Effect of Substrate and Molecular Weight on the Stability of Thin Films of Semicrystalline Block Copolymers

Langmuir ◽  
2007 ◽  
Vol 23 (7) ◽  
pp. 3673-3679 ◽  
Author(s):  
Guo-Dong Liang ◽  
Jun-Ting Xu ◽  
Zhi-Qiang Fan ◽  
Shao-Min Mai ◽  
Anthony J. Ryan
Keyword(s):  
Thin Films ◽  
Molecular Weight ◽  
Block Copolymers ◽  
The Stability

Degradation in a Methyl-phenyl Co-Polymeric Polysilane for LED Applications

2003 ◽  
Vol 769 ◽  
Author(s):  
Asha Sharma ◽  
Deepak ◽  
Monica Katiyar ◽  
Satyendra Kumar ◽  
V. Chandrasekhar ◽  
...  
Keyword(s):  
Thin Films ◽  
Molecular Weight ◽  
Light Source ◽  
Room Temperature ◽  
Light Exposure ◽  
Room Temperature Photoluminescence ◽  
Pl Spectrum ◽  
Pl Intensity ◽  
Methyl Phenyl

AbstractThe optical degradation of polysilane copolymer has been studied in spin cast thin films and solutions using light source of 325 nm wavelength. The room temperature photoluminescence (PL) spectrum of these films show a sharp emission at 368 nm when excited with a source of 325 nm. However, the PL intensity deteriorates with time upon light exposure. Further the causes of this degradation have been examined by characterizing the material for its transmission behaviour and changes occurring in molecular weight as analysed by GPC data.

Thermodynamic Stability of Hexagonal and Rhombohedral Bn at Cvd Conditions from Van der Waals Corrected First Principles Calculations

2019 ◽  
Author(s):  
Henrik Pedersen ◽  
Björn Alling ◽  
Hans Högberg ◽  
Annop Ektarawong
Keyword(s):  
Thin Films ◽  
Thermodynamic Stability ◽  
First Principles ◽  
Thermal Equilibrium ◽  
Density Functional ◽  
Van Der Waals ◽  
Chemical Vapor ◽  
First Principles Calculations ◽  
Functional Theory ◽  
The Stability

Thin films of boron nitride (BN), particularly the sp<sup>2</sup>-hybridized polytypes hexagonal BN (h-BN) and rhombohedral BN (r-BN) are interesting for several electronic applications given band gaps in the UV. They are typically deposited close to thermal equilibrium by chemical vapor deposition (CVD) at temperatures and pressures in the regions 1400-1800 K and 1000-10000 Pa, respectively. In this letter, we use van der Waals corrected density functional theory and thermodynamic stability calculations to determine the stability of r-BN and compare it to that of h-BN as well as to cubic BN and wurtzitic BN. We find that r-BN is the stable sp<sup>2</sup>-hybridized phase at CVD conditions, while h-BN is metastable. Thus, our calculations suggest that thin films of h-BN must be deposited far from thermal equilibrium.

scholarly journals Development and Characterization of Two Types of Surface Displayed Levansucrases for Levan Biosynthesis

Catalysts ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 757
Author(s):  
Huiyi Shang ◽  
Danni Yang ◽  
Dairong Qiao ◽  
Hui Xu ◽  
Yi Cao
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Molecular Weight ◽  
Large Scale ◽  
Surface Display ◽  
Yeast Surface Display ◽  
Fusion Partner ◽  
Whole Cell ◽  
Food Industries ◽  
Yeast Surface ◽  
The Stability

Levan has wide applications in chemical, cosmetic, pharmaceutical and food industries. The free levansucrase is usually used in the biosynthesis of levan, but the poor reusability and low stability of free levansucrase have limited its large-scale use. To address this problem, the surface-displayed levansucrase in Saccharomyces cerevisiae were generated and evaluated in this study. The levansucrase from Zymomonas mobilis was displayed on the cell surface of Saccharomyces cerevisiae EBY100 using a various yeast surface display platform. The N-terminal fusion partner is based on a-agglutinin, and the C-terminal one is Flo1p. The yield of levan produced by these two whole-cell biocatalysts reaches 26 g/L and 34 g/L in 24 h, respectively. Meanwhile, the stability of the surface-displayed levansucrases is significantly enhanced. After six reuses, these two biocatalysts retained over 50% and 60% of their initial activities, respectively. Furthermore, the molecular weight and polydispersity test of the products suggested that the whole-cell biocatalyst of levansucrase displayed by Flo1p has more potentials in the production of levan with low molecular weight which is critical in certain applications. In conclusion, our method not only enable the possibility to reuse the enzyme, but also improves the stability of the enzyme.

scholarly journals Effect of the molecular weight on the depth profiling of PMMA thin films using low‐energy Cs + sputtering

2021 ◽  
Author(s):  
Amal Ben Hadj Mabrouk ◽  
Christophe Licitra ◽  
Antoine Chateauminois ◽  
Marc Veillerot
Keyword(s):  
Thin Films ◽  
Molecular Weight ◽  
Depth Profiling ◽  
Low Energy

scholarly journals Tetrabutylammonium cations for moisture-resistant and semitransparent perovskite solar cells

2017 ◽  
Vol 5 (42) ◽  
pp. 22325-22333 ◽  
Author(s):  
Isabella Poli ◽  
Salvador Eslava ◽  
Petra Cameron
Keyword(s):  
Thin Films ◽  
Solar Cells ◽  
Perovskite Solar Cells ◽  
Ambient Conditions ◽  
The Stability ◽  
Moisture Resistant

Tetra-butylammonium cations have been partially substituted for methylammonium cations in perovskite thin films. The stability of devices stored under ambient conditions was enhanced by the presence of TBA and cells with high mol% TBA were found to have reasonable efficiencies while being semi-transparent.

Chemistry and Properties of Imide Oligomers from Phenylethynyl-Containing Diamines

2000 ◽  
Vol 12 (1) ◽  
pp. 213-223 ◽  
Author(s):  
J G Smith ◽  
J W Connell
Keyword(s):  
Thin Films ◽  
Molecular Weight ◽  
Research Effort ◽  
Average Molecular Weight ◽  
Number Average Molecular Weight ◽  
Similar Composition ◽  
Imide Oligomers ◽  
Calculated Number

As an extension of work on pendent phenylethynyl-containing imide oligomers, three new diamines containing pendent phenylethynyl groups were prepared and characterized. These diamines were used to prepare pendent and pendent and terminal phenylethynyl imide oligomers via the amide acid route in N-methyl-2-pyrrolidinone at a calculated number average molecular weight of 5000 g mol−1. The pendent phenylethynyl groups were randomly distributed along the oligomer backbone and provided a means of controlling the distance between reactive sites. The imide oligomers were characterized and thermally cured, and the cured polymers evaluated as thin films and compared with materials of similar composition prepared from 3,5-diamino-4′-phenylethynylbenzophenone. This work was performed as part of a continuing research effort to develop structural resins for potential aeronautical applications.

On the “Lamellar” Morphology of Poly(p-Phenylene Terephthalamide) and Poly(p-Phenylene Benzobisthiazole)

1988 ◽  
Vol 134 ◽  
Author(s):  
Eric J. Roche
Keyword(s):  
Thin Films ◽  
Molecular Weight ◽  
Quench Rate ◽  
Lamellar Morphology

ABSTRACTRow-nucleated structures in PPTA and PBZT thin films are compared and their dependence upon quench rate and molecular weight illustrated. It is proposed that the lamellar appearance of the morphology is due to a coherent periodic twisting of fibrillar ribbons. The role of crystallosolvate phases is discussed.

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