Hole Nucleation and Growth Induced by Crystallization and Microphase Separation of Thin Semicrystalline Diblock Copolymer Films
writer：Fu, J.; et al.
keywords：Microphase separation, semicrystalline, block copolymer, thin film
source：期刊
specific source：Macromolecules, 2004, 37, 6918-6925.
Issue time：2004年
We have investigated the hole nucleation and growth induced by crystallization of thin crystalline-coil diblock copolymer films. Semicrystalline rodlike assemblies from neutral/selective binary solvent are used as seeds to nucleate crystallization at temperatures above the glass transition temperature (Tg) but below melting point (Tm). The crystallization of nanorods drives neighboring copolymer chains to diffuse into the growing nanorods. Depletion of copolymer chains yields hole nucleation and growth at the edge of the nanorods. Simultaneously, the polymer chains unassociated into the nanorods were oriented by induction from the free surface and the substrate, leading to limitation of the hole depth to the lamellar spacing, ~ 20 nm. The holes, as well as the nanorods, grow as ta, where t is the annealing time and a crossover in the exponent a is found. The orientation and stretching of the copolymer chains by the surface and interface are believed to accelerate the crystallization, and in turn, the latter accelerates the growth rate of the holes. At T > Tm, the grains melt and the copolymer chains relax and flow into the first layer of the film.