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

Copolycondensation of regular functional silane and siloxane in aqueous emulsion using B(C6F5)3 as a catalyst

International audienceThe copolycondensation of siloxane and silane bearing hydrido and methoxy groups, resp., was carried out in a surfactant-free aq. emulsion, at room temp. and using B(C6F5)3 as a water-tolerant Lewis acid. Several characterization techniques, including triple detection SEC, 29Si NMR and MALDI-TOF, confirmed the generation of linear polymers (no macrocycles), of av. molar masses ranging between 30 and 80 000 g×mol-1, and bearing silanol end-groups. Colloidal evolution with time showed that a stable surfactant-free emulsion was generated before some coalescence occurs by decreasing the content of silanol groups suspected to stabilize the emulsion. The kinetics of reaction was followed by SEC, and revealed the generation of small cycles, along with linear oligomers, before converting them to poly(dimethylsiloxane) chains. A tentative mechanism, where ring-opening polymn. of the most stranded cyclosiloxane and polycondensation of polymer chains are considered, is proposed

Photopolymerization without Photoinitiator of Bismaleimide-Containing Oligo(oxypropylene)s: Effect of Oligoethers Chain Length

International audienceThis article describes the synthesis and characterization of a series of poly(propylene glycol bismaleimide) (PPGM) with molecular weights (Mws) in the range of 390–2 600 g mol1. Their photopolymerization rates without photoiniator were similar to that of an acrylate resin in the presence of a photoinitiator. The reactivities and degrees of conversion of these PPGM oligomers, thermal and mechanical properties of the resulting materials were studied as a function of Mw. Rigid materials were obtained except for that containing the longest PPGM, which exhibited mechanical properties of a rubber. The glass transition temperature values and the thermal stability were found to decrease when Mw of used oligomers was increased. Crosslinking density was the parameter that controlled both mechanical and thermal properties

Photoinitiator-Free, Open-Air Acceptor/Donor Copolymerization of Bismaleimides: Simple Polymerization Conditions for New Thermoplastic Elastomer Production

International audienceA photoinitiator-free acceptor-donor copolymerization between a mixture of bismale imides containing oligo(propyleneglycol)s as acceptor monomers and divinyl ether as the donor monomer under UV is described. The copolymerization without any photoinitiator is faster than homopolymerization of the sole maleimide, thanks to an acceptor-donor charge-transfer complex. The thermal and mechanical properties of the cured materials depend essentially on the cross-linking densities and on the number of repeated units in the bismaleimide backbone. Most copolymerizations produce elastomers with remarkable rubbery properties on a large temperature scale. The simple chemistry presented here can easily compete with acrylate photochemistry since neither photoinitiator nor oxygen removal is needed

Synthesis of Glutarimides from PMMA Copolymers, Part 3: Use of Functional Amines

International audienceImidization reactions onto PMMA copolymers were performed in the presence of primary amines. This study allowed establishing a correlation between the functional group of the primary amine and the reactivity of the primary amine toward ester groups of PMMA. This correlation was allowed by using model PMMA/PMAA copolymers, i.e., obtained using a chain transfer agent by radical polymerization. According to the suggested mechanism of PMMA imidization, methylamine afforded higher content of glutarimide groups, hence leading to high Tg values of about 160C. The use of bulky groups for the primary amine instead, i.e., cyclohexyl, decreased the content of glutarimide function. Thermogravimetric analysis revealed a high thermostability of imidized PMMA with a starting degradation temperature of about 400C, also dependant of the amine functional group

Syntheses of donor acceptor biobased photocurable water-soluble resins based on poly-L-lysine

International audienceWe report a new kind of coating using UV waterborne technique with a biobased poly(amino acid) resin. Firstly we performed the thermal polycondensation of L-lysine during 15 hours at 150 °C in order to synthesize water-soluble oligomers of poly-L-lysine (PLL) with 5-6 monomer units. These oligomers were then transformed in mild conditions to give photocurable water-soluble resins. We grafted on the poly-L-lysine backbone, allyl and maleamic acid functional groups, with a grafting rate close to 65% thanks to allyl glycidyl ether and maleic anhydride respectively. The influence of the reaction time and the reagents ratio on the grafting rate was investigated. Hence, the donor/acceptor photopolymerization of the mixture of allyl ether-poly-L-lysine (PLL-g-AE) with maleamic acid-poly-L-lysine (PLL-g-MA) in aqueous solution gave yellow transparent films. The degree of conversion and other kinetic parameters have been studied and detailed. This work contributes to the development of materials based on renewable resources and cleaner processes. It opens a new pathway to both fundamental and applied-driven research

Metodi integrati di rilevamento urbano: applicazioni nell'area della "Piazzetta degli Ariani" a Ravenna

Il contributo prende in esame l'approccio metodologico del rilevamento urbano, individuando per il caso in esame una procedura che integra diverse metodiche ricorrenti, sia di rilievo indiretto che diretto. L'obiettivo è la ricostruzione dell'immagine di un brano di città caratterizzato dalla presenza di importanti Beni Culturali e dal rapporto di questi con aree degradate e inaccessibili, e parallelamente, quasi per ricaduta, la costruzione di un documento tecnico che possa essere di supporto per le future operazioni di riqualificazione e recupero dell'area e anche di valorizzazione e fruizione del patrimonio artistico presente nella stessa