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Green Materials for Waterborne Polyurethanes
Published in Ram K. Gupta, Ajay Kumar Mishra, Eco-Friendly Waterborne Polyurethanes, 2022
Felipe M. de Souza, Prashant Kote, Ram K. Gupta
Hydroformylation involves the addition of CO and H2 to an alkene to form an aldehyde. The aldehydes produced by hydroformylation are normally reduced to alcohol via hydrogenation, which is a reaction with hydrogen under pressure and catalysts such as Pt or Raney Ni. Hydroformylation is usually carried out in the presence of Rh or Co carbonyls as catalysts. Rh catalysts are very efficient, avoid oligomerization, and deliver almost 100% conversions; however, they are not cost-effective. On the other hand, hydroformylation with Co allows some oligomerization, likely due to transesterification at higher temperatures. Petrovic et al. made an interesting study on the property of several polyols based on soybean that was synthesized through the hydroformylation/reduction method [15]. This approach presents some advantages, such as the introduction of primary hydroxyl groups, which are more reactive toward isocyanate and the high conversion of aldehydes into hydroxyl groups, leading to a higher functionality of the polyols. When targeting for WPU, a high functionality may not be desired in the early stages of WPU synthesis, since it may lead to crosslinking yielding polymers that swell in solution instead of dispersing. It is possible to control the functionality by partially blocking the hydroxyl groups by performing esterification.
Sensors Used to Evaluate Nanotoxicity
Published in Vineet Kumar, Nandita Dasgupta, Shivendu Ranjan, Nanotoxicology, 2018
Isotopic labeling is a technique for tracking the passage of a sample of substance through a system. The water-soluble hydroxylated carbon SWNTs have been labeled with radioactive 125I atoms and then traced to study their distribution in mice, and show a quantitative analysis of carbon nanotubes accumulated in animal tissues (Wang et al. 2004). Two other nuclear imaging modalities have been used for the quantitative analysis of quantum dots, including the single photon emission computed tomography nuclear imaging (SPECT) and positron emission tomography (PET) (Pic et al. 2009). In addition, other workers showed that the bioactivities of fullerene derivatives were greatly altered with the change of outer modified hydroxyl groups (Sayes et al. 2005). Since traditional methods, such as X-ray photoelectron spectroscopy (XPS) and nuclear magnetic resonance (NMR), were not precise enough to determine the exact number of hydroxyl groups, a further measurement of the hydroxyl number was performed using synchrotron radiation X-ray photoemission spectroscopy (SRT), where intensities for the non-functionalized and hydroxylated carbons were achieved (Chen et al. 2005).
Plastics Properties and Testing
Published in Manas Chanda, Plastics Technology Handbook, 2017
Hydroxyl Groups. A careful examination of the hydroxyl stretching region (Table 3.11) can often be valuable in the determination of structure of unknown polymeric compounds. Thus, the presence of a band in the 3700–3150 cm−1 (2.7–3.2 μm) region is a very reliable indication of the presence of hydroxyl groups. [Note, however, the following two exceptions. Since water shows strong absorption in this region, the sample must be fully dry for hydroxyl observation. Halide powders being rarely dry, halide disks for sample preparation are thus best avoided for measurement of hydroxyl groups. Also, N–H groups, if present, can cause interfering absorptions in the hydroxyl region (see Table 3.11).]
