The Synthesis of Fluorine Containing Polysiloxanes. Part 1. The Synthesis of Fluorine Containing Cyclosiloxanes

A new facile preparative method for the synthesis of semifluorinated organocyclosiloxanes is reported. Ring closure of the dichlorosilanes with NaHCO₃ and pyridine gave a mixture of semifluorinated organocyclosiloxanes with cyclotrisiloxane as the main product in yields 95–98% with yield of cyclotrisiloxanes up to 80%.     

Theoretical investigation of the phase behaviour of model ternary mixtures containing n-alkanes,perfluoro-n-alkanes,and perfluoroalkylalkane diblock surfactants

We have used the hetero-SAFT-VR approach developed by McCabe and collaborators [Mol. Phys. 104, 571 (2006)] to investigate the phase equilibria of a number of binary and ternary mixtures of n-alkanes, perfluoro-n-alkanes, and perfluoroalkylalkane diblock surfactants. We focused our work on the understanding of the microscopic conditions that control the phase behaviour of these mixtures, with a particular emphasis of the effect on the liquid–liquid separation and the stabilisation of n-alkane + perfluoro-n-alkane mixtures when a diblock surfactant is added. We used very simple molecular models for n-alkanes, and perfluoro-n-alkanes that describe the molecules as chains with tangentially bonded segments with molecular parameters taken from the literature. In the particular case of semifluorinated alkanes or SFA surfactants, we used an hetero-segmented diblock chain model where the parameters for the alkyl and perfluoroalkyl segments taken from the corresponding linear alkanes and perfluoroalkanes, as shown in our previous work [J. Phys. Chem. B 111, 2856 (2007)]. Our goal was to identify the main effects on the phase behaviour when different perfluoroalkylalkane surfactants are added to mixtures of n-alkanes and perfluoro-n-alkanes. We selected the n-heptane + perfluoromethane binary mixture, and studied the changes on the phase behaviour when a symmetric (same number of alkyl and perfluoroalkyl chemical groups) or an asymmetric (different number of alkyl and perfluoroalkyl chemical groups) diblock surfactants is added to the binary mixture. We have obtained the phase diagrams of a wide range of binary and ternary mixtures at different thermodynamic conditions. We have found a variety of interesting behaviours as we modify the alkyl or/and the perfluoroalkyl chain-length of the diblock surfactants: the usual changes in the vapour–liquid phase separation, changes in the type of phase diagrams (typically from type I to type V phase behaviour according to the Scott and Konynenburg classification), azeotropy, and Bancroft points. We noted that the main effect of adding a symmetric or an asymmetric surfactant to the n-heptane + perfluoromethane mixture is to stabilise the system, i.e. to decrease the two-phase (liquid–liquid) immiscibility region of the ternary diagram as the surfactant concentration is increased. This effect becomes larger as the chain length of the surfactant is increased, which is consistent with a higher number of alkyl–alkyl and perfluoroalkyl–perfluoroalkyl favourable interactions in the mixture.     

Synthesis and characterization of semifluorinated polymers and block copolymers

The goal of the investigation presented here was to evaluate the influence of semifluorinated side chains on the bulk structure and the surface properties of polysulfones with different chain structure. Thus, segmented block copolymers consisting of polysulfone and semifluorinated aromatic polyester segments as well as polysulfones having semifluorinated side chains randomly distributed over the polymer backbone were synthesized and characterized. Oxydecylperfluorodecyl side chains were used because of their strong tendency for self-organization. The influence of the chain architecture on the self-organization as well as on the surface properties, particularly the wetting behavior, was examined. It could be shown that despite of the higher self-organizing tendency of block copolymers the surface properties of both polymer types are comparable and depend only on the concentration of side chains.     

Synthesis and characterization of a biphenyl perfluorocyclobutyl (BP‐PFCB) polyethylene glycol (PEG) blend compatibilizer

