We report on the synthesis, characterization, and optoelectronic properties of the novel trimethylsulfonium lead triiodide perovskite, (CH)SPbI. At room temperature, the air-stable compound adopts a hexagonal crystal structure with a 1D network of face-sharing [PbI] octahedra along the c axis. UV-vis reflectance spectroscopy on a pressed pellet revealed a band gap of 3.1 eV, in agreement with first-principles calculations, which show a small separation between direct and indirect band gaps. Electrical resistivity measurements on single crystals indicated that the compound behaves as a semiconductor. According to multi-temperature single-crystal X-ray diffraction, synchrotron powder X-ray diffraction, Raman spectroscopy, and differential scanning calorimetry, two fully reversible structural phase transitions occur at -5 and ca. -100 °C with reduction of the unit cell symmetry to monoclinic as temperature decreases. The role of the trimethylsulfonium cation regarding the chemical stability and optoelectronic properties of the new compound is discussed in comparison with APbI (A = Cs, methylammonium, and formamidinium cation), which are most commonly used in perovskite solar cells.

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In this study, the effect of sorbed water on the tensile mechanical properties of noncrosslinked, thermally treated poly(vinyl alcohol) (PVA) films was studied. The Young's modulus, elongation at break, and tensile strength of the PVA films equilibrated at different relative humidities (0-86%) are reported, together with the depression of the glass transition of the polymer at each equilibrating humidity, as determined by temperature-modulated differential scanning calorimetry. The results indicate that drastic changes in the tensile properties were correlated with the transition of the hydrated polymer from the glassy to the rubbery state.

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SYNOPSISA theoretical model, which takes proper account of the simultaneous uptake of a liquid leachant by a polymer matrix and the consequent release of a bioactive or other solute incorporated therein, is presented and the kinetics of release predicted under various conditions is investigated. This model is shown to be both more rigorous and much more widely applicable than previous attempts to approach the above problem. Furthermore, it can be easily modified or extended, in accordance with the information available about any particular system. It is, therefore, expected that the model introduced here will prove useful as a basis for the design of monolithic controlled-release devices of this type or for the evaluation of the leachability of low-level and medium-level radioactive wastes "immobilized" in polymeric matrices.Keywords: controlled release of active agents from swellable polymer matrices networks, controlled release of active agents by liquid leachants from swellable polymer matrices, model for leaching of solutes from 717

A previously developed model of solute release from a swellable polymeric matrix induced by solvent uptake that obeys Fickian kinetics is here extended to cover the case of non‐Fickian solvent uptake caused by slow structural relaxation of the swelling polymer. For this purpose, we have adopted a model description of the absorption process (also previously developed in our laboratory), which has been shown to be capable of realistically simulating a wide range of non‐Fickian kinetics (including the well‐known two‐stage sorption and case II regimes). The aforementioned structural relaxation phenomena constitute important characteristics of glassy polymeric matrices. Accordingly, the predictions of the resulting combined model have been investigated in some detail in this series of articles. This particular article is concerned with the simplest version of the model, involving constant uptake kinetic parameters (diffusion coefficient and relaxation frequency) for both osmotically inactive and osmotically active solutes. Emphasis is put on possibilities of achieving and sustaining nearly constant release rates, and it is shown that such possibilities are considerably more numerous here than under conditions of Fickian solvent uptake kinetics. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1171–1188, 2002

ABSTRACT:The release process of three osmotically active solutes with various solubilities in water (NaCl, CsNO 3 , and CsCl) from silicone rubber matrices is presented. The kinetics of release for different initial loads of the salts were supplemented by measurements of the kinetics of concurrent water uptake. To gain insight on the relevant non-Fickian transport mechanisms, the morphology, the diffusion and sorption properties and the physicochemical state of water in the salt-depleted matrices were studied. In addition, both salt-loaded and saltdepleted matrices were characterized with respect to their mechanical properties. The combined information, derived from these techniques, supported the operation of a release mechanism carried out through the formation of microscopic cracks, interconnecting the permanently formed cavities inside the matrices. The results indicate that these microscopic cracks may have healed upon drying.

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