Preparation and rheological investigation of tough PAAm hydrogel by adding branched polyethyleneimine

In this article, tough hydrogels are prepared by introducing the polyethyleneimine (PEI) with branched structure and a large number of -NH2 and -NH- groups into permanently crosslinked polyacrylamide (PAAm) hydrogels matrix. To investigate the effects of B-PEI and chemical crosslinking agent (Bis) on the strength and toughness of hydrogels, a series of B-PEI/PAAm hydrogels with different mass percentage of Bis and B-PEI were manufactured and the rheological and swelling properties were compared. For all hydrogels, the storage modulus (G ') was much higher than the loss modulus (G '') in the linear viscoelastic region through the whole frequency range. The solid-like behavior and elastic nature (G ' > G '') are attributed to the permanent covalence crosslinking. Therefore, G ' increased when more Bis was added. For the nonlinear oscillatory shear measurement, hydrogels with B-PEI broke at larger gamma than the pure PAAm hydrogels, indicating that the toughness of B-PEI/PAAm hydrogels has been improved by introducing B-PEI. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48541.