The amount of data needed for training machine learning methods is an open question. Here, we use... more The amount of data needed for training machine learning methods is an open question. Here, we use a problem from chemistry for examining this question. The problem is a special case of a graph data analysis. It can be tackled inter alia by using graph convolutional networks. We show that newer methods can provide good results, but need large amounts of data, which are not always available. In some cases, older methods may be preferable for low amounts of data. In the longer term, open databases can help with this problem.
... a Dipartimento di Chimica, Materiali e Ingegneria Chimica, Politecnico di Milano, 7, via Manc... more ... a Dipartimento di Chimica, Materiali e Ingegneria Chimica, Politecnico di Milano, 7, via Mancinelli, I-20131 Milano, Italy. b Solvay-Solexis, R&D Centre, 20, viale Lombardia, I-20021 Bollate (MI), Italy. Received 19 March 2008; revised 29 May 2008; accepted 29 May 2008. ...
Perfluoroalkyl radicals, generated by thermal decomposition of perfluorodiacyl peroxides, react s... more Perfluoroalkyl radicals, generated by thermal decomposition of perfluorodiacyl peroxides, react selectively with quinone rings of 1,4-naphthoquinones. In the presence of a non-conjugated alkene such as 1-hexene, perfluoroalkyl radicals add to the double bonds of the olefin forming a radical adduct, which selectively adds to the naphthoquinone ring. Several perfluorodiacyl peroxides have been synthesized and used for the direct and alkene-mediated functionalization of naphthoquinones. Geometrical parameters and electron density topology of all perfluorodiacyl peroxides have been calculated by the density functional formalism and quantum theory of atoms in molecules to attempt a rationalization of the experimental reactivity.
In this paper, we have directly buried microchannels in a fused silica substrate using femtosecon... more In this paper, we have directly buried microchannels in a fused silica substrate using femtosecond laser irradiation followed by chemical etching. By exploiting a synergic effect between gaseous hydrofluoric acid and fluorine (F2), we have obtained microchannels having an outstanding aspect ratio of 86 with a relative etching speed of 17 µm min−1. Using fluorine we successfully regenerated the etchant 'in situ', thus providing a way to control the bore shape, in particular, the strong conically shaped microchannel can be adjusted by modifying the etching mixture composition. We have avoided water formation during the microchannel construction, thus overcoming one of the major limits that prevents any further increase in the length and the aspect ratio.
The photocatalytic activity promoted by anodized titanium surfaces coated with different amorphou... more The photocatalytic activity promoted by anodized titanium surfaces coated with different amorphous perfluoropolymers was evaluated. A copolymer between tetrafluoroethylene and perfluoro-4-trifluoromethoxy-1,3-dioxole and two perfluoropolyethers containing ammonium phosphate and triethoxysilane functionalities, respectively, were tested as coating materials. These coatings revealed good adhesion to the anodized titanium substrate and conferred to it both hydrophobicity and oleophobicity. The photocatalytic activity of the coating on anodized titanium was evaluated by monitoring the degradation of stearic acid via Infrared spectroscopy. The degradation rate of stearic acid was reduced but not set to zero by the presence of the fluorinated coatings, leading to the development of advanced functional coatings. The morphological variations of the coatings as a result of photocatalysis were also determined by atomic force microscopy.
In the present work, a novel process for Fe-Ga thin films electrodeposition is addressed and the ... more In the present work, a novel process for Fe-Ga thin films electrodeposition is addressed and the magnetic properties of the films are studied. The electrodeposition was carried out under ambient conditions using an ionic liquid electrolyte consisting of a mixture of choline chloride and ethylene glycol in the molar ratio 1:2, containing 0.3 M FeCl2 and 0.1 M GaCl3, either in the absence or in the presence of oxalic acid at 4 or 17 mM concentration. The effect of oxalic acid on the discharge reaction of the single ionic species Fe2+ and Ga3+ and on their codeposition was investigated by linear sweep voltammetry, suggesting a specific action of oxalic acid on the cathodic reduction of Ga3+ ionic species. Depending on deposition potential and oxalic acid concentration, alloy films with Ga content variable in the range up to about 20 at.% could be obtained. The Fe-Ga thin films showed a disordered body-cantered cubic phase (A2) with (110) preferred orientation and columnar microstructure, with a drastic change from pyramidal to granular surface morphology revealed raising the deposition potential. No superlattice reflections, indicating the formation of the D03 structure, were observed. A vibrating sample magnetometer was employed to measure hysteresis loops by applying longitudinal and transversal magnetic field on the Fe-Ga film plane. The saturation magnetization of as-deposited film reached 1.75 T for Fe83Ga17 thin films, confirming that good quality films were obtained. For the same alloy composition, the coercivity values were 67 Oe and 200 Oe, with applied field parallel and perpendicular to the film plane, respectively.
