Self-Assembly and Post-Fabrication Functionalization of Microphase Separated Thin Films of a Reactive Azlactone-Containing Block Copolymer

Abstract

We report on the thin film self-assembly and post-fabrication functionalization of cylinder-forming poly­(styrene-block-2-vinyl-4,4-dimethylazlactone) (PS-b-PVDMA) block copolymers (BCPs). Thermal annealing of an asymmetric BCP composition, to drive microphase separation in thin films, results in high defect densities and poor long-range order. Using FTIR spectroscopy and ellipsometry, we demonstrate that thermal annealing results in reactions between the azlactone groups and the underlying substrate leading to BCP “pinning”. We demonstrate that solvent annealing circumvents these issues and drives high fidelity microphase separation of the BCP in thin films. The solvent annealing approach also enables control over domain orientation; we show that parallel and perpendicularly oriented cylinders with diameters of 11.7 ± 1.2 nm and a center-to-center distance of 25.2 ± 2.6 nm can be obtained using a BCP with M n = 29.5 kDa and f S = 0.75. The PVDMA segments in these self-assembled thin films remain available for reaction with primary amine-functionalized nucleophiles. X-ray photoelectron spectroscopy (XPS) depth-profiling reveals that reactions between azlactone groups and incoming amines occur primarily in the top few nanometers of the reactive domains. Finally, we demonstrate that the azlactone groups in both parallel and perpendicularly oriented cylindrical thin films can selectively incorporate trimethylaluminum vapor, which can be subsequently converted into Al2O3 nanowires and nanodots with dimensions of 16 and 12 nm, respectively.

Facile and Efficient Modification of Polystyrene-block-poly(methyl methacrylate) for Achieving Sub-10 nm Feature Size

“…19,20 Mahanthappa and co-workers designed a new BCP system consisting of polystyrene and poly(vinyl azlactone), which undergo selective and quantitative reactions with functional primary amines, to yield the corresponding PS-bpolyacrylamide. 21,22 The effective interaction parameter (χ eff ) of the BCP clearly increased after the conversion from poly(vinyl azlactone) to polyacrylamide, thereby leading to the microphase separation even at a low N. Importantly, the χ eff can be controlled by changing the functional amines. Hayakawa also developed the postpolymerization modification of polysiloxanebased BCPs via the thiol−ene reaction to control χ eff .…”

Phase Behavior of Mixed Polymer Brushes Grown from Ultrathin Coatings

“…We conducted a systematic study of the optimal thermal annealing conditions for mixed brushes as predominantly only solvent annealing has been reported in the literature. It is well-known from the BCP thin film studies that solvent annealing is a kinetically controlled process, with the morphology heavily dependent on the environment and annealing time . Hence, thermal annealing is usually preferred, as the thermodynamically stable morphology can be accessed in a reproducible manner.…”

“…It is wellknown from the BCP thin film studies that solvent annealing is a kinetically controlled process, with the morphology heavily dependent on the environment and annealing time. 34 Hence, thermal annealing is usually preferred, as the thermodynami-cally stable morphology can be accessed in a reproducible manner. An early work on thermal annealing of symmetric mixed PMMA/PS brushes did not show any ripple phase, 35 contrary to theoretical predictions.…”

Fit-for-purpose block polymer membranes molecularly engineered for water treatment

“…Recent studies have been focused on membranes equipped with a highdensity of functional groups amenable to several of these reaction mechanisms. [126][127][128][129][130][131] The thiol-ene mechanism demonstrates the flexibility associated with these approaches. In one study, the covalent linkage is realized by using membranes that contain reactive thiol groups, such as polystyrene-b-poly(4-vinylpyridine)-b-poly(propylene sulfide) (PS-P4VP-PPS) to attach the dye tetramethyl rhodamine-5 to the membrane surface.…”