Transport properties of hydrolyzed polyacrylonitrile

Dabrovská, L.; Praus, R.; Stoy, V.; Vacı́k, J.

doi:10.1002/jbm.820120503

Cited by 8 publications

(5 citation statements)

References 10 publications

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“…The transport properties of different solutes in HEMAbased hydrogels have been studied by measuring the permeability of membranes prepared from the copolymers. [30][31][32][33] The determination of the diffusion coefficients from these measurements is complicated by the need to determine independently the partition coefficients of the diffusant for the system membranesolvent; such information has been obtained only for inorganic salts. The main conclusions derived from such studies are the increased permeability with increasing water content in the gels and with decreasing degree of cross-linking and the higher permeability of inorganic salts across ampholytic membranes (that contain the same amounts of weak acidic and weak basic groups) compared with neutral membranes.…”

Section: Introductionmentioning

confidence: 99%

Measurements of Diffusion Processes in HEMA-DEGMA Hydrogels by ESR Imaging

Schlick¹,

Pilař²,

Kweon³

et al. 1995

Macromolecules

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The diffusion coefficients of small paramagnetic tracers (nitroxide spin probes) and spinlabeled poly(ethylene oxide) in hydrogels were measured at 300 K, using two-dimensional spatial-spectral ESR imaging (ESRI). The gels were prepared by copolymerization of 2-hydroxyethyl methacrylate (HEMA) and 2-(2-hydroxyethoxy)ethyl methacrylate (DEGMA), in the presence of a fixed molar concentration of glycol dimethacrylate as the cross-linker and 4,4'-azobis(4-cyanopentanoic acid) as the initiator. Variation of the amount of water in equilibrium with the gel was achieved by polymerizing different molar ratios of the monomers.Experimental concentration profiles of the diffusant were measured as a function of time, and each profile was obtained by image reconstruction, from a complete set of projections. The diffusion coefficients were determined by simulating all experimental profiles, using the Fick model of diffusion for an initially confined tracer diffusing into a finite system. The diffusion coefficients depend on the amount of water in the gels. The variation of the diffusion coefficients D with the weight fraction of the copolymer in the gel is consistent with the free volume model. The variation of D with the molecular mass M of the diffusant scales as M~°'s in gels containing >67 wt % water and as M~1A for the gel containing 55 wt % water. The advantages and present limitations of 2D spatial-spectral ESRI for measuring transport properties in polymers are discussed.

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Section: Introductionmentioning

confidence: 99%

Measurements of Diffusion Processes in HEMA-DEGMA Hydrogels by ESR Imaging

Schlick¹,

Pilař²,

Kweon³

et al. 1995

Macromolecules

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“…Beside its scientific interest, this conclusion appears to have some practical significance. Indeed, acidic PAN hydrolysis at low temperatures by action of HNO 3 6 or a H 2 SO 4 /H 3 PO 4 mixture 16 is the only method to prepareAN−AAm multiblock copolymers testified for various applications. − , Note that 13 C NMR spectrometry gives the valuable but limited set of the HPAN structure parameters. Meanwhile, the theory of the neighboring group effect enables one to calculate any parameter of the reaction product structure as soon as the rate constants k 0 , k 1 , and k 2 are estimated .…”

Section: Resultsmentioning

confidence: 99%

“…2 On the contrary, PAN hydrolysis by concentrated acids at 15-50 °C leads to the formation of a AN-AAm copolymer, sometimes containing also small amounts of acrylic acid groups. [6][7][8][9][10][11] At elevated temperature (110 °C), AAm groups cyclization occurs with formation of glutarimide (GI) cycles. 10,11 (GI cycles were never observed in the products of alkaline PAN hydrolysis because of their extreme instability in an alkaline medium as shown by Sawant and Morawetz.…”

Section: Introductionmentioning

confidence: 99%

Acidic Hydrolysis of Polyacrylonitrile: Effect of Neighboring Groups

et al. 2001

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Hydrolysis of polyacrylonitrile (PAN) was carried out in 65% HNO3 at 21 °C. The composition and structure of hydrolyzed samples (HPAN) were determined using 13 C NMR spectrometry. The HPAN are multiblock copolymers containing acrylonitrile (A) and acrylamide (B) units. A set of individual rate constants for the reaction of central A units in AAA, AAB + BAA, and BAB triads, k0, k1, and k2, respectively, describes fairly well both the reaction kinetics and the HPAN distribution of units. Thus, the accelerating effect of neighboring groups (k0:k1:k2 ) 1:18:36) is the principal, if not exclusive, factor determining the peculiarities of the acidic PAN hydrolysis. Less than 3% of acrylamide groups are involved in cyclization (formation of glutarimide cycles) under the hydrolysis conditions used, so that cyclization may be neglected in the analysis of the hydrolysis kinetics and the HPAN structure within the framework of the neighbor effect.

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“…In one of papers from our Institute e.g. (58),it was shown that compounds with molecular weight up to 64 030 may pass through membranes of hydrolyzed polyacrylonitrile with the water content 7 4 wt.%.…”

Section: B) Mutual Interaction Between Soluble Compounds Of Naturalmentioning

confidence: 99%