Effect of physiological temperature on the mechanical properties and network structure of biodegradable poly(propylene fumarate)-based networks

Authors: Timmer M.D.; Horch R.A.; Ambrose C.G.; Mikos A.G.

Source: Journal of Biomaterials Science, Polymer Edition, Volume 14, Number 4, 2003 , pp. 369-382(14)

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Abstract:

Poly(propylene fumarate) (PPF)-based networks have exhibited increases in mechanical properties during their initial stages of degradation. This study was designed to investigate whether physiological temperatures are the source of this reinforcing behavior by influencing the formation of additional crosslinks within the network. Utilizing a model PPF network formed with the crosslinking agent poly(propylene fumarate)-diacrylate (PPF-DA), cylindrical specimens were stored in an inert environment and conditioned at -20 and 37°C while their mechanical properties and network structure were monitored over a six week period. The PPF/PPF-DA specimens exposed to physiological temperatures showed an increase in compressive modulus from 1674 ± 88 to 2059 ± 75 MPa. The double bond conversion improved as well, from 64 ± 1 to 70 ± 1%, indicating that crosslinks were being formed in the network. The additional reactivity occurred exclusively with unreacted fumarate bonds. PPF/PPF-DA networks stored at -20°C showed no changes in mechanical properties; however, they increased when subsequently conditioned at 37°C. The results were used to explain that PPF-based networks undergo a biphasic degradation behavior due to the competing hydrolytic degradation and thermal induced crosslinking. In addition, heat treating the networks at higher temperatures can be utilized as a means to further reinforce PPF-based materials.

Keywords: POLY PROPYLENE FUMARATE; CROSSLINKING; DEGRADATION; MECHANICAL PROPERTIES; MECHANICAL REINFORCEMENT

Document Type: Research article

DOI: http://dx.doi.org/10.1163/156856203321478874

Publication date: 2003-04-01