Cross-linking Characteristics and Mechanical Properties of an Injectable Biomaterial Composed of Polypropylene Fumarate and Polycaprolactone Co-polymer

In this work, a series of co-polymers of polypropylene fumarate-co-polycaprolactone (PPF-co-PCL) were synthesized via a three-step polycondensation reaction of oligomeric polypropylene fumarate (PPF) with polycaprolactone (PCL). The effects of PPF precursor molecular weight, PCL precursor molecular weight and PCL fraction in the co-polymer (PCL feed ratio) on the maximum cross-linking temperature, gelation time and mechanical properties of the cross-linked co-polymers were investigated. The maximum cross-linking temperature fell between 38.2 +/- 0.3 and 47.2 +/- 0.4 degrees C, which increased with increasing PCL precursor molecular weight. The gelation time was between 4.2 +/- 0.2 and 8.5 +/- 0.7 min, and decreased with increasing PCL precursor molecular weight. The compressive moduli ranged from 44 +/- 1.8 to 142 +/- 7.4 MPa, with enhanced moduli at higher PPF precursor molecular weight and lower PCL feed ratio. The compressive toughness was in the range of 4.1 +/- 0.3 and 17.1 +/- 1.3 kJ/m(3). Our data suggest that the cross-linking and mechanical properties of PPF-co-PCL can be modulated by varying the composition. Therefore, the PPF-co-PCL co-polymers may offer increased versatility as an injectable, in situ polymerizable biomaterial than the individual polymers of PPF and PCL. (C) Koninklijke Brill NV, Leiden, 2011