Maleic anhydride (CMA) and itaconic anhydride modified collagen (CITA) were prepared as precursors for production of interpenetrated polymer networks (IPN). Calculated values for Huggins coefficient in aqueous diluted and semi-diluted solutions of modified collagen indicated a slightly tendency of aggregation for itaconic anhydride-modified collagen. In semi-diluted solution collagen (Coll) and CMA present slightly differences in the thixotropic behavior, while CITA has a pronounced thixotropic behavior. Flow and oscillatory measurements revealed an elastic behavior of the collagen solutions, pure and modified with MA or ITA, as the storage modulus (G′) has always a superior value compared with the loss modulus (G″). The denaturation temperature (Td) of unmodified collagen increased from 34oC to 40oC for CMA and to 39oC for CITA respectively, by formation of covalent bonds that stabilize the triple helix. © 2013 Wiley Periodicals, Inc. Biopolymers 101: 228–236, 2014.