When poly(2-vinyl pyridine) is combined with Pd-pincer-based organometallic surfactants, a mesomorphic structure forms due to weak stacking interactions between the pyridine units and the Pd-pincer headgroups. The weak binding between the surfactant and the polymer competes with the tendency of the aliphatic tails of the surfactant to crystallize. Here, we demonstrate that over extended periods of incubation, the crystallization tendency of the surfactant tails causes the surfactant molecules to detach from the polymer and gives rise to additional packing modes of the alkyl tails featuring higher crystalline order. The dynamic behavior of these aged structures was investigated by variable-temperature small-angle X-ray scattering (SAXS) and solid-state 13CNMR, and revealed the influence of thermal changes on the molecular level, and how these changes propagate to the mesoscale structure.

Selective segregation of surfactant molecules to one domain type of block copolymers in the melt leads to the formation of hierarchical structures. Here we show that combining an organometallic, Pd-pincer-based surfactant (Pd-SCS) with a polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymer leads to hierarchical structures due to weak stacking interactions between the Pd-pincer complex and the pyridine units. These structures feature a different morphological behavior than analogous systems, including the formation of perforated lamellae (PL) over a wide range of surfactant filling fractions and a distinct swelling anisotropy behavior of the copolymer chains by the added surfactant molecules. The results suggest that the strength of interaction between the surfactant and the compatible block influences the degree of segregation between the blocks. This study lays the foundations for the creation of organized, hierarchical arrays of inorganic nanoclusters that are periodic on two different length scales.

The coassembly of A B diblock copolymers with B’-type nanoparticles (i.e., nanoparticles that are slightly incompatible with the B domain) leads to hierarchical structures, where the block copolymer phase separates first and the nanoparticles create close-packed arrays within the B domains due to a slower, secondary phase separation process. Here we report the results of a comprehensive study, which focused on two aspects: the influence of the nanoparticle shape (spherical vs rod-like) and the effect of the volume composition of the blocks. Three polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) copolymers featuring similar molecular weights but differing in PS volume fraction were mixed with spherical and rod-shaped poly(ethylene oxide)- (PEO-) capped CdS nanoparticles at different filling fractions and cast as thin films. Our results highlight the mutual influence between the block copolymer and the nanoparticles on the resulting morphology, demonstrating the ability to control the film morphology by the filling fraction of the nanoparticles and their tendency to localize at the film surface, and by confinement-induced nanoparticle aggregation. Most importantly, the results reveal the influence of the nanoparticle shape on the structure of the film.