Lucia Ricci

Stochastic hybrid 3D matrix: learning and adaptation of electrical properties

Memristive devices are electronic elements with memory properties. This feature marks them out as possible candidates for mimicking synapse properties. Development of systems capable of performing simple brain operations demands a high level of integration of elements and their 3D organization into networks. Here, we demonstrate the formation and electrical properties of stochastic polymeric matrices. Several features of the network revealed similarities with those of the nervous system. In particular, applying different training protocols, we obtained two kinds of learning comparable to the “baby” and “adult” learning in animals and humans. To mimic “adult” learning, multi-task training was applied simultaneously resulting in the formation of few parallel pathways for a given task, modifiable by successive training. To mimic “baby” learning (imprinting), single task training was applied at one time, resulting in the formation of multiple parallel signal pathways, scarcely influenced by successive training.

Improving compatibility in LDPE–silica dispersions by photo-grafting reaction. Preparation and solid state NMR investigation

A TSPM-modified silica has been prepared and employed as a filler in LDPE films, in which a photo-grafting reaction between polymerizable groups present on the functionalized filler and the polymer has been performed with the aim of obtaining stable composites with improved properties. Besides FT-IR, TGA and SEM characterization, both the TSPM-modified silica and the polymer-filler blends have been extensively investigated by means of solid state NMR, through a combined analysis of several high- and low-resolution experiments, performed on 29Si, 1H and 13C nuclei. This allowed us on one hand to obtain detailed and quantitative information on the silica functionalisation reaction and on the other hand, to get an insight into the change of the dynamic properties of LDPE due to the presence of the filler. The NMR results and several macroscopic properties of the blend LDPE–silica–TSPM, such as Youngs modulus and oxygen permeability, were compared with those of the corresponding blend prepared with unfunctionalized silica.

Synthesis, Characterization, and Solid-State NMR Investigation of Organically Modified Bentonites and Their Composites with LDPE

Polymer/clay nanocomposites show remarkably improved properties (mechanical properties, as well as decreased gas permeability and flammability, etc.) with respect to their microscale counterparts and pristine polymers. Due to the substantially apolar character of most of the organic polymers, natural occurring hydrophilic clays are modified into organophilic clays with consequent increase of the polymer/clay compatibility. Different strategies have been developed for the preparation of nanocomposites with improved properties, especially aimed at achieving the best dispersion of clay platelets in the polymer matrix. In this paper we present the preparation and characterization of polymer/clay nanocomposites composed of low-density polyethylene (LDPE) and natural clay, montmorillonite-containing bentonite. Two different forms of the clay have been considered: the first, a commercial organophilic bentonite (Nanofil 15), obtained by exchanging the natural cations with dimethyldioctadecylammonium (2C18) cations, and the second, obtained by performing a grafting reaction of an alkoxysilane containing a polymerizable group, 3-(trimethoxysilyl)propyl methacrylate (TSPM), onto Nanofil 15. Both the clays and LDPE/clay nanocomposites were characterized by thermal, FT-IR, and X-ray diffraction techniques. The samples were also investigated by means of (29)Si, (13)C, and (1)H solid-state NMR, obtaining information on the structural properties of the modified clays. Moreover, by exploiting the effect of bentonite paramagnetic (Fe(3+)) ions on proton spin-lattice relaxation times (T1s), useful information about the extent of the polymer-clay dispersion and their interfacial interactions could be obtained.

pH-responsive host–guest polymerization and blending

In this work, we demonstrate – in two different settings – the potential of the recognition motif made by tetraphosphonate cavitand/N-methyl ammonium salt for the development of supramolecular polymer chemistry. In the first part a novel pH sensitive supramolecular homopolymer was assembled by proper design of the corresponding monomer, and monitoring the self-assembling process by several analytical tools, including NMR spectroscopy and light scattering techniques. These measurements provided the evidence for the formation of the homopolymer and its pH responsiveness. In the second study, the two recognition groups – tetraphosphonate cavitand (Host) and sarcosine hydrochloride (Sarc) – introduced in polystyrene (PS–Host) and poly(butyl methacrylate) (PBMA–Sarc) respectively, led to the mixing of the two otherwise immiscible polymers thanks to the energetically favourable host–guest interactions between the polymer chains. The polymer blending was verified by the presence of a single glass transition temperature (Tg) and showed its homogeneous morphology by atomic force microscopy (AFM).