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Hypothesis Multi-component supramolecular hydrogels are gaining increasing interest as stimuli-responsive materials. To fully understand and possibly exploit the potential of such complex systems, the hierarchical structure of the gel network needs in-depth investigations across multiple length scales. We show that a thorough structural and rheological study represents a crucial pillar for the exploitation of this class of functional materials. Experiments Supramolecular hydrogels are prepared by self-assembly of hexadecyltrimethylammonium bromide (CTAB) and azobenzene-4,4′-dicarboxylic acid (AZO) in alkaline aqueous solution. The CTAB/AZO concentration was varied from ϕ = 0.25 to 4 wt% keeping the CTAB:AZO molar ratio fixed at 2:1. The systems were thoroughly studied through a combination of X-ray scattering, microscopy, rheological and spectroscopic analyses. Findings The CTAB/AZO solutions form a self-supporting gel with nanofibrillar structure below ~30 °C. The critical gelation concentration is ϕc = 0.45 wt%. Above this threshold, the gel elasticity and strength increase with CTAB/AZO content as ~(ϕ-ϕc)1. The hydrogels exhibit self-healing ability when left at rest after a stress-induced damage. Moreover, the light-induced isomerization of the AZO moieties provides the gel with light-responsiveness. Overall, the multi-stimuli responsiveness of the studied CTAB/AZO hydrogels makes them a solid starting point for the development of sensors for mechanical vibrations and UV/visible light exposure.

A study of the mechanical behavior of isotactic 1,2-poly(E-3-methyl-1,3-pentadiene) (iP3MPD) and of the structural and morphological transformations that take place upon stretching is presented. Amorphous samples do not show viscous flow but show high ductility, strain hardening, and elastomeric behavior. An unusual double yielding appears in the stress- strain curves that may be correlated to occurrence of events typical of yielding at low deformation followed by stress-induced crystallization of a mesomorphic form at higher deformation (200-300%). The yielding stress and an endothermic hysteresis effect at the glass transition simultaneously increase upon aging of the amorphous glass due to a local densification or formation of local order in the amorphous glass upon physical aging. The elasticity is accompanied by the crystallization of the mesophase during deformation and its melting upon relaxation. During successive cycles of tensile deformation and elastic recovery the yielding peak is still observed during every stretching step. The elasticity of iP3MPD is an unusual case of a polymer that shows rubbery elastomeric properties below the glass-transition temperature.

We set up a facile approach for fabrication of supports with tailored nanoporosity for immobilization of enzymes. To this aim block copolymers (BCPs) self-assembly has been used to prepare nanostructured thin films with well-defined architecture containing pores of tailorable size delimited by walls with tailorable degree of hydrophilicity. In particular, we employed a mixture of polystyrene-block-poly(l-lactide) (PS-PLLA) and polystyrene-block-poly(ethylene oxide) (PS-PEO) diblock copolymers to generate thin films with a lamellar morphology consisting of PS lamellar domains alternating with mixed PEO/PLLA blocks lamellar domains. Selective basic hydrolysis of the PLLA blocks generates thin films, patterned with nanometric channels containing hydrophilic PEO chains pending from PS walls. The shape and size of the channels and the degree of hydrophilicity of the pores depend on the relative length of the blocks, the molecular mass of the BCPs, and the composition of the mixture. The strength of our approach is demonstrated in the case of physical adsorption of the hemoprotein peroxidase from horseradish (HRP) using 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) with H2O2 as substrate. The large surface area, the tailored pore sizes, and the functionalization with hydrophilic PEO blocks make the designed nanostructured materials suitable supports for the nanoconfinement of HRP biomolecules endowed with high catalytic performance, no mass-transfer limitations, and long-term stability.

The resolution of the crystal structure and the physical properties of isotactic 1,2-poly(E-3-methyl-1,3-pentadiene) (iPE3MPD) are presented. This new polymer is one of the very few examples of known crystalline isotactic 1,2-polydienes. It does not crystallize by cooling from the melt but crystallizes by aging the amorphous samples at room temperature for several days and successive annealing. The stretching of amorphous or low crystalline compression-molded samples gives oriented fibers of a highly disordered mesomorphic form. Well-oriented fibers of the ordered crystalline form of iPE3MPD have been prepared by stretching amorphous or low crystalline compression-molded samples and successive annealing at 60-70 degrees C under tension. The crystalline structure of iPE3MPD is characterized by macromolecules in 7/2 helical conformation packed in an orthorhombic unit cell with parameters a = 17.4 angstrom, b = 16.5 angstrom, c = 15:3 angstrom according to the space group P2(1)ab. iPE3MPD has shown interesting mechanical properties of high deformability with elastic behavior associated with the crystallization during deformation of the mesophase that melts upon relaxation.

π-Conjugated ionic liquid crystals are a very interesting class of salts where the coupling of ionic and electronic functions with the anisotropy typical of liquid crystals may give rise to materials with advanced bulk properties. Defect-free active thin films obtainable by simple mesophase self-assembly of these materials may be exploited in a number of different electro-optical devices. Here we show that the rich mesomorphism of the thienoviologen salts 4,4′-(2,2′-bithiophene-5,5′-diyl)bis(1-alkylpyridinium), which includes smectic, columnar, and nematic phases, significantly depends on the counterion type and the length of the promesogenic alkyl chains, highlighting the delicate balance among ion/ion, π–π stacking, and hydrophobic interactions. These salts show notable fluorescence properties in the bulk, strongly dependent on the self-assembling.