Fluoroalcohols as nucleating agents in supersaturated vapors: Efficient clustering with water in the vapor phase

Fluoroalcohols in small concentrations in the vapor phase display striking enhancing effects on homogeneous nucleation of supersaturated aliphatic alcohols, and on the formation of water clusters by supersonic expansion. The enhanced nucleationeffects are attributed to the surfactant properties of fluoroalcohols, which lower the surface tension of the growing droplets, and therefore lower the barrier to nucleation

Colossal Dielectric and Electromechanical Responses in Self Assembled Polymeric Nanocomposites

An electroactive polymer nanocomposite, in which high dielectric constant copper phthalocyanine oligomer (o-CuPc) nanoparticles are incorporated into the block polyurethane (PU) matrix by the combination of “top down” and “bottom up” approaches, was realized. Such an approach enables the nanocomposite to exhibit colossal dielectric and electromechanical responses with very low volume fraction of the high dielectric constant o-CuPc nanofillers (~3.5%) in the composite. In contrast, a simple blend of o-CuPc and PU composite with much higher o-CuPc content (~16% of o-CuPc) shows much lower dielectric and electromechanical responses

Use of synchrotron radiation in plastics analysis

We demonstrate the application of synchrotron small angle X-ray scattering (SAXS) in measuring the thermodynamic properties of polymer blends. The polymers under investigation consist of poly(cyclohexyl acrylate) (PCHA) blended with the ortho and meta isomer of poly(bromostyrene) (P2BrS, P3BrS). Measurements of the absolute scattered intensity enable the determination of the second derivative of the Gibbs free energy of mixing with respect to the concentration, the location of the spinodal temperature, and the Flory-Huggins χ-parameter

Effect of isomer on polymer blends miscibility: A synchrotron small angle X-ray investigation

We use synchrotron small angle X-ray scattering (SAXS), calorimetry and cloud point measurements to investigate the thermodynamic of mixing in blends of poly(cyclohexyl acrylate) with the ortho and meta isomer of poly(bromostyrene) [P2BrS, P3BrS]. PCHA is miscible with P2BrS and P3BrS with lower critical solution temperature (LCST). Measurements of the absolute scattered intensity enable determination of the Flory-Huggins χ-parameter within the framework of the de Gennes random phase approximation. The following order is observed: χ(PCHA/P2BrS)<χ(PCHA/P3BrS). © 1998 Elsevier Science Ltd

Closed-loop immiscibility in a ternary mixture of homopolymers

Light scattering and calorimetric techniques were used to investigate the isothermal phase behaviour of a ternary polymer blend consisting of three pairwise miscible homopolymers. These homopolymers, polystyrene (PS), poly(2-chlorostyrene) (P2CIS) and polycyclohexylacrylate (PCHA), are apparently the first known examples of homopolymers that form a closed loop in the ternary isothermal phase diagram. The phase diagram of the ternary blend was determined by light scattering at 433 K, where all three pairs are below their respective lower critical solution temperature (LCST). The miscible compositions exhibit a single glass transition temperature (Tg) which follow a simple volume additivity relationship. Inside the immiscible closed-loop region, single Tgs are also observed, but these are shown to be consistent with the presence of two phases. Two binary interaction parameters (for the pairs PS-P2CIS and PS-PCHA) were determined from the locations of LCSTs. The interaction parameter between P2CIS-PCHA was determined by approximating the observed closed-loop region of immiscibility by the Flory-Huggins lattice model. In analogy with systems comprised of a mixture of two polymers and a solvent, the closed-loop immiscibility gap results from an asymmetry in the interaction parameters between the three pairs (a 'Δχ' effect). The following ordering was observed: χPCHA-P2CIS < χPCHA-PS ≈ χPS-P2C1S. This trend is consistent with the curvatures of the composition-dependent glass transition Tg(φ) plots. © 1994