Owing to inevitable thermal/moisture instability for organic–inorganic hybrid perovskites, pure inorganic perovskite cesium lead halides with both inherent stability and prominent photovoltaic performance have become research hotspots as a promising candidate for commercial perovskite solar cells. However, it is still a serious challenge to synthesize desired cubic cesium lead iodides (CsPbI3) with superior photovoltaic performance for its thermodynamically metastable characteristics. Herein, polymer poly-vinylpyrrolidone (PVP)-induced surface passivation engineering is reported to synthesize extra-long-term stable cubic CsPbI3. It is revealed that acylamino groups of PVP induce electron cloud density enhancement on the surface of CsPbI3, thus lowering surface energy, conducive to stabilize cubic CsPbI3 even in micrometer scale. The cubic-CsPbI3 PSCs exhibit extra-long carrier diffusion length (over 1.5 μm), highest power conversion efficiency of 10.74% and excellent thermal/moisture stability. This result provides important progress towards understanding of phase stability in realization of large-scale preparations of efficient and stable inorganic PSCs.

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Surface passivation engineering strategy to fully-inorganic cubic CsPbI 3 perovskites for high-performance solar cells

Hydrogen bonds in polymer blends

Synthesis and characterization of thermo- and pH-responsive bacterial cellulose/acrylic acid hydrogels for drug delivery

Hydrogen bonding in polymer blends is a topic of great interest to polymer scientists because such systems have many potential applications. Introducing functional groups to one component to make it capable of forming hydrogen bonds to another, thereby enhancing the miscibility of otherwise immiscible blends, is one of the major achievements during the past 20 years of polymer science. The Painter–Coleman association model generally describes these interactions accurately. This Review discusses in detail the effects of hydrogen bonding on the miscibility and thermal properties of polymer blend systems.

Hydrogen-bonding in polymer blends

The aim of this study was to gain some fundamental knowledge on the thermal degradation pathways of poly(N-vinyl pyrrolidone) using Thermogravimetry coupled with Fourier Transform Infrared Spectroscopy (TG–FTIR) in addition to IR and 1H NMR spectroscopic studies of the partially degraded samples. It was found that the vinyl pyrrolidone is the main volatile products of the thermal degradation of PVP which implies that the predominant mechanism during thermal degradation of this polymer is the depolymerization to monomer of the polymeric main chain; however, it is evident that simultaneous reactions may be involved yielding oligomers. FTIR and 1H NMR spectra of partially degraded samples of PVP exhibited very similar characteristics to that observed for undegraded samples although the 1H NMR spectra suggest the presence of simultaneous reactions as the fragmentation of polymeric main chain.

A TG/FTIR study on the thermal degradation of poly(vinyl pyrrolidone)

A study of blending and complexation of poly(acrylic acid)/poly(vinyl pyrrolidone)

The miscibility, intermolecular interactions and thermal behavior of the poly(hydroxy ether of Bisphenol A) (Phenoxy)/poly(ethyl oxazoline) (PEOx) blends were investigated by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and high-resolution solid-state nuclear magnetic resonance (NMR) spectroscopy Each composition of the Phenoxy/PEOx blends investigated displays a single glass transition temperature (Tg), which is intermediate between those of the pure components and regularly varies with blend composition The results of FTIR showed that there are intermolecular interactions between the pendant hydroxyl groups of Phenoxy and the carbonyl groups of PEOx Spin-lattice relaxation times in both the laboratory and the rotating frame determined by high-resolution solid state 13 C NMR spectroscopy reveal that the spin-diffusion among all protons in the blends averages out the whole relaxation process, suggesting that the blends are intimately mixed on the scale of 10-15 A

Miscibility, intermolecular interactions, and thermal behavior of poly(hydroxy ether of Bisphenol A)/poly(ethyl oxazoline) blends

We employed high-resolution 13C cross-polarization/magic-angle-spinning/dipolar-decoupling NMR spectroscopy to investigate the miscibility and phase behavior of poly(vinyl chloride) (PVC)/poly(methyl methacrylate) (PMMA) blends. The spin–lattice relaxation times of protons in both the laboratory and rotating frames [T1(H) and T1ρ(H), respectively] were indirectly measured through 13C resonances. The T1(H) results indicate that the blends are homogeneous, at least on a scale of 200–300 A, confirming the miscibility of the system from a differential scanning calorimetry study in terms of the replacement of the glass-transition-temperature feature. The single decay and composition-dependent T1ρ(H) values for each blend further demonstrate that the spin diffusion among all protons in the blends averages out the whole relaxation process; therefore, the blends are homogeneous on a scale of 18–20 A. The microcrystallinity of PVC disappears upon blending with PMMA, indicating intimate mixing of the two polymers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2390–2396, 2001

Cheryl Lau

Papers

A study of blending and complexation of poly(acrylic acid)/poly(vinyl pyrrolidone)

Miscibility, intermolecular interactions, and thermal behavior of poly(hydroxy ether of Bisphenol A)/poly(ethyl oxazoline) blends

Investigation at the chain segmental level of the miscibility of poly(vinyl chloride)/atactic poly(methyl methacrylate) blends