Roberto Avolio

Amorphized cellulose as filler in biocomposites based on poly(ɛ-caprolactone)

Amorphous cellulose particles, obtained through a solvent-free mechano-chemical process, have been tested for the first time as a potential filler for biodegradable composites based on poly(ɛ-caprolactone) (PCL). Commercial cellulose fibers have been also tested for comparison. An effective interfacial strategy based on a compatibilizing agent, a modified PCL, has been used to improve the polymer/filler interfacial adhesion. Composites have been tested through physico-mechanical characterizations and soil burial degradation tests, in order to evaluate the influence of cellulose structure and morphology and polymer/filler interfacial adhesion on the final properties of the realized materials. The use of the amorphous cellulose particles combined with the presence of a suitable interfacial agent has allowed to modulate relevant technological properties of the realized composites, such as tensile and thermal properties, water absorption, water vapor transmission rate and biodegradation kinetic.

Rational design of nanoparticle/monomer interfaces: a combined computational and experimental study of in situ polymerization of silica based nanocomposites

Interfaces between methylmethacrylate monomers, oligomers and silica nanoparticles (NPs) were explored by molecular dynamics simulations, infrared and solid state nuclear magnetic resonance spectroscopy. This knowledge allowed the control of the structure of the interfaces by employment of MMA macromonomers, and the design of an improved process for in situ polymerizations with a remarkable increase of NP dispersion.

Multifunctional Thin Films and Coatings from Caffeic Acid and a Cross-Linking Diamine

The exploitation of easily accessible and nontoxic natural catechol compounds for surface functionalization and coating is attracting growing interest for biomedical applications. We report herein the deposition on different substrates of chemically stable thin films by autoxidation of 1 mM caffeic acid (CA) solutions at pH 9 in the presence of equimolar amounts of hexamethylenediamine (HMDA). UV-visible, mass spectrometric, and solid state 13C and 15N NMR analysis indicated covalent incorporation of the amine during CA polymerization to produce insoluble trioxybenzacridinium scaffolds decorated with carboxyl and amine functionalities. Similar coatings are obtained by replacing CA with 4-methylcatechol (MC) in the presence of HMDA. No significant film deposition was detected in the absence of HMDA nor by replacing it with shorter chain ethylenediamine, or with monoamines. The CA/HMDA-based films resisted oxidative and reductive treatments, displayed efficient Fe(II) and Cu(II) binding capacity and organic dyes adsorption, and provided an excellent cytocompatible platform for growing embryonic stem cells. These results pointed to HMDA as an efficient cross-linking mediator of film deposition from natural catechols for surface functionalization and coatings.

Effect of cellulose structure and morphology on the properties of poly(butylene succinate-co-butylene adipate) biocomposites.

Composites based on poly(butylene succinate-co-butylene adipate) (PBSA) containing amorphized and crystalline cellulose reinforcements have been prepared and characterized. In order to improve the polymer/filler interfacial adhesion, an efficient compatibilizing agent has been synthesized by chemical modification of PBSA and characterized by FT-IR, FT-NIR and (1)H NMR spectroscopy. Uncompatibilized and compatibilized composites have been tested through morphological, mechanical, calorimetric and thermogravimetric analysis. Moreover, water vapor permeability and biodegradation kinetics of composites have been investigated. The addition to PBSA of cellulose fillers differing from each other by crystallinity degree and morphology, and the use of a compatibilizing agent have allowed modulating tensile and thermal properties, water vapor transmission rate and biodegradation kinetic of the composites.

Synthesis and adsorption study of hyper-crosslinked styrene-based nanocomposites containing multi-walled carbon nanotubes

New nanocomposite microporous materials obtained by adding functionalized multi-walled carbon nanotubes (MWCNT) to styrene/vinylbenzyl chloride/divinylbenzene hyper-crosslinked resins were prepared and characterized. In order to promote the embedding of the MWCNT within the gel-type precursor, a suitable surface modification strategy was set up, based on the grafting of a poly(vinylbenzyl chloride) (PVBC) resin, able to participate in the hyper-crosslinking step, onto the nanotube surface. Characterization of the nanocomposites by FTIR spectroscopy and electron microscopy enabled the assessment of the effect of the nanotubes on the structure and the morphology of the resin. Moreover, gas sorption measurements indicated that by addition of nanotubes it is possible to modulate the pore size distribution, the uptake of CO2 and H2 and the CO2/N2 selectivity. Finally, modified MWCNT are also able to improve the adsorption capacity of phenol from water solutions, suggesting the possible application of the new microporous nanocomposites for water remediation.

Unilateral NMR investigation of multifunctional treatments on stones based on colloidal inorganic and organic nanoparticles.

