Structure of Tough Multiple Network Elastomers by Small Angle Neutron Scattering

Abstract

The chain conformation of model interpenetrated network elastomers was studied by small angle neutron scattering. Model double networks (DN) were made by first polymerizing and cross-linking partially deuterated ethyl acrylate in the presence of toluene, then by swelling these networks with either ethyl or methyl acrylate monomers subsequently polymerized. Model triple networks (TN) were made by repeating these swelling/polymerization steps one more time. The samples were then placed in the neutron beam at different stretching levels and the scattering patterns were acquired. We found that the swollen deuterated network only stretched affinely with the macroscopic strain above a critical length scale ξc For the DN, the critical length scale was of the order of the first network mesh size, while for the TN, the deuterated network polymerized first, stretched affinely down to a third of the mesh size clearly showing the high level of stretching of these chains inside the material.