Conventional crosslinked hydrogels typically have poor fracture toughness (&lt; 10 J/m2), due to the absence of a molecular mechanism for energy dissipation. Recent research on double network hydrogels1, physical (supramolecular) hydrogels2 and hybrid hydrogels with covalent and physical crosslinks3 has shown that hydrogels with fracture toughness (i.e., the fracture energy release rate) of G &gt; 103 J/m2 are possible. For polyamphiphilic hydrogels4 G ~ 4000 J/m2 and for hybrid hydrogels with ionic and covalent networks3 G ~ 9000 J/m2. This talk describes the structure and properties of supramolecular, responsive hydrogels made from copolymers of N-isopropylacrylamide (NIPAM) and 2-(N-ethylperfluorooctane sulfonamido)ethyl acrylate (FOSA) containing 5 - 22 mol% FOSA. The copolymer microstructure consisted of ~6 nm diameter core-shell fluorocarbon nanodomains within a poly(NIPAM) continuous phase that persisted when the copolymer was swollen with water. The nanodomains behaved as multi-functional, physical crosslinks. The hydrogels exhibited an LCST that decreased with increasing FOSA concentration. Below the LCST, the water content decreased with increasing FOSA concentration. Stress disrupts the supramolecular bonds, but the network is reversible. Below the LCST the hydrogels were very tough (G ~ 8000 J/m2), strong (σu ~1 MPa), stiff (E &gt; 1 MPa) and stretchable, εu &gt; 500%. Copolymer hydrogels based on N,N’-dimethyl acrylamide (DMA), instead of NIPAM, also had similar microstructure and were strong, tough materials. In contrast, hydrogels made from triblock copolymers5 of FOSM-b-DMA-b-FOSM (FOSM = methacrylate version of FOSA) had poor properties. The differences between the properties of the statistical and block copolymer hydrogels are due the copolymer architecture and the relaxation of the physical bonds. 1 Gong, JP; Katsuyama, Y; Kurokawa, T; Osada, Y Adv. Mater. 2003,15,1155. 2 Abdurrahmanoglu, S; Can, V, Okay, O Polymer 2009, 50, 5449. 3 Sun, JY; Zhao, X; Illeperuma, WRK.; Chaudhuri, O; Oh, KH; Mooney, DJ; Vlassak, JJ; Suo, Z Nature 2012, 489, 133. 4 Sun, TL; Kurokawa, T; Kuroda, S; Ihsan, AB; Akasaki, T; Sato, K; Haque, MA; Nakajima, T; Gong, JP Nat Mater 2013, 12, 932. 5 Niu, H; Wang, F, Weiss, RA Macromolecules, 2015, 48, 645. This research was supported by a grant from the Civil, Mechanical and Manufacturing Innovation (CMMI) Division of the Directorate of Engineering of the National Science Foundation, Grant 1300212.

Tough supramolecular hydrogels and the effect of molecular architecture on properties

250th National Meeting (2015)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.