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Luminescent core–shell polymer particles carrying amino groups for covalent immobilization of enzymes were synthesized for practical applications in immunoassays. The polystyrene core particles were synthesized by miniemulsion polymerization of oil-in-water emulsion styrene droplets dissolving 2-(2-chloropropionyl)ethyl methacrylate and the europium complex emulsified with 2-methacryloyloxyethyl-N,N-dimethyl-N–n-dodecylammonium bromide. The red luminescence attributed to europium complexes embedded in the core particles was observed upon UV irradiation. The PSt-g-POEGMAx-NH2 aminated core–shell particles were prepared by surface-initiated atom transfer radical polymerization of oligo(ethylene glycol) methyl ether methacrylate (OEGMAx), followed by Gabriel synthesis. The densities of grafted chains were determined by the composition, the hydrodynamic diameters, and the fluorescence labeling method. POEGMAx-grafted chains were found to affect the dispersion stability of the particles. The nonspecific adsorption of bovine serum albumin was suppressed by the POEGMAx-grafted chains. The enzymatic activity of horseradish peroxidase covalently bound to the terminal amino groups of POEGMAx-grafted chains was evaluated by colorimetric immunosorbent assay.

The design of molecular systems with high-fidelity self-assembly pathways that include several levels of hierarchy is of primary importance for the understanding of structure-function relationships, as well as for controlling the functionality of organic materials. Reported herein is a high-fidelity self-assembly system that comprises two hydrogen-bonding molecular semiconductors with regioisomerically attached short alkyl chains. Despite the availability of both discrete cyclic and polymeric linear hydrogen-bonding motifs, the two regioisomers select one of the two motifs in homogeneous solution as well as at the 2D-confined liquid-solid interface. This selectivity arises from the high directionality of the involved hydrogen-bonding interactions, which renders rerouting to other self-assembly pathways difficult. In thin films and in the bulk, the resulting hydrogen-bonded assemblies further organize into the expected columnar and lamellar higher-order architectures via solution processing. The contrasting organized structures of these regioisomers are reflected in their notably different miscibility with soluble fullerene derivatives in the solid state. Thus, electron donor-acceptor blend films deliver a distinctly different photovoltaic performance, despite their virtually identical intrinsic optoelectronic properties. Currently, we attribute this high-fidelity control via self-assembly pathways to the molecular design of these supramolecular semiconductors, which lacks structure-determining long aliphatic chains.

The intramolecular photochemical processes excimer formation and charge-transfer (CT) complex formation were investigated by comparing the behavior of α,ω-di(1-naphthyl)permethyloligosilanes ((1-naphthyl)-(SiMe2) n -(1-naphthyl); NS n N, n = 1, 3, and 6) and 1-(1-naphthyl)permethyloligosilanes ((1-naphthyl)-(SiMe2) n -Me; NS n, n = 1, 3, and 6) by use of stationary and time-resolved fluorescence (TR-FL) measurements. Formation of excimer and CT complexes is highly dependent on the silicon chain length and polarity of the medium. Intramolecular excimer formation between the two naphthyl groups and charge transfer interactions between the naphthyl and silane moieties were investigated by use of a time-correlated single-photon counting method.

Ditopic melamines possessing one (1) or two (2) perylene bisimide (PBI) chromophores were synthesized and their self-aggregation and coaggregation with dodecyl cyanurate (dCA) or barbital (Bar) were investigated. Optically transparent organogels were formed through self-aggregation of 1 and coaggregation of 1 or 2 with dCA or Bar in nonpolar solvents. X-ray diffraction of the xerogels exhibited typical diffraction patterns assignable to lamellar structures, suggesting the formation of tapelike hydrogen-bonded motifs. Remarkably low critical gelation concentrations (cgc) of 8.0 × 10−4 M were revealed for all organogels, thus they can be classified as supergelators. Comparison of the thermal stabilities of the gels revealed that the gels containing 2 have higher melting temperatures (Tm) than those containing 1. Scanning electron microscopy and atomic force microscopy showed that the gels containing 1 are composed of sheetlike microstructures, whereas those containing 2 are composed of fibrous nanostructures, consistent with the difference in their thermal stabilities. The different self-assembled structures of our PBI aggregates can be related to whether extended stacks of PBI dyes along the hydrogen-bonded strands are possible or not. Ditopic hydrogen bonding melamines possessing perylene bisimide chromophores were synthesized and their self-aggregation and coaggregation with complementary guest molecules were investigated. In this system, 2-D lamellar structures of perylene bisimides were constructed through hierarchical organization of hydrogen-bonded tapes, which can gelate aliphatic and aromatic solvents. The resulting gels are highly transparent and exhibit remarkably low critical gelation concentrations of 8.0 × 10−4 M. The thermal stabilities and the mesoscopic morphologies of these organogels could be reasonably explained by the number of perylene bisimide chromophores introduced in the melamine components.

The supramolecular design of photochromic molecules has produced various smart molecular assemblies that can switch their structures and/or functions in response to light stimuli. However, most of these assemblies require large structural changes of the photochromic molecules for an efficient conversion of assembled states, which often suppresses the photoreactivity within the self-assemblies. Here we report molecular assemblies, based on a photo-cross-linkable chromophoric dyad, in which a small amount of ultraviolet-generated photochemical product can guide the entire system into different assembly processes. In apolar solution, the intact dyad self-assembles into right-handed superhelical fibrils. On ultraviolet-irradiation of these fibrils, an effective photoreaction affords a sole photo-cross-linked product. When right-handed helical fibrils, containing a minor amount of the photoproduct, are thermally reconstructed, the intact molecule and the photoproduct undergo a co-assembly process that furnishes superhelical fibrils with different molecular packing structures. This molecular design principle should afford new paradigms for smart molecular assemblies., The ability to switch structure or function in response to an external stimulus is highly desirable for many applications. Here, the authors report the guidable supramolecular assembly of photocross-linkable molecules into different complex superstructures, dependant on their exposure to UV light.

π-Conjugated compounds that exhibit tunable luminescence in the solid state under external mechanical stimuli have potential applications in sensors and imaging devices. However, no rational designs have been proposed that impart these mechano-responsive luminescent properties to π-conjugated compounds. Here we demonstrate a strategy for mechano-responsive luminescent materials by imparting amphiphilic and dipolar characteristics to a luminescent π-conjugated system. The oligo(p-phenylenevinylene) luminophore with a didodecylamino group at one end and a tri(ethylene glycol) ester group at the other end yields segregated solid structures by separately aggregating its hydrophobic and hydrophilic moieties. The segregated structures force the molecules to align in the same direction, thereby generating a conflict between the side-chain aggregation and dipolar stabilization of the π-system. Consequently, these metastable solid structures can be transformed through mechanical stimulation to a more stable structure, from a π-π stacked aggregate to a liquid crystal and further to a crystalline phase with variable luminescence.