Dithienopyrrole-based materials: development of new polymeric derivatives

The possibility to control molar mass and termination of the growing chain is fundamental to create well-defined, reproducible materials. For this reason, in order to apply polydithienopyrrole (PDTP) as organic conjugated polymer, the possibility of controlled polymerization needs to be verified. Another aspect that is still not completely explored is bound to the optical activity of the PDTP, which bearing appropriate substituents may adopt a helical conformation. The configuration of the helix, built up from achiral co-monomers, can be established in an enantiopure way by using only a small percentage of the chiral monomer co-polymerized with achiral co-monomer. The effect, called “sergeants and soldiers effect”, is expressed by the nonlinear increase of the chiral response vs the ratio of the chiral co-monomer used for the polymerization. To date, this effect is still not completely explored for PDTP. In this framework the project will investigate, firstly, the possibility to obtain a controlled polymerization of PDTP. Then, monomers with different side chains and organometallic functions will be screened for a CTCP-type polymerization. Also a Lewis-acid based cationic polymerization will be performed. Moreover the chemical derivatization of dithienopyrrole DTP is explored: the research is going to concern also block copolymers, built up by DTP and monomers of different nature. The research will be extended also to the investigation of optically active derivates of PDTP, using a chiral monomer for the synthesis. The possibility to develop a supramolecular distribution of the polymeric chains, together with the “sergeants and soldiers effect” will be checked investigating a series of polymers with increasing amounts of chiral monomer.

Analytical pyrolysis to study microplastics and other polymers in the environment

Synthetic polymers constitute a wide class of materials which has enhanced the quality of human life, providing comforts and innovations. Anyway, the increasing production and the incorrect waste management, are leading to the occurrence of polymers in the environment, generating concern. To understand the extent of this issue, analytical investigation holds an essential position. Standardised methods have not established yet, and additional studies are required to improve the present knowledge. The main aim of this thesis was to provide comprehensive information about the potential of pyrolysis coupled with gas-chromatography and mass spectrometry (Py-GC-MS) for polymers investigation, from their characterisation to their identification and quantification in complex matrices. Water-soluble (poly(dimethylsiloxanes), PDMS bearing poly(ethylene glycol), PEG, side chains) and water-insoluble polymers (microplastics, MPs, and bioplastics) were studied. The different studies revealed the possibility to identify heterogeneous classes of polymers, fingerprinting the presence of PDMS copolymers and distinguishing chemically different polyurethanes (PURs). The occurrence of secondary reactions in pyrolysis of polymer mixtures was observed as possible drawback. Pyrolysis products indicative of secondary reactions and their reaction mechanisms were identified. Py-GC-MS also revealed its fundamental role for the identification of polymers composing commercial bioplastics items based. The results aided to identify chemicals that have the potential to migrate in sea waters. Investigations of environmental samples demonstrated the capability of Py-GC-MS to provide reliable, reproducible and comparable results about polymers in complex matrices (PEG-PDMS in sewage sludges and PURs and other MPs in road dusts and spider webs). Criticisms were especially found in quantitation, such as the retrieval reference materials, the construction of reliable calibration protocols and the occurrence of bias due to interferences between pyrolysis products. This thesis pursues the greater purpose to develop harmonised and standardised methods for environmental investigations of polymers, that is fundamental to assess the real state of the environment.

