Effect of water soluble molecules on the stability and flexibility of lyotropic lamellar structures. Polymer molecular weight influence

•Acrylamide and polyacrylamide have been incorporated in a lamellar liquid crystal.•Polyacrylamide perturbs the interlayer interaction.•Polymer coils smaller than the thickness of water layers are confined in the lamellae.•Larger polymer coils are segregated promoting the coexistence of an isotropic phase.•The fraction of polymer segregated from lamellae is calculated.