BEH.462/3. 962J Molecular Principles of Biomaterials Spring 2003 Structure of covalent hydrogel biomaterials Chemical and physical structure Structure and swelling of hydrogel materials network chain polymerization solution hydrogel dilution swelling Networks formed by stitching together monomers in aqueous solutions via cross-linkers that are multifunctional units o Draw an example of a crosslinker: bisacrylamide networks from hydrophilic vinyl monomers hydroxyethyl methacrylate poly(ethylene glycol)methacrylate acrylic acid acrylamide, N-isopropylacrylamide Common crosslink PEGDMA EGDMA Hydrogels undergo swelling in analogy to dilution of free polymer chains in solution o Difference lies in limit to'dilution when chains are cross-linked together(ENTROPIC Poly (2-hydroxyethyl methacrylate)hydrogels One of the first biomedical hydrogels; applied to contact lenses in late 1950s Lecture 7-Hydrogels 1 6of15BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 Structure of covalent hydrogel biomaterials Chemical and physical structure Structure and swelling of hydrogel materials Ôineffective network = = = x = x x x x x x chainÕ Ô effective network chainÕ = x = = = x = polymerization solution hydrogel dilution swelling • Networks formed by stitching together monomers in aqueous solutions via cross-linkers that are multifunctional units o Draw an example of a crosslinker: bisacrylamide • networks from hydrophilic vinyl monomers • hydroxyethyl methacrylate • poly(ethylene glycol) methacrylate • acrylic acid • acrylamide, N-isopropylacrylamide • Common crosslinkers: ƒ PEGDMA, EGDMA ƒ bis-acrylamide • Hydrogels undergo swelling in analogy to dilution of free polymer chains in solution o Difference lies in limit to ‘dilution’ when chains are cross-linked together (ENTROPIC) • Poly(2-hydroxyethyl methacrylate) hydrogels 6 • One of the first biomedical hydrogels; applied to contact lenses in late 1950s Lecture 7 – Hydrogels 1 6 of 15