Vibro-acoustic analysis of additively manufactured acoustic metamaterials

In the last decade it emerged the interest in new types of acoustic insulating materials, called acoustic metamaterials. These materials are composed by a host and inclusions and are arranged periodically or non-periodically in sub-wavelength elements called meta-atoms. Their inclusions and internal geometries can be manipulated to tailor the acoustic properties, reducing weight, and increasing at the same time their efficiency. Thanks to the high absorbing characteristics that they can achieve, their usage is of particularly interest as material of the core in sandwich panels of aerospace structures to reduce vibrations and noise inside passengers aircraft’s cabin. In addition, since the low frequency signals are difficult to be damped with conventional materials, their usage can guarantee a high transmission loss at low frequencies, obtaining a positive benefit on passengers’ comfort. The performances and efficiency of these materials are enhanced thanks to the new additive manufacturing techniques opposed to the conventional ones uncapable to pro- duce such complex internal geometries. The aim of this work is to study, produce and redesign micro-perforated sandwich panels of a literature case study to achieve high performances in the low frequency range, e.g., below 2000 Hz. Some geometrical parameters, such as perforation ratio and diameter of holes, were considered to realize different models and see the differences in the sound transmission loss. The models were produced by means of Fused Deposition Modelling using an Acrylonitrile Butadiene Styrene (ABS Plus p430) material on a commercial additive manufacturing system. Finally, the frequency response analysis was carried out with Mul2 software, based on the Carrera’s Unified Formulation (CUF) to understand the acoustic and structural properties of the material employed, analyzing the plates’ displacements and the TL results.

Design, preparazione e studio applicativo di nuovi metallopolimeri luminescenti a base di complessi ciclometallati di Ir(III)

The research project of my experimental thesis deals with the design, synthesis and characterization of a new series of luminescent metallapolymers to be exploited for their peculiar photophysical and opto-electronic properties. To this end, our design strategy consisted in the incorporation of brightly luminescent and colour tuneable Ir(III) cyclometalated complexes with general formula [Ir(C^N)2(N^N)]+, where C^N represents various phenyl piridine based cyclometalating ligands and N^N is an aromatic chelating N-heterocyle, into methyl methacrylate (MMA) based copolymers. Whereas the choice of the cyclometalating ligands was driven by the possibility to obtain different emission colours, the design of the N^N ligands was aimed to obtain a molecule capable of providing the chelate coordination to the metal centre and, at the same time, of being susceptible to polymerisation reactions. To fulfil these requirements, a new molecule (abbreviated as L) consisting in an alkylated 2-pyrydyl tetrazole structure equipped with a styryl unit was designed and successfully prepared. The preparation of the target cationic metallapolymers was accomplished by the complexation of the preformed MMA-L copolymers with different amounts of an appropriate Ir(III) dimeric precursor [(Ir(C^N)2Cl)2]. The investigation of the photophysical features of the new hybrid compounds in the solid state at r.t. suggested how these metallapolymers displayed brightly intense phosphorescent emissions, whose colour was found to span from blue to yellow according to the nature of the cyclometalating ligands. In all cases, the emissive performances were superior to those displayed by the corresponding mononuclear “model” complexes. These promising results pave the way for the application of this new class of metallapolymers as Luminescent Solar Concentrators for the photovoltaic technology and/or to solid state lighting.

Formulazione e caratterizzazione di idropitture con materie prime “Bio-Based”

The market for paint products with raw materials derived from renewable sources is growing rapidly in the building industry. When high performance in wet scrub resistance is required, “washable” paints are used. However, formulating products with Bio-Based raw materials generally results in a decrease in performances compared to similar products with raw materials from fossil sources. Therefore, a new formulation approach is needed to characterize polymeric binders from renewable sources and to consider the synergistic effects given by blends of polymeric binders of different origin and chemical structure. To date, the development of new formulations that imply less environmental impact is necessary if these products have to remain competitive in the marketplace. During the trainingship in IVAS S.p.A., washable paints with different PVC (Pigment Volume Concentration) were formulated and tested, evaluating whether the performance of paints with polymeric binders obtained from renewable sources was comparable to those with polymeric binders from fossil sources. The binders were chemically characterized by DSC, FT-IR and NMR analysis. Characterization tests of paints were focused on the evaluation of degree of whiteness, hiding power, dirt setting, and wet scrub resistance. Following the results obtained from the available binder combinations, it was possible to formulate two washable paints with comparable performances to those from fossil sources: paint A with 20 % of alkydic polymer and 80 % styrene/acrylic polymer and paint B with 40 % of alkydic polymer and 60 % styrene/acrylic polymer. Finally, the formulation was completed by adding the mainly Bio-Based derived additives generally used for this category of paints.