Synthesis and characterization of novel Schiff base polyurethanes

Abstract

Eight different types of novel polyurethanes (PUs) were synthesized through the polyaddition reaction of 4,4 0 -(ethane-1,2-diylidenedinitrilo)diphenol and 4,4 0 -(pentane-1,5-diylidenedinitrilo)diphenol with four different diisocyanates: 4,4 0 -diphenylmethane diisocyanate, toluene 2,4-diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate. The resulting PUs were soluble in polar, aprotic solvents. Structures of the diols and PUs were established with ultraviolet-visible, fluorescence, Fourier transform infrared (FTIR), 1 H-NMR, and 13 C-NMR spectroscopy data. FTIR and NMR spectral data indicated the disappearance of both hydroxyl and isocyanate groups in the PUs. The thermal properties were investigated with thermogravimetry and differential scanning calorimetry. The weight losses, glass transitions, onset temperatures, and crystalline melting temperatures were measured. All the PUs exhibited semicrystalline and amorphous morphologies, as indicated by X-ray diffraction.

Radiation Crosslinking of Polyurethanes: Characterization by FTIR, TGA, SEM, XRD, and Raman Spectroscopy

“…All samples of irradiated and unirradiated polyurethane thermally coincide until temperature 298 ∘ C, where TGA data indicate that the MDI-based PUs exhibited better thermal stability and this is attributed to the presence of biphenyl groups on the main chains [36]. Some difference was observed between 333 and 480 ∘ C as shown in Figure 7 where the thermal stability of radiation crosslinking polyurethane is greatly improved.…”

Synthesis and characterization of novel polyurethanes based on 2,6‐bis(4‐hydroxybenzylidene) cyclohexanone hard segments

“…These results are in good agreement with our previous reports. [9][10][11] This could be due to variations in the unsaturated nature of the monomer.…”

“…To overcome these difficulties, the modification of their structures is necessary by the introduction of bulky or asymmetric groups on the pendant polymer backbone or the incorporation of noncoplanar structural units on the main polymer chain. [5][6][7][8] In our earlier studies, [9][10][11] we prepared Schiff-base PUs and azo-based diol-containing PUs with 2,2 0 -[ethane-1,2-diylbis(nitrilomethylylidene)] diphenol, 2,2 0 -[hexane-1,6-diylbis(nitrilomethylylidene)] diphenol, 4,4 0 -(ethane-1,2-diylidenedinitrilo) diphenol and 4,4 0 -(pentane-1,5-diylidene-dinitrilo) diphenol, 4, 4 0 -[1,4-phenylenedi-diazene-2,1-diyl] bis (2-carboxyphenol), and 4,4 0 -[1,4-phenylenedi-diazene-2,1-diyl] bis(2-chlorophenol) with different diisocyanates. In continuation of these studies, we now propose the synthesis of PUs based on chalcone groups containing diols such as 2,6-bis(4-hydroxybenzylidene) cyclohexanone (BHBC) as hard segments with 4,4 0 -diphenylmethane diisocyanate (MDI), toluene 2,4-diisocyanate (TDI), isophorone diisocyanate (IPDI), and hexamethylene diisocyanate (HDI).…”

Synthesis and characterization of novel polyurethanes based on N1,N4‐bis[(4‐hydroxyphenyl)methylene]succinohydrazide hard segment

“…To overcome such difficulties, polymer structure modification is necessary, wherein one can introduce asymmetric or bulky groups on the pendant polymer backbone or incorporate noncoplanar structural units on the main polymer chain 11–14. In our previous papers,15–17 Schiff‐based PUs, chalcone‐based PUs and azo‐based diol containing PUs have been prepared using 2,2′‐{ethane‐1,2‐diylbis(nitrilomethylylidene)}diphenol, 2,2′‐{hexane‐1,6‐diylbis(nitrilomethylylidene)} diphenol, 2,2′‐{1,4‐phenylenebis‐[nitrilomethylylidene]}diphenol, 2,2′‐{4,4′‐methylene di‐2‐methylphenylene‐1,1′‐bis[nitrilomethylylidene]}diphenol, 2,6‐bis(4‐hydroxy‐benzylidene)cyclohexanone, 4,4′‐[1,4‐phenylenedi‐diazene‐2,1‐diyl]bis(2‐carboxy‐phenol), and 4,4′‐[1,4‐phenylenedi‐diazene‐2,1‐diyl]bis(2‐chlorophenol) with different diisocyanates.…”