Liquid Crystalline Bispropargyl Thermosets

Abstract

A series of rigid-rod bispropargyl thermoset monomers have been synthesized. These monomers were examined by differential scanning calorimetry (DSC) and hot stage polarized optical microscopy. Enantiotropic or monotropic nematic liquid crystalline phases were observed for all but two monomers. Partial curing of these reactive liquid crystalline monomers resulted in the formation of stable liquid crystalline phases with broad nematic phase ranges. In one example, a monomer that was neither enantiotropic nor monotropic exhibited a stable nematic phase after partial curing. DSC investigations indicated that the onset temperature of thermally induced cross-linking was approximately 260°C and insensitive to the phase type. The rate of cure was insensitive to the phase in which the cure occurred due to the unusual reaction mechanism for the propargyl end group.

New liquid crystals and liquid crystalline thermosets based on wholly aromatic rigid-rod mesogens

“…This distribution of peaks is very common: in DSC heating scans most LCs with reactive end-groups exhibit melting endotherms followed by an exotherm corresponding to the cross-linking process. 23,24 The thermal properties of the LCs and LCTs are listed in Table II.…”

Side chain cholesteric liquid crystalline elastomers: synthesis and phase behaviour

“…Introduction Present day materials science is directed towards the development of multifunctional and oriented structures. One example of such supramolecular systems is the liquid crystalline networks (LCN) where research into materials with anisotropic properties has recently expanded rapidly [1][2][3][4][5][6][7][8][9][10]. Networks with cholesteric structures have attracted special interest, because of their unique properties and potential application in, for example, flat-panel displays, non-linear optics and organic pigment [11][12][13][14].…”

Liquid crystalline vinyl ester resins for structural adhesives

“…By locking a highly oriented structure, such as that of a liquid crystal, in a cured system, the properties of liquid crystals can be combined with those typical of thermosetting systems. The resulting materials are characterized by high tenacity, high chemical resistance, high resistance to water permeability, and, mainly, by the possibility of being oriented by magnetic or electric elds on curing [24,25]. This class of materials represents a signi cant improvement over conventional resins, as the next generation of highperformance thermosets for advanced applications.…”