Maria Emanuela Errico

Eco-Challenges of Bio-Based Polymer Composites

In recent years bio-based polymer composites have been the subject of many scientific and research projects, as well as many commercial programs. Growing global environmental and social concern, the high rate of depletion of petroleum resources and new environmental regulations have forced the search for new composites and green materials, compatible with the environment. The aim of this article is to present a brief review of the most suitable and commonly used biodegradable polymer matrices and NF reinforcements in eco-composites and nanocomposites, with special focus on PLA based materials.

Biodegradable PVOH-based foams for packaging applications

Biodegradable poly(vinyl alcohol) (PVOH) based foams were prepared through an ecofriendly methodology. Different amount of recycled multilayer cartons (MC), composed of cellulose and low-density polyethylene (80/20 wt/wt), were added as a direct cellulose source to PVOH. Foams were realized through a modified overrun process without using chemical agents or promoting chemical reactions. In particular, the air entrapped during the high-speed mixing of the PVOH/MC water dispersion was able to create a porous morphology. The effects of the addition of MC on microstructure, swelling behavior, and mechanical and thermal properties of foams were investigated. Materials were characterized by a dual-pore structure. Improvements of the swelling behavior, mechanical properties, and thermal stability were recorded as a function of MC content. These findings can be considered as a result of a good interaction between filler and polymer.

Polyvinyl alcohol biodegradable foams containing cellulose fibres

The preparation of polyvinyl alcohol (PVOH) based foams containing pulp cellulose fibres and microfibrillated cellulose (MFC) fibre is reported, aiming at the realization of sustainable “green-composites.” Foams were obtained through an eco-friendly preparation method able to generate a pore structure by entrapping air into the polymer/filler aqueous dispersion during a high-speed mixing. The effect of pulp cellulose fibres (Bc1000) and MFC on foam microstructure, water vapor absorption behavior, and mechanical properties was studied. The addition of small amount of MFC (1–5 wt%) induced a progressive decrease of the average cell diameter and an increase of the cell density; whereas Bc1000 cellulose fibres affected the cell shape and regularity of PVOH based foams. A reduction of the water vapor absorption in PVOH/MFC and PVOH/Bc1000 was recorded with respect to neat PVOH foam, in particular for foams containing pulp cellulose fibres. Finally, both MFC and Bc1000 increased the Young modulus and the compression deflection of PVOH based foams.

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.

Artificial Biomelanin: Highly Light-Absorbing Nano-Sized Eumelanin by Biomimetic Synthesis in Chicken Egg White

The spontaneous oxidative polymerization of 0.01-1% w/w 5,6-dihydroxyindole (DHI) in chicken egg white (CEW) in the absence of added solvents leads to a black, water-soluble, and processable artificial biomelanin (ABM) with robust and 1 order of magnitude stronger broadband light absorption compared to natural and synthetic eumelanin suspensions. Small angle neutron scattering (SANS) and transmission electron microscopy (TEM) analysis indicated the presence in the ABM matrix of isolated eumelanin nanoparticles (≤100 nm) differing in shape from pure DHI melanin nanoparticles (SANS evidence). Electron paramagnetic resonance (EPR) spectra showed a slightly asymmetric signal (g ∼ 2.0035) similar to that of solid DHI melanin but with a smaller amplitude (ΔB), suggesting hindered spin delocalization in biomatrix. Enhanced light absorption, altered nanoparticle morphology and decreased free radical delocalization in ABM would reflect CEW-induced inhibition of eumelanin aggregation during polymerization accompanied in part by covalent binding of growing polymer to the proteins (SDS-PAGE evidence). The technological potential of eumelanin nanosizing by biomimetic synthesis within a CEW biomatrix is demonstrated by the preparation of an ABM-based black flexible film with characteristics comparable to those of commercially available polymers typically used in electronics and biomedical applications.

Radical polymerization of methyl methacrylate in the presence of biodegradable poly(L-lactic acid). Preparation of blends, chemical-physical characterization and morphology

Poly(L-lactic) (PLLA)-based containing poly(methyl methacrylate) (PMMA) as dispersed phase are reported in the present paper. The blends are prepared by reactive (NR-type blends) as well as non reactive (NR-type blends) methodologies, according to the preparation of the blends either polymerizing the acrylic monomer in the presence of PLLA or melt mixing the two polymers (PLLA and PMMA) in bulk. Thermal as well as morphological studied performed on both R and NR blends have revealed an intimate dispersion of PLLA and PMMA. Unlikely previous studies carried out on different aliphatic polyesters but following similar chemical approach, mechanical tests on the PLLA-type blends. The results are interpreted on the basis of extensive cross-linking of the system caused by the high sensitivity of PPLA to radical attack. The copolymeric phase formed during the reactive blending is isolated and characterised by NMR technique.

PVA/PTFE nanocomposites: Thermal, mechanical, and barrier properties

In the last 20 years a great scientific and industrial interest has been focused on nanostructured materials [1–2]. In this scientific area a particular interest has been devoted to polymeri-based nanostructured materials [3–8]. They are multiphase systems where one phase (inorganic or organic) is present on the nanometer level. If well dispersed in the polymeric matrix, the nanometer phase offers a major specific surface area enhancement of the interfacial interactions with the matrix compared to conventional reinforcements, and consequently improves the physical properties of the material [9–16]. In recent years many researchers focused on the introduction of a new class of polymeric commodity nanocomposites and to develop the related technologies to help solving clear user problems [17]. A particular interest is devoted on new polymeric high-performance thermoforming nanocomposites for packaging with enhanced mechanical and barrier properties. In this communication, results concerning poly(vinyl alcohol) (PVA) filled with polytetrafluoroethylene (PTFE) nanospheres are reported. PVA polymers are strong, tough materials that can be easily obtained in a variety of molecular weights and they exhibit susceptibility to biodegradation. They are characterized by a low gas and vapor permeability and by a complete transparency. Unfortunately, they also have a poor thermal stability and the gas permeability tends to increase with the increase of moisture. Moreover, tensile strength and Young’s modulus decrease with increasing relative humidity. These drawbacks reduce their exploitation in many packaging applications [18]. Finally, another limit in using poly(vinyl alcohol) is that it is generally not melt-processable, since its decomposition temperature is lower than its melting point. On the other hand, PTFE is an indispensable material for industry because of its unique combination of high thermal, chemical, aging and weather resistance, excellent inertness, low flammability with high purity, and lubricant and dielectric properties. Recently, Solvay Solexis technology [19] has allowed the preparation of PTFE particles from 10 to 100 nm by utilizing the perfluorinated microemulsion polymerisation with a high conversion latex concentration and relating low surfactant content.

Design of pectin-sodium alginate based films for potential healthcare application: Study of chemico-physical interactions between the components of films and assessment of their antimicrobial activity

In this study, pectin based films including different amounts of sodium alginate were prepared by casting method. All the films, with and without polyglycerol as plasticizer, were crosslinked with zinc ions in order to extend their potential functionality. The development of junction points, occurring during the crosslinking process with zinc ions, induced the increasing of free volume with following changing in chemico-physical properties of films. The inclusion of alginate in pectin based formulations improved the strength of zinc ions crosslinking network, whereas the addition of polyglycerol significantly improved mechanical performance. Finally, zinc-crosslinked films evidenced antimicrobial activity against the most common exploited pathogens: Staphylococcus Aureus, Escherichia Coli and Candida Albicans. These results suggest that zinc-crosslinked based films can be exploitable as novel bio-active biomaterials for protection and disinfection of medical devices.

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.