Mattia Bassi

Some physical chemical properties of α–ω dihydroperfluoropolyethers

Abstract This paper describes the physico-chemical characterization and some properties of several α–ω dihydroperfluoropolyethers. Characterization has been carried out on the following properties: vapour pressure, density and viscosity as a function of temperature, glass transition temperature, refractive index and dielectric constant. The boiling point T b and the vaporization enthalpy Δ H v (calculated from vapour pressure data by means of the Clausius–Clapeyron equation) increase with the number of the backbone atoms N ; both T b and Δ H v are higher than the corresponding values for compounds with the non-polar chain end CF 3 and the difference decreases, but does not disappear, when the number of chain atoms is as large as 10–15. The cohesive energy density and the solubility parameter δ are also found to be larger. It is shown that the increase with respect to CF 3 terminated homologues has to be attributed, as expected, to the polar component due to the CF 2 H end group. The p – V – T properties can be predicted through a modified Peng–Robinson equation, where the critical temperature and pressure are obtained by group contributions. The comparison with the experimental data shows that the best group contribution data are those reported by Joback. The density increases and the expansion coefficient decreases with increasing chain length, as expected; at the same chain length the density is lower for materials with a CF 2 H end group; the difference decreases with increasing N . The viscosity also increases with molecular weight; its dependence on temperature is described by the well-known Arrhenius equation. The activation energy is a function of Δ H v , as predicted by the hole theory of Eyring for simple liquids. The glass transition temperatures are very low and depend both on the chain length and on the structure of the compound. While the refractive index is a weak function of chain length and structure, the dielectric constant is a strong function of both variables; a relationship between the dielectric constant and the polar component of the solubility parameter is suggested. Finally the group contributions of the CF 2 H group to the molar volume, vaporization energy, molar refractivity and molar polarizability have been determined, so that these data can be used to predict properties of new molecules.

Multispot, label-free biodetection at a phantom plastic–water interface

Recognizing and quantifying specific biomolecules in aqueous samples are constantly needed in research and diagnostic laboratories. As the typical detection procedures are rather lengthy and involve the use of labeled secondary antibodies or other agents to provide a signal, efforts have been made over the last 10 y to develop alternative label-free methods that enable direct detection. We propose and demonstrate an extremely simple, low-cost, label-free biodetector based on measuring the intensity of light reflected by the interface between a fluid sample and an amorphous fluoropolymer substrate having a refractive index very close to that of water and hosting various antibodies immobilized in spots. Under these index-matching conditions, the amount of light reflected by the interface allows straightforward quantification of the amount of antigen binding to each spot. Using antibodies targeting heterologous immunoglobulins and antigens commonly used as markers for diagnoses of hepatitis B and HIV, we demonstrate the limit of detection of a few picograms per square millimeter of surface-bound molecules. We also show that direct and real-time access to the amount of binding molecules allows the precise extrapolation of adhesion rates, from which the concentrations of antigens in solution can be estimated down to fractions of nanograms per milliliter.

Phase behavior and some calorimetric and physical properties of diurethanes from perfluoropolyether macromonomers

Density and calorimetric measurements have been carried out on copolymeric perfluoropolyethers of molecular weight ranging between 500 and 4700, terminated at both chain ends either with CH2OH or ethylurethane groups. Samples of the second series are models for perfluoropolyethers based polyurethanes. Density measurements point out that the terminal alcoholic group brings about a negative excess volume, which increases with decreasing the molecular weight; a lower excess volume is found for urethane-terminated molecules. Calorimetric traces, Tg, and Δcp at Tg show that alcoholic-terminated molecules are amorphous and one phase systems, while urethane-terminated compounds are crystalline; phase separation is observed for this last series when the molecular weight of the fluorinated segment is larger than 1000. The trend of Tg with molecular weight is discussed for one- and two-phase systems in the light of current theories for the glass transition. The decrease of the melting point with increasing the molecular weight for the urethane series can be described by the Flory equation for random copolymers.

Dispersed phantom scatterer technique reveals subtle differences in substrate recognition by phospholipase D inactive mutants

Stretch out: An elastic light‐scattering‐based method that makes use of phantom nanoparticles as a substrate organizer (see illustration) allowed the quantitative evaluation of the molecular recognition events between a series of inactivated mutants of phospholipase D and lysophosphatidylcholine. The results highlight the remarkable effects on binding capability caused by single amino acid substitutions.

A Measurement System For Investigating The Dielectric Properties Of Low-Loss Polymers

Abstract Polymers with low dielectric losses are largely used in several electromagnetic applications, for example in telecommunications cables, antennas, and microwave devices and components. The interest in studying their dielectric properties has a twofold motivation: (1) a scientific motivation, because the study of polymers is one of the main fields of material science; and (2) an industrial one, because a material with better dielectric characteristics—i.e. lower dielectric losses—is commercially more suitable for the market. The measurement of both dielectric constant and losses is not a straightforward task when dealing with low-loss materials. In this paper we describe a measurement system, based on a revisitation of the well known method of re-entrant cavity, which by a thorough electrical modeling of the sample holder allows absolute measurements to be performed on dielectrics with loss tangent as low as 10−4. The technique is validated on low-loss substrate materials of known characteristics. Measurement examples are reported concerning two fluorinated polymers based on TFE and ECTFE.

Portable, Multispot, Label-Free Immunoassay on a Phantom Perfluorinated Plastic

Despite the continuous advancements in bio-molecular detection methods and fluidic integration approaches, the realization of portable and high performance devices for diagnostic applications still presents major difficulties, mostly due to the need of combining adequate sensitivity with low cost of production, operational simplicity and rapidity. In this context, we have previously proposed a compact device composed of a smartphone and a custom-designed cradle, containing only a disposable sensing cartridge, a tiny magnetic stirrer and a few passive optical components. The detection principle is named Reflective Phantom Interface and is based on measuring the intensity of light reflected by the surface of an amorphous fluoropolymer substrate having a refractive index very similar to that of water. The reflectivity of dozens of spots is monitored in real time by the smartphone’s camera using the embedded flash LED as the illumination source. We tested the sensitivity and the repeatability of the combined device analyzing multiple spots of antibodies targeting an antigen commonly used as marker for diagnoses of HIV. Target concentrations as low as a few ng/ml can be rapidly and robustly determined by comparing the rate of increase of the signal after the addition of the sample with that measured after the subsequent addition of a standard solution with known concentration.