4 research outputs found
Activated carbonates:Enabling the synthesis of differentiated polycarbonate resins via melt transcarbonation
\u3cp\u3eActivated carbonates facilitate the preparation of polycarbonates based on monomers that are unsuitable for traditional melt polymerization at high temperatures. Bis(methyl salicyl) carbonate (BMSC) clearly shows reactivity benefits over diphenyl carbonate in melt polymerization reactions, resulting in shorter reaction times and reduced heat exposure during polymerization. The increased reactivity enables the melt polymerization of a wide range of monomers, as demonstrated by two examples using volatile resorcinol and sterically hindered tert-butyl hydroquinone as monomers in the preparation of (co)polycarbonates.\u3c/p\u3
Thermotropic Polyesters from 2,5-Furandicarboxylic Acid and Vanillic Acid: Synthesis, Thermal Properties, Melt Behavior, and Mechanical Performance
In this work, we address the synthesis
of novel aromatic–aliphatic
biobased polyesters showing thermotropic behavior in the melt. Successful
incorporation of different biobased monomers such as 2,5-furandicarboxylic
acid (2,5-FDCA), suberic acid (SuA), and vanillic acid (VA) in thermotropic
liquid crystalline polymers (TLCPs) is made possible by performing
synthesis at low temperatures. The chemical structures, molecular
weights, phase transitions, thermal behavior, and mechanical performance
of the synthesized polymers are studied using polarization optical
microscopy, WAXD, DSC, TGA, DMTA, solid-state NMR spectroscopy, rheology,
and tensile tests. It is shown that the incorporation of the rigid,
aromatic 2,5-FDCA moiety enhances the formation of blocky copolymers,
whereas the VA moiety tends to decrease the block formation. However,
when combined, nonblocky TLCPs containing 2,5-FDCA and VA with high
aromatic content can be obtained. These materials show a low temperature
transition from the crystalline to the nematic phase, and stable nematic
phases up to 300 °C and higher. Furthermore, in such polymers,
the 2,5-FDCA and VA moieties require more thermal energy to become
mobile compared to the phenyl rings in hydroxybenzoic acid, hydroquinone,
and 4,4′-biphenol. Mechanical analysis shows that the performance
of these polymers is correlated to their crystallinity. Surprisingly,
a higher crystallinity results in ductile behavior, whereas a lower
crystallinity results in a higher modulus, a higher stress at break,
and a lower strain at break