Interrogating the Network Structure in Crosslinked Polymer Networks via Neutron Porosimetry

Many technologies and industries are dependent on the use of highly crosslinked polymer networks. These industries can range from coatings to water filtration to pharmaceuticals. The nature of the crosslinks can vary from covalent crosslinks to physical entanglements or hydrogen bonded networks. One key factor in understanding how these materials will function is a deeper understanding of their network structure over a variety of length scales. For example, in water filtration and desalination, highly crosslinked polyamides are often used. The function of the membrane and mechanism of filtration is directly related to pore or mesh size of the network. We have used a vapor flow cell to perform small-angle neutron scattering (SANS) porosimetry on crosslinked polymer networks. Information about the crosslink density, mesh size and the interaction between the solvent and polymer can be determined by swelling the network in-situ. Using SANS, we can probe the length scales that are relevant to the crosslink structure (nm to 100s of nm), as well as taking advantage of contrast match solvents to estimate a distribution in mesh sizes found within the network.