Fluorine depth profiling by high-resolution 1D magnetic resonance imaging

NMR Profiling of Reaction and Transport in Thin Layers: A Review

Reaction and transport processes in thin layers of between 10 and 1000 µm are important factors in determining their performance, stability and degradation. In this review, we discuss the potential of high-gradient Nuclear Magnetic Resonance (NMR) as a tool to study both reactions and transport in these layers spatially and temporally resolved. As the NMR resolution depends on gradient strength, the high spatial resolution required in submillimeter layers can only be achieved with specially designed high-gradient setups. Three different high-gradient setups exist: STRAFI (STRay FIeld), GARField (Gradient-At-Right-angles-to-Field) and MOUSE (MObile Universal Surface Explorer). The aim of this review is to provide a detailed overview of the three techniques and their ability to visualize reactions and transport processes using physical observable properties such as hydrogen density, diffusion, T1- and T2-relaxation. Finally, different examples from literature will be presented to illustrate the wide variety of applications that can be studied and the corresponding value of the techniques.

Synthesis and characterization of fluorinated polyurethane containing carborane in the main chain: Thermal, mechanical and chemical resistance properties

In this study, two fluorinated polyurethanes (FPU) containing carborane groups in the main chains were firstly designed and synthesized via the reaction of hexamethylene diisocyanate trimer (HDI trimer) with fluorinated polyesters (CFPETs) having hydroxyl-terminated carborane groups at room temperature. The structures of carborane fluorinated polyesters (CFPETs) and polyurethanes (CFPUs) were characterized by gel permeation chromatography (GPC), Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) measurements. The thermal stability, mechanical properties, Shore A hardness, solvent resistance and acid-alkali resistance of the carborane fluorinated polyurethane films were also studied. Thermogravimetric analysis (TGA) tests manifested that the introduction of carborane groups into the main chain of fluorinated polyurethane endowed the obtained fluorinated polyurethane with excellent thermal stability. The thermal decomposition temperature of carborane fluorinated polyurethane (CFPU) increased by 190 °C compared with that of the carborane-free fluorinated polyurethane (FPU). Even at 800 °C, CFPU showed the char yield of 66.5%, which was higher than that of FPU (34.3%). The carborane-containing fluorinated polyurethanes also showed excellent chemical resistance and prominent mechanical property even after the cured films being immersed into Jet aircraft oil or 37% HCl for 168 h or at high temperature (700 °C). It is found that the structural characteristics of carborane group and the compacted structure of CFPU effectively improve the thermal stability, mechanical property, solvent resistance and acid-alkali resistance of the carborane-free fluorinated polyurethane. These excellent properties make CFPU as the useful raw materials to prepare the high temperature resistant coatings or adhesives for automotive engines, engine or fuel tank of aircraft and other equipment working in high-temperature or high concentrations of acid-alkali environments.

Quantitative grafting of peptide onto the nontoxic biodegradable waterborne polyurethanes to fabricate peptide modified scaffold for soft tissue engineering

Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP) peptide has frequently been used in the biomedical materials to enhance adhesion and proliferation of cells. In this work, we modified the nontoxic biodegradable waterborne polyurethanes (WBPU) with GRGDSP peptide and fabricated 3-D porous scaffold with the modified WBPU to investigate the effect of the immobilized GRGDSP peptide on human umbilical vein endothelial cells (HUVECs) adhesion and proliferation. A facile and reliable approach was first developed to quantitative grafting of GRGDSP onto the WBPU molecular backbone using ethylene glycol diglycidyl ether (EX810) as a connector. Then 3-D porous WBPU scaffolds with various GRGDSP content were fabricated by freeze-drying the emulsion. In both of the HUVECs adhesion and proliferation tests, enhanced cell performance was observed on the GRGDSP grafted scaffolds compared with the unmodified scaffolds and the tissue culture plate (TCP). The adhesion rate and proliferation rate increased with the increase of GRGDSP content in the scaffold and reached a maximum with peptide concentration of 0.85 μmol/g based on the weight of the polyurethanes. These results illustrate the necessity of the effective control of the GRGDSP content in the modified WBPU and support the potential utility of these 3-D porous modified WBPU scaffolds in the soft tissue engineering to guide cell adhesion, proliferation and tissue regeneration.