Bio-Sourced Networks from Thermal Polyaddition of a Starch-Derived α-Azide-ω-Alkyne AB Monomer with an A2B2 Aliphatic Cross-linker

A sun eh-derived alpha-azide-omega-alkyne 1,4 3,6-dianhydrohexitol AB monomer and a novel symmetrical heterofunctional A(2)B(2) aliphatic cross-linker, i c 2,2-bis(azidomethyl)-1.3-bis(O-propargyl) propanediol, were copolymerized at various molar ratios to generate biosourced networks through thermal 1,3-dipolar Huisgen polyaddition The investigation of the cross-linking reactions through DSC analyses confirmed the highly exothermic character of the azide/alkyne cycloaddition (Delta H-(total) = 232 +/- 5 kJ/mol of functional groups of type A or B) and as predicted clearly underlined a one-to-one relationship between the glass transition temperature and the conversion Experimental values of conversion at the gel point estimated from DSC and rheological measurements deviated significantly from the ideal main-field theory of network formation On the basis of statistical calculations, this behavior was assigned to the occurrence of intramolecular cyclizations during the network formation Although a significant fraction of intramolecular cycles was generated during the curing process, the AB + A(2)B(2) thermal 1,3-dipolar Huisgen polyaddition strategy afforded relatively high glass transition temperature polytriazole networks (T-g >= 140 degrees C) using versatile processing conditions and in the absence of additives.