ABSTRACT
This work shows how furan ring-opening reactions were controlled by polymerization conditions to tune the cross-link density in bio-based poly(furfuryl alcohol) (PFA). The influence of water and isopropyl alcohol (IPA) on the polymerization of furfuryl alcohol, and particularly on furan ring-opening, was investigated by means of 13 Câ NMR and FT-IR spectroscopy. Results indicated that formation of open structures were favored in the presence of solvents, thus leading to modification of the thermo-mechanical properties compared to PFA cross-linked without solvent. Dynamic mechanical analyses showed that when slightly more open structures were present in PFA it resulted in an important decrease of the cross-link density. Despite lower glass-transition temperature and lower elastic modulus for PFA polymerized with solvent, the thermal stability remains very high (>350 °C) even with more open structures in PFA.
ABSTRACT
Furfuryl alcohol (FA) is a biobased monomer derived from lignocellulosic biomass. The present work describes its polymerization in the presence of protic polar solvents, i.e., water or isopropyl alcohol (IPA), using maleic anhydride (MA) as an acidic initiator. The polymerization was followed from the liquid to the rubbery state by combining DSC and DMA data. In the liquid state, IPA disrupts the expected reactions during the FA polymerization due to a stabilization of the furfuryl carbenium center. This causes the initiation of the polymerization at a higher temperature, which is also reflected by a higher activation energy. In the water system, the MA opening allows the reaction to start at a lower temperature. A higher pre-exponential factor value is obtained in that case. The DMA study of the final branching reaction occurring in the rubbery state has highlighted a continuous increase of elastic modulus until 290 °C. This increasing tendency of modulus was exploited to obtain activation energy dependences (Eα) of FA polymerization in the rubbery state.
