Highly Oriented and Ordered Arrays from Block Copolymers via Solvent Evaporation

Abstract

tion of individual protein molecules or complexes than an extended, homogeneous surface. Of course, this hypothesis needs to be tested by biological activity. ExperimentalSize-selected metal (Au) clusters, with size between 1 and 100 atoms, were generated by an RF (radio-frequency) magnetron sputtering, gas condensation [20,21] cluster beam source and mass selected to within 5 % by a novel, lateral time-of-flight mass filter to control the cluster size, as described previously [22]. The energetic beam of ionized Au clusters was deposited on a graphite substrate with sufficient kinetic energy to ªpinº the clusters to their individual points of impact on the surface. The underlying mechanism of pinning is the displacement of a surface carbon atom to create a reactive binding site which prevents the characteristic diffusion and aggregation of clusters observed at lower incident energies [15,16]. In this work we found that such monodispersed cluster films were stable not only at room temperature but also at temperatures up to 200 C. They are also stable when placed in an autoclave (130 C for 2 h in high pressure steam) to sterilize the surface. The Au 17 + clusters were produced with an Ar flow of 60 sccm and a He flow of 25 sccm (total gas pressure of 0.4 mbar). Typical sputtering parameters were: RF power 25 W; self-bias voltage of the target 372 V. The cluster samples were imaged in ambient conditions with a bench-top STM (DME Rasterscope 4000). Typical imaging parameters were 0.4 V and 0.4 nA (using mechanically cut Pt/Ir tips). All AFM measurements were collected from a Digital Instruments DI3100 equipped with a Nanoscope IIIa controller and a liquid cell holder. Commercial oxide sharpened silicon nitride tips with nominal spring constant of either 0.38 or 0.60 N m ±1 were used for imaging.

Self-assembly of liquid crystal block copolymer PEG-b-smectic polymer in pure state and in dilute aqueous solution

“…In the past decade, electric fields, 6 temperature gradients, 7 directional solidification, 8 modification of substrate surfaces, 9 shearing, 10 solvent evaporation, 11 and roll casting 12 These responses should help achieve nanostructure control. Liquid crystalline (LC) rod-coil block copolymers are good candidates because they respond to multiple stimuli including electric and magnetic fields, temperature and light (if the mesogen is a chromophore).…”

Controlled Ordering of Block Copolymer Thin Films by the Addition of Hydrophilic Nanoparticles

“…To overcome these challenges, it has recently been demonstrated that diblock/triblock copolymer films based on poly(styrene-bethylene oxide) (PSt-b-PEO) and poly(styrene-b-methyl methacrylate-b-ethylene oxide) (PSt-b-PMMA-b-PEO) exhibited cylindrical microdomains with a high degree of lateral ordering after solvent annealing under controlled humidity conditions. [26][27][28] In these examples, no neutralization layer is required, and it is believed that the relative humidity plays an important role in a lateral ordering of the block copolymer thin films, presumably by a strong interaction between the water vapor and the hydrophilic PEO domains during the solvent annealing process. 26 While such a process does not work directly with PSt-b-PMMA block copolymers, it is an intriguing possibility if a similar lateral ordering and vertical orientation can be induced in these hydrophobic systems by simple introduction of "external" hydrophilic moieties into PSt-b-PMMA copolymers.…”

“…[17][18][19] This neutralization layer is not required for poly(ethylene oxide) (PEO)-based block copolymer systems where the morphologies and orientation of the thin films are controlled and greatly affected by the relative humidity during a solvent annealing process, though removal of the PEO domain is difficult. [25][26][27][28] In this case, it was found that interaction between the water vapor in the atmosphere and the PEO domains leads to lateral ordering of the PEO microdomains, and application of this process to PSt-b-PMMA systems did not lead to orientation. In this paper, we demonstrate a novel method to control the orientation of PSt-b-PMMA block copolymer thin films using hydrophilic nanoparticles without the need for a neutralization layer, greatly improving the processability of PSt-b-PMMA systems.…”

Highly oriented and ordered double-helical morphology in ABC triblock terpolymer films up to micrometer thickness by solvent evaporation

“…5,18,19 Some studies have also shown that the orientation of microphase-separated structures can be controlled by exposing block copolymer films to solvent vapor and drying at a controlled evaporation rate. 13,18,[20][21][22][23][24][25][26][27] We have reported the experimental visualization of a threedimensional (3D) helical morphology for a polystyrene-block-polybutadiene-block-poly(methyl methacrylate) triblock terpolymer (SBM) using transmission electron microtomography (TEMT). 28 The TEMT observations revealed that the double-helical structure was composed of polybutadiene (PB) helical microdomains around hexagonal-packed polystyrene (PS) cylinder cores in a poly(methyl methacrylate) (PMMA) matrix, even though the block copolymer was not chiral.…”