Association of polyacrylonitrile solutions

synopsisAn examination of data obtained from viscometric measurements of the association occurring in solutions of polyacrylonitrile in dimethylformamide, 7-butyrolactone, and dimethylacetamide has shown that the solubility parameter of the solvent-nonsolvent liquid mixture at the aggregation point is closely related to the molecular volume of the nonsolvent used to bring about association.The kinetic features of the association occurring in solutions of polyacrylonitrile in N,N'-dimethylformamide (DMF) have been examined in some detail.' Viscometric measurements made over a range of temperatures2 and with a variety of nonsolvents3 have established that association occurs through dipolar interaction between CN groups along the polymer molecule. It has been shown1 that large changes occur in the viscosity number of the solution over a narrow range of nonsolvent composition. It has been found convenient to characterize the association by determining the vol-% nonsolvent P at which the association rate constant has a value of 1 X sec-'. Although qualitatively the association of the various solvent-nonsolvent systems so far examined is similar, the primary effect of the nonsolvent is to determine the volume concentration at which association occurs. It has been shown3 that a relationship exists between the solubility parameter SNS of the nonsolvent and P as follows:where A and B are constants. Calculations carried out subsequently as a result of an examination of the effect of variation of the solvent on the associa.tion in polyacrylonitrile solutions has shown that the solubility parameter of the liquid mixture 6 , at a composition corresponding to P showed much less variation than the values of SNS. Initially it was considered that 6, had a constant value for a particular solvent or nonsolvent system, but since association can be observed in systems for which SS 2 SNS, then clearly this supposition was unrealistic. Subscripts S and NS are here taken to denote the solvent and nonsolvent components, respectively. A misplaced parameter led to calculations being made of the molecular volumes of the nonsolvents used, and it was found that variation in S , , although subjected

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Unperturbed dimensions of polyacrylonitrile

Kamide

Fujii

Kobayashi

1968

Makromol. Chem.

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The intrinsic viscosities [q] of polyacrylonitrile (PAN) in mixed solvent of ethylene carbonate and water (85 :15, in weight) a t temperatures from 30 to 44OC have been measured to establish the KUHN-MARK-HOUWINK-SAKURADA relation, [q] = KmMa. The samples used in the determination were prepared under different conditions. The FLORY constant K was estimated from viscosity data using three different methods. Method 1, from Km when the exponent a equals 0.50. Method 2, from the plot of [ T ] / M~/~ against M'/z (the STOCK-MAYEWFIXMAN plot). Method 3, from the plot of -log Km + log [l + 2{(a-0.5)-1-2}-1] against (a -0.5) (KAMIDE et al.'s treatment). I n applying the method 3, the viscosity data of PAN in dimethylformamide (obtained by KAMIDE et al. as well as in literature) wereutilized. As a result, K = (2.8 5 0.2).10-3 was found to be independent of the preparative conditions of the samples. Both the solvent effect on K and the contribution of the draining effect to [q] were found to be negligible. The conformational parameter a, the ratio of the end to end distance of the polymer chain in the unperturbed state to that in the freely rotating state, was found to be 2.37. ZUSAMMENFASSUNG:Die spezifische Viskositat [q] von Polyacrylnitril (PAN) in einem Mischlosungsmittel aus Athylencarbonat und Wasser (85 :15 Gew.-%) wurde bei Temperaturen zwischen 30 und 44OC bestimmt, um die KUHN-MARK-HOUWINK-SAKURADA-Beziehung [q] = KmMa z u ermitteln. Die bei der Bestimmung benutzten Proben wurden unter verschiedenen Bedingungen hergestellt. Die FLoRY-Konstante K wurde aus Viskositatsdaten unter Anwendung der foigenden drei Methoden abgeschatzt : nach Methode 1, aus Km, wenn der Exponent a gleich 0.50 ist, nach Methode 2, aus der Auftragung von [q]M1/2 gegen (nach STOCK-MAYER-FIXMAN), nach Methode 3, aus der Auftragung von -log Km + log [l + 2 {(a -0,5)-l-2}-l] gegen (a -0,5) (nach KAMIDE u. Mitarb.). Bei Anwendung von Methode 3 wurden die Viskositatsdaten von PAN in Dimethylformamid, die nach KAMIDE u. Mitarb. oder aus der Literatur erhalten worden waren, eingesetzt. Es wurde gefunden, daB K = (2,8 & 0,2).10-3unabhangig von den Herstellungsbedingungen der Proben ist. Weiterhin zeigte sich, daB sowohl der Losungsmitteleffekt auf K als auch der Beitrag des Durchspiilungseffektes auf [q] zu vernachlassigen sind. Der Konformationsparameter 0, das ist das Verhiiltnis des Kettenendenabstandes der Kette des Polymeren in ungestortem Zustand zu dem Verhdtn i s in frei rotierendem Zustand, ergab die Zahl 2.37.

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Association of polyacrylonitrile solutions

Cited by 20 publications

References 22 publications

Sedimentation Coefficients, Diffusion Coefficients, Partial Specific Volumes, Frictional Ratios, and Second Virial Coefficients of Polymers in Solution

Sedimentation Coefficients, Diffusion Coefficients, Partial Specific Volumes, Frictional Ratios, and Second Virial Coefficients of Polymers in Solution

Dependence of association in polyacrylonitrile solutions on the molecular volume of the nonsolvent

Unperturbed dimensions of polyacrylonitrile

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