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(Poly)Vinyl Alcohol As A Humectant

Vinyl alcohol, also known as ethenol, is a highly unstable monomer. The individual use of vinyl alcohol is rarely applied due to its high instability(1). In order for vinyl alcohol to be utilized as a humectant it must first become polyvinyl alcohol. To form polyvinyl alcohol two processes are used: polymerization and hydrolysis. Vinyl alcohol itself is not used in this process due to its high instability but vinyl acetate, a monomer, undergoes polymerization--a process in which monomers are formed together through a chemical reaction to form a polymer chain(2). After polymerization, hydrolysis occurs--this process separates chemical bonds with the addition of water. After this process is complete, the product polyvinyl alcohol is formed [take note that vinyl alcohol is not used for the formation of polyvinyl alcohol, but rather vinyl acetate's structure undergoes polymerization and hydrolysis in order to model a structure similar to the chemical framework of vinyl alcohol](3). (much of the information in this paragraph is unnecessary, only include 1-2 sentences that state the difference between vinyl alcohol and pva)

How It Works (this title is inconsitant with Wikipedia practices)

Polyvinyl alcohol is hygroscopic which allows it to attract and retain moisture from the surrounding environment(4). This property also classifies polyvinyl alcohol as a humectant. How humectants work to retain moisture is attributed to hydrogen bonding. Certain molecules, like water, have different polarities. For example, in water (H20) slightly negative oxygen atoms are attracted to slightly positive hydrogen atoms. Because of this attraction, the opposite atoms form a hydrogen bond(5). Humectants, including polyvinyl alcohol, favor hydrogen bonding. Applying polyvinyl alcohol onto a product allows the applied product to attract water from the environment and retain the moisture(6).

What sets vinyl alcohol apart from other humectants is how their strengths and weaknesses compliment in order to fulfill the needed task. For example, in the pharmaceutical field the demand for humectants is for the purpose that there are certain moisture-sensitive pills that need help preserving their water content so that there is no drug degradation(7). For this specific purpose, vinyl alcohol and methacrylate-methymethacrylates was found to be the most effective for this situation because of their high tensile strength and reactive potency to the ingredients used in the production of most medicine pills. Other humectants that are widely used such as propylene glycol are not used for this purpose due to their freezing point depression towards water as well as their particular toxicity towards animals and humans(8). Having varying humectants with their distinct properties allow us to use whichever humectant is most effective for the given circumstance.

Absorption vs Adsorption (this section seems unrelated to the previous section)

Humectants promote adsorption rather than absorption. Absorption occurs when a substance soaks in moisture, whereas adsorption occurs when a substance keeps the moisture on the surface without allowing it to soak in(9). The property of adsorption is essential to the classification of humectants. All humectants promote adsorption rather than absorption.

Other uses for polyvinyl alcohol:


 * Pharmaceutical products: retains moisture within pills that would otherwise be lost(10).
 * Cosmetic products: hair gels, shampoos, conditioners, moisturizers, lotions- reduces water loss, increases water content and repairs skin barrier(11).
 * Fishing products: keeps bait moist to lengthen expiration date
 * Industrial products: lubricants, adhesives, fibers, emulsifiers, anti-static coating - "steroids" certain active ingredients within products(12).

References  (this is NOT the proper way to cite sources, you need to use the template provided. ==References==


 * 1) 	Smith, B. & Radon, L. (1990) “Structure of Vinyl Alcohol: A Resolution of the Discrepancy between Theory and Experiment” http://pubs.acs.org/doi/pdf/10.1021/ja00177a011.
 * 2) 	Smith, B. & Radon, L. (1990).
 * 3) 	G. F Blehn, M. L Ernsberger (1948) "Polyvinyl Alcohol as an Emulsifying Agent" http://pubs.acs.org/doi/pdf/10.1021/ie50464a024
 * 4) 	"The Ultimate Guide to Humectants and Hair." The Ultimate Guide to Humectants and Hair. N.p., n.d. Web. 17 Mar. 2014. Bley, O. Siepmann, J. & Bodmeier R (2009). http://www.naturallycurly.com/curlreading/ingredients/the-ultimate-guide-to-humectants-and-hair.
 * 5) 	Bley, O. Siepmann, J. & Bodmeier R (2009). “Protection of moisture-sensitive drugs with aqueous polymer coatings: importance of coating and curing conditions’http://www.ncbi.nlm.nih.gov/pubmed/19477253.
 * 6) 	Bley, O. Siepmann, J. & Bodmeier R (2009).
 * 7) 	G. F Blehn, M. L Ernsberger (1948).
 * 8) 	Horvath-Szabo, G. Nagy, M. Heiland, H. & Maham, Y. (2002) “Volumetric Properties of Poly (Vinyl Alcohol, Vinyl Sulfate Ester Salt) Polyelectrolytes in Salt Free Aqueous Solutions” http://web.a.ebscohost.com/ehost/pdfviewer/pdfviewer?sid=3d016942-b0ad-4cf6-84ad-653f6b5c1093%40sessionmgr4003&vid=5&hid=4204.
 * 9)       Kawai, Takae (2014) "Adsorption characteristics of polyvinyl alcohols on modified zeolites." http://link.springer.com/article/10.1007%2Fs00396-013-3135-2/fulltext.html
 * 10) 	Bley, O. Siepmann, J. & Bodmeier R (2009).
 * 11) 	"The Ultimate Guide to Humectants and Hair." The Ultimate Guide to Humectants and Hair. N.p., n.d. Web. 17 Mar. 2014. Bley, O. Siepmann, J. & Bodmeier R (2009). http://www.naturallycurly.com/curlreading/ingredients/the-ultimate-guide-to-humectants-and-hair.
 * 12) 	Smith, B. & Radon, L. (1990).