Improved NMR characterization of high‐molecular‐weight polymers and polyelectrolytes through the use of preliminary ultrasonic degradation

Kulicke, Werner‐Michael; Otto, M. Alexander; Baar, Andreas

doi:10.1002/macp.1993.021940301

Cited by 50 publications

(15 citation statements)

References 39 publications

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“…[19][20][21] The tertiary structure of schizophyllan which forms a triple helix in water is still intact after ultrasonic degradation. [22] The following contribution aims to prove whether a series of molar masses which were produced by ultrasonic degradation is suitable for establishing structure-property relationships.…”

Section: Introductionmentioning

confidence: 99%

Producing homologous series of molar masses for establishing structure-property relationships with the aid of ultrasonic degradation

Schittenhelm

Kulicke²

2000

Macromol. Chem. Phys.

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Ultrasonic degradation was shown to be a very effective method for creating homologous series of molar masses in order to establish structure‐property relationships such as the Mark‐Houwink equation and the RG‐M relation. It was tested mainly for cellulose derivatives. The detection of the molar masses, the radii of gyration and of their distributions was carried out by means of size‐exclusion chromatography coupled with multi‐angle laser light scattering and a refractometer (SEC/MALLS/DRI). The results were compared with existing data and checked according to their suitability. It was shown that the calculated data generally agree very well with the experimental results. Only the exponents of charged polymers were slightly lower than the calculated values. Thus the change in polydispersity has no effect on the establishment of the relationships. Furthermore the influence of the chemical structure on the degradation process of cellulose and starch derivatives was examined with special regard to the limiting molar mass and the degradation constant proposed by Ovenall et al. It was revealed that the conformation of the polymers in solution plays an important role on the degradation process. The change in the molar degree of substitution and the introduction of a second substituent of cellulose derivatives have no effect on the decomposition pattern because the slightly expanded conformation remains undisturbed. In contrast the degradation process of strongly coiled hydroxyethyl starch is slowed down and the limiting molar mass lies above that of cellulose derivatives. First investigations with the synthetic polyacrylamide (PAAm) which was grafted with starch showed that even small amounts of starch side groups lead to a retardation of degradation.

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Section: Introductionmentioning

confidence: 99%

Producing homologous series of molar masses for establishing structure-property relationships with the aid of ultrasonic degradation

Schittenhelm

Kulicke²

2000

Macromol. Chem. Phys.

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“…In this way a stable triple helix can form, which, however, only exists in a neutral medium and changes into a single helix at higher pH values. Scleroglucan underwent ultrasonic treatment for up to 3 h. After this time, under the selected conditions, a limiting molar mass is reached which cannot be further reduced even with longer sonication time 19) . The congo red analysis for scleroglucan with differing degradation times is shown in Fig.…”

Section: Influence Of Ultrasonic Degradation On the Secondary Structurementioning

confidence: 99%

“…A suitable means of determining structure-activity relationships can often be achieved by means of homologous molar mass series, which can be readily obtained through ultrasonic degradation by varying the duration of sonication 19) . During this process cavitation generates high mechanical energies which cause the polymer chain to break in the middle of the molecule.…”

Section: Influence Of Ultrasonic Degradation On the Secondary Structurementioning

confidence: 99%

Influence of the glycosidic linkage on the solution conformation of glucans

Kath

Lange

Kulicke³

1999

Angew. Makromol. Chem.

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In order to gain a better understanding of the influence of β‐glycosidic linkages on the solution conformation of glucans, a comparison was made between the carboxymethyl derivatives of cellulose (CMC, 100% 1,4‐), barley glucan (CMGG, 30 : 70 1,3 : 1,4‐) and curdlan (CMCd, 100% 1,3‐glycosidic), each with an average degree of substitution of DS = 1.0–1.5 and molar masses of 144 000–720 000 g mol–1. For this purpose curdlan and barley glucan were chemically modified, whereas carboxymethylcellulose was available as a commercial sample. Via congo red analysis it was proved for the microbial β‐1,3‐glucans curdlan (unsubstituted) and scleroglucan (one β‐1,6‐linked glucose side group on every third monomer unit) that substituents in glucan derivatives weaken an existing helical structure but that reduction of the molar mass with ultrasound has no influence on the helices. The molecular parameters Mw, Mn, RG, LP and [η] were determined by means of SEC/MALLS measurements and viscometry and the chain mobility was quantified using the 13C NMR relaxation times, T1, of the different polymers. From this it was possible to derive [η]‐Mw relationships. For all samples, the exponent ν of the RG‐MW relationship lay in the range 0.54–0.59, from which it is possible to deduce a coiled solution structure. However, β‐1,3‐glucans occupy 25% less volume than β‐1,4‐glucans and exhibit less chain mobility. Hence β‐1,4‐glucans should be considerably more viscous than β‐1,3‐glucans, as was indeed demonstrated by rheological flow curves of 6% solutions of the carboxymethylglucan derivatives. The zero‐shear viscosity, η0, decreases by 3 decades in the order of CMC > CMGG > CMCd.

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“…Methods are required which degrade the polymer in a specific manner without side reactions and without the occurrence of monomeric or dimeric components. Of the mechanical methods for reducing molar mass, ultrasonic degradation is the most suitable for preparing NMR-spectroscopy samples 26) . The lower section of Fig.…”

Section: High-resolution Nmr Spectroscopy On Reduced-molarmass Nacmcmentioning

confidence: 99%

Development and evaluation of methods for determining the pattern of functionalization in sodium carboxymethylcelluloses

Käuper

Kulicke²,

Horner

et al. 1998

Angew. Makromol. Chem.

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Sodium carboxymethylcellulose (NaCMC) with varying degrees of substitution (DS) was investigated with different analytical methods in order to characterize the functional group distribution. The following methods were tested and adapted: high‐resolution 13C NMR spectroscopy in the solid state (13C CP/MAS NMR) and 13C NMR spectroscopy on solutions of NaCMC samples with a reduced molar mass. Partial degradation was accomplished by ultrasonic means and with the enzyme endoglucanase. Combining the two techniques resulted in the greatest reduction in molar mass and hence in the best spectral resolution. Analysis of the NaCMC fragments following ultrasonic and/or endoglucanase degradation also reveals another interesting experimental finding. It appears that ultrasonic degradation is favored at unsubstituted areas near the center of the chain. These methods were compared with the following already familiar techniques of analysis: titrimetric techniques; 13C and 1H NMR spectroscopy as well as HPLC on completely hydrolysed solutions (hydrolysis with perchloric acid, trifluoroacetic acid and sulfuric acid). All of the methods characterize the samples as a series with increasing DS, the values of which range from 0.9 to 2.4. Methods that permit analysis of the partial degree of substitution produced the distribution x2 > x6 > x3. Therefore, they are in principle suited for determining the functionalization pattern of the NaCMC samples relative to one another. The most suitable method can therefore be selected according to the objectives and the apparatus available. However, the measured values do exhibit considerable spread, variances of approx. 20%, thus, place restrictions on using the values of DS or xi in absolute comparisons beyond these methods.

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Improved NMR characterization of high‐molecular‐weight polymers and polyelectrolytes through the use of preliminary ultrasonic degradation

Cited by 50 publications

References 39 publications

Producing homologous series of molar masses for establishing structure-property relationships with the aid of ultrasonic degradation

Producing homologous series of molar masses for establishing structure-property relationships with the aid of ultrasonic degradation

Influence of the glycosidic linkage on the solution conformation of glucans

Development and evaluation of methods for determining the pattern of functionalization in sodium carboxymethylcelluloses

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