Frustrating the lamellar ordering transition of polystyrene-block-polyisoprene with a C60 additive

Abstract

Thermal fluctuations in block copolymer (BCP) materials characteristically drive the ordering phase transition order from second to first order by the well known Brazovskii mechanism and there have been many observations of jumps in x-ray and neutron scattering intensity data at the order-disorder transition (ODT) that signal this phenomenon. However, the existence of quenched disorder can either destroy the ODT or restore the second-order nature of this type of phase transition. The present work considers how the dispersion of C(60) ("buckyballs"), which is prone to clustering in polymeric media, into poly(styrene)-block-poly(isoprene) to see how this nanoparticle additive alters the qualitative character of the BCP ordering. Small angle x-ray scattering indicates that a small amount (approximately = 1 mass %) of C(60) causes the BCP to remain disordered over a wide temperature range so that a phase transition no longer exists. This phenomenon offers both technological problems and opportunities.

Nanoparticle Network Formation in Nanostructured and Disordered Block Copolymer Matrices

“…This second event is absent in the neat copolymer, as well as in the system modified with CS, whereas neither SM/FS nanocomposite exhibits a discernible ODT. Similar disappearance of the ODT is observed [21] in the case of nanocomposites modified with C 60 buckyballs. Over the range from 160 to 200°C, the dynamic moduli measured from the SM-based nanocomposites described in Fig.…”

“…Addition of FS or CS nanoparticles up to 10 wt% reduces the ODT by as much as ~7°C, depending on surface functionality. This change in ODT is markedly different from that observed in block copolymer nanocomposites composed of a poly(styrene- b -isoprene) diblock copolymer modified with C 60 buckyballs [21]. In that case, the ODT is found by dynamic rheology to decrease by 21°C upon incorporation of only 0.04 wt% C 60 .…”

Phase behavior under the averaging over disorder realizations

“…(10), (15) in the context of the present study). Based on this we may argue that the absence of reliable evidences of a sharp phase behavior in the experiments [25,27] with disordered systems can be explained by their self-averaging nature, involving a superposition of different disorder realizations. In this respect a development of methods [29] which are not based on the criticality could be quite promising for the characterization of disordered media (e.g.…”

“…Thus, changing the system composition with a small fraction of impurities may completely ''eliminate'' the ordered phase. Note that quite recent experiments [25] on lamellar ordering transitions in doped block copolymers reveal that a very small concentration (≈1%) of the doping agent suppresses the ordered phase. One might argue that the quenched variable distributions used in the simulation or theoretical studies are already given as averaged over realizations Ψ (h).…”

Order–Disorder Transition of Nanocomposites: Polystyrene-block-Poly(methyl methacrylate) with Palladium Nanoparticles

“…The nanocomposites made of the bcp templates and nanoparticles have attracted much attention, because bcps are well-known to organize into diverse multiphase structures with nanoscale periodicity, − and the incorporation of the nanoparticles is of great importance for manufacturing electromagnetic, optical, and mechanical devices. − The added nanoparticles have the potential to perturb the nature of the phase transitions of bcps also and influence the ordering process of bcps. ,− As a consequence, T ODT of the nanocomposites shifts upward or downward. Theoretically, the magnitude of the T ODT shift is predicted to be dependent on the size, shape of the nanoparticles, and the nature of the surface interactions between the nanoparticles and the bcps. ,, Some experimental evidence on the shift of T ODT and its relationship with the nature of the nanoparticles were also reported lately, including our previous work .…”