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Swelling, elasticity and structure of hydrogels prepared via bis‐macromonomers of poly(ethylene oxide)
Author(s) -
Dubrovskii Sergey A.,
Lagutina Marina A.,
Vasiljev Vitalij V.
Publication year - 2003
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.200351015
Subject(s) - macromonomer , swelling , materials science , polymer chemistry , ethylene oxide , self healing hydrogels , methacrylate , polymerization , ethylene glycol , copolymer , polymer , composite material , chemical engineering , engineering
The effect of swelling on the shear modulus was studied for hydrogels prepared by radical polymerization of methacrylate‐terminated poly(ethylene oxide) (PEO) bis‐macromonomers of different molecular weight. Gels made of long chains ( M = 12000 or 6000) display classical softening upon swelling, whereas gels made of shorter chains ( M = 4000 or 2000) remain rigid or even stiffen. The abnormal behaviour is explained by a specific character of network junctions presented by polymethacrylate chains in which each unit is linked with a PEO network chain. It is assumed that the interactions among densely grafted PEO chains result in their stretching on polymerization and non‐affine deformation on swelling, which stiffen the gel. This is verified by the data on copolymer (macromonomers ‐ 2‐hydroxyethyl methacrylate) gels that have lesser densities of PEO chains attached to the junctions and show weaker stiffening on swelling. The osmotic pressure of gels was estimated from the swelling pressure and shear modulus. Similar to the mixing pressure of equivalent PEO solutions, it varies as the 9/4 power of polymer concentration. At the same time, it is lower than the mixing pressure. This indicates that the junctions make only quantitative changes in the osmotic properties of macromonomer chains.