Recent findings in the synthesis of perfluoro-hypofluorites, their reactivity and their use in th... more Recent findings in the synthesis of perfluoro-hypofluorites, their reactivity and their use in the preparation of important perfluoro monomers are herein summarized and analyzed. The experimental conditions to induce free radical or electrophilic reactivity as well as their use as initiation system in the oxidation and oxypolimerization of fluorinated olefins are also presented.
Particular emphasis is dedicated to safety issues since organic hypofluorites have the tendency to self-decompose forming gaseous compounds.The hypofluorites considered in this review are: CF3OF, CF2(OF)2, CF3CF2OCF2OF, CF3OCF2CF2OCF2OF, CF3O(CF2O)nCF2OF, CF3OCF2CF2OF, (CF3)2CFOF (CF3)3COF, FS(O)2CF2CF2OF, CF3OCF2CF2CF2OF, cyclo-(CF2OCF2OCF)-CF2OF, (CF3)2N-CF2OF
In the reaction between perfluoroolefins and perfluoroalkylhypofluorites the existence of two dif... more In the reaction between perfluoroolefins and perfluoroalkylhypofluorites the existence of two different free radical reaction mechanisms is demonstrated by the presence of characteristic byproducts. These kinetic schemes can be experimentally controlled by tuning the hypofluorite concentration in the reaction media. In particular, in the reactions between trifluoromethyl hypofluorite and highly reactive perfluoroolefins like CF2CFOCF3 and CF2CF2, the free radical oligomerization and dimerization products can be suppressed by utilizing the opportune experimental conditions. The pure perfluorinated ethers obtained, having low Ostwald coefficient, can be utilized as contrast agents for diagnostic ultrasound imaging injectable microbubbles composition.
The products deriving from the addition of CF2=CFOCF3 to CF3OF are proved to be low Ostwald coeff... more The products deriving from the addition of CF2=CFOCF3 to CF3OF are proved to be low Ostwald coefficient fluids suitable for producing high stable micro bubbles that can be used as ultrasound imaging contrast agents. The standard gas-liquid fast radical chain reaction between trifluoromethyl hypofluorite CF3OF and reactive perfluoroolefins like CF2=CFOCF3produces oligomerization and dimerization byproducts. Therefore a purification procedure is needed in order to separate the low Ostwald coefficient products from the reaction mixture. Surprisingly we have found that the selectivity of the reaction can be increased by modifying the experimental reaction conditions adopted. This behaviour is an experimental evidence for the presence of two different reaction schemes that can be switched by tuning the hypofluorite concentration in the reaction media.
Perfluorodiacyl peroxides are suitable tools for thecovalent linkage of fluorinated groups on sub... more Perfluorodiacyl peroxides are suitable tools for thecovalent linkage of fluorinated groups on substrates containing aromatic moieties. The thermal decomposition process of such fluorinated peroxides allows the covalent linkage of fluorinated radicals on the polycyclic aromatic structure of a graphitic carbon black. Depending on the perfluorodiacyl peroxide involved during the chemical treatment, several fluorinated chains, i.e. perfluoroethyl, CF3CF2-, perfluoro-n-propyl, CF3CF2CF2- and perfluoro- iso-propyl, (CF3)2CF-residues have been bonded covalently on the surface of a conductive carbon black. At the characteristic temperature of perfluorocarbons thermolysis (400°C), thermogravimetric analyses revealed weight losses in agreement with the fluorine contents on the modified carbon blacks.
Femtosecond laser irradiation followed by chemical etching (FLICE) with hydrofluoric acid (HF) is... more Femtosecond laser irradiation followed by chemical etching (FLICE) with hydrofluoric acid (HF) is an emerging technique for the fabrication of directly buried, three-dimensional microfluidic channels. With liquid HF, the etching process is diffusion-limited and is self-terminating, leading to maximum microchannel lengths of ≈1.5 mm. A strategy to overcome this limitation would be to perform iterative etching, periodically removing the exhausted products and replenishing the partially etched channel with fresh acid; this procedure is, however, quite cumbersome in the liquid phase. In this paper we present what is to our knowledge the first implementation of the FLICE technique with low-pressure gaseous HF etchant. The use of a gas-phase etchant naturally lends itself to the application of iterative etching techniques, since it is very easy to remove the etchant, by pumping vacuum in the reaction chamber after each etching step. We demonstrate that iterative etching in the gas phase overcomes the limitations of wet etching and allows to achieve nearly constant etching rate for a microchannel length up to ≈3 mm.
The progresses in the magnetic media technology
brought to the application of liquid lubricant f... more The progresses in the magnetic media technology
brought to the application of liquid lubricant films on
diamond-like carbon (DLC) coatings. Hard surfaces are
typically lubricated with fluorinated or perfluorinated organic
compounds, such as perfluoropolyethers (PFPE) (1). Many
attempts have been done to obtain a stable layer of PFPE
lubricant on the DLC surface by dip-coating or by vapour
deposition so as to minimize any friction and wear (2, 3).
