Synthesis and characterization of poly(N-vinyl formamide) hydrogels-A potential alternative to polyacrylamide hydrogels

The synthesis and characterization of solution‐cast, molded gels of N‐vinyl formamide (NVF) has not been previously reported even though NVF is an isomer of acrylamide (AAm) and polyacrylamide (PAAm) hydrogels have many commercial applications. Aqueous NVF solutions were cross‐linked into gels using a novel cross‐linker, 2‐(N‐vinylformamido)ethylether, and the thermally‐activated initiator VA‐044. For a given formulation, PNVF gels swell up to twice that of PAAm gels cross‐linked with N,N′‐methylenebisacrylamide. From swelling and compression measurements, PNVF gels were found to be more hydrophilic than PAAm gels. Flory‐Huggins solubility parameters were χ = 0.38ϕ2 + 0.48 for PNVF and χ = 0.31ϕ2 + 0.49 for PAAm, where ϕ2 is the polymer volume fraction. The shear moduli for PNVF and PAAm scale with ϕ 22.0 and ϕ 22.5 respectively, consistent with good solvent behavior, also suggesting PNVF is more hydrophilic than PAAm. Similarity of mechanical properties for both gels as a function of ϕ2 suggests that network structures of PNVF and PAAm gels are similar. Fracture strains of both gels declined with ϕ2 by the same linear function while fracture stresses were about 500 kPa regardless of formulation. Since NVF is a liquid monomer, less toxic than AAm and can be hydrolyzed to a cationic form, PNVF gels could become technologically significant. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 N‐vinyl formamide (NVF) is an isomer of acrylamide (AAm), yet PNVF gels have not been synthesized and characterized, unlike widely used PAAm gels. Because NVF is liquid, less toxic than AAm, and because PNVF gels can be efficiently hydrolyzed to polyvinylamine, PNVF gels could also have significant technological utility. Thus solution‐cast, molded poly(N‐vinyl formamide) hydrogels were created by copolymerization/crosslinking of aqueous NVF with a novel cross‐linker, 2‐(N‐vinylformamido) ethylether (NVEE). PNVF gels are slightly more hydrophilic than PAAm gels in terms of the χ parameter, but gels of the same polymer volume fraction have the same moduli and fracture properties.