Macromolecules, 2016, vol 49, 9, pp. 3352-3360
DOI:10.1021/acs.macromol.5b02609
Abstract
For well-ordered block copolymer (BCP) nanocomposites containing nanoparticles (NPs), the ratio of NP core diameter (dcore) and BCP domain width (L) has been generally limited with dcore/L < 0.3 when NP/BCP interactions are relatively neutral or weak. Here, we systematically investigate the spatial distribution of gold nanoparticles (NP) ranging in size up to 0.8 times that of the target domain width in symmetric polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) using a hydrogen-bonding-mediated (H-bonding) assembly. NPs with core diameters (dcore) 2, 5, 9, and 15 nm are coated with ligands bearing phenol groups as the hydrogen-donating sites for H-bonding including 2-(11-mercaptoundecyl)hydroquinone and thiol-terminated poly(4-hydroxystyrene). These hydroxylated NPs are selectively incorporated into the P2VP block (domain width L = 7–37 nm) over a wide range of volume fractions (ϕ = 3–26 vol %). Particle distributions are biased toward the center of in the P2VP domains when dcore/L is greater than 0.3 and are otherwise uniformly distributed within the target domain. The H-bonding interactions between NP and BCP provide favorable enthalpic interaction to overcome the inherent entropy penalties mainly arising from polymer chain stretching upon the sequestration of large particles. This strong thermodynamic driving force provides a means of incorporating relatively large NPs within BCP templates to further enable the preparation of well-ordered composites that can take advantage of the attractive size-dependent properties of NPs.
