The name polyols refers to
alcoholscontaining multiple hydroxylgroups. In two technological disciplines polyols have special meaning: food scienceand polymer chemistry. For information as it pertains to food ingredients, please see the article on sugar alcohols.
Polyols in food science
Sugar alcohols, a class of polyols, are commonly added to foods because of their lower caloric content than sugars; however, they are also, in general, less sweet, and are often combined with high-intensity sweeteners. They are also added to chewing gumbecause they are not metabolized (broken down) by bacteria in the mouth, so they do not contribute to tooth decay. Maltitol, sorbitol, and Isomaltare some of the more common types. Sugar alcohols may be formed under mild reducing conditions from their analogue sugars.
Polyols in polymer chemistry
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.
The main use of polymeric polyols is as reactants to make other polymers, They can be reacted with
isocyanatesto make polyurethanes, and this use consumes most polyether polyols [cite web |url=http://www.sriconsulting.com/CEH/Public/Reports/688.3000/ |title=Polyether Polyols for Urethanes (abstract only without subscription)|last=Chinn |first=Henry| coauthors=Akihiro Kishi and Uwe Loechner |date=April, 2006 |work= |publisher=SRI Consulting] These material are ultimately used to make elastomericshoe soles, fibers ( Spandexfor example), foam insulation for appliances ( refrigerators and freezers), adhesives, mattresses, automotive seats and so on.
Monomeric polyols such as
pentaerythritol, ethylene glycoland glycerinoften serve as the starting point for polymeric polyols. Naturally occurring polyols like castor oiland sucrosecan also be used to make synthetic polymeric polyols. These materials are often referred to as the "initiators" for the polymeric polyols, but 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.
The polymeric chains built out from the initiator are usually
polyestersor polyethers. Polyether polyols are made by reacting epoxideslike ethylene oxideor propylene oxidewith the multifunctional initiator in the presence of a catalyst, often a strong base such as potassium hydroxideor more exotic metal cyanides. [cite journal
coauthors =J. L. Garcia, E. J. Jang
title =New heterogeneous catalysis for the synthesis of poly(ether polyol)s
journal =Journal of Applied Polymer Science
date =4 Sep 2002
format =abstract] 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 oxideor 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. [cite web|url=http://www.dow.com/voractiv/news/20051017bs.htm|title=Dow Polyurethanes and Thermoset Systems, uses and innovations|accessdate=2007-09-14] Another class of polymeric polyols is the polyesters. Polyesters are formed by condensation or step-growth polymerizationof diols and dicarboxylic acids (or their derivatives), for example diethylene glycolreacting with phthalic acid. [ cite journal
coauthors =Oleg Kadkin, Karol Osajda, Thomas A. Barber
title =Polyester Polyols: Synthesis and Characterization of Diethylene Glycol Terephthalate Oligomers
journal =Journal of Polymer Science: Part A: Polymer Chemistry
accessdate =2008-08-09] 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.A specialist class of polyol is the hydroxyl-terminated polybutadienes. These polyols are extensively used in formulations for polyurethanes.
The production of polyester polyols from
vegetable oilsis becoming increasingly important. These materials are known as natural oil polyols, or NOPs.
* http://polyols.synair.com/about_polyols.htm Website
* [http://www.roquette.com/eng/products/polyolsmaltitolmannitolsorbitolxylitol.htm Food polyols overview]
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