Synthesis and characterization of biodegradable network poly(ethylene glycol) films with elastic properties

Novel biodegradable network films with elastic properties were prepared from trimesic acid (Y) and poly(ethylene glycol)s (PEGs) with different molecular weights (MW) and/or 4,7,10‐trioxa‐1,13‐tridecanediamine (I). Prepolymers prepared by a melt polycondensation were cast from N , N ′‐dimethylformamide solution and postpolymerized at 290°C for various times to form a network. The resultant films were transparent, flexible, and insoluble in organic solvents. The X‐ray diffraction scattering pattern showed that all network films are amorphous. The densities of the network films decreased, whereas their water uptake increased with increasing MWs of PEG. The thermal and tensile properties were measured in dry and wet conditions and were affected remarkably not only by MWs of PEG, but also by the water uptake of the films. The glass transition temperatures ( T g ) decreased with increasing MWs of PEG. YPEG 200 and YPEG 1000 films showed good elastomeric properties with an ultimate elongation of 225 and 277%, respectively, in dry condition. The tensile strength of 13 MPa and Young's modulus of 214 MPa were the highest for YPEG 200 among the network elastic films studied. All sample films in wet condition had lower T g 's and tensile properties. The hydrolytic degradation was measured by the weight loss of network films in a buffer solution with or without Rhizopus delemar lipase at 37°C. The degree and the rate of the degradation increased with increasing MWs of PEG, which is compatible with the increase in water uptake of the films. Incorporation of large amount of I moiety into YPEG 1000 film increased the glass transition temperatures, tensile strength and Young's modulus, but depressed elastic nature of the films. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007