Thermotropic polyesters are an important class of materials for high erformance applications. Their low melt viscosities, low thermal expansion coefficients, high use temperatures, and ease in processing allow for the production of high strength and high modulus fibers, films, or compression-molded articles. In this work we explore the synthesis, melt extrusion, fiber spinning, and performance of thermotropic liquid-crystalline polyesters from renewable resources (BioLCP). Special focus is on the application of the bio-based monomers vanillic acid and 2,5-furandicarboxylic acid and their added value and functionality on BioLCP properties.
Through the application of a melt-polycondensation reaction at mild temperatures (< 260 °C), we have successfully synthesized a range of BioLCP containing various aliphatic and aromatic monomers with molecular weights (Mn) of 10,000 g/mol and higher . Using various characterization tools, we demonstrate that a careful selection of the aromatic and aliphatic monomers gives excellent control over the glass transition temperatures, melting temperatures, overall crystallinity, and the degree of segmental block formation inside the polymeric chains. Furthermore, we demonstrate that the ease in processing expected from such BioLCP persists and fiber spinning can successfully be conducted, yielding fibers with tensile moduli up to 20 GPa.  Lastly, we explore and discuss the application of the developed BioLCP as fillers for the development of fully renewable composites. We demonstrate that the developed materials are highly efficient fillers in polyester blends: Detailed TEM, DSC, SAXS, and tensile analysis indicate that these BioLCP fillers act as both reinforcement and nucleating agent.  This provides a unique opportunity to control the composite morphology, and thereby provides a tool to develop composites with enhanced stiffness, strengths and high elongations at break (> 600 %). Overall this technique allows for control over the crystallization morphology in processed products by simply controlling the morphology and placement of the LCP filler.
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Wilsens, C.H.R.M.; Pepels, M.P.F.; Spoelstra, A.B.; Portale, G.; Auhl, D.; Deshmukh, Y.S.; Harings, J.A.W.; Macromolecules, 2016, 49, 2228.