Evolution in surface morphology during rapid microwave annealing of PS‐b‐PMMA thin films

Abstract

Microwave annealing enables rapid (60 s) ordering and orientation of block copolymer films. The developed morphology in polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) thin films depends on details of the heating rate that is controlled by microwave output energy as well as the sample location in the microwave. Over a wide heating rate (1.1-2.7 8C/ s), perpendicular orientation of the cylindrical mesostructure at the surface is >50% after 60 s, but goes through a maximum at 1.8 8C/s leading to approximately 97% perpendicular cylinders at the surface. The propagation of this perpendicular surface morphology through the film thickness is also dependent upon the microwave annealing conditions. The surface structure evolves with the microwave annealing time from imperfect ordering to perpendicular cylinders to parallel cylinders as the annealing time increases. This work demonstrates the importance of controlling the heating rate during microwave annealing, which will be critical for optimizing microwave conditions for directed self-assembly.

Transformation of Block Copolymer Nanoparticles from Ellipsoids with Striped Lamellae into Onionlike Spheres and Dynamical Control via Coupled Cahn–Hilliard Equations

“…37,38 Cavicchi and Russell developed a technique that involved exposing the polymer to vapor of a good solvent, and they managed to complete the annealing process within 1 h. 39 The transformation time can be considerably reduced from several weeks to a few minutes by using microwaves as a source of heat. 38,40,41 Because it is desirable to carry out experiments in a short amount of time, this method is a notable contribution.…”

Controlled Preparation of Thermally Stable Fe-Poly(dimethylsiloxane) Composite by Magnetic Induction Heating

“…PDMS based systems are fabricated by molding, casting or soft lithography [4]. PDMS have been shown to be very useful to generate shear fields to align block copolymer patterns [5,6,7]. PDMS is a highly viscous flowing liquid, which also possesses optical transparency, non-flammability, non-toxicity, and biocompatibility for biological assays [8].…”

Developing Anisotropy in Self‐Assembled Block Copolymers: Methods, Properties, and Applications

“…Thermal annealing of PS-b-PMMA thin films within a specific temperature window has been extensively studied for achieving this neutrality since the surface energy difference between PS and PMMA domains vanishes at high temperatures. [100,331,345,346] Alternatively, solvent vapor annealing of BCP thin films at optimized processing conditions, such as selected vapor pressures, can produce a neutral free surface. [88,90,91,326,347,348] Since the neutral surface is only present during processing in the aforementioned methods, many methods often require a sequential step of rapid cooling or fast solvent removal to kinetically trap oriented BCP domains.…”

“…[88,90,91,326,347,348] Since the neutral surface is only present during processing in the aforementioned methods, many methods often require a sequential step of rapid cooling or fast solvent removal to kinetically trap oriented BCP domains. [90,92,100,167,[349][350][351] Furthermore, the effectiveness of these methods is largely dependent on polymer chemistry and can be challenged when a BCP consists of segments with large differences in surface energy.…”

“…[82][83][84][85][86][87][88] This methodology also enables manipulation of nanostructural orientation by varying processing parameters such as solvent selection and vapor removal rate, [89][90][91][92] which will be discussed in detail in the next section. Readers who are interested in other emerging methods for rapid ordering of block copolymers, such as thermal-assisted solvent vapor annealing, [93][94][95] direct solvent immersion annealing, [96][97][98] microwave annealing, [94,[99][100][101] and laser annealing, [102,103] can be directed to an excellent review by Majewski and Yager for relevant fundamentals of BCP ordering kinetics with different annealing approaches. [80] The advantages of bottom-up control over order, including low manufacturing costs and widely tunable morphologies, render BCPs to be critical structure-directing agents for a wide array of nanotechnology applications (Figure 3).…”