Diamond-like carbons are formed by an amorphous mixture
of sp3 and sp2 hybridized carbon atoms with hydrogen atoms
incorporated in the structure (a-C:H DLC). We have established
a specific methodology for the straight-forward introduction
of perfluorinated groups with carbon-carbon bond formation
on a variety of unsaturated materials (4-8). Indeed, by using
this methodology, perfluorinated radicals can directly bond
to the sp2 sites of the DLC structure avoiding any spacer, that
usually decreases both thermal and chemical stabilities of the
resulting fluorinated layers.
The α,ω-dialkoxyfluoropolyethers (DA-FPEs) characterized by structureRHO(CF2CF2O)n(CF2O)mRH
have... more The α,ω-dialkoxyfluoropolyethers (DA-FPEs) characterized by structureRHO(CF2CF2O)n(CF2O)mRH
have been recently developed as a new class of environmental friendly hydrofluoropolyethers (HFPEs) suitable as solvents,refrigerants and heat transfer.The synthetic methodologies for the preparation of this new class of uid have been reviewed and physical properties of selected α,ω-dimethoxyfluoropolyethers have been evaluated and compared with analogous hydrofluoropolyethers (H-FPEs) having -OCF2H as end-groups.Atmospheric implications and global warming potentials(GWP) of selected α,ω-dimethoxyfluoropolyethers have been also considered.
Many attempts to obtain a clean stream of COF2 have been carried out in the past by means of the ... more Many attempts to obtain a clean stream of COF2 have been carried out in the past by means of the direct fluorination of carbon monoxide with elemental fluorine or by electrochemical fluorination. The reaction is highly exothermic, therefore difficult to control. It can easily develop into a thermal runaway with a poor selectivity. We have successfully circumvented these critical issues by using a stainless steel parallel channel microreactor (surface/volume ratio ≈ 1 × 104 m−1, residence time τ ≈ 0.1 s) for the direct fluorination of carbon monoxide. Its performance in terms of operability and selectivity is compared to that of a standard reactor assembly, namely a fluorine burner reactor coupled with a water cooled heat exchanger. While the microreactor assembly succeeded to control the exothermic reaction, in the same experimental conditions the standard assembly reactor underwent serious corrosion issues that lead to nozzle meltdown lack of selectivity and consequent plant shutdowns.
Femtosecond laser irradiation followed by chemical etching (FLICE) with hydrogen fluoride (HF) is... more Femtosecond laser irradiation followed by chemical etching (FLICE) with hydrogen fluoride (HF) is an emerging technique for the fabrication of directly buried, three-dimensional microfluidic channels in silica. The procedure, as described in literature, consists of irradiating a silica slab followed by chemical etching using hydrogen fluoride. With aqueous HF the etching process is diffusion-limited and is self-terminating, leading to maximum microchannel lengths of about 1.5 mm, while the use of low-pressure gaseous HF etchant can quickly produce 3 mm long channels with an aspect ratio (Length/Diameter) higher than 25. By utilizing this methodology the aspect ratio is not constant, but depends on the length of the channel. When the microchannel is short the aspect ratio increases quickly until it reaches a maximum length at around 1400 µm. Thereafter the aspect ratio starts to decrease slowly. In this paper we present a variation of the low-pressure gaseous HF etching method, which is based on the dynamic displacement of the etchant. This method results in a 13% increase in the aspect ratio (L/D = 29) at the expense of a low etching speed (4 µm/min).
The α,ω-dialkoxyfluoropolyethers (DA-FPEs) characterized by the structure RHO(CF2CF2O)n(CF2O)mRH ... more The α,ω-dialkoxyfluoropolyethers (DA-FPEs) characterized by the structure RHO(CF2CF2O)n(CF2O)mRH have been developed as a new class of environmentally friendly hydrofluoroethers (HFEs) suitable as solvents, long-term refrigerants, cleaning fluids, and heat transfer fluids. Synthetic methodologies for DA-FPEs described here consist of radical-initiated oxypolymerization of olefin, peroxy-elimination reaction in peroxidic perfluoropolyethers (P-PFPEs) and further chemical modification of α,ω-diacylfluoride PFPE. The physical properties of selected α,ω-dimethoxyfluoropolyethers (DM-FPEs) have been evaluated and compared with analogous hydrofluoropolyethers (HFPEs) having -OCF2H as end-groups. Atmospheric implications and global warming potentials (GWPs) of selected DA-FPEs are also considered.
The reactivity of CF3OF (FTM) has been widely studied especially in halogenated olefinic systems ... more The reactivity of CF3OF (FTM) has been widely studied especially in halogenated olefinic systems and its use in pharmaceutical synthesis as a mild radical and electrophilic fluorinating agent is well documented. On the other hand, the chemical behavior of the perfluoro-methyl-hypofluorite with aromatic substrates is much less studied. Up to now few and scattered data regarding its use as electrophilic fluorinating agent of variously substituted aromatic compounds are found in the literature. In this work the reactivity of CF3OF with simple electron rich and electron poor aromatics (α,α,α-trifluoro-toluene, toluene, benzene, chloro-benzene, methoxybenzene) has been investigated. The possibility of selectively bind the trifluoro-methoxy group (via radical mechanism) or the fluorine atom (via electrophilic addition) by varying the reaction conditions has been explored. In particular we have observed that the trifluoro-methoxy free radical substitution can be the main synthetic pathway if the reaction is promoted by an independent and steady source of CF3O radical.
