Sulfonated poly(arylene ether sulfone)s (SPESs) were synthesized from sulfonated 4,4Ј-dichlorodiphenylsulfone (S-DCDPS), 4,4Ј-dichlorodiphenylsulfone (DC-DPS), and 4,4Ј-biphenol through variations in the molar ratio of S-DCDPS to DCDPS from 10/90 to 40/60. The S-PES sodium form was characterized with Fourier transform infrared, 1 H-NMR, thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis, and the intrinsic viscosity and solubility were also evaluated. The sodium form was then subjected to acidification by immersion in 1.5M HCl for 24 h at room temperature, which was followed by washing with deionized water. The S-PES adhesive properties were measured with single laboratory shear samples with aluminum alloys, and the failure mode was investigated. The synthesized S-PESs exhibited increased glass-transition temperatures with increased S-DC-DPS/DCDPS ratios; their acid forms provided much lower glass-transition temperatures than their sodium forms. In addition, the S-PES sodium form exhibited a high intrinsic viscosity, which indicated a high molecular weight. The S-PES acid form exhibited an adhesion strength similar to that of the sodium form, and the single-lap-shear strength increased with 10% S-PES and then decreased with 20, 30, and 40% S-PES.
Although surface engineering has been regarded to be a great approach to modulate the optical and electrical properties of nanomaterials, the spontaneous covalent functionalization on semiconducting 2H-MoS 2 is a notoriously difficult process, while several reactions have been performed on metallic 1T-MoS 2 . This limitation in functionalization is attributed to the difficulty of electron transfer from 2H-TMD to the reacting molecules due to its semiconducting property and neutral charge state. Unfortunately, this is an all too important prerequisite step toward creating chemically reactive radical species for surface functionalization reactions. Herein, an electrochemical approach was developed for facilitating direct surface functionalization of 2H-MoS 2 with 4bromobenzene diazonium tetraborate (4-BBDT). Successful functionalization was characterized using various microscopic and spectroscopic analyses. During the course of investigating the change of optical transition seen for modified 2H-MoS 2 using photoluminescence measurement combined with theoretical calculations, our study uncovered that the controlling S−C bond and sulfur vacancy generation could tune the electronic structure of functionalized 2H-MoS 2 .
A highly reproducible route for the epitaxial growth
of single-crystalline
monolayer MoS2 on a C-plane sapphire substrate was developed
using vapor-pressure-controllable inorganic molecular precursors MoOCl4 and H2S. Microscopic, crystallographic, and spectroscopic
analyses indicated that the epitaxial MoS2 film possessed
outstanding electrical and optical properties, excellent homogeneity,
and orientation selectivity. The systematic investigation of the effect
of growth temperature on the crystallographic orientations of MoS2 revealed that the surface termination of the sapphire substrate
with respect to the growth temperature determines the crystallographic
orientation selectivity of MoS2. Our results suggest that
controlling the surface to form a half-Al-terminated surface is a
prerequisite for the epitaxial growth of MoS2 on a C-plane
sapphire substrate. The insights on the growth mechanism, especially
the significance of substrate surface termination, obtained through
this study will aid in designing efficient epitaxial growth routes
for developing single-crystalline monolayer transition metal dichalcogenides.
Novel polyimides were synthesized from 1-[3Ј,5Ј-bis(trifluoromethyl)phenyl] pyromellitic dianhydride (6FPPMDA) by a conventional two-step process: the preparation of poly(amic acid) followed by solution imidization via refluxing in p-chlorophenol. The diamines used for polyimide synthesis included bis(3-aminophenyl)-3,5-bis(trifluoromethyl)phenyl phosphine oxide, bis(3-aminophenyl)-4-trifluoromethylphenyl phosphine oxide, and bis(3-aminophenyl)phenyl phosphine oxide. The synthesized polyimides were designed to have a molecular weight of 20,000 g/mol by off-stoichiometry and were characterized by Fourier transform infrared, NMR, differential scanning calorimetry, and thermogravimetric analysis. In addition, their intrinsic viscosity, solubility, water absorption, and coefficient of thermal expansion (CTE) were also measured. The adhesion properties of the polyimides were evaluated via a T-peel test with bare and silane/Cr-coated Cu foils, and the failure surfaces were investigated with scanning electron microscopy. The 6FPPMDA-based polyimides exhibited high glass-transition temperatures (280 -299°C), good thermal stability (Ͼ530°C in air), low water absorption (1.46 -2.16 wt %), and fairly low CTEs (32-40 ppm/°C), in addition to good adhesion properties (83-88 g/mm) with silane/Cr-coated Cu foils.
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