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Kinetic Analysis of Cryotropic Gelation of Poly(Vinyl Alcohol)/Water Solutions by Small-Angle Neutron Scattering

  • Claudio De Rosa
  • Finizia AuriemmaEmail author
  • Rocco Di Girolamo
Chapter
Part of the Advances in Polymer Science book series (POLYMER, volume 263)

Abstract

Graphical Abstract

Aqueous poly(vinyl alcohol) (PVA) solutions subjected to cryogenic treatment form strong physical gels. The cryogenic treatment basically consists of freezing an initially homogeneous polymer solution at low temperatures, storing in the frozen state for a definite time, and defrosting. These gels are of great interest for biotechnology, medicine, the food industry, and many other applications. The outstanding properties of these systems depend on a complex macroporous architecture, whereby PVA chains and water molecules are organized over different hierarchical length scales. The structure and the principal processes subtending the formation of these systems are discussed in the framework of our current understanding of polymer gels. These processes involve formation of ice crystals, PVA crystallization, liquid–liquid phase separation, hydrogen bonding, and entanglements. Small angle neutron scattering is used to follow the cryotropic gelation of PVA/water solutions and detailed information is extracted concerning the gelation mechanism and kinetic parameters related to the formation of these complex systems.

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Keywords

Cryotropic gelation Poly(vinyl alcohol) hydrogels Time-resolving small angle neutron scattering Ostwald stage-rule Confined polymer crystallization 

Abbreviations

a-PS

Atactic polystyrene

BP

Berghmans point

CLSM

Confocal laser scanning microscopy

Cp

Polymer concentration

\( \raisebox{1ex}{$ d\sigma $}\!\left/ \!\raisebox{-1ex}{$ d\varOmega $}\right. \)

Scattering cross-section

ds

Surface fractal dimension

DSC

Differential scanning calorimetry

F

Free energy

Φ

Order parameter

fc(DSC)

Fractions of crystalline phase from DSC analysis

fc(NMR)

Fraction of rigid protons from NMR measurements

fc(XR)

Crystallinity index from WAXS analysis

LL

Liquid–liquid phase separation

NMR

Nuclear magnetic resonance

PEG

Poly(ethylene glycol)

PVA

Poly(vinyl alcohol)

q

Scattering vector

SANS

Small angle neutron scattering

SEM

Scanning electronic microscopy

TEM

Transmission electron microscopy

Tg

Glass transition temperature

Tm

Melting temperature

TR-SANS

Time resolving-SANS

UCST

Upper critical solution temperature

WAXS

Wide angle X-ray scattering

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Copyright information

© Springer International Publishing Switzerland 2014

Authors and Affiliations

  • Claudio De Rosa
    • 1
  • Finizia Auriemma
    • 1
    Email author
  • Rocco Di Girolamo
    • 1
  1. 1.Dipartimento di Scienze ChimicheUniversità di Napoli Federico IINapoliItaly

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