Femtosecond laser irradiation followed by chemical etching (F.L.I.C.E.) is an emerging technique ... more Femtosecond laser irradiation followed by chemical etching (F.L.I.C.E.) is an emerging technique for the fabrication of directly buried, three-dimensional microfluidic channels in silica. The procedure attested in literature, which has been widely studied in the past years, consists of irradiating a glass slab and subsequently apply a chemical etching step. The results obtained by different research groups vary widely. In this paper we present a review of the most recent advancements of this technique discussing several critical factors that affect the aspect ratio, the length and the etching speed of the microchannel.
The amount of data needed for training machine learning methods is an open question. Here, we use... more The amount of data needed for training machine learning methods is an open question. Here, we use a problem from chemistry for examining this question. The problem is a special case of a graph data analysis. It can be tackled inter alia by using graph convolutional networks. We show that newer methods can provide good results, but need large amounts of data, which are not always available. In some cases, older methods may be preferable for low amounts of data. In the longer term, open databases can help with this problem.
... a Dipartimento di Chimica, Materiali e Ingegneria Chimica, Politecnico di Milano, 7, via Manc... more ... a Dipartimento di Chimica, Materiali e Ingegneria Chimica, Politecnico di Milano, 7, via Mancinelli, I-20131 Milano, Italy. b Solvay-Solexis, R&D Centre, 20, viale Lombardia, I-20021 Bollate (MI), Italy. Received 19 March 2008; revised 29 May 2008; accepted 29 May 2008. ...
Perfluoroalkyl radicals, generated by thermal decomposition of perfluorodiacyl peroxides, react s... more Perfluoroalkyl radicals, generated by thermal decomposition of perfluorodiacyl peroxides, react selectively with quinone rings of 1,4-naphthoquinones. In the presence of a non-conjugated alkene such as 1-hexene, perfluoroalkyl radicals add to the double bonds of the olefin forming a radical adduct, which selectively adds to the naphthoquinone ring. Several perfluorodiacyl peroxides have been synthesized and used for the direct and alkene-mediated functionalization of naphthoquinones. Geometrical parameters and electron density topology of all perfluorodiacyl peroxides have been calculated by the density functional formalism and quantum theory of atoms in molecules to attempt a rationalization of the experimental reactivity.
In this paper, we have directly buried microchannels in a fused silica substrate using femtosecon... more In this paper, we have directly buried microchannels in a fused silica substrate using femtosecond laser irradiation followed by chemical etching. By exploiting a synergic effect between gaseous hydrofluoric acid and fluorine (F2), we have obtained microchannels having an outstanding aspect ratio of 86 with a relative etching speed of 17 µm min−1. Using fluorine we successfully regenerated the etchant 'in situ', thus providing a way to control the bore shape, in particular, the strong conically shaped microchannel can be adjusted by modifying the etching mixture composition. We have avoided water formation during the microchannel construction, thus overcoming one of the major limits that prevents any further increase in the length and the aspect ratio.
The photocatalytic activity promoted by anodized titanium surfaces coated with different amorphou... more The photocatalytic activity promoted by anodized titanium surfaces coated with different amorphous perfluoropolymers was evaluated. A copolymer between tetrafluoroethylene and perfluoro-4-trifluoromethoxy-1,3-dioxole and two perfluoropolyethers containing ammonium phosphate and triethoxysilane functionalities, respectively, were tested as coating materials. These coatings revealed good adhesion to the anodized titanium substrate and conferred to it both hydrophobicity and oleophobicity. The photocatalytic activity of the coating on anodized titanium was evaluated by monitoring the degradation of stearic acid via Infrared spectroscopy. The degradation rate of stearic acid was reduced but not set to zero by the presence of the fluorinated coatings, leading to the development of advanced functional coatings. The morphological variations of the coatings as a result of photocatalysis were also determined by atomic force microscopy.
In the present work, a novel process for Fe-Ga thin films electrodeposition is addressed and the ... more In the present work, a novel process for Fe-Ga thin films electrodeposition is addressed and the magnetic properties of the films are studied. The electrodeposition was carried out under ambient conditions using an ionic liquid electrolyte consisting of a mixture of choline chloride and ethylene glycol in the molar ratio 1:2, containing 0.3 M FeCl2 and 0.1 M GaCl3, either in the absence or in the presence of oxalic acid at 4 or 17 mM concentration. The effect of oxalic acid on the discharge reaction of the single ionic species Fe2+ and Ga3+ and on their codeposition was investigated by linear sweep voltammetry, suggesting a specific action of oxalic acid on the cathodic reduction of Ga3+ ionic species. Depending on deposition potential and oxalic acid concentration, alloy films with Ga content variable in the range up to about 20 at.% could be obtained. The Fe-Ga thin films showed a disordered body-cantered cubic phase (A2) with (110) preferred orientation and columnar microstructure, with a drastic change from pyramidal to granular surface morphology revealed raising the deposition potential. No superlattice reflections, indicating the formation of the D03 structure, were observed. A vibrating sample magnetometer was employed to measure hysteresis loops by applying longitudinal and transversal magnetic field on the Fe-Ga film plane. The saturation magnetization of as-deposited film reached 1.75 T for Fe83Ga17 thin films, confirming that good quality films were obtained. For the same alloy composition, the coercivity values were 67 Oe and 200 Oe, with applied field parallel and perpendicular to the film plane, respectively.
