Transition Mechanisms for Complex Ordered Phases in Block Copolymer Melts

Abstract

We describe microstructural aspects of phase transitions between the lamellar (L), perforated layer (PL), and gyroid (G) morphologies in diblock copolymer melts. Using small-angle scattering, dynamic mechanical spectroscopy, and transmission electron microscopy, we show that these transformations proceed through the nucleation and growth of the final phase, in contrast to recent calculations that assume evolution from a thermodynamically unstable initial state. Direct L → G transitions are suppressed by the high surface tension associated with L−G grain boundaries; the formation of the metastable PL structure under such conditions reflects the ease with which the L → PL transition can occur, compared to L → G. Similar effects dominate the G → L transition. Mismatches in spacings between epitaxially related lattice planes also influence relaxation kinetics; the P → LG transition rate depends strongly on the relative spacings of the PL [10] and G [211] planes, and the considerable discrepancy between the G [211] and L [10] spacings at the L−G boundary may further retard that transformation. Similar factors have been shown to govern the evolution of amphiphilic systems, supporting geometrically inspired attempts to understand this phase behavior.

Biomimetic block copolymer particles with gated nanopores and ultrahigh protein sorption capacity

“…The transition from lamella to gyroid phases was observed for the first time in self-assembled BCP nanoporous particles. This transition has been mostly previously observed for diblock copolymers in melts [32][33][34] . (3) Gyroid to Schwarz P structure transition (Fig.…”

Nanostructured Morphologies by Self-Assembly of Diblock Copolymers: A Review

“…{220} DG became the grain boundary plane. The previously cited L to HPL to G transitions have also been found for films from other copolymers such as PEO-b-PBO [35], PEP-b-PDMS or PEO-b-PPE [33] prepared by melt-pressing. Their mechanisms have been well explained.…”

“…Even if in the bulk state, the perforated lamellar morphology of block copolymers has been reported to be a metastable state of the gyroid (G) phase, under thin film confinement conditions, one-dimensional confinement provides stability to the phase [26,27] and has been found for different diblock copolymer thin films under several conditions [26][27][28][29][30][31][32][33][34][35]. For thin films of poly(styrene-b-dimethylsiloxane) (PS-b-PDMS) diblock copolymer spin coated onto silicon wafers modified with hydroxyl-terminated PDMS subject to solvent vapor annealing, depending on the film thickness, its commensurability with the microdomain period, and the ratio of toluene/heptane vapors used for the solvent annealing process, perforated lamellae morphology can be obtained [26], besides spheres, cylinders, or gyroids.…”

“…For the same copolymer but with 65% of PS [33], it was concluded that order-order transitions between the L, HPL, and G phases proceeded through nucleation and growth.…”

Characterization of the Spindle Morphology Nanomicelles Assembled from Sericin and Gelatin

“…It included PB-PDMS, PE-PEE, PS-PI, PI-PS, PEO-PEE PI-PS-P2VP, PS-PEB-PMMA, PS-PI-P2VP, PS-PB-P2VP, and PI-PS-PI; it can self-organize into spherical, cylindrical, lamellar, gyroid morphologies, and so on [4][5][6][7][8][9][10][11][12][13].…”