Two novel methods for synthesizing poly (propylene fumarate): Technical aspects and role of vacuum and N2 purging effects

Poly (propylene fumarate) (PPF), a linear unsaturated polyester consisting of alternating propylene glycol and fumaric acid units, can be cured in vivo to fill the skeletal defects with minimal surgical intervention. Many different methods have been reported for synthesizing PPF, but none of them gives a clear method. The present paper introduces two new methods in PPF synthesis: Modified reflux system (MRS) and mixed reflux-distillation system (MRDS). Similarly, the effects of applying vacuum (vacuum sequence, time, vacuum applying position, and the distance between vacuum applying position and reactor) as well as nitrogen gas (used continuously or only as an N2 blanket) on the PPF synthesis have been studied. The PPF obtained using optimum reaction condition has been characterized by using NMR, FTIR, and GPC analyses. It is demonstrated that the efficiency of MRDS in synthesizing PPF is higher than that of MRS. Nitrogen gas, vacuum applying position, continuously/stepwise-continuously applying vacuum and other parameters show an important role in the polymerization of PPF in both the MRDS and MRS systems.