Determination of molecular weight distributions of novolac resins by gel permeation chromatography

Abstract

The number‐ and weight‐average molecular weights of several statistical and high ortho novolac resins were determined using gel permeation chromatography (GPC). The standards used were pure compounds having between 2 and 12 phenol units bridged via methylene linkages. Three series of compounds were studied: (i) those with methylene linkages substituted in only the ortho positions relative to the phenolic hydroxyl group; (ii) those in which all para positions, together with sufficient ortho positions, were used to synthesize the compounds; and (iii) those in which the methylene linkages were substituted at a mixture of ortho and para positions. Such compounds, having known molecular architecture and units similar to the segments of industrial novolac resins, provide for a more exact measurement of the molecular weight than do the commonly used poly(styrene) standards. Using these new standards the number average molecular weights of the resins determined by GPC were in good agreement with the average molecular weight obtained by 1H‐NMR spectra of the resins, particularly for low molecular weight resins. GPC analysis of higher molecular weight resins tends to underestimate the molecular weights because of complications introduced by hydrogen bonding. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1399–1407, 1997

Cardanol‐based novolac resins as curing agents of epoxy resins

“…The other peaks at 20.22 and 19.67 min can be attributed to tetramer and pentamer, respectively. At higher molecular weights, the GPC analysis is rather convoluted because of the dramatic increase in the number of possible isomers as the number of cardanol units increases,28 resulting in a difficult assignment of other peaks. Since polystyrene standards were used for GPC calibration, the data obtained can be considered qualitatively only 28.…”

“…At higher molecular weights, the GPC analysis is rather convoluted because of the dramatic increase in the number of possible isomers as the number of cardanol units increases,28 resulting in a difficult assignment of other peaks. Since polystyrene standards were used for GPC calibration, the data obtained can be considered qualitatively only 28. Consequently, 1 H‐NMR studies were performed to determine the average number of cardanol units in Nov‐I and Nov‐II, which were found to be 3.8 and 5.2, respectively.…”

Unsaturated polyester resins for thermoset applications using renewable isosorbide as a component for property improvement

“…The results of this method are summarized in Table II, and their corresponding molecular weights as determined by GPC using the retention time of polystyrene standards calculated using the Waters Empower GPC Software. 30,31 The accuracy of NMR method is ultimately determined by the precision of the final AN titration and the interpretation of the NMR spectra for the quantified peak areas. Using this method, the calculated M n can be drastically affected by end point determination in the AN titration and surplus breadth in the integral range of the quantified peaks.…”

Preparation and characterization of a foam regulator with ultra‐high molecular weight

“…The values of K and α have nothing to do with molecular weight of polymer within a certain range, but effected by polymer's structure, morphology, interaction between polymer and solvent, temperature, and so on . So we must make sure of polymer, solvent, and temperature these three factors before obtaining the values of K and α.…”