Polyol

In [|polymer chemistry], polyols are compounds with multiple [|hydroxyl] [|functional groups] available for [|organic reactions]. A molecule with two hydroxyl groups is a diol, one with three is a triol, one with four is a tetrol and so on. Monomeric polyols such as [|glycerin], pentaerythritol, [|ethylene glycol] and [|sucrose] often serve as the starting point for polymeric polyols. These materials are often referred to as the "initiators" and reacted with [|propylene oxide] or [|ethylene oxide] to produce polymeric polyols. However, they should not be confused with [|free radical] "initiators" used to promote other polymerization reactions. The functional group used as the starting point for a polymeric polyol need not be a hydroxyl group; there are a number of important polyols which are built up from [|amines]. A primary amino group (-NH2) often functions as the starting point for two polymeric chains, especially in the case of polyether polyols. Polymeric polyols are generally used to produce other polymers. They are reacted with [|isocyanates] to make [|polyurethanes] used to make [|mattresses], foam insulation for appliances ( [|refrigerators] and [|freezers] ), home and automotive seats, [|elastomeric] shoe soles, fibers (e.g. [|Spandex] ), and [|adhesives]. [|[2]] Polymeric polyols are usually [|polyethers] or [|polyesters]. Polyether polyols are made by reacting [|epoxides] like ethylene oxide or propylene oxide with the multifunctional initiator in the presence of a [|catalyst], often a strong base such as [|potassium hydroxide] or a double metal cyanide catalyst such as zinc hexacyanocobaltate-t-butanol complex. [|[3]] Common polyether diols are [|polyethylene glycol], [|polypropylene glycol] , and [|poly(tetramethylene ether) glycol]. The examples shown below are fairly low molecular weight triols based on [|glycerin] (a triol) being reacted with [|propylene oxide], [|ethylene oxide] or a combination of the two. In reality, the chains would not be of equal length in any one molecule and there would be a distribution of molecular weight polyols within the material. Polyether polyols account for about 90% of the polymeric polyols used industrially; the balance is polyester polyols. [|[4]] Another class of polymeric polyols is the [|polyesters]. Polyesters are formed by condensation or [|step-growth polymerization] of diols and [|dicarboxylic acids] (or their derivatives), for example [|diethylene glycol] reacting with [|phthalic acid]. [|[5]] Alternatively, the hydroxyl group and the carboxylic acid (or their derivatives) may be within the same molecule, as in the case of [|caprolactone]. The example below is an idealized structure that could be obtained by reacting [|pentaerythritol] (a tetrol) with [|gamma-butyrolactone]. [|Hydroxyl-terminated polybutadiene] is a polyol used to produce [|polyurethane]. Polyester polyols from [|vegetable oils], known as [|natural oil polyols] or NOPs, are replacing some epoxide-based polyols.

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Polyol is an alcohol containing multiple hydroxyl groups. The term polyol is used in food science and polymer chemistry. It can be available for organic reactions. However, polymeric polyols can be used to produce other polymers.