Synthesis and characterization of novel polyureas based on benzimidazoline‐2‐one and benzimidazoline‐2‐thione hard segments

Abstract

Six novel polyureas were prepared from benzimidazolin-2-one and benzimidazolin-2-thione, which acted as hard segments, with two aromatic diisocyanates (4,4Ј-diphenylmethane diisocyanate and toluene 2,4-diisocyanate) and one aliphatic diisocyanate (hexamethylene diisocyanate). The polymers that formed were fully characterized with Fourier transform infrared spectroscopy, 13 C-NMR cross-polarization/magic-angle spinning, differential scanning calorimetry, and thermogravimetry. X-ray diffraction revealed that the polymers contained crystalline and amorphous regions that varied with the nature of the backbone structures. All the polyureas were insoluble in common organic solvents, and this made it difficult to investigate their solution properties.

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

“…1,2 However, the majority of PUs and polyureas are insoluble in common organic solvents due to their rigid backbone structures; 3,4 this prohibits their application due to difficulty in processing. 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.…”

Synthesis and Characterization of Pyridine-Based Polyurethanes

“…Hard segmented PUs show poor solubility in common organic solvents due to their rigid backbones [7,8], which limits their application and makes it difficult to process them. In order to overcome such difficulties, the polymer structure modification is necessary, wherein one can introduce the bulky or asymmetric groups on the polymer backbone or incorporate the non-coplanar structural units on the main polymer chain [9,10].…”

Synthesis, characterization, and acoustic properties of new soluble polyurethanes based on 2,2′‐[1,4‐phenylenebis(nitrilomethylylidene)diphenol and 2,2′‐[4,4′‐methylene‐di‐2‐methylphenylene‐1,1′‐bis(nitrilomethylylidene)]diphenol

“…Blackwell and Lee 30 studied multiple melting in the MDI-based PUs that were oriented and thermally annealed. Recently, Raghu and coworkers 18,19 observed two to five endothermic transitions associated with hard-segmented PUs and polyureas. In light of these reports, it is obvious that the melting behavior of PUs is highly dependent on the procedure adopted for their preparation.…”

“…18,19 However, because of the presence of Schiff's base moieties in the main chain, these PUs are soluble in polar solvents such as N 0 -methyl-2-pyrrolidone, DMF, and DMSO. All the PUs are insoluble in water, acetone, methanol, chloroform, diethyl ether, tetrahydrofuran, and hexane because of more lyophobic groups on the backbone.…”

“…However, the utility of substituted aromatic monomers prevents the close packing of macromolecular chains, so improved solubility of the polymers is exhibited. 17 As part of our continuing research into the synthesis of PUs 1,18 and polyureas, 19 we have prepared eight novel PUs by reacting 4,4 0 -diphenylmethane diisocyanate (MDI), toluene 2,4-diisocyanate (TDI), isophorone diisocyanate (IPDI), and hexamethylene diisocyanate (HDI) with 2,2 0 -[1,4-phenylenebis(nitrilomethylylidene)]diphenol (PbNMD) and 2,2 0 -[4, 4 0 -methylene-di-2-methylphenylene-1,1 0 -bis(nitrilomethylylidene)]diphenol (MdMPbNMD). The structures of PbNMD and MdMPbNMD have been confirmed with Fourier transform infrared (FTIR) spectroscopy, 1 H-NMR, and 13 C-NMR spectral data.…”