Slow-mode diffusion of poly(vinylpyrrolidone) in the semidilute regime

Eisele, Michael; Burchard, Walther

doi:10.1021/ma00138a038

Cited by 43 publications

(25 citation statements)

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“…This slow relaxation time has been predicted and observed to be q -independent. Good solvent, semidilute systems are not expected to display slow mode behavior, and this has been found to be generally true for hydrocarbon systems. , However, various aqueous, good solvent systems have been found to display slow mode behavior in the semidilute region. ,− To our knowledge, the physical cause of this anomalous behavior has not been explained. In this paper we present some experimental results on PVP in water and denatured water in an attempt to elucidate the origin of this slow mode.…”

Section: Introductionmentioning

confidence: 93%

“…PVP has a wide variety of commercial applications, finding use in the medical, food, and pharmaceutical industries for such diverse uses as a blood plasma substitute, binding agent for drug delivery, and food thickener. , Because of its many uses and its structural similarity to biopolymers, PVP has been extensively studied through nearly every technique used in the characterization of macromolecules including viscometry, osmometry, NMR, and light scattering. − Past light scattering experiments have been somewhat limited. The molecular weight scaling behavior has been not quantified for the dilute concentration regime, nor has there been a complete investigation of the slow mode, discovered in the autocorrelation function in the semidilute region . Of particular interest is the origin of this slow mode.…”

Section: Introductionmentioning

confidence: 99%

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Aggregation Behavior in the Semidilute Poly(N-vinyl-2-pyrrolidone)/Water System

Sun

King

1996

Macromolecules

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Dynamic and static light scattering experiments were performed on aqueous solutions of poly(N-vinyl-2-pyrrolidone) in the dilute and semidilute regime. In the dilute regime, typical good solvent behavior is found. In the semidilute regime, we observe two relaxation times in the autocorrelation functions and intense forward scattering. The short time relaxation has a typical q 2 dependence, characteristic of diffusion, and the long time relaxation an approximately q 3 dependence, characteristic of intraparticle dynamics. This behavior is not consistent with predicted semidilute, good solvent system behavior but instead indicates the presence of aggregates. Using combined static and dynamic scattering, we show these aggregates to be approximately 2-3 times the size of the dilute-solution radius of gyration. We attribute this anomalous behavior to the unique, tetrahedral hydrogen bond network of water and show that denaturing the water through the addition of denaturing agents known to disrupt the water structure significantly diminishes the aggregate size. We also show through pressure denaturation that the aggregation process is reversible.

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Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Aggregation Behavior in the Semidilute Poly(N-vinyl-2-pyrrolidone)/Water System

Sun

King

1996

Macromolecules

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“…This phenomenon is well known for many polymers. In particular, for PVP, in a study of its solutions in a wide range of concentrations, it was shown that, whereas in solutions with a low concentration a single mode is observed on analogous dependences, with increase in the polymer concentration a second (slow) mode begins to appear on the dependences, refl ecting the formation of associates of macromolecules in the solution [14].…”

Section: Experimental Correlation Functions Of Dynamic Lightmentioning

confidence: 99%

Aggregation in an Aqueous Solution of Amino Acid Derivatives of Poly-N-vinylpyrrolidone

Rizos

Tashmukhamedov

Tsatsakis

et al. 2008

International Polymer Science and Technology

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“…Αν και η ποσοτική ανάλυση των πειραματικών δεδομένων για την "αργή" διεργασία χαλάρωσης αποδείχθηκε προβληματική, ποιοτικά συμπε ράσματα μπορούν να εξαχθούν τα οποία σε συνδυασμό με δεδομένα της βιβλιογραφίας μπορούν να οδηγήσουν στον καθορισμό της φύσης και προέ λευσης της συγκεκριμένης διεργασίας. Κατ' αρχάς πέρα από τις διακυμάνσεις πυκνότητας, συγκέντρωσης και προσανατολισμού, έχει παρατηρηθεί η ύπαρξη μιας αργής διεργασίας χαλάρωσης σε διαλύματα υψηλών συγκεν τρώσεων πολυμερικών συστημάτων [117][118][119][120] καθώς και σε περιπτώσεις καθαρών [121] και δυαδικών μιγμάτων απλών μη πολυμερικών υγρών [122]. Στις παραπάνω μελέτες θεωρήθηκε ότι οι αργές κινήσεις συσσωματωμάτων (clusters) είναι υπεύθυνες για την αργή διεργασία χαλάρωσης καθώς και για την περίσσεια σκεδαζόμενης έντασης πέρα από αυτή που προβλέπεται από τη θεωρία (βλέπε εξ.…”

