Waterborne polyurethane biomaterials

An aqueous waterborne PU dispersion is a binary colloid system in which PU particles range in size from 0.01 to 5.0 pm [55]. The effective method for making PU dispersible in water is to introduce ionic and/or nonionic hydrophilic moieties into its backbone structure. The most important and practical type of waterborne PU is the anionic type. This type of waterborne PU possesses pendant ionized carboxylic acid groups [56]. Anionic waterborne PUs with carboxylic acid groups can be synthesized by a four-step process, which is schematically presented in Eigure 4.9. 

Most conventional waterborne PUs derived from petroleum resources are not biorenewable or biodegradable. The most common method to obtain biorenewable and/or biodegradable waterborne PU is to incorporate bio-based and/or biodegradable components into a waterborne PU backbone during polymer synthesis. 

1 Introduction of bio-based materials into waterborne polyurethanes 

Chain extenders can also be substituted with bio-based components in the synthesis of waterborne PUs. For example, chitosan, a derivative of abundant naturally occurring polysaccharides that has active amino groups, can be used to chain-extend waterborne PUs in water. Chitosan possesses unique biological properties such as nontoxicity, biocompatibility, anticoagulant properties, and biodegradability. Waterborne PU films synthesized with chitosan as a chain extender exhibited excellent mechaiucal and anti-coagulating properties, as well as antibacterial and antifungal activities [63]. 

2 Introduction of biodegradable polyesters into waterborne polyurethanes 

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S.H. Hsu, H.J. Tseng, YC. Lin, The biocompatibihty and antibacterial properties of waterborne polyurethane-sUver nanocomposites. Biomaterials 31 (September 2010) 6796-6808. 

Yoo, H.J., Kim, H.D., 2008. Synthesis and properties of waterborne polyurethane hydrogels for wound healing dressings. Journal of Biomedical Materials Research Part B Applied Biomaterials 85, 326-333. 

Jiang, X., Yu, R, Wang, Z., Li, J., Tan, H., Ding, M., Fu, Q., 2010. Fabrication and characterization of waterborne biodegradable polyurethanes 3-dimensional porous scaffolds for vascular tissue engineering. Journal of Biomaterials Science Polymer Edition 21, 1637-1652. 

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