title: Free-standing urethane/urea elastomer films undoped and doped with ferro-nano-particles.
abstract: We report on an experimental study of the structures presented by urethane/urea elastomeric films without and with ferromagnetic nanoparticles incorporated. The study is made by using the X-ray diffraction, nuclear magnetic resonance (NMR), optical, atomic and magnetic force (MFM) microscopy techniques, and mechanical assays. The structure of the elastomeric matrix is characterized by a distance of 0.46 nm between neighboring molecular segments, almost independent on the stretching applied. The shear casting performed in order to obtain the elastomeric films tends to orient the molecules parallel to the flow direction thus introducing anisotropy in the molecular network which is reflected on the values obtained for the orientational order parameter and its increase for the stretched films. In the case of nanoparticles-doped samples, the structure remains nearly unchanged although the local order parameter is clearly larger for the undoped films. NMR experiments evidence modifications in the molecular network local ordering. Micrometer size clusters were observed by MFM for even small concentration of magnetic particles.
authors.affiliation: Instituto de Física, Universidade de São Paulo, Caixa Postal 66318, 05314-970 São Paulo, Brazil. cleidios@if.usp.br
authors.forename: C
authors.initials: C
authors.lastname: Sena
authors.forename: M H
authors.initials: MH
authors.lastname: Godinho
authors.forename: P J
authors.initials: PJ
authors.lastname: Sebastião
authors.forename: D
authors.initials: D
authors.lastname: Sousa
authors.forename: Figueiredo A M
authors.initials: FA
authors.lastname: Neto
mesh_terms: D020724:Elastomers / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D053768:Metal Nanoparticles / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D010316:Particle Size; D053838:Scattering, Small Angle; D013499:Surface Properties; D014508:Urea / Q000737:chemistry*; D014520:Urethane / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D020724:Elastomers; D014520:Urethane; D014508:Urea; D007501:Iron