A simple method for determining protic end-groups of synthetic polymers by 1H NMR spectroscopy

Degradation and Recyclability of Poly (Ethylene Terephthalate)

“…Pohl has shown as early as in 1954 that hydrolytic degradation of polyester chains can be studied by end-group measurements, which consists of dissolving the sample in benzyl alcohol at high temperature followed by titration using standard alkali [16,17]. There are reports on investigation of degradation using measurements of viscosity, optical microscopy, FTIR and UV methods [18][19][20][21][22]. W. Chaouch et al [23] have investigated the effects of hydrolytic aging of a series of PET vascular prostheses and compared their chemical properties between the virgin prosthesis using nuclear magnetic resonance spectroscopy (1H-NMR) and have used the latter technique to determine the OH group concentrations and the number average molecular weight of the polymer subjected to in-vitrio conditions and validated the data using the classical titration and viscosity methods.…”

Determination of the Hydroxy and Carboxylic Acid Groups in Natural Complex Mixtures of Hydroxy Fatty Acids by 1H Nuclear Magnetic Resonance Spectroscopy

“…2,5 When the former technique is used the depolymerization mixtures are obtained in the form of free carboxylic acids, while in the case of alcoholysis, the corresponding alkyl esters are instead obtained. Gas chromatography-mass spectroscopy (GC-MS) analyses of these mixtures showed that the x-hydroxyalkanoic and a,x-alkanedioic acids are characterized by the presence of even-numbered aliphatic chains (C 16 to C 26 ), with a predominance of the C 18 and C 22 homologues. C 18 homologues containing a 9,10-epoxy group, or the corresponding 9,10-dihydroxy derivative, are often significant components of such fractions.…”

“…Gas chromatography-mass spectroscopy (GC-MS) analyses of these mixtures showed that the x-hydroxyalkanoic and a,x-alkanedioic acids are characterized by the presence of even-numbered aliphatic chains (C 16 to C 26 ), with a predominance of the C 18 and C 22 homologues. C 18 homologues containing a 9,10-epoxy group, or the corresponding 9,10-dihydroxy derivative, are often significant components of such fractions. [1][2][3][4][5][6] The 1 H nuclear magnetic resonance (NMR) analyses of depolymerized cork suberin are consistent with the GC-MS evidence just described, showing essentially a predominance of the aliphatic methylenic protons and lower percentages of methoxy protons and of protons attached to carbon atoms bearing hydroxy groups.…”

“…14,20,21 End-group analyses have also been routinely investigated by NMR spectroscopy of the derivatized functional groups, 13,15,17,18 with the advantage of requiring only small amounts of both sample and solvent. One interesting approach in this context is the esterification of the hydroxy and carboxylic acid groups with fluorinated compounds followed by 19 F NMR analyses, which usually requires the use of an internal standard.…”

“…One interesting approach in this context is the esterification of the hydroxy and carboxylic acid groups with fluorinated compounds followed by 19 F NMR analyses, which usually requires the use of an internal standard. 17,19 Other authors 13,15,18 have reported the use of a trichloroacetyl isocyanate (TAI) at room temperature to generate rapidly and quantitatively derivatives that can be directly analyzed by 1 H NMR. Although, the 1 H NMR spectrum of the non-derivatized depolymerized suberin is well known, 6 to the best of our knowledge a derivatization procedure prior to NMR analyses, aimed at gaining relevant quantitative information about its functional groups, has not been reported.…”