Functionality of polyols

Filter/dry OH-functionality of polyol depends on structure of R Difficult to "cap all 2° OH groups with EO Side reactions (esp. proton abstraction) limit functionality of Urethane-grade polyol product and create unwanted functional groups... 

Figure 3.22. Fluorescence titrations of anthrylboronic acid 16 (0.75 jiM) at pH 7.4 (20 mAf phosphate buffer) as a function of polyol concentration (+, fructose , t,l,l-tris(hydroxymethyl)ethane a, glucose +, ethylene glycol). All solutions contain 1% (v/v) dimethylsulfoxide (DMSO). (Reproduced from Ref. 26. Copyright 1992 American Chemical Society.)...

Figure 7. Elastically effective cross-link density versus bake temperature for an acrylic-urethane coating as a function of polyol to isocyanate ratio.

The third factor important in obtaining high-flame-endurance foams is the choice of molecular weight, functionality of polyol and aliphaticity index (65). The polyol content, which is largely responsible for the low flammability of isocyanurate foams, is expressed by the aliphaticity index, as defined by the following equation ... 

Figure 5. Soft segment glass transition temperature, T as a function of polyol molecular weight. 9...

Theoretical hydroxyl numbers of the polyols resulting from epoxidised soybean oil hydrolysis are in the range 440-450 mg KOH/g. If the epoxidised soybean oil has 4 epoxy groups/mol, the resulting functionality of polyol obtained by hydrolysis is 8 hydroxyl groups/mol. 

Figure 1. Time-course study of molecular weight increase as a function of polyol structure. Polymerizations were performed at 90 "C, catalyzed by N435. The right Y-axis showed the schedule of applied vacuum during reactions. (Reproducedfrom Macromolecules 2006, 39, 6789-6792. Copyright 2006 American Chemical Society.)...

Direct site-selective functionalization of natural products is a powerful tool for the discovery of drug candidates because nature provides a rich pool of unique molecular frameworks with diverse biological profiles [32,33], Acylation of a particular hydroxy group among multiple hydroxy groups in polyol natural products has been well studied by means of enzymatic protocol [34], For example, acylation of rapamycin, an immunosuppressive agent, took place at C(42)-OH selectively in the presence of PSL-C to provide an anticancer agent, temsirolimus (Scheme 13) [35]. Inspired by these achievements, extensive efforts have been devoted to develop the non-enzymatic counterparts toward site-selective functionalization of polyol natural products [4],... 

Reactivity of polyols was estimated by the rise in viscosity with time. Since the functionality of polyols is almost constant, chemical reactivity is the main factor contributing to the viscosity increase. Figure 2 shows the... 

Properties of polyurethanes depend on crosslinking density, which was kept approximately constant by keeping functionality of polyols constant at about 3.7. Glass transition was measured by DSC and dynamic mechanical analysis. Figure 3 shows a linear relationship between the primary hydroxyl content and glass transition as measured by DSC. 

The specialty class of polyols includes poly(butadiene) and polycarbonate polyols. The poly(butadiene) polyols most commonly used in urethane adhesives have functionalities from 1.8 to 2.3 and contain the three isomers (x, y and z) shown in Table 2. Newer variants of poly(butadiene) polyols include a 90% 1,2 product, as well as hydrogenated versions, which produce a saturated hydrocarbon chain [28]. Poly(butadiene) polyols have an all-hydrocarbon backbone, producing a relatively low surface energy material, outstanding moisture resistance, and low vapor transmission values. Aromatic polycarbonate polyols are solids at room temperature. Aliphatic polycarbonate polyols are viscous liquids and are used to obtain adhesion to polar substrates, yet these polyols have better hydrolysis properties than do most polyesters. 

Joost H-G, Thorens B (2001) The extended GLUT-family of sugar/polyol transport facilitators - nomenclature, sequence characteristics, and potential function of its novel members. Mol MembrBiol 18 247-256... 

These results have been fit to experimental data obtained for the reaction between a diisocyanate and a trifunctional polyester polyol, catalyzed by dibutyltindilaurate, in our laboratory RIM machine (Figure 2). No phase separation occurs during this reaction. Reaction order, n, activation energy, Ea, and the preexponential factor. A, were taken as adjustable parameters to fit adiabatic temperature rise data. Typical comparison between the experimental and numerical results are shown in Figure 7. The fit is quite satisfactory and gives reasonable values for the fit parameters. Figure 8 shows how fractional conversion of diisocyanate is predicted to vary as a function of time at the centerline and at the mold wall (remember that molecular diffusion has been assumed to be negligible). 

Figure 10. Four different ways of controlling the kinetics of polyol reduction and the corresponding morphologies observed for the Pt nanostructures. As the same amount of PVP was present in all four syntheses illustrated here, the striking differences in morphology were not caused by variation in the PVP concentration. It is assumed that the PVP molecules in these syntheses function only as a stabilizer to prevent the resultant nanoparticles from aggregating into larger structures. (Reprinted from Ref [270], 2005, with permission from Wiley-VCH.)...

The presence of particles in the brains of experimental rats and humans exposed to asbestos has been reported (Pontefiart and Cunningham, 1973 Auerbach et al., 1980). In experimental studies, particles of Teflon, a reflux paste, enter the brain via intravascular transport when injected into the bladder (Aaronson et al., 1993). Encephalitic reactions to accumulated calcium oxalate crystals in the brain as a result of infusions of glucose surrogate polyol solutions have been described (PciflPcr etal., 1984). Such studies indicate the capacity of particulates to enter the brain and thus pose a potential pathological threat to the functioning of the central nervous system (CNS). 

Pristine CNTs are chemically inert and metal nanoparticles cannot be attached [111]. Hence, research is focused on the functionalization of CNTs in order to incorporate oxygen groups on their surface that will increase their hydrophilicity and improve the catalyst support interaction (see Chapter 3) [111]. These experimental methods include impregnation [113,114], ultrasound [115], acid treatment (such as H2S04) [116— 119], polyol processing [120,121], ion-exchange [122,123] and electrochemical deposition [120,124,125]. Acid-functionalized CNTs provide better dispersion and distribution of the catalysts nanoparticles [117-120],... 

Measurements of D carried out at a selected temperature (20°C) as a function of the concentration of organic solvent from 10 to 100% have been published elsewhere (Douzou, 1977a,b). There is a marked proportional decrease in the dielectric constant as the concentration of organic solvent is increased. This effect is very pronounced in the case of methanol and MPD and less pronounced for dimethylformamide and polyols. Adding 50% of most of the organic solvents selected decreases the di-... 

Polymerization of the oxiranes is typically propagated from a starter molecule that is chosen to define the functionality if) of the final polyol. The functionality and the molecular weight of polyols are the main design features that define the polyurethane properties in the end-use applications. Additionally, the balance of EO and PO in the polyether polyols, mainly for flexible foam polyols, is tailored to enhance the compatibility of formulations and the processability of the foam products. The exact composition of the polyols defines the crucial performance features of the final polyurethane product. Even seemingly small differences in polyol composition can result in changes to polyol processabihty and polyurethane performance. This becomes a crucial issue when replacing conventional petrochemical polyols with polyols from different feedstocks. To demonstrate the sensitivity of commercial formulations to changes in feedstocks, a simple example is offered below. 

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