Polymeric Materials Chemistry Lab

The PMC-Lab group currently consists of 3 permanent researchers, two associated researchers, two post-docs, and one PhD student. The research activity is mainly focused to the preparation and the characterization of functional polymer materials by post-polymerization reactions and of multi-functional polymer nanocomposites by finely dispersing nanostructured inorganic substrate.

The main goal of the modification of polymer materials is to graft functional groups on the polymer chain that provide specific chemical reactivity or physico-chemical feature/response. The approaches investigated grant to finely control both the final composition and macromolecular architecture by minimizing the side reactions. The possibility to modulate the final composition and macromolecular structure independently of the polymer nature (oil and bio-based polymers) allows designing functional materials with specific final properties transferred to the polymer matrix via the covalent insertion of functional low molecular weigh compounds.

The preparation of nanocomposites is another effective tool to modify and tune polymer properties. Also in this case, the control of the final morphology through the fine-tuning of the blending conditions and the use of suitable compatibilizers allow the preparation of composites having functional properties deriving from the use of ad-hoc modified inorganic fillers. Strictly connected with the preparation of composites and with the study of their properties is the understanding of the interfacial interactions between the different components constituting the final composites. Finally, related to all of the subjects previously discussed, the group has also developed skills in the study of the compatibilization of polymer blends through the formation of specific interfacial interactions between the different polymers. All the tools/methodologies used to provide materials perform the requirements of many industrial applications. Several application fields of industrial polymer-based materials are being investigated, with particular focus on those most closely related to packaging, automotive and building applications. The group has in fact a consolidated experience, in the preparation of functionalized polyolefins suitable as compatibilizers, adhesives, primers by free radical post-reactor reactions as well as in the preparation and characterization of polymer nanocomposites (suitable for flexible films or rigid materials for packaging application with smart response). Recently our intersts are also dedicated to the modification of bio-based polymer matrix like for example PLA and other aliphatic biodegradable polyesters with the aim to study the possibility to extend our consolidated knowledges acquired onto polyolefins to bio-based materials.

