Control of Phase Morphology of Binary Polymer Grafted Nanoparticle Blend Films via Direct Immersion Annealing

Abstract

While the phase separation of binary mixtures of chemically different polymer-grafted nanoparticles (PGNPs) is observed to superficially resemble conventional polymer blends, the presence of a “soft” polymer-grafted layer on the inorganic core of these nanoparticles qualitatively alters the phase separation kinetics of these “nanoblends” from the typical pattern of behavior seen in polymer blends and other simple fluids. We investigate this system using a direct immersion annealing method (DIA) that allows for a facile tuning of the PGNPs phase boundary, phase separation kinetics, and the ultimate scale of phase separation after a sufficient “aging” time. In particular, by switching the DIA solvent composition from a selective one (which increases the interaction parameter according to Timmerman’s rule) to an overall good solvent for both PGNP components, we can achieve rapid switchability between phase-separated and homogeneous states. Despite a relatively low and non-classical power-law coarsening exponent, the overall phase separation process is completed on a time scale on the order of a few minutes. Moreover, the roughness of the PGNP blend film saturates at a scale that is proportional to the in-plane phase separation pattern scale, as observed in previous blend and block copolymer film studies. The relatively low magnitude of the coarsening exponent n is attributed to a suppression of hydrodynamic interactions between the PGNPs. The DIA method provides a significant opportunity to control the phase separation morphology of PGNP blends by solution processing, and this method is expected to be quite useful in creating advanced materials.

Solvent Processing and Ionic Liquid-Enabled Long-Range Vertical Ordering in Block Copolymer Films with Enhanced Film Stability

“…Heptane is a poor solvent and swells PS-PMMA to a low degree, and toluene is a good solvent for both, displaying almost a neutral behavior. 13 Figure 1 shows the AFM morphology of the films cast by flow coating of PS-PMMA 33k−33k (lamellar, l-BCP) of thickness about 60−70 nm (1−2 L o ). It is seen that without IL, there is no ordering present on the surface.…”

“…The near-neutral solvent mixture, in this case, is a 3:1 relative volume fraction ratio of heptane and toluene mixture. Heptane is a poor solvent and swells PS-PMMA to a low degree, and toluene is a good solvent for both, displaying almost a neutral behavior …”

“…12 There is then a need for a solvent-based processing technique that can alter the thermodynamic interaction between the blocks 9 and also provide a medium through the liquid surface to interact with the polymer to form more desired vertical features, while providing a higher mobility for enhanced ordering kinetics compared to melt annealing. 13 Solvent annealing includes two major types, solvent vapor annealing (SVA) and direct immersion annealing (DIA). 9,14,15 SVA is a well-studied time-intensive processing technique that sets up an equilibration of the vapor pressure of a solvent or a mixture of different solvents, and the relative affinity to each block determines how the solvent partitions in the polymer blocks and affects the overall BCP χ.…”

“…There is then a need for a solvent-based processing technique that can alter the thermodynamic interaction between the blocks and also provide a medium through the liquid surface to interact with the polymer to form more desired vertical features, while providing a higher mobility for enhanced ordering kinetics compared to melt annealing …”

Development of a magnetic hybrid material capable of photoinduced phase separation of iron chloride by shape memory and photolithography

“…Partially tuning the magnetic susceptibility, rather than changing the magnetic susceptibility of the entire material, could enhance utility in magnetic storage media. [33][34][35][36][37] The order of nanoparticles and polymer crystals in a polymer matrix is controlled by shape memory polymers (SMPs). [38][39][40][41] SMPs are an emerging class of intelligent materials that deform temporarily and change shape, but recover their original shape under environmental stimuli, such as heat, 42,43 light, 44,45 and an electric field.…”