Section: J Fq C T>t Cunclassified

“…Τα παραπάνω χαρακτηριστικά της δυναμικής συμπεριφοράς της "αργής" διεργασίας έρχονται σε συμφωνία με αυτά που παρατηρήθηκαν σε μίγματα πολυμερικής και μη φύσης, και αποδόθηκαν στην ύπαρξη μεγάλων εκτεταμένων δομών (τύπου clusters) που διαχέονται αργά μέσα στον κύριο όγκο του υγρού [117][118][119][120][121][122]. Είναι αξιοσημείωτο ότι στη συστηματική μελέτη PCS των δυαδικών μιγμάτων Van der Waals υγρών (o-terphenyl (ΟΤΡ) -BCDE, OTP-BKDE) των Gerhartz et al προσδιορίσθηκε μια μέση διάμετρος clusters ~ 1000 Α, η οποία θεωρήθηκε υπεύθυνη για την εξάρτηση της σκεδαζόμενης έντασης από τις γωνίες θ. Λαμβάνοντας υπόψη την ιδιόμορφη δομή του ZnCI 2 (βλέπε Κεφ.…”

Section: J Fq C T>t Cunclassified

Σκεδαση Φωτος Απο Αλογονιδια Ψευδαργυρου Στην Υγρη Και Υαλωδη Κατασταση

Παυλατου¹

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Photon Correlation Spectroscopy has been applied in order to study the dynamic behavior of structural rearrangements in glassy ZnCI 2 at tempera tures 25-420°C. The structural properties of the glassy systems ZnCI 2 -ZnBr 2 and liquid ZnCI 2 -ACI (A=Li, Cs) have been studied by Raman spectroscopy in the range 25-700°C.The autocorrelation functions of scattered light of pure ZnCI 2 indicate the existence of two at least relaxation processes occurring near Τ The first "main" process is attributed to local density fluctuations and is very well represented by the KWW equation, exp(-t/i)ß, with ß=0.706±0.012 insensitive to temperature variations in the region T g ->T g +80-^C. The high value of ß(ß-»1 ) categorizes ZnCI 2 in the class of relative "strong" glasses, with an nearly Arrhenius temperature dependence of relaxation time τ through T g -^T m +200°C. The second "slow" process could be tentatively attributed to "slow" motions of large "clusters" formed in the 3D-network structure.The temperature dependence of reduced Raman spectra of pure ZnX 2 (X=CI, Br) indicates the presence of different bonding states in the "network" structure, where halogen atom sharing of the ZnX 4 tetrahedral groups occurs. Furthermore, at elevated temperatures the "network" breaks up, creating ZnX 3 units. The spectra of binary ZnCI 2 -ZnBr 2 system show that the mixtures are formed by random closest packing of X atoms. In the ZnCI 2 -ACI mixtures the breaking of the "network" structure occurs both with increasing temperature and AGI composition. The tetrahedral structure around Zn is preserved but one, three of four "terminal" atoms X are formed in the melt with A+ as nearest neighbors.

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Slow-mode diffusion of poly(vinylpyrrolidone) in the semidilute regime

Abstract: Theseworkers claim that the complex of poly(acrylic acid) and polyethylene imine) can be transformed into a ladder-like structure of condensed nine-membered rings. See also: Ka-

Cited by 43 publications

References 3 publications

Aggregation Behavior in the Semidilute Poly(N-vinyl-2-pyrrolidone)/Water System

Aggregation Behavior in the Semidilute Poly(N-vinyl-2-pyrrolidone)/Water System

Aggregation in an Aqueous Solution of Amino Acid Derivatives of Poly-N-vinylpyrrolidone

Σκεδαση Φωτος Απο Αλογονιδια Ψευδαργυρου Στην Υγρη Και Υαλωδη Κατασταση

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