrolyte and the saltin-MEEP electrolytes have shown a comparable ability of dendrite inhibition. The MEEP based gel polymer electrolytes containing~50 wt % of a 1 : 1 mixture of EC/DMC, however, showed a much-enhanced ability of inhibition towards dendrite formation made evident by increased dendrite onset time (t0) and short-circuit time (ts) when observed in special visualization cells. This could be explained by an increased lithium ion conductivity, an increased lithium transference number and a lower interface resistance at the interface Li/MEEP gel polymer electrolyte. Among the three different salts investigated in the MEEP based polymer electrolytes, LiBOB and LiTFSI show much better stability at the lithium metal interface as compared to LiPF6 which hints to a more stable and conductive SEI at the Li/ MEEP interface with dissolved LiBOB and LiTFSI. For MEEP/LiBOB polymer electrolytes, the dendrites grow directly towards the positive electrode with a fast velocity at the early stage which then decays with time in a later phase. This can be explained by the stress in electrolyte and the 'competitive growth' of dendrite tips.
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