Polymers of n-vinylpyrrolidone: Synthesis, characterization and uses

Abstract

Polyvinylpyrrolidone (PVP) having molecular weights (Mw) from 2500 to about 1 million is mainly obtained by radical polymerization in solution. The higher molecular weight type products are polymerized in aqueous solution mostly using hydrogen peroxide as initiator. The polymers thus obtained have hydroxyl and carbonyl end groups. More stable end groups can be obtained by polymerization in solvents, which may act as chain transfer agents and which produce low molecular weight type products. Copolymers especially with monomers such as vinyl acetate and with various acrylic compounds may also be produced by solution polymerization. Popcorn polymerization leads to insoluble PVP. Thereby VP is polymerized without initiator in the presence of small amounts of bifunctional monomers. The polymeric flakes thus formed are highly cross-linked, mainly due to entanglements. The molecular weight distribution of soluble PVP is broad due to transfer reactions. An unusual property of PVP is its solubility in water as well as in various organic solvents. The glass transition temperature of high molecular weight polymers (Mw=1 million) is about 175°C and falls to values under 100°C with decreasing molecular weight Mw=2500). PVP forms complexes with various compounds, especially with H-donors such as phenols and carboxylic acids. The complex formed with cross-linked PVP and polyphenols is used commercially for the clarification of beverages. Another commercial use is the complexation of iodine with linear PVP, which leads to effective disinfectants of very low toxicity. Further important applications of PVP in the pharmaceutical field are their use as binding or film forming agents for tablets, and as solubilizing agents for injections. The swelling ability of cross-linked PVP in water is used in disintegrating agents for tablets. In the cosmetic field VP polymers are used as film formers for hair dressing products. Examples of technical applications are adhesives, textile auxiliaries and dispersing agents. © 1985 The Society of Polymer Science, Japan. All Rights Reserved.