Recent findings in the synthesis of perfluoro-hypofluorites, their reactivity and their use in th... more Recent findings in the synthesis of perfluoro-hypofluorites, their reactivity and their use in the preparation of important perfluoro monomers are herein summarized and analyzed. The experimental conditions to induce free radical or electrophilic reactivity as well as their use as initiation system in the oxidation and oxypolimerization of fluorinated olefins are also presented.
Particular emphasis is dedicated to safety issues since organic hypofluorites have the tendency to self-decompose forming gaseous compounds.The hypofluorites considered in this review are: CF3OF, CF2(OF)2, CF3CF2OCF2OF, CF3OCF2CF2OCF2OF, CF3O(CF2O)nCF2OF, CF3OCF2CF2OF, (CF3)2CFOF (CF3)3COF, FS(O)2CF2CF2OF, CF3OCF2CF2CF2OF, cyclo-(CF2OCF2OCF)-CF2OF, (CF3)2N-CF2OF
In the reaction between perfluoroolefins and perfluoroalkylhypofluorites the existence of two dif... more In the reaction between perfluoroolefins and perfluoroalkylhypofluorites the existence of two different free radical reaction mechanisms is demonstrated by the presence of characteristic byproducts. These kinetic schemes can be experimentally controlled by tuning the hypofluorite concentration in the reaction media. In particular, in the reactions between trifluoromethyl hypofluorite and highly reactive perfluoroolefins like CF2CFOCF3 and CF2CF2, the free radical oligomerization and dimerization products can be suppressed by utilizing the opportune experimental conditions. The pure perfluorinated ethers obtained, having low Ostwald coefficient, can be utilized as contrast agents for diagnostic ultrasound imaging injectable microbubbles composition.
The products deriving from the addition of CF2=CFOCF3 to CF3OF are proved to be low Ostwald coeff... more The products deriving from the addition of CF2=CFOCF3 to CF3OF are proved to be low Ostwald coefficient fluids suitable for producing high stable micro bubbles that can be used as ultrasound imaging contrast agents. The standard gas-liquid fast radical chain reaction between trifluoromethyl hypofluorite CF3OF and reactive perfluoroolefins like CF2=CFOCF3produces oligomerization and dimerization byproducts. Therefore a purification procedure is needed in order to separate the low Ostwald coefficient products from the reaction mixture. Surprisingly we have found that the selectivity of the reaction can be increased by modifying the experimental reaction conditions adopted. This behaviour is an experimental evidence for the presence of two different reaction schemes that can be switched by tuning the hypofluorite concentration in the reaction media.
Perfluorodiacyl peroxides are suitable tools for thecovalent linkage of fluorinated groups on sub... more Perfluorodiacyl peroxides are suitable tools for thecovalent linkage of fluorinated groups on substrates containing aromatic moieties. The thermal decomposition process of such fluorinated peroxides allows the covalent linkage of fluorinated radicals on the polycyclic aromatic structure of a graphitic carbon black. Depending on the perfluorodiacyl peroxide involved during the chemical treatment, several fluorinated chains, i.e. perfluoroethyl, CF3CF2-, perfluoro-n-propyl, CF3CF2CF2- and perfluoro- iso-propyl, (CF3)2CF-residues have been bonded covalently on the surface of a conductive carbon black. At the characteristic temperature of perfluorocarbons thermolysis (400°C), thermogravimetric analyses revealed weight losses in agreement with the fluorine contents on the modified carbon blacks.
Femtosecond laser irradiation followed by chemical etching (FLICE) with hydrofluoric acid (HF) is... more Femtosecond laser irradiation followed by chemical etching (FLICE) with hydrofluoric acid (HF) is an emerging technique for the fabrication of directly buried, three-dimensional microfluidic channels. With liquid HF, the etching process is diffusion-limited and is self-terminating, leading to maximum microchannel lengths of ≈1.5 mm. A strategy to overcome this limitation would be to perform iterative etching, periodically removing the exhausted products and replenishing the partially etched channel with fresh acid; this procedure is, however, quite cumbersome in the liquid phase. In this paper we present what is to our knowledge the first implementation of the FLICE technique with low-pressure gaseous HF etchant. The use of a gas-phase etchant naturally lends itself to the application of iterative etching techniques, since it is very easy to remove the etchant, by pumping vacuum in the reaction chamber after each etching step. We demonstrate that iterative etching in the gas phase overcomes the limitations of wet etching and allows to achieve nearly constant etching rate for a microchannel length up to ≈3 mm.
