Orientational Behavior of Ellipsoidal Silica‐Coated Hematite Nanoparticles Integrated within an Elastomeric Matrix and its Mechanical Reinforcement

Abstract

The mechanical and orientational properties of IOENs consisting of integrated ellipsoidal SCH spindle‐type nanoparticles within an elastomeric matrix are reported. The influence of the SCH surface chemistry, leading either to dispersed nanoparticles or crosslinked nanoparticles within the surrounding elastomeric matrix, is studied by mechanical uniaxial deformation (stress‐strain) and SAXS measurements under stress. Without surface modifications, the SCH nanoparticles act as defects, and the Young's modulus of the elastomeric matrix remains unmodified. Surface‐modified SCH nanoparticles acting as crosslinkers increase Young's modulus by a factor 1.2. SAXS measurements demonstrate that the integrated ellipsoidal nanoparticles orient upon a deformation larger than 50% independently of the specific integration strategy. magnified image

Liquid‐Crystalline Elastomer‐Nanoparticle Hybrids with Reversible Switch of Magnetic Memory

“…In the SAXS pattern the azimuthal intensity distribution at the characteristic nanoparticle length scale (red curve) shows two intensity maxima that indicate an orientation of the mean particle long axes parallel to the stretching direction with an order parameter S * = 0.56 (calculated around a director in z ‐direction). This is in agreement with an earlier, similar study 23…”

“…One major issue in the preparation of hybrid nanocomposites is the suppression of segregation of the nanoparticles from the polymer matrix. Creeping of the polymer matrix and aggregation of the nanoparticles at high temperatures can be avoided when crosslinkable polymers and particles are used; a concept that has already been applied for isotropic networks 23, 24. Therefore we have selected chemically compatible end‐functional groups for the two components: hydroxyl groups for the liquid‐crystalline polymer and amino groups for the inorganic nanoparticles, which can be mutually crosslinked into a covalent network with a tri‐functional isocyanate (see Supporting Information).…”

Nanoparticle-Liquid Crystalline Elastomer Composites

“…After the partially cross-linked film was carefully removed from the reactor, the LC mesogens were aligned mechanically by applying uniaxial extension in order to produce uniform distribution of the local nematic director along the stretching direction. Anisotropic particles embedded in this rubbery elastic medium experience a similar alignment effect; they choose a preferred orientation during the stretching [71]. Even in a rubber such as ordinary PDMS, which contains no LC mesogens, stretching forces embedded CNTs to align [72].…”

Strain- and field-induced anisotropy in hybrid elastomers with elongated filler nanoparticles

“…We investigate the strain-and field-induced geometric and magnetic orientation of the elongated magnetic filler particles in an elastomeric matrix, and how this interplay is influenced by the network architecture and by an intrinsic preorientation of the filler particles. 15 Therefore, we compare conventionally crosslinked poly(dimethylsiloxane) elastomers filled with spindle-like hematite nanoparticles with materials of similar composition, but with an architecture based on covalent particle crosslinking. The latter materials are recently introduced by us as a novel architecture of elastomers, that are crosslinked exclusively via surface-attachment of the polymer chains to magnetic nanoparticles.…”