Polyethylene glycol (PEG) end‐capped trifluorovinyl ether (TFVE) telechelomer was synthesized in one step via esterification of 4‐(trifluorovinyloxy) benzoic acid. The new telechelomer was characterized by attenuated total reflectance Fourier transform infrared (ATR‐FTIR), elemental analysis, and by ¹⁹F and ¹H nuclear magnetic resonance (NMR) spectroscopy. The telechelomer and 4,4′‐bis(4‐trifluorovinyloxy)biphenyl (BPVE) were thermally copolymerized via step‐growth [2 + 2] cycloaddition at 160°C. The polymerization afforded PEG enchained biphenyl perfluorocyclobutyl (BP‐PFCB) copolymers that are solution processable and film forming. These copolymers were characterized by ATR‐FTIR, ¹⁹F NMR, and ¹H NMR. Gel permeation chromatography (GPC) gave number‐average molecular weight (M_n) ranging 11,000 to 12,000. Compatibilization of PEG and a commercial polymer BP‐PFCB was achieved utilizing the new PEG BP‐PFCB copolymer, 3‐co2‐4 . It was found that 5 wt% of 3 ‐ co2 ‐ 4 was ideal to reduce interfacial tension by scanning electron microscope (SEM). In addition, phase homogeneity was studied by differential scanning calorimetry (DSC). Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis of semifluorinated block copolymers by atom transfer radical polymerization

Two sets of styrene‐based semifluorinated block copolymers, one with a perfluoroether pendant group and another with a perfluoroalkyl group, were synthesized by atom transfer radical polymerization. Microphase separation of the block copolymers was established by small‐angle X‐ray scattering and differential scanning calorimetry (DSC). DSC measurements also showed that the perfluoroether‐based polymer had a low glass‐transition temperature (?44 °C). Contact‐angle measurements indicated that the semifluorinated block copolymers had low surface energies (ca. 13 mJ/m²). These materials hold promise as low‐surface‐energy additives or surfactants for supercritical CO₂ applications. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 853–861, 2004     

Simulations of inelastic electron tunneling spectroscopy of semifluorinated hexadecanethiol junctions

The inelastic electron tunneling spectroscopy (IETS) of semifluorinated hexadecanethiol junctions is theoretically studied. The numerical results show that the C-F vibration modes of semifluorinated alkanethiol series can not be detected, and the C-H stretching mode in IETS is related to the CH₂ vibration. It is demonstrated that the Raman modes are preferred over IR modes in IETS, which is in good agreement with the experimental measurements presented by Beebe et al. [Nano Lett., 2007, 7(5): 1364].      

Synthesis of amino terminated semifluorinated long-chain alkanethiols

The α,ω-diiodoperfluorooctane is added to undecyl-10-en-1-ol through AIBN initiation yielding the monoadduct in good yield (1,2-dichloroethane, 52%). This is added to N-allylphthalimide (AIBN initiation, 1,2-dichloroethane, 81%). The resulting diiodo compound is hydrodeiodinated with Bu₃SnH (toluene, 70%) and the alcohol function is converted to thioacetate through the Mitsunobu reaction (PPh₃, DIAD, THF, 75%). The two protecting groups, phthalimide and thioacetate, are removed with hydrazine to give the expected amino terminated semifluorinated long-chain alkanethiol (ethanol, 80%). This compound has been designed in order to form mixed fluorinated self-assembled monolayers (SAMs) with semifluorinated long-chain alkanethiol giving access to a new platform system for biosensors. Similar results are reported starting from the α,ω-diiodoperfluorohexane.     

Influence of Perfluorohexane-Enriched Atmosphere on Viscoelasticity and Structural Order of Self-Assembled Semifluorinated Alkanes at the Air-Water Interface

Abstract : Semifluorinated alkanes FnHm self-assemble into nanometer-sized surface micelles at the air-water interface. In this study, we investigated how an atmosphere enriched with perfluorohexane (PFH) influences the interfacial viscoelasticity and structural order of a monolayer of FnHm by the combination of dilational rheology and grazing-incidence small-angle X-ray scattering (GISAXS). The monolayers behaved predominantly elastic which can be attributed to the strong dipole repulsions of the surface domains. Enrichment of the atmosphere with PFH lead to an increase of the compressibility and a decrease of the elastic modulus without altering the structural ordering of the FnHm molecules into highly correlated nanodomains, suggesting the adsorption of PFH molecules to the free spaces between the domains. The capability of FnHm domains to retain the structural integrity in the presence of PFH gas is promising for the fabrication of stable microbubbles for sonographic imaging.     

Raman Study of Molecular Motions in Organic Solids

The paper presents Raman investigation of the nature of phonon motions in various organic solids and discusses chemical, physical as well as some practical applications of phonon studies. In order to characterize the nature of these motions. delocalization and relaxation of phonons are studied using the mixed crystal technique and temperature dependence of phonon spectra. The application of phonon spectra to investigate chemical perturbation of crystal structure in a group of closely related compounds is discussed. Some preliminary studies are presented on application of phonon spectra in solid state reactions. In regard to practical applications, it is shown that phonon spectra can be used to identify truly random solid solutions as well as various polymorphic forms of a given compound.