This study elucidates the complex morphology and the related spectroscopic response of poly(vinylidene fluoride- co -trifluoroethylene) copolymer, with 80% molar VDF content, namely P(VDF-TrFE) (80/20).

A theoretical approach based on Periodic Boundary Conditions (PBC) and a Linear Combination of Atomic Orbitals (LCAO) in the framework of the density functional theory (DFT) is used to investigate the molecular mechanism that rules the piezoelectric behavior of poly(vinylidene fluoride) (PVDF) polymer in the crystalline β-phase. We present several computational tests highlighting the peculiar electrostatic potential energy landscape the polymer chains feel when they change their orientation by a rigid rotation in the lattice cell. We demonstrate that a rotation of the permanent dipole through chain rotation has a rather low energy cost and leads to a lattice relaxation. This justifies the macroscopic strain observed when the material is subjected to an electric field. Moreover, we investigate the effect on the molecular geometry of the expansion of the lattice parameters in the (a, b) plane, proving that the rotation of the dipole can take place spontaneously under mechanical deformation. By band deconvolution of the IR and Raman spectra of a PVDF film with a high content of β-phase, we provide the experimental phonon wavenumbers and relative band intensities, which we compare against the predictions from DFT calculations. This analysis shows the reliability of the LCAO approach, as implemented in the CRYSTAL software, for calculating the vibrational spectra. Finally, we investigate how the IR/Raman spectra evolve as a function of inter-chain distance, moving towards the isolated chain limit and to the limit of a single crystal slab. The results show the relevance of the inter-molecular interactions on the vibrational dynamics and on the electro-optical features ruling the intensity pattern of the vibrational spectra.

Innovative nanostructured materials offer the possibility of enhancing the tribological performance of traditional materials like graphite and molybdenum disulfide (MoS₂). In this study, the scratch resistance of two different copper powders, dendritic and spherical, and their composites with traditional MoS₂, nanometric MoS₂, and graphene nanoplatelets was investigated. Metal powder metallurgy was employed to produce composite materials with 5 wt% and 10 wt% of each solid lubricant. A ball milling step was employed to grind and mix the matrix copper powder with the lubricants. The use of a cold press combined with the sintering in inert atmosphere at 550 °C limited the oxidation of the copper and the degradation of the solid lubricants. The so-produced materials were characterized through a variety of techniques such as micro-indentation hardness, electrical resistivity, contact angle wettability, X-ray diffraction, Raman scattering, and scanning electron microscopy. Moreover, micro-scratch tests were performed on both pure copper and composite materials for comparing the apparent scratch hardness and friction coefficients. The scratches were examined with confocal laser scanning microscopy (CLSM), to identify the evolution of the damage mechanisms during the formation of the groove. The results highlighted the important difference between the dendritic and spherical copper powders and demonstrated a way to improve wear behavior thanks to the use of nanometric powders as solid lubricants.

Aligned polymer nanofibres are prepared by means of the electrospinning of a chlorobenzene solution containing regioregular poly(3-hexyltiophene-2,5-diyl), P3HT, and poly(ethylene oxide), PEO. The PEO scaffold is easily dissolved with acetonitrile, leaving pure P3HT fibres, which do not show structural modification. Polymer fibres, either with or without the PEO supporting polymer, are effectively doped by exposure to iodine vapours. Doping is monitored following the changes in the doping-induced vibrational bands (IRAVs) observed in the infrared spectra and by means of Raman spectroscopy. Molecular orientation inside the fibres has been assessed by means of IR experiments in polarised light, clearly demonstrating that electrospinning induces the orientation of the polymer chains along the fibre axis as well as of the defects introduced by doping. This work illustrates a case study that contributes to the fundamental knowledge of the vibrational properties of the doping-induced defects—charged polarons—of P3HT. Moreover, it provides experimental protocols for a thorough spectroscopic characterisation of the P3HT nanofibres, and of doped conjugated polymers in general, opening the way for the control of the material structure when the doped polymer is confined in a one-dimensional architecture.

We present a conjugated copolymer designed as a near‐infrared (NIR) emitter for organic light‐emitting diodes (NIR‐OLEDs). The low bandgap donor‐acceptor copolymer, comprising a terthiophene derivative (3T) and benzothiadiazole (BT), is end‐capped with bulky triphenyalmine (TPA) groups (3TBT‐TPA). Compared with the parent homologue capped with simple phenyl rings, 3TBT‐TPA shows enhanced solubility in organic solvents with improved photoluminescence quantum yield thanks to a reduced close packing of chains. 3TBT‐TPA, used both as neat emitting layer and blended with fluorene‐benzothiadiazole (F8BT) host copolymer in a NIR‐OLEDs, shows external quantum efficiency up to 0.58%. Additionally, chiral induction is achieved in the F8BT:3TBT‐TPA blend film using a commercial chiral dopant, yielding circularly polarized (CP), photoluminescence (PL) and electroluminescence (EL) in the range 500–800 nm with a maximum dissymmetry factor in the range of 10⁻². This is the first example of CP‐NIR EL from a conjugated polymer. This work highlights the potential of TPA‐capped strategy for low bandgap copolymers for efficient NIR‐OLEDs and opens new perspectives in the use of conjugated polymers in NIR photonic applications.