Xide Chang,Xu Dong,Xianhua Liu,Yindong Tong,Kaixiang Li,Zhenguo Li,Yiren Lu
Mixed-phase composites with an optimal phase ratio show greater light utilization than their monophasic counterparts. This approach can be applied to develop mixed-phase photochromic tungsten oxide (WO 3 ), which shows a rapid photoresponse and high-contrast coloring. Therefore, this paper optimized the phase ratio of hexagonal WO 3 ( h -WO 3 ·0.33H 2 O) and orthorhombic WO 3 ·H 2 O ( o -WO 3 ·H 2 O) to form a homojunction. To enhance its photochromism, nanostructured WO 3 was produced via a one-step hydrothermal strategy, in which its phase structure and morphology were controlled by regulating the reaction temperature during precursor synthesis. Various material characterization techniques were carried out to reveal the complex crystal nucleation and growth of phase junctions. h -WO 3 ·0.33H 2 O nanoparticles dominated the systems, while o -WO 3 ·H 2 O nanoblocks also appeared from 41.77 wt% to 56.50 wt% at a low hydrothermal synthesis temperature, producing a mixture of both polymorphs. The improved photochromic properties (from light yellow to black-green) of the mixed-phase WO 3 composite compared with pure h -WO 3 ·0.33H 2 O (from gray-white to dark gray) was attributed to the formation of a phase junction between h -WO 3 ·0.33H 2 O and o -WO 3 ·H 2 O. The photoelectrochemical results showed that this resulted in highly efficient charge carrier separation and transfer. The strong visual rendering of the black-green state may be useful for developing intelligent displays and similar devices.
Mengru Ding,Lingling Ni,Ying Zheng,Bao Wang,Chengtao Yu,Guorong Shan,Yongzhong Bao,Junfeng Liu,Pengju Pan
Long-spaced aliphatic polyesters are typical sustainable polyethylene (PE)-like polymers. However, the presence of a low amount of ester groups can exert a profound effect on the crystalline structure of such PE-like polymers. Herein, we synthesized a series of long-spaced aliphatic polyesters bearing two proximate ester groups from ethylene glycol (EG) and n-methylene diacids (n = 9–18) and investigated their polymorphic crystallization and phase transitions. We find that the EG-based polyesters exhibit unique crystal polymorphism and phase transition behaviors. They can form a metastable hexagonal phase (form II) with nontilted, extended chain conformations at low temperatures or during rapid cooling but adopt the thermally stable orthorhombic phase (form I) with tilted chain packing at high temperatures or under slow cooling. Form I demonstrates a more densely packed chain structure and displays distinct mechanical properties compared to form II. The metastable hexagonal phase can transform into an orthorhombic phase during heating through a melt-recrystallization mechanism. This study advances the current understanding of the multiphase crystallization of PE-like long-spaced polyesters.
危险品化学品经营许可证（带存储）