Interactions
Affecting the Mechanical Properties of
Macromolecular Microsphere Composite Hydrogels
- Publication date
- Publisher
Abstract
Macromolecular
microsphere composite (MMC) hydrogel is a kind of
tough hydrogel fabricated by using peroxidized macromolecular microspheres
as polyfunctional initiating and cross-linking centers (PFICC). The
contribution of chemical cross-linking (covalent bonding) and physical
cross-linking (chain entanglement and hydrogen bonding) to the mechanical
properties are understood by testing the hydrogels, which were swollen
in water or aqueous urea solutions to different water contents. The
as-prepared MMC gels exhibited moderate moduli (60–270 kPa),
high fracture tensile stresses (up to 0.54 MPa), high extensibilities
(up to 2500%), and high fracture energies (270–770 J m<sup>–2</sup>). The moduli of the swollen gels decrease dramatically,
but there are no significant changes in fracture tensile strength
and fracture strain, even slight increases. More interestingly, the
swollen gels show much-enhanced fracture energies, higher than 2000
J m<sup>–2</sup>. A gradual decrease in the hysteresis ratio
and residual strain is also found in the cyclic tensile testing of
the hydrogels that were swollen to different water contents. The covalent
bonding determines the tensile strength and fracture energy of the
MMC gels, whereas the physical entanglement and hydrogen bonding among
the polymer chains contributes mainly to the modulus of the MMC gels,
and they are also the main reason for the presence of hysteresis in
the loading–unloading cycles
