Abstract:
In our previous paper (Bulletin of the Karaganda University. Chemistry series, 2019, 2(94), P. 35–43) we
considered the behavior of quenched (or strongly charged) polyampholytes based on fully charged anionic
monomer — 2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt (AMPS) and cationic monomer —
(3-acrylamidopropyl) trimethylammonium chloride (APTAC) in aqueous-salt solutions. In the present paper
we report the mechanical properties of quenched polyampholyte hydrogels synthesized by free-radical copolymerization of the same monomers in the presence of N,N-methylenebisacrylamide (MBAA) as crosslinking
agent. The hydrogel samples in dependence of the molar amount of AMPS were abbreaviated as AMPS-75H,
AMPS-50H and AMPS-25H. The swelling, rheological, and mechanical properties of quenched
polyampholyte hydrogels were evaluated for different compositions of copolymers at fixed initial monomer
concentration C0 = 0.5 wt.% and constant amount of [MBAA] = 20 mol.%. The formation of hydrogels in the
course of (co)polymerization of oppositely charged monomers in presence of MBAA was monitored by
rheometric measurements using oscillatory deformation tests at an angular frequency ω = 6.3 rad⋅s−1 and
strain amplitude γo = 0.01. The strain-stress curves of as-prepared and swollen polyampholyte gels demonstrate
that the highest values of Young’s modulus E, fracture stress σf and elongation ε% are characteristic for
as-prepared AMPS-75H and swollen AMPS-50H samples. These results are interpreted in terms of polyelectrolyte and polyampholyte effects.
