Polyacrylamide hydrogels make up a category of widely
used oilfield
water-plugging agents. However, their poor mechanical properties and
insufficient heat resistance severely limit their applications. In
this work, a novel strategy for the construction of tough and heat-resistant
polyacrylamide hydrogels using vinylated modified polylysine (PLL)
as a multifunctional cross-linker (named APLL) is proposed. The multifunctionality
of APLL leads to a three-dimensional network of hydrogels containing
a uniform network structure that distributes stress and a dynamic
cross-linked structure that dissipates energy. Meanwhile, APLL retains
the thermal stabilization properties of PLL, and its use as a cross-linking
site in the polymer network can effectively improve the heat resistance
of hydrogels. As a result, hydrogels exhibit ultrastretchability to
3295%, excellent notch-insensitivity (75% prefabricated notched samples
still have a fracture energy of 15,728 J/m2), and good
heat resistance (better aging performance than N, N-methylene bis-acrylamide cross-linked hydrogels at 130 °C).
In addition, the saline suspension composed of preformed gel particles
of APLL cross-linked hydrogels can age at 80 °C for more than
10 days and effectively seal the pores with a sealing rate of 95%
in percolation experiments. Such mechanical properties, notch insensitivity,
and heat resistance enable the APLL cross-linked hydrogels to serve
as a potential temporary water-plugging agent for heterogeneous reservoirs
of the oilfield.