The progresses in the magnetic media technology
brought to the application of liquid lubricant f... more The progresses in the magnetic media technology
brought to the application of liquid lubricant films on
diamond-like carbon (DLC) coatings. Hard surfaces are
typically lubricated with fluorinated or perfluorinated organic
compounds, such as perfluoropolyethers (PFPE) (1). Many
attempts have been done to obtain a stable layer of PFPE
lubricant on the DLC surface by dip-coating or by vapour
deposition so as to minimize any friction and wear (2, 3).
Diamond-like carbons are formed by an amorphous mixture
of sp3 and sp2 hybridized carbon atoms with hydrogen atoms
incorporated in the structure (a-C:H DLC). We have established
a specific methodology for the straight-forward introduction
of perfluorinated groups with carbon-carbon bond formation
on a variety of unsaturated materials (4-8). Indeed, by using
this methodology, perfluorinated radicals can directly bond
to the sp2 sites of the DLC structure avoiding any spacer, that
usually decreases both thermal and chemical stabilities of the
resulting fluorinated layers.
The α,ω-dialkoxyfluoropolyethers (DA-FPEs) characterized by structureRHO(CF2CF2O)n(CF2O)mRH
have... more The α,ω-dialkoxyfluoropolyethers (DA-FPEs) characterized by structureRHO(CF2CF2O)n(CF2O)mRH
have been recently developed as a new class of environmental friendly hydrofluoropolyethers (HFPEs) suitable as solvents,refrigerants and heat transfer.The synthetic methodologies for the preparation of this new class of uid have been reviewed and physical properties of selected α,ω-dimethoxyfluoropolyethers have been evaluated and compared with analogous hydrofluoropolyethers (H-FPEs) having -OCF2H as end-groups.Atmospheric implications and global warming potentials(GWP) of selected α,ω-dimethoxyfluoropolyethers have been also considered.
Many attempts to obtain a clean stream of COF2 have been carried out in the past by means of the ... more Many attempts to obtain a clean stream of COF2 have been carried out in the past by means of the direct fluorination of carbon monoxide with elemental fluorine or by electrochemical fluorination. The reaction is highly exothermic, therefore difficult to control. It can easily develop into a thermal runaway with a poor selectivity. We have successfully circumvented these critical issues by using a stainless steel parallel channel microreactor (surface/volume ratio ≈ 1 × 104 m−1, residence time τ ≈ 0.1 s) for the direct fluorination of carbon monoxide. Its performance in terms of operability and selectivity is compared to that of a standard reactor assembly, namely a fluorine burner reactor coupled with a water cooled heat exchanger. While the microreactor assembly succeeded to control the exothermic reaction, in the same experimental conditions the standard assembly reactor underwent serious corrosion issues that lead to nozzle meltdown lack of selectivity and consequent plant shutdowns.
Femtosecond laser irradiation followed by chemical etching (FLICE) with hydrogen fluoride (HF) is... more Femtosecond laser irradiation followed by chemical etching (FLICE) with hydrogen fluoride (HF) is an emerging technique for the fabrication of directly buried, three-dimensional microfluidic channels in silica. The procedure, as described in literature, consists of irradiating a silica slab followed by chemical etching using hydrogen fluoride. With aqueous HF the etching process is diffusion-limited and is self-terminating, leading to maximum microchannel lengths of about 1.5 mm, while the use of low-pressure gaseous HF etchant can quickly produce 3 mm long channels with an aspect ratio (Length/Diameter) higher than 25. By utilizing this methodology the aspect ratio is not constant, but depends on the length of the channel. When the microchannel is short the aspect ratio increases quickly until it reaches a maximum length at around 1400 µm. Thereafter the aspect ratio starts to decrease slowly. In this paper we present a variation of the low-pressure gaseous HF etching method, which is based on the dynamic displacement of the etchant. This method results in a 13% increase in the aspect ratio (L/D = 29) at the expense of a low etching speed (4 µm/min).
The α,ω-dialkoxyfluoropolyethers (DA-FPEs) characterized by the structure RHO(CF2CF2O)n(CF2O)mRH ... more The α,ω-dialkoxyfluoropolyethers (DA-FPEs) characterized by the structure RHO(CF2CF2O)n(CF2O)mRH have been developed as a new class of environmentally friendly hydrofluoroethers (HFEs) suitable as solvents, long-term refrigerants, cleaning fluids, and heat transfer fluids. Synthetic methodologies for DA-FPEs described here consist of radical-initiated oxypolymerization of olefin, peroxy-elimination reaction in peroxidic perfluoropolyethers (P-PFPEs) and further chemical modification of α,ω-diacylfluoride PFPE. The physical properties of selected α,ω-dimethoxyfluoropolyethers (DM-FPEs) have been evaluated and compared with analogous hydrofluoropolyethers (HFPEs) having -OCF2H as end-groups. Atmospheric implications and global warming potentials (GWPs) of selected DA-FPEs are also considered.
