Abstract
ABSTRACTBenzoxazine monomers based on sesamol and aliphatic diamines with a systematic variation of chain lengths were synthesized to study the influence of the diamine chain lengths on thermal and thermo‐mechanical properties. Differential scanning calorimetry analysis revealed an even‐odd effect as the melting point for monomers with an odd chain length was at least 35°C lower compared to their even counterparts. In addition, longer diamine chain lengths increased the beginning of the polymerization from 187°C for diaminoethane (DAE) up to 218°C for diaminohexane (DAH). Rheological analysis revealed a short time frame between the melting and polymerization for monomers based on diaminoethane, ‐propane or ‐butane preventing a polymerization. Polymerization was successful for sesamol benzoxazine with diaminopentane (S‐DAPe) and ‐hexane (S‐DAH) resulting polymers with high glass transition temperatures of up to 228°C for poly(S‐DAPe) and 231°C for poly(S‐DAH), respectively. Remarkably, it was found that S‐DAH could also be polymerized at a lower temperature of 155°C yielding a Tg of 175°C. Furthermore, MCC results showed that peak heat release rate and total heat release of the diamine based polybenzoxazines decrease with decreasing chain length. In comparison to other sesamol based benzoxazines the presence of diamine linkers result in bisbenzoxazines with higher Tg.
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