(The) synthesis and characterization of biodegradable PU/PEGDA IPNs

Abstract

In this dissertation, we synthesized biodegradable hydrophobic polyrurethane(PU)/hydrophilic poly(ethylene glygol)diacrylate (PEGDA) IPNs having micro-separated structure to overcome the problems caused in the long-term clinical use. Polyurethane was modified using biocompatible and biodegradable PCL diol and the hydorxyl group of PEG was substituted to crosslinkable acrylate group. PU/PEGDA IPNs were synthesized changing the molecular weight of PEGDA and crosslink density of PU to investigate the effect of crosslink density on morphology, bulk and surface hydrophilicity and mechanical properties. From the DSC results, it was shown that all PU/PEGDA IPNs had one broad Tg between the Tgs of two pure components except IPN 1K(25:75) and IPN 1K(50:50) due to its faster network forming rate of PEGDA 1K. All PU/PEGDA IPNs had micro-separated structure with co-continuous morphology. The domain size of PU/PEGDA IPNs decreased as decreasing the molecular weight of PEGDA, which indicated an increase in the intermixing between the PU-rich phase and the PS-rich phase. The equilibrium-swelling ratio in water decreased with decreasing the molecular weight of PEGDA in the same composition due to the increased crosslink density of PEGDA and decreased with increasing the PU content in the same molecular weight of PEGDA. Also the interfacial energy of PEGDA homo networks and PU/PEGDA IPNs was decreased with increasing the molecular weight of PEGDA in the same composition and decreased with decreasing the PU content in the same molecular weight of PEGDA. From the mechanical properties, it was shown that IPN (75:25) with 2,000 $\over \Huge {Mc}$ of PU had very high tensile modulus, showed synergistic behavior of interpenetration. The modulus shows higher value when the PEGDA crosslink density is increased.