The reactivity of CF3OF (FTM) has been widely studied especially in halogenated olefinic systems ... more The reactivity of CF3OF (FTM) has been widely studied especially in halogenated olefinic systems and its use in pharmaceutical synthesis as a mild radical and electrophilic fluorinating agent is well documented. On the other hand, the chemical behavior of the perfluoro-methyl-hypofluorite with aromatic substrates is much less studied. Up to now few and scattered data regarding its use as electrophilic fluorinating agent of variously substituted aromatic compounds are found in the literature. In this work the reactivity of CF3OF with simple electron rich and electron poor aromatics (α,α,α-trifluoro-toluene, toluene, benzene, chloro-benzene, methoxybenzene) has been investigated. The possibility of selectively bind the trifluoro-methoxy group (via radical mechanism) or the fluorine atom (via electrophilic addition) by varying the reaction conditions has been explored. In particular we have observed that the trifluoro-methoxy free radical substitution can be the main synthetic pathway if the reaction is promoted by an independent and steady source of CF3O radical.
Femtosecond laser irradiation followed by chemical etching (F.L.I.C.E.) is an emerging technique ... more Femtosecond laser irradiation followed by chemical etching (F.L.I.C.E.) is an emerging technique for the fabrication of directly buried, three-dimensional microfluidic channels in silica. The procedure attested in literature, which has been widely studied in the past years, consists of irradiating a glass slab and subsequently apply a chemical etching step. The results obtained by different research groups vary widely. In this paper we present a review of the most recent advancements of this technique discussing several critical factors that affect the aspect ratio, the length and the etching speed of the microchannel.
The present invention relates to a method for exchanging heat with an object said method comprisi... more The present invention relates to a method for exchanging heat with an object said method comprising using a heat transfer fluid wherein said heat transfer fluid comprises one or more fluorinated nitrocompounds according to the general formula (I) wherein:- at least two of R1, R2, R3 and R4 are independently selected from H, Cl and F, with the proviso that at least one is either H or Cl. - those of R1, R2, R3 and R4 which are not H, F or Cl, are selected from, partially halogenated alkyl, fully halogenated alkyl, wherein the alkyl chain is C1-C4 and halogens are selected from Cl and F.
The present invention relates to a processes for the manufacture of 1,2,3,4-tetrachloro-hexafluor... more The present invention relates to a processes for the manufacture of 1,2,3,4-tetrachloro-hexafluoro-butane in a microreactor.
1,2,3,4-tetrachloro-hexafluoro-butane (also known as “A316”) is used as an intermediate compound in the synthesis of hexafluoro-1,3-butadiene (also known as “C4F6” or “HFBD”), a stable gas which is used in the semiconductor industry, in particular as etching gas for semiconductor fine processing.
The Applicant noted that despite 1,2,3,4-tetrachloro-hexafluoro-butane (A316) can be prepared by the methods known in the art, the productivity of the methods disclosed in the previous cited prior art documents was from about 1 Kg/h*m3 to about 200 Kg/h*m3.
The Applicant has surprisingly found that when the synthesis of 1,2,3,4-tetrachloro-hexafluoro-butane (A316) is performed in a microreactor, it is possible to obtain productivity significantly higher than the productivity obtained with the synthesis known in the art. More in particular, the productivity increases from hundreds of kilos to tons, despite the fact that the residence time is reduced of 104 times with respect to the synthesis known in the art.
Perfluoro ethers Rf-O-CX1X2-CX3X4-F are prepared by addition reaction of perfluorinated hypofluor... more Perfluoro ethers Rf-O-CX1X2-CX3X4-F are prepared by addition reaction of perfluorinated hypofluorites RfOF with perfluoroolefins CX1X2:CX3X4. The process is characterized by a molar ratio of hypofluorite to olefin in the reaction medium which is greater than unity. In the above formulas, Rf is linear or branched C1-5 perfluoroalkyl or perfluoro(oxy)alkylene containing at least one O atom and optionally an SO2F or COF group; X1-4 are independently F or ORf. For example, a flow of 3.3 N L/h CF3OF dild. with 6.6 N L/h He and a flow of 3.0 N L/h CF3OCF=CF2 were directed into CFC 316 (100 g) at -60°C for 7 h, followed by flushing of excess CF3OF with 3.3 N L/h He for 30 min, to show a 99.6% yield of addition products, these being the desired CF3OCF2CF2OCF3 and the undesired (CF3O)2CFCF3, with a selectivity of 99.9%. In a comparison example, where the flow of both reactants was 3.3 N L/h, selectivity for the desired isomer dropped to 71.2%. In a similar example using CF2=CF2 as the olefin, selectivity for CF3OCF2CF3 over dimerization and polymerization products was likewise improved, from 48.3% with a slight excess of olefin, to 99.3% using an excess of hypofluorite according to the invention.
