Synthesis and Characterization of Liquid Crystalline Polyesters Containing α,β-unsaturated Ketone Moiety in the Main Chain Derived from 2,6-bis(4-hydroxybenzylidene)cyclohexanone

Abstract

A series of polyesters containing a photosensitive benzylidene chromophore in the main chain were synthesized from 2,6-bis(4-hydroxybenzylidene)cyclohexanone with various aliphatic and aromatic diacid chlorides by interfacial polycondensation technique. The intrinsic viscosity of the synthesized homo and copolymers determined by Ubbelohde viscometer and found to be 0.13-0.18 dL/g. The molecular structure of the monomer and polymers was confirmed by Fourier Transform infrared, 1 H NMR and 13 C NMR spectroscopic techniques. These polymers were studied for their thermal stability and photochemical properties. Thermal properties were evaluated by thermogravimetric analysis and differential scanning calorimetry. It was found that the polymers were stable up to 238°C and start degrading thereafter. Increase in acid methylene spacer length decreases the thermal stability. The self-extinguishing property of the synthesized polymers was studied by calculating the limiting oxygen index value using Van Krevelen equation. The influence of the length of methylene spacer on phase transition was investigated and it was found that isotropic temperature decreases on increasing the acid methylene spacer length. Hot-stage optical polarizing microscopic study showed that synthesized polymers exhibit grainy texture in the temperature range of 115-127°C. The photolysis of liquid crystalline polyesters revealed that α,β-unsaturated ketone moiety in the main chain dimerizes through 2π+2π cycloaddition reaction to form a cyclobutane derivative that leads to crosslinking.

Synthesis and Characterization of Sustainable Curcumin‐Based Bio‐benzoxazines for Antimicrobial and Anticorrosion Applications

“…The LOI value of curcumin based poly benzoxazines, poly(CU‐a), poly(CU‐ffa) and poly(CU‐oda) calculated from corresponding char yield are 49, 48 and 40, respectively (Table 2). The three poly benzoxazines produced in the current work all had LOI values larger than the threshold value of 26, which suggests that they all have outstanding flame retardant properties [35] …”

“…The three poly benzoxazines produced in the current work all had LOI values larger than the threshold value of 26, which suggests that they all have outstanding flame retardant properties. [35] Water contact angle studies…”

Photosensitive Benzoxazines Derived from Divanillidene Cyclopentanone/Cyclohexanone for Hydrophobic and Optical Applications

“…The title compounds, divanillidene cyclopentaone (DVCP) and divanillidene cyclohexanone (DVCH) were prepared by crossed-aldol condensation of vanillin and cyclopentanone/cyclohexanone, respectively, as reported in the literature. [14,16,21,22]…”

Synthesis and characterization of aromatic copolyesters derived from bisphenol B and phenol red

“…11,12 There has been research focusing on overcoming its defects and increasing its processing mobility. The main approaches are: the introduction of flexible spacer groups in the polymer chain, 5,[13][14][15] bulky pendant groups, 12,16,17 heterocyclic or nonlinear units, 18,19 copolymerization, 20 and so forth. Introducing pendant groups or flexible monomers in the polymer chain to prepare aromatic copolyesters is the most noteworthy among all methods.…”