Mechanical Properties and Deformation Behavior of the Double Gyroid Phase in Unoriented Thermoplastic Elastomers

Abstract

The mechanical properties of the double gyroid (DG) cubic phase in glassy−rubbery block copolymer systems are examined. The stress−strain properties of an isoprene-rich polystyrene/polyisoprene/polystyrene (SIS) triblock and a polystyrene/polyisoprene (SI) starblock DG, both comprised of two separate interpenetrating glassy networks embedded in rubbery matrices, are compared to those of the sphere, cylinder, and lamellar morphologies. This 3-dimensionally interpenetrating periodic nanocomposite is found to have superior properties over those of its classical counterparts, attributable to the morphology rather than to the volume fraction of the glassy component, the architecture of the molecule, or the molecular weight. The DG is the only polygranular/isotropic thermoplastic elastomer morphology which exhibits necking and drawing and which requires considerably higher stresses for deformation up to 200% strain than any of the three classical microdomain morphologies. The deformation behavior of the DG is further investigated as a function of applied strain using in situ synchrotron small-angle X-ray scattering. Yielding and necking are observed at ∼20% strain, accompanied by sudden changes in the SAXS patterns: the characteristic Bragg rings of the DG disappear and are replaced by a lobe pattern containing streaks and diffuse scattering. Analysis of the {211} reflection in the SAXS data indicates that PS networks play a large role in governing the deformation behavior. The necking behavior of the DG suggests a different deformation mechanism. The DG samples recover both microscopically and macroscopically upon unloading and annealing, indicating that the complex interconnected nanocomposite structure was not permanently damaged, even after having been stretched to 600% strain.

Effect of different plasticizers on the properties of bio-based thermoplastic elastomer containing poly(lactic acid) and natural rubber

“…The stress-strain curves of TPEs with and without plasticizer are shown in Figure 2. Their tensile behavior looked similar to a typical thermoplastic elastomer such as a poly(styrene-isoprene-styrene) block copolymer [18], poly(styrene-butadiene/butylene-styrene) block copolymer [19], silicone rubber [20], PE/nitrile rubber TPE [21] and nylon-6/EPDM TPE [22]. The tensile strength or the stress at break and the strain at break of all TPEs are displayed in Figure 3.…”

Molecular, Nanostructural and Mechanical Characteristics of Lamellar Triblock Copolymer Blends: Effects of Molecular Weight and Constraint

“…The data corresponding to W I = 0.54 are, however, considerably less dependent on x, which is consistent with a bicontinuous morphology such as the gyroid. [60] While TEM analysis of this blend reveals the existence of a lamellar morphology, the SAXS pattern in Figure 5 a is inconclusive. Moreover, the blend with W I = 0.56 clearly exhibits a non-lamellar (bicontinuous) morphology.…”

Polydispersity effects in poly(isoprene-b-styrene-b-ethylene oxide) triblock terpolymers

“…13 Ͻ f O Ͻ 0.24͒ along this isopleth in nearly monodisperse ISO materials. [50][51][52] Multiply continuous network mesostructures are of interest because they can have superior mechanical properties ͑compared to the one dimensional and 2D counterparts͒ [53][54][55] and could be employed in, for example, catalysis, 56 photonic materials, 57 solar cell, 58,59 or separation 60 applications. Our two previous ISO polydispersity studies assessed the stability of these network mesostructures in polydisperse systems.…”