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Particular emphasis is dedicated to safety issues since organic hypofluorites have the tendency to self-decompose forming gaseous compounds.The hypofluorites considered in this review are: CF3OF, CF2(OF)2, CF3CF2OCF2OF, CF3OCF2CF2OCF2OF, CF3O(CF2O)nCF2OF, CF3OCF2CF2OF, (CF3)2CFOF (CF3)3COF, FS(O)2CF2CF2OF, CF3OCF2CF2CF2OF, cyclo-(CF2OCF2OCF)-CF2OF, (CF3)2N-CF2OF
brought to the application of liquid lubricant films on
diamond-like carbon (DLC) coatings. Hard surfaces are
typically lubricated with fluorinated or perfluorinated organic
compounds, such as perfluoropolyethers (PFPE) (1). Many
attempts have been done to obtain a stable layer of PFPE
lubricant on the DLC surface by dip-coating or by vapour
deposition so as to minimize any friction and wear (2, 3).
Diamond-like carbons are formed by an amorphous mixture
of sp3 and sp2 hybridized carbon atoms with hydrogen atoms
incorporated in the structure (a-C:H DLC). We have established
a specific methodology for the straight-forward introduction
of perfluorinated groups with carbon-carbon bond formation
on a variety of unsaturated materials (4-8). Indeed, by using
this methodology, perfluorinated radicals can directly bond
to the sp2 sites of the DLC structure avoiding any spacer, that
usually decreases both thermal and chemical stabilities of the
resulting fluorinated layers.
have been recently developed as a new class of environmental friendly hydrofluoropolyethers (HFPEs) suitable as solvents,refrigerants and heat transfer.The synthetic methodologies for the preparation of this new class of uid have been reviewed and physical properties of selected α,ω-dimethoxyfluoropolyethers have been evaluated and compared with analogous hydrofluoropolyethers (H-FPEs) having -OCF2H as end-groups.Atmospheric implications and global warming potentials(GWP) of selected α,ω-dimethoxyfluoropolyethers have been also considered.
Particular emphasis is dedicated to safety issues since organic hypofluorites have the tendency to self-decompose forming gaseous compounds.The hypofluorites considered in this review are: CF3OF, CF2(OF)2, CF3CF2OCF2OF, CF3OCF2CF2OCF2OF, CF3O(CF2O)nCF2OF, CF3OCF2CF2OF, (CF3)2CFOF (CF3)3COF, FS(O)2CF2CF2OF, CF3OCF2CF2CF2OF, cyclo-(CF2OCF2OCF)-CF2OF, (CF3)2N-CF2OF
brought to the application of liquid lubricant films on
diamond-like carbon (DLC) coatings. Hard surfaces are
typically lubricated with fluorinated or perfluorinated organic
compounds, such as perfluoropolyethers (PFPE) (1). Many
attempts have been done to obtain a stable layer of PFPE
lubricant on the DLC surface by dip-coating or by vapour
deposition so as to minimize any friction and wear (2, 3).
Diamond-like carbons are formed by an amorphous mixture
of sp3 and sp2 hybridized carbon atoms with hydrogen atoms
incorporated in the structure (a-C:H DLC). We have established
a specific methodology for the straight-forward introduction
of perfluorinated groups with carbon-carbon bond formation
on a variety of unsaturated materials (4-8). Indeed, by using
this methodology, perfluorinated radicals can directly bond
to the sp2 sites of the DLC structure avoiding any spacer, that
usually decreases both thermal and chemical stabilities of the
resulting fluorinated layers.
have been recently developed as a new class of environmental friendly hydrofluoropolyethers (HFPEs) suitable as solvents,refrigerants and heat transfer.The synthetic methodologies for the preparation of this new class of uid have been reviewed and physical properties of selected α,ω-dimethoxyfluoropolyethers have been evaluated and compared with analogous hydrofluoropolyethers (H-FPEs) having -OCF2H as end-groups.Atmospheric implications and global warming potentials(GWP) of selected α,ω-dimethoxyfluoropolyethers have been also considered.
1,2,3,4-tetrachloro-hexafluoro-butane (also known as “A316”) is used as an intermediate compound in the synthesis of hexafluoro-1,3-butadiene (also known as “C4F6” or “HFBD”), a stable gas which is used in the semiconductor industry, in particular as etching gas for semiconductor fine processing.
The Applicant noted that despite 1,2,3,4-tetrachloro-hexafluoro-butane (A316) can be prepared by the methods known in the art, the productivity of the methods disclosed in the previous cited prior art documents was from about 1 Kg/h*m3 to about 200 Kg/h*m3.
The Applicant has surprisingly found that when the synthesis of 1,2,3,4-tetrachloro-hexafluoro-butane (A316) is performed in a microreactor, it is possible to obtain productivity significantly higher than the productivity obtained with the synthesis known in the art. More in particular, the productivity increases from hundreds of kilos to tons, despite the fact that the residence time is reduced of 104 times with respect to the synthesis known in the art.