Polymer Bulletin

, Volume 12, Issue 6, pp 515–521 | Cite as

Phase transition in swollen gels

8. The photoelastic behaviour of polyacrylamide networks in the collapse region
  • Jaroslav Hrouz
  • Michal Ilavský
Photoelastic Behaviour


The photoelastic behaviour of two networks — polyacrylamide (PAAm) and of a network prepared by the copolymerization of acrylamide with 5 mol.% sodium methacrylate — was investigated in water-acetone mixtures. For the PAAm network the dependence of all photoelastic characteristics on the composition of the mixture is continuous. At 54 vol.% acetone in the mixture, the ionized network undergoes a transition which gives rise to jumpwise changes in the shear modulus, deformational-optical coefficient, C, and in the refractive index of the gel, ng. While in the collapsed state the optical anisotropy of the statistical segment is negative, Δα ∼ −3×10−24 cm3 (indicating an interaction between the side chains), in the expanded state it is positive, Δα ∼ 0.5 × 10−24 cm3. The dependence of all optical characteristics on the composition of the mixtures suggests that: (a) in both networks we have a transition between two conformational states of the chain; while for the ionized network the transition is a discrete one, for the nonionized network it takes place in the range between ∼30 and ∼45 vol.% acetone in the mixture; (b) in both networks the gels are optically homogeneous throughout the whole range of compositions of the mixtures (and thus also in the close vicinity of the collapse of the ionized network).


Phase Transition Refractive Index Methacrylate Shear Modulus Acrylamide 


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Copyright information

© Springer-Verlag 1984

Authors and Affiliations

  • Jaroslav Hrouz
    • 1
  • Michal Ilavský
    • 1
  1. 1.Institute of Macromolecular ChemistryCzechoslovak Academy of SciencesPrague 6Czechoslovakia

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