Characterization of thermal decomposition of oxygenated organic compounds in FIGAERO-CIMS
Published in Aerosol Science and Technology, 2021
Laura Hyesung Yang, Masayuki Takeuchi, Yunle Chen, Nga Lee Ng
Table 1 specifies the “Type” and “Group” of each compound. “Type” corresponds to the type of functional groups associated with each compound. The chemical standards are classified into five “Types” to investigate the effect of functional groups on thermal decomposition behavior. Alcohols (used interchangeably with polyalcohols in this work) include compounds that solely contain hydroxyl groups. Monoacids, diacids, and polyacids represent compounds solely composed of carboxyl groups. Multifunctional acids comprise compounds with two or more types of functional groups (hydroxyl, carbonyl, carboxyl, and acetal). For instance, sucrose is classified as multifunctional instead of alcohol as it has both hydroxyl and acetal functional groups. A subset of the chemicals is also categorized into four “Groups” (numbered as 1 to 4 in Table 1) to evaluate the effect of chemical structure on thermal decomposition behavior. Figure 1 depicts the visualization of these groups. Group 1 includes diacids with four carbons in the backbone and allows for investigating how the presence of a hydroxyl or carbonyl group affects thermal decomposition behavior. Group 2 compounds all have identical functional groups (two carboxyl groups and one carbonyl group) but contain different numbers of carbons. Group 3 allows for examining the effect of the structure (i.e., linear or ring) of carboxylic acids on thermal decomposition behavior. Lastly, Group 4 compounds are alcohols and allow for investigating the influence of the number of hydroxyl groups and the effect of adding acetal to the alcohol on thermal decomposition.
Preparation and evaluation of vitamin C and folic acid-coloaded antioxidant liposomes
Published in Particulate Science and Technology, 2019
Zhen Jiao, Xiudong Wang, Yuting Yin, Jingxin Xia
As shown in Figure 2, VCFA-Lip exhibits the highest scavenging activity among the prepared liposomes, while FA-Lip shows the worst (p < 0.01). It is proved that hydroxyl groups play an important role in the antioxidant (Mensor et al. 2001). FA contains one hydroxyl group in its lactim form and VC contains two hydroxyl groups. Therefore, VC-Lip exhibits a higher scavenging activity than FA-Lip. Morever, VC can alter the form of FA to the tetrahydro derivate, a reduced form (Gursu et al. 2004). This might explain why VCFA-Lip shows the highest scavenging activity. In short, the experimental results indicate a synergistic scavenging activity of combinations of VC and FA on DPPH.
In vitro antioxidant activity evaluation of pine nut peptides (Pinus koraiensis) fermented by Bacillus subtilis LS-45
Published in Preparative Biochemistry & Biotechnology, 2023
Jiajia Sun, Zhi Zhang, Kexin Yang, Gang Wei, Yanxia Li
Figures 3 and 4 show that both EPP and PFF showed a potent ability to scavenge Hydroxyl radicals. As sample concentration increased in a specific range, the rate at which the Hydroxyl radical was scavenged likewise steadily increased. VC had a mass concentration of 1.230 mg/mL of Hydroxyl radical half-inhibitory activity, EPP had a mass concentration of 8.250 mg/mL, and FPP had a mass concentration of 4.218 mg/mL. The scavenging capability of the FPP was much more than the EPP and less than VC when the concentration was lower than 9.0 mg/mL. The scavenging rates were greater than 80% when the concentrations of the three samples were greater than 15 mg/mL. The mass concentration of the three samples and the rate of Hydroxyl radical scavenging were significantly positively correlated (the R2 value of VC was 0.9369, the R2 value of EPP was 0.9549, R2 value of FPP was 0.9371). The most dangerous free radical is known to be the Hydroxyl radical. Any biomolecule in the production site can react with it. A type of reactive oxygen species that can destroy red blood cells and degrade NDA, the Hydroxyl radical is nearly exclusively responsible for the damage brought on by oxidative stress. Free radicals generated by lipid peroxidation are crucial in the development and growth of tumors by modern medicine. Therefore, it is clear that Hydroxyl radicals have harmful effects on the human body. An important role for Hydroxyl radical scavengers is in preventing and treating diseases brought on by free radicals and slowing down physical aging.[35] The findings demonstrated that pine nut protein peptides made by fermentation had a better capacity for scavenging Hydroxyl radicals than pine nut protein peptides made through enzymatic hydrolysis.[36]