Novel perfluoropolyalkylethers monomers: synthesis and photo-induced cationic polymerization

Several difunctional oligomers were synthesized by functionalizing perfluoropolyalkylether (PFPAE) chains with different vinyl ethers and epoxides end-groups. Due to their innate synthetic challenges and demanding purification protocols, the PFPAE derivatives were obtained in low yield and with an average functionality lower than 2. However, the functionalized PFPAE oligomers were successful in being used in photo-induced cationic polymerization processes, obtaining transparent and soft films. The influences of the fluorinated chains, and various end-groups on the photopolymerization process were investigated, as well their chemical stability, thermal degradation, and surface properties

Synthesis of α,β-unsaturated esters of perfluoropolyalkylethers (PFPAEs) based on hexafluoropropylene oxide units for photopolymerization

α,β-unsaturated esters are usually synthesized for polymer applications. However, the addition of maleate (cis-configuration) to a fluorinated moiety is challenging due to its potential isomerization during esterification. Various synthetic routes were attempted and led to very low conversion or side-products. The immiscibility of both reagents combined with an easy isomerization or attack on the double bond were potential explanations. In this paper, the synthesis of maleates oligo(hexafluoropropylene oxide) is reported by Steglich esterification and the reaction conditions are discussed depending on the molecular weight of the fluorinated moieties. After UV-curing, hydrophobic polymers were obtained by copolymerization with vinyl ethers by electron acceptor–donor systems

Photoinduced Ring Opening Copolymerization of Perfluoropolyalkylethers

Perfluoropolyalkylethers (PFPAEs), based on structural units such as –(CF2O)–, –(CF2CF2O)–, –(CF2CF2CF2O)– and –(CF(CF3)CF2O)–, represent a special class of fluoropolymers with remarkable properties (low glass transition temperature, high chemical and thermal inertness, low surface energy and refractive index, excellent ageing, weather and flame resistances)[1]. They can be a non-toxic alternative to the long perfluoroalkyl chains presently banned in many countries[2], and be used in many high technology areas such as aerospace, aeronautic (seals, gaskets), automotive industry, microelectronics, optics or even for antifouling and release coatings or textile treatment. The purpose of our work is to synthesize new PFPAEs by anionic ring-opening polymerization of hexafluoropropoxide (HFPO) and functionalize them with different reactive groups. Here we describe the synthesis of PFPAE monofunctional alcohols (HFPOn-MA) with different molecular weight and their use in photoinduced ring-opening polymerization of non-fluorinated diepoxides. The bulk properties of the UV-cured copolymers were practically unaffected by the presence of the fluorinated comonomers when added in low amount (less than 5%wt), but their addition reflected on the surface properties, that were strongly modified

SiO2/Ladder-Like Polysilsesquioxanes Nanocomposite Coatings: Playing with the Hybrid Interface for Tuning Thermal Properties and Wettability

The present study explores the exploitation of ladder-like polysilsesquioxanes (PSQs) bearing reactive functional groups in conjunction with SiO2 nanoparticles (NPs) to produce UV-curable nanocomposite coatings with increased hydrophobicity and good thermal resistance. In detail, a medium degree regular ladder-like structured poly (methacryloxypropyl) silsesquioxane (LPMASQ) and silica NPs, either naked or functionalized with a methacrylsilane (SiO2@TMMS), were blended and then irradiated in the form of a film. Material characterization evidenced significant modifications of the structural organization of the LPMASQ backbone and, in particular, a rearrangement of the silsesquioxane chains at the interface upon introduction of the functionalized silica NPs. This leads to remarkable thermal resistance and enhanced hydrophobic features in the final nanocomposite. The results suggest that the adopted strategy, in comparison with mostly difficult and expensive surface modification and structuring protocols, may provide tailored functional properties without modifying the surface roughness or the functionalities of silsesquioxanes, but simply tuning their interactions at the hybrid interface with silica fillers

Novel perfluoropolyalkylethers (PFPAEs): from synthesis to applications

L'abstract è presente nell'allegato / the abstract is in the attachmen

Evaluation of nanocomposites containing graphene nanoplatelets: Mechanical properties and combustion behavior

Polypropylene (PP) nanocomposites containing graphene nanoplatelets (GNPs) with different loadings were fabri- cated via masterbatch compounding–melt blending processing technique. Morphological studies showed that the method employed provided uniform GNPs dispersion in the matrix, orienting the nanoplatelets along the same direction the flow of matter. Enhancements of storage and Young’s modulus occurred, increasing GNP content, and the improvement was more obvious when a compatibilizer, the PP-grafted-maleic anhydride, was introduced to achieve a better GNP dispersion and distribution within the matrix. For all the nanocomposites, even for those com- patibilized, it was not possible to fully exploit the GNP toughening effect since a stiffening and embrittling effect prevailed. Thermogravimetric analysis showed that GNP incorporation has improved the thermal stability of the nanocomposites. In addition, cone calorimetry results showed that GNPs can act as intumescent flame retardant and significantly reduced the heat release rate, thus improving the flame retardancy of the PP matrix

Novel perfluoropolyalkylethers (PFPAEs): photo-induced cationic polymerization and copolymer characterization

Perfluoropolyalkylethers (PFPAEs) show low polarizability, strong electronegativity, high C-F bond energy, and exceptional mobility thanks to the oxygen bridges; they represent a special class of fluoropolymers with remarkable properties (low glass transition temperature, high thermal stability, excellent chemical inertness, low surface energy, tunable mechanical properties), and are commercially available mostly obtained from the photooxidation of perfluoroolefins. In this work PFPAEs were synthesized by anionic polymerization of dodecafluorooctanedioyl difluoride, chain extended with different alkyl groups and functionalized with vinyl ether or epoxy end groups. The oligomers were photo-homopolymerized: the curing process was monitored by Photo-DSC and FT-IR-ATR spectroscopies; the crosslinked networks were characterized by DSC, TGA, refractive index and surface measurements

Controlling perfluoropolyalkylether rearrangements at the surface of photocured networks

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Perfluoropolyalkylether Maleimides for Protection From Oxygen Inhibition and Surface Modification of Photoinitiator-Free UV-Cured Polymers

Maleimides are attractive systems for photopolymerize for two major reasons: (1) they follow a radical mechanism without requiring a photoinitiator and (2) their rate of polymerization corresponds similarly to acrylates, which are commonplace in the industry. In this work, bismaleimide polypropylene oxide was cured under UV light forming thin films. Their surface properties were modified by copolymerization them with fluorinated comonomers. To this goal, perfluoropolyalkylethers (PFPAEs) with maleimide groups were synthesized, varying their chain structure, their functionality degree and consequently their intrinsic viscosity. These PFPPAE comonomers were highlighted to segregate at the surface, assuring omniphobic properties and acting as a protective layer against oxygen inhibition. These phenomenon were observed even when added at a concentration ≤5% w/w with respect to the main polypropylene oxide monomer. XPS analyses confirmed the segregation of the fluorine atoms at the surface during the UV-curing process of the coatings