This paper reports on experiments intended for investigating the feasibility of preparing hybrid thermoreversible gels from covalent polymers and noncovalent self-assembling pi-conjugated molecules. The formation and the degree of dispersion of these hybrid gels have been studied with polystyrenes of various tacticities and oligo(p-phenylenevinylene) molecules (OPV) in different nonpolar organic solvents. Detailed investigations of the systems have been carried out by DSC, SAXS, and AFM. It is shown that no liquid-liquid phase separation is involved, indicating that the systems are highly compatible, and that the growth of one type of gel does not interfere with the other. These studies reveal that the resultant hybrid gels are composed of the intermingled fibrillar architectures of both gels.

To develop fluorescent organic nanoparticles with tailored properties for imaging and sensing, full control over the size, fluorescence, stability, dynamics, and supramolecular organization of these particles is crucial. We have designed, synthesized, and fully characterized 12 nonionic fluorene co-oligomers that formed self-assembled fluorescent nanoparticles in water. In these series of molecules, the ratio of hydrophilic ethylene glycol and hydrophobic alkyl side chains was systematically altered to investigate its role on the above-mentioned properties. The nanoparticles consisting of π-conjugated oligomers containing polar ethylene glycol side chains were less stable and larger in size, while nanoparticles self-assembled from oligomers containing nonpolar pendant chains were more stable, smaller, and generally had a higher fluorescence quantum yield. Furthermore, the dynamics of the molecules between the nanoparticles was enhanced if the number of hydrophilic side chains increased. Energy transfer studies between naphthalene and benzothiadiazole fluorene co-oligomers with the same side chains showed no exchange of molecules between the particles for the apolar molecules. For the more polar systems, the exchange of molecules between nanoparticles took place at room temperature or after annealing. Self-assembled nanoparticles consisting of π-conjugated oligomers having different side chains caused self-sorting, resulting either in the formation of domains within particles or the formation of separate nanoparticles. Our results show that we can control the stability, fluorescence, dynamics, and self-sorting properties of the nanoparticles by simply changing the nature of the side chains of the π-conjugated oligomers. These findings are not only important for the field of self-assembled nanoparticles but also for the construction of well-defined multicomponent supramolecular materials in general.

This paper examines the possibility of sheathing polymer nanofibrils, prepared from a thermoreversible gel, by nanotubules, obtained through self-assembly of a complex ester. The method for preparing this hybrid system consists of cooling ternary solutions until gelation is achieved. The sheathing mechanism most probably occurs through heterogeneous nucleation: polymer fibrils act as heterogeneous nuclei, and so trigger the growth of nanotubules around them. The occurrence of the sheathing process is investigated by DSC, AFM, SAXS and SANS. In the latter case, the contrast variation method is used.

Thermoreversible gels of poly(vinylidene fluoride) (PVF2) in organic diesters [(CH2) n −(COOEt)2] were dried by replacing the high boiling diesters with a guest solvent cyclohexane and followed by leaching with methanol. The porosity of the samples was measured using mercury intrusion porosimetry (MIP) for pore size > 6 nm and by nitrogen adsorption porosimetry using the Barett−Joyner−Halenda (BJH) technique for pore size 3−6 nm. Samples dried from gels in diethyl adipate (n = 4), diethyl suberate (n = 6), and diethyl azelate (n = 7) were studied. Porosity in different dimensions, e.g., micro, meso, and macro sizes, was observed in the same sample making them as multiporous materials. Both nano- and macroporosity increase with increasing “n” of diesters, and pore volumes and surface areas were also found to increase in a similar fashion. Field emission scanning electron micrographs also support the above points. The differential scanning calorimeteric thermograms at higher heating rate (40 °C/min) show two peaks; the higher melting peak increases with decreasing “n”. The porous PVF2 materials have α-polymorphic structure as evidenced from X-ray diffraction. Both nano- and macroporosity decrease with increasing polymer concentration in the gel. The materials show hysteresis loop in the intrusion and extrusion histograms of MIP and nitrogen adsorption porosimetry, indicating ink bottle or interconnected channel structure in the material. Samples dried from increased polymer concentration in the gel have lower nanopore concentration, lower surface area, and lower pore volume.