Quantitative IR characterization of urea groups in waterborne polyurethanes

Abstract

The purpose of this study is to propose a correlation between IR spectra and the urea fraction of waterborne polyurethanes (PUs) to investigate the side reaction, that is, isocyanate–water reaction, during polymerization. This method is based on the decomposition of the spectrum in amide I range, that is, 1600–1800 cm−1, where the bands of interest overlap. Several individual bands present in this region were resolved by employing Fourier self‐deconvolution (FSD) and Gaussian curve‐fitting techniques, and the intensity ratio of urethane's CO to urea's CO was determined. To realize some quantitative measurements, a calibration curve was established with some polyurethane‐urea samples, characterized by 1H NMR, which were used as standards. The concentration ratios of urethane groups to urea groups were determined from 1H NMR. A good correlation was evidenced between IR and 1H NMR measurements. Moreover, waterborne PUs were prepared by miniemulsion polymerization of IPDI with diols. From quantitative IR analysis, it was shown that a vinylic monomer, as a solvent of polyaddition, restrained the isocyanate–water reaction, and this side reaction was influenced by the hydrophilicity of the vinylic monomers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2433–2444, 2008

Novel nucleophilic/basic and acidic organocatalysts for reaction between poorly reactive diisocyanate and diols

“…The urea comes mainly from the capping reaction with DBA; however, the starting PGME also contains about 0.015 wt% of water that could react with IPDI leading to additional alkyl urea functions exactly in the same δ range; this could account for the slightly higher integration of the urea peak (1.098 instead of 1.00 for the urethane). [42] NMR spectra of the pure IPDI-TMG adduct and of the IPDI-PPG prepolymer synthesized in the presence possible thermally induced, at least partial re-dissociation of the adduct to yield free TMG molecules could occur at 80 °C (possibly activated by the presence of OH groups). Guanidines and amidines have indeed been mentioned as blocking agents for isocyanates, but this remains rather occasional.…”

Fluorescent Polyurethane Nanocapsules Prepared via Inverse Miniemulsion: Surface Functionalization for Use as Biocarriers

“…By comparing the peak intensity at 1 700 cm −1 to the one at 1 640 cm −1 , the ratio of urethane and urea could be determined. In this case the equal absorption coefficient of both peaks is taken into account 32. The results showed a comparable amount of urea to urethane formation (for values see Table 1), which could be mainly attributed to the high reactivity of TDI, that could be readily hydrolyzed to yield amine groups.…”

“…This might be due to the fact that the urethane bond might be prone to cleavage by the presence of excess strong acid from MCA in the reaction mixture (pH 3) 1, 36. In contrast, both the hydroxy and amino groups were highly activated to react with MCA by the addition of a high NaOH concentration at elevated temperatures 31, 32. The increase in carboxy groups at the nanocapsule surface was hence observed.…”

Water‐Induced Transitions from Ellipsoidal Micelles to Chain‐Like Nanostructures Self‐Assembled by the Coil‐Rod‐Coil Block Copolymer Based on Hydrogen‐Bonding Urea Groups

“…The obtained triblock copolymer was dried under vacuum at 80 °C for 12 h. The triblock polymer was characterized by 13 C‐NMR spectrum (Figure S1, Supporting Information), 1 H‐NMR spectrum (Figure S2, Supporting Information), FT‐IR spectrum (Figure S3, Supporting Information), and MALDI‐TOF MS spectra (Figure S4a,b, Supporting Information), respectively. 13 C‐NMR (500 MHz, solid): δ = 162.7 ppm (HN( C O)NH), 74 ppm (O C H 2 C H 2 O), 20–60 ppm (aliphatic carbons of IPDI and IPDA); 1 H‐NMR (500 MHz, solid): δ = 7.0–8.0 ppm (O(CO)N H CH), 5.0–6.0 ppm (N H (CO)N H ),2.0–5.0 ppm (OC H 2 C H 2 O,C H of the IPDI and IPDA); FT‐IR (KBr): ν = 1645 cm −1 (CO of the urea), 3370 cm −1 (NH of the urea), 1558 cm −1 (NH of amide II band), 1244 cm −1 (amide III band), 650 cm −1 (amide IV band), and 771 cm −1 (amide V band), 2954 cm −1 and 2918 cm −1 (CH 2 ‐, CH 3 ‐ of IPDI, IPDA, and MPEG).…”