Dewetting Instabilities in Thin Block Copolymer Films:  Nucleation and Growth

Abstract

We examined the dynamics of dewetting of a thin symmetric diblock copolymer film on a substrate above the bulk order−disorder transition temperature, T ODT, of the copolymer using atomic force microscopy. The dewetting mechanism proceeded with the formation of discrete holes without their characteristic peripheral rims. During this early stage, the hole radii R increased exponentially with time. This stage was followed by a narrow intermediate regime where the rim develops and R ∼ t. When the rim was fully developed, R increased as t 2/3. The shape of the rim was highly asymmetrical and its width L increased as t 1/2. At the final stage of the process, droplets of the copolymer, a few microns in diameter and with heights on the order of tens of nanometers, existed on a dense copolymer “brush” of uniform thickness 7 nm anchored to the substrate. This clearly indicates that the process is autophobic, a phenomenon first documented in small molecule liquids.

Surface-tension-driven dewetting of Newtonian and power-law fluids

“…In particular, [16] considered polymer films for which the dewetting radius was found to grow exponentially for small time, followed by a period of linear growth (the width of the "rim" of fluid was found to grow as t 1/2 , consistent with [12] and with the analysis below), before a final regime in which the dewetting radius goes like t 2/3 ; in addition, [16][17][18] found the dewetting radius to grow linearly for a variety of Newtonian fluids. The role of inertia in high-speed dewetting is discussed in [19].…”

Surface pattern based on an azobenzene-containing copolymer thin film and its light-driven morphology modulation

“…Recently, self-organizational processes, as alternative means to producing surfaces with highly controlled and ordered structures, are attractive due to their convenience and broad tunability. Meanwhile, microphase separation and dewetting are two important self-organizational processes and are usually used to fabricate some well-defined structures on the microscale in the polymer films (Limary and Green, 1999;Thompson, 2012). Some typical highly ordered periodic geometries, such as spherical, lamellar, cylindrical, or bicontinuous nanostructures, have been formed based on microphase separation in the block copolymers (Ruzette et al, 2006;Kim and Han, 2010;Wang et al, 2012).…”

“…Some typical highly ordered periodic geometries, such as spherical, lamellar, cylindrical, or bicontinuous nanostructures, have been formed based on microphase separation in the block copolymers (Ruzette et al, 2006;Kim and Han, 2010;Wang et al, 2012). Conversely, polymer dewetting is associated with interfacial tensions in solid/liquid, liquid/air, and solid/air phases (Limary and Green, 1999;Green and Limary, 2001). Usually, bicontinuous or island morphology can be formed based on the dewetting process.…”

“…To date, only Li et al (2012) have reported on the photoinduced surface pattern modulation in an azobenzene-containing poly(propyleneimine) dendrimer film. There is few work reporting on the morphologies modulation in linear block copolymer films through controlling dewetting behaviors by light (Limary and Green, 1999;Yan et al, 2011). Herein, we synthesized a novel azobenzenecontaining photoresponsive block copolymers by atom transfer radical polymerization (ATRP).…”

Directed self-assembly of PS-b-PMMA block copolymer using HSQ lines for translational alignment

“…Since hole growth in thin lms is signicantly inuenced by both interfacial and hydrodynamic forces we believe the toluene only cleaned substrates produce more defects and hole growth due to these intermolecular forces with a bare silicon surface in comparison to substrates that were chemically functionalized with EG. 39 Also both a mixture of perpendicular and parallel cylinders has yet to be shown in asymmetric PS-b-P4VP when annealed in a THF atmosphere. Here we employed THF only but THF-toluene (80 : 20) was also studied and produced the same results.…”