title: Surface morphology diagram for cylinder-forming block copolymer thin films.
abstract: We investigate the effect of the ordering temperature (T) and film thickness (h(f)) on the surface morphology of flow-coated block copolymer (BCP) films of asymmetric poly(styrene-block-methyl methacrylate). Morphology transitions observed on the ordered film surface by atomic force microscopy (AFM) are associated with a perpendicular to a parallel cylinder BCP microphase orientation transition with respect to the substrate with increasing h(f). "Hybrid" surface patterns for intermediate h(f) between these limiting morphologies are correspondingly interpreted by a coexistence of these two BCP microphase orientations so that two "transitional" h(f) exist for each T. This explanation of our surface patterns is supported by both neutron reflectivity and rotational SANS measurements. The transitional h(f) values as a function of T define upper and lower surface morphology transition lines, h(fu) (T) and h(fl) (T), respectively, and a surface morphology diagram that should be useful in materials fabrication. Surprisingly, the BCP film surface morphology depends on the method of film formation (flow-coated versus spun-cast films) so that nonequilibrium effects are evidently operative. This morphological variability is attributed primarily to the trapping of residual solvent (toluene) within the film (quantified by neutron reflectivity) due to film vitrification while drying. This effect has significant implications for controlling film structure in nanomanufacturing applications based on BCP templates.
authors.affiliation: Polymers Division, National Institute of Standards and Technology (NIST), Gaithersburg, Maryland 20899, USA.
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Zhang
authors.forename: Brian C
authors.initials: BC
authors.lastname: Berry
authors.forename: Kevin G
authors.initials: KG
authors.lastname: Yager
authors.forename: Sangcheol
authors.initials: S
authors.lastname: Kim
authors.forename: Ronald L
authors.initials: RL
authors.lastname: Jones
authors.forename: Sushil
authors.initials: S
authors.lastname: Satija
authors.forename: Deanna L
authors.initials: DL
authors.lastname: Pickel
authors.forename: Jack F
authors.initials: JF
authors.lastname: Douglas
authors.forename: Alamgir
authors.initials: A
authors.lastname: Karim
mesh_terms: D000327:Adsorption; D018625:Microscopy, Atomic Force; D053758:Nanoparticles / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry; D036103:Nanotechnology / Q000379:methods*; D009502:Neutrons; D011108:Polymers / Q000737:chemistry*; D019904:Polymethyl Methacrylate / Q000737:chemistry; D011137:Polystyrenes / Q000737:chemistry; D012542:Scattering, Radiation; D012997:Solvents / Q000737:chemistry; D013499:Surface Properties; D013696:Temperature; D013816:Thermodynamics; D014050:Toluene / Q000737:chemistry
chemical_list: D011108:Polymers; D011137:Polystyrenes; D012997:Solvents; C522519:poly(styrene-block-methyl methacrylate); D014050:Toluene; D019904:Polymethyl Methacrylate