Consolidation and protection are among the most important treatments usually carried out in conservation of stone artifacts and monuments. In this paper, portable unilateral NMR and conventional techniques were used for investigating new multifunctional treatments based on tetraethoxysilane, silica, and polytetrafluoroethylene nanoparticles. The study was carried out on a very complex and heterogeneous porous stone such as tuff. NMR study allowed to obtain detailed information on the penetration depth of treatments, the hydrophobic effect, and changes in the open porosity caused by treatments. Physical and chemical inhomogeneities between the impregnated layers of tuff and the layers underneath were also detected. The average pores radius and pores interconnection obtained from NMR diffusion measurements were used for the first time to compare effects of different consolidating and/or protective treatments on stone. Because unilateral NMR technique is neither destructive nor invasive, investigation of treatments can be also carried out and optimized directly on buildings and monuments of interest for Cultural Heritage. Copyright

Pure titanium particle loaded nanocomposites: study on the polymer/filler interface and hMSC biocompatibility

The integration of inorganic nanoparticles into polymer matrices allows for the modification of physical properties as well as the implementation of new features for unexplored application fields. Here, we propose the study of a new metal/polymer nanocomposite fabricated by dispersing pure Ti nanoparticles into a poly(methylmetacrilate) matrix via solvent casting process, to investigate its potential use as new biomaterial for biomedical applications. We demonstrated that Ti nanoparticles embedded in the poly(methylmetacrilate) matrix can act as reinforcing agent, not negatively influencing the biological response of human mesenchymal stem cell in terms of cytotoxicity and cell viability. As a function of relative amount and surface treatment, Ti nanoparticles may enhance mechanical strength of the composite—ranging from 31.1 ± 2.5 to 43.7 ± 0.7 MPa—also contributing to biological response in terms of adhesion and proliferation mechanisms. In particular, for 1 wt% Ti, treated Ti nanoparticles improve cell materials recognition, as confirmed by higher cell spreading-quantified in terms of cell area via image analysis—locally promoting stronger interactions at cell matrix interface. At this stage, these preliminary results suggest a promising use of pure Ti nanoparticles as filler in polymer composites for biomedical applications.

Effect of Microfibrillated Cellulose on Microstructure and Properties of Poly(vinyl alcohol) Foams

Poly(vinyl alcohol) foams, containing different amounts of microfibrillated cellulose, were prepared through an eco-friendly procedure based on high-speed mixing and freeze-drying. The effect of filler amount on cell shape and regularity was studied by scanning electron microscopy (SEM) and the evolution of the microstructure was assessed through dynamic cryo-SEM. Fourier Transformed Infrared Analysis and Differential Scanning Calorimetry measurements revealed the presence of hydrogen bond interaction among cellulosic filler and the matrix. The modulus and compression deflection of neat PVA were significantly improved by increasing the amount of microfibrillated cellulose content with respect to foams realised with pulp cellulose fibers.

Degradation of Biodegradable Plastic Buried in Sand

This study aims to investigate the degradation of biodegradable polymers such as poly(lactic acid) (PLA) and polycaprolactone (PCL), polyhydroxybutyrate (PHB) and polybutylene succinate adipate (PBSA) buried in sand, to verify the behaviour of these polymers in habitat where plastic waste can be stranded when carried by the sea.

Eco-Sustainable Finishing Treatment of Polyamide Fabrics to Reduce the Release of Microplastics During Washing Processes

The washing processes of synthetic clothes have been lately identified as a main source of microplastic pollution in marine environment. During a common washing process, synthetic fabrics undergo mechanical and chemical stresses that induce the detachment of microfibers from the main yarns. Such microfragments remain in the wastewater, eventually reaching marine ecosystems where they represent a serious threat for the flora and fauna. A possible solution that could mitigate such source of microplastic pollution is the application of functional finishing treatments able to protect fabrics during washings, reducing the amount of microfibres released. The present work proposes an innovative finishing treatment of polyamide fabrics by using pectin, a natural polysaccharide extracted from fruits. Pectin was chemically modified by reaction with glycidyl methacrylate (GMA), whose vinylic groups were exploited to graft pectin on the surface of the polyamide fabric, creating a coating on the fibres. The effectiveness of the surface treatment was assessed by using the following characterization techniques: scanning electron microscopy (SEM), solid-state nuclear magnetic resonance spectroscopy (NMR) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Furthermore, washing tests of untreated and treated fabrics were carried out to assess the release of microplastics. The washing effluents were filtered and the filters were analysed by SEM to evaluate the amount of microfibres released. The obtained results showed that the application of the pectin-based coating, could reach a reduction of more than 80% of the number of microplastics released by untreated polyamide fabrics during a domestic washing process.