Research topics

  • Radical functionalization of polymers by specific targeted polymer modification methodologies
    Spoiler: Highlight to view
    The preparation of functionalized polymers, such as polyolefins or aliphatic biodegradable polyesters, in extruders or mixers by free radical post-reactor reactions is still a challenge. The method suffers of a series of limitations due to the formation of extremely reactive free radical species, thereby making difficult to control the process as far as the main grafting reaction is concerned, which competes with side reactions. In particular, a significant effort is dedicated to devising new reactive molecules and modification routes to obtain functionalized polymers with appreciable degrees of functionalization and preserved macromolecular structure. Accordingly, the development of selective processes through a fine-tuning selection of radical reactions and reagents, as a tool to introduce specific functionalities and control the macromolecular structure/architecture, is investigated. In particular, the use of heteroaromatic-based push-pull molecules as co-agents of the process appears an efficient method. Similarly nitroxyl free radicals, TEMPO derivatives, can be successfully used to introduce functional groups on polyolefin and bio-polyester macromolecules by preserving the structure and molecular weight of pristine polymers. In addition, similar chemical transformations are investigated for the surface modification of polyolefin films and fibers by UV irradiation.
  • Responsive polymers
    Spoiler: Highlight to view
    Significant advances have recently been made in the development of functional polymers that are able to undergo light-induced shape changes or that generally have some specific functionality. With the purpose to obtain light-responsive polymer based materials suitable for smart packaging applications and by using the nitroxide functionalization procedure previously discussed, ad-hoc synthesized nitroxide bearing chromophores have been covalently grafted on the polymer backbone of both polyolefins and aliphatic biodegradable polyesters by coupling reaction with macroradical species. The availability of a radical functionalization methodology that allows the control of the macromolecular architecture and the composition of the final materials suggests the possibility to prepare functional polymers having different functionalities. For example the preparation of TEMPO derivatives bearing antioxidant groups or dyes can allow the preparation of functional polymers having the antioxidant or the dye molecules covalently linked to the polymer backbone thus avoiding the migration of these additives.
  • Multifunctional nanocomposites from oil and bio-based polymers
    Spoiler: Highlight to view
    Multifunctional nanocomposites can be prepared by using different inorganic fillers, among others, phyllosilicates, also known as cationic clays, are the most popular layered inorganic system investigated to prepare polyolefin or aliphatic bio-degradable polyesters nanocomposites. Recently a different class of layered materials known as layered double hydroxides (LDHs) has attracted great interest for the preparation of polymer-based nanocomposites. LDHs are anionic clays whose structure consists of two octahedral brucite-like layers in which parts of the divalent cations are replaced by trivalent cations, thus generating a positive charge balanced by interlayer anions. It has been demonstrated that the surface polarity of both macromolecules and inorganic filler has to be matched to allow the polymer matrix to fully wet and intercalate inorganic filler tactoids through specific polymer chain-filler surface interactions. To increase the interactions between the polymer matrix and the filler, organo-modification of both cationic and anionic fillers can be performed by an ionic exchange with organic ions like for example ammonium salts in the case of phyllosilicates and carboxylates in the case of LDH. The versatility of the organomodifier that can be inserted between the layers, especially of LDH, allows the planning of functional fillers that after dispersion in a polymer matrix can transfer these properties to the final composites. In this contest, all aspects related to the optimization of the dispersion of the filler, for example by using specifically designed compatibilizers, and the accurate morphological, spectroscopic, and thermal characterization of the samples allowed gaining a deeper insight into the structure/architecture of nanocomposites as well as into the chemical nature of interactions at the interface.
  • Polymer blends
    Spoiler: Highlight to view
    The need of recycling (re-using) complex polymer-based materials trough easy and green methodologies has increased the interest for reactive and reactor blending procedures. In particular, used tyres and their derivatives like ground tyre rubber (GTR) are characterized by high chemical stability resulting from the crosslinked polymer structure and the presence of stabilizers and other additives. Two major approaches to solve this problem are the recycle / reuse of scrap tyres, and the reclaiming of the raw materials constituting them. Material manufacturers often include small pieces of scrap tyres in hybrid rubber or thermoplastic / rubber composites; these pieces are granulates (with average particle size lying in the range of 0.5-15 mm) or powders having a particle size inferior to 0.5 mm. The final products obtained from these materials include outdoor sport surfaces, interior floor covering, playground facilities, footwear, inks and paintings, noise absorbing sheets, floor tiles and paving blocks. Since the economic relevance of these applications is still limited, life cycle thinking is not predominant among tyre producers. This amplifies the importance of research in recycling processes. The reactor blending approach that means to grow a polymer substrate from the surface or inside the scrap particle leads to a much more uniform filler distribution, if compared to conventional mechanical melt blending process, and a significant enhanced interfacial adhesion, even at high filler content. This result is due to an effect of de-segregation of the filler particles and to their coating by the polymer that generate, a remarkable improvement of final mechanical properties.
  • Structure/Properties relationships
    Spoiler: Highlight to view
    All the common techniques of polymer characterization are used to highlight and study the relationships between the structural characteristics of polymer materials (by spectroscopy like as FT-IR, NMR or SEC measurements) and their thermal and mechanical properties (by DSC, TGA, DMTA). The expertise of the group in this field is testified by the appreciable number of publications carried out in collaboration with other research groups aimed at the characterization of new polymeric materials, often in relation to new catalytic systems of potential industrial interest.

Expertise

  • Modification of oil and bio-based polymers by radical functionalization carried out in the melt and in solution
  • Preparation of “functional” materials by modification of polymers with ad hoc designed and synthesized low molecular weight compounds
  • Characterization of polymers by FT-IR, TGA, DSC, SEC, UV-VIS and fluorescence emission spectroscopy
  • Surface modification of polymers by photo-grafting
  • Organo modification of lamellar LDHs and clays with “functional” molecules and study of their dispersion and activity in polymer matrices
  • Study of compatibilization of polymer blends also from recycled plastics
  • Study of the structure/properties relationship
  • Instruments

  • DSC 4000 Perkin Elmer
  • DMA 7e Perkin Elmer
  • TG/DTA 7200 Exstar
  • FT-IR ATR Spectrum two Perkin Elmer
  • GPC Agilent Technologies 1260 Infinity with Refractive Index detector
  • UVA-CUBE chamber Honle, with H-lamp 400F/2 and F-lamp 400F/2
  • Carver hot-press