Molecular engineering of photoactive liquid crystalline polyester epoxies containing benzylidene moiety

Abstract

A series of photoactive liquid crystalline polyester epoxies incorporating bisbenzylidene segments as photoactive mesogenic cores were synthesized by polyaddition of diepoxy monomers and terephthalic acid/trimesic acid. To investigate the influence of structural parameters such as, molecular architecture, structural rigidity of mesogenic unit and substituents on thermal, mesogenic, and photoactive properties, the bisbenzylidene segment was incorporated into one acyclic and two cycloalkanone units with two and four substituents, respectively in both linear and hyperbranched architectures. Degree of branching of hyperbranched polymers was found to be in the range of 0.49–0.62. All polymers exhibited nematic mesophase (nematic droplets). Photo induced (2π + 2π) cycloaddition reaction, upon exposure to light at 365 nm, was examined. Inter molecular photocycloaddition was confirmed by photoviscosity measurement of UV irradiated polymer solutions. Faster photo induced reactivity of polymers in hyperbranched architecture was observed when compared to linear structure. Acyclic units facilitated photocycloaddition, and five‐membered ring showed higher photoactivity compared to six‐membered ring. The steric hindrance caused by substituents decreased the photoactivity of polymers. Refractive index change was found to be in the range of 0.015–0.024. Substantial variation of refractive index indicates that these polymers could be used for optical recording. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7637–7655, 2008

Bio-Based Aromatic Epoxy Monomers for Thermoset Materials

“…Rao and Samui [ 174 ] synthesized diepoxy monomers including bisbenzylidene segments by reaction between vanillin or syringaldehyde with acetone ( 40 ) and cycloaliphatic ketones ( 41 ) followed by glycidylation with epichlorohydrin ( Scheme 13 ). These monomers were used to synthesize linear polyesters for photoactive liquid crystal applications but also reacted with benzene-1,3,5-tricarboxylic acid to obtain dendrimers, although their protocol seems more likely to yield crosslinked materials.…”

“… Synthesis of di-epoxy monomers from vanillin and syringaldehyde with acetone or cycloaliphatic ketones according to Rao and Samui [ 174 ]. …”

Mechanical Properties and Morphology Studies of Thermosets from a Liquid‐Crystalline Epoxy Resin with Biphenol and Aromatic Ester Groups

“…With ordered structures, these materials have many advantages like greater thermal and orientational stabilities, low shrinkage upon curing, low thermal expansion coefficient, low dielectric constant and enhanced reaction rate because of the close proximity of the reacting groups 1–4. Many groups have studied the synthesis,5, 6 mechanical properties,7, 8 optical properties,9, 10 curing behavior,11–13 and orientational behavior14–16 of LCETs.…”

Biobased phenol and furan derivative coupling for the synthesis of functional monomers

“…These reactions were also studied by the group of Samui. 80 Bio-based phenols were synthesized from vanillin or syringaldehyde with good yields from 65 to 78 % ( Figure 21 -(1) and (3)). These dimers were epoxidized and carboxylic acids with different functionalities (2 or 3) were used to open the epoxy ring.…”

“…Aldolisation/crotonisation reactions between vanillin or syringaldehyde and aliphatic ketones 79,80. …”