Jerome B. Lando

An infrared study of phase‐III poly(vinylidene fluoride)

Infrared spectra representative of crystalline regions of cast films of phase‐III poly(vinylidene fluoride) (PVF2) have been obtained by absorbance subtraction techniques using a FT‐IR instrument. The spectra contain more bands than previously reported and are not consistent with current models for the crystal structure. Several possible models and their relationship to the corresponding crystalline spectra of phase II and phase I are discussed.

Polymorphism of poly(vinylidene fluoride): potential energy calculations of the effects of head‐to‐head units on the chain conformation and packing of poly(vinylidene fluoride)

Potential‐energy calculations have been used to investigate the effects of head‐to‐head defects on the chain conformation and packing of poly(vinylidene fluoride). The calculations have demonstrated that such positional isomerism can contribute to the polymorphism exhibited by PVF2. We have shown that increased concentration of head‐to‐head defects or tetrafluoroethylene comonomer can cause the phase‐I form to become the favored structure for poly(vinylidene fluoride). The calculations have also proven capable of reflecting some of the subtle changes arising from the insertion of such defects. Packing calculations have shown that isomorphous replacement significantly affects the way in which PVF2 chains pack into a crystalline array. The differences in the structures proposed by Tadokoro and by Doll and Lando for phase II of poly(vinylidene fluoride) have been attributed to the inclusion of head‐to‐head defects in the polymer chains. In general, the potential‐energy functions have proven useful qualitativ...

The crystal structure of phase IV of poly(vinylidene fluoride)

The crystal structure of phase IV (polar α or δ phase) poly(vinylidene fluoride) was studied by x‐ray diffraction. Oriented phase IV was obtained by orienting phase II (α phase) and then corona poling at approximately 2 MV/cm. The resulting material is a mixture of phases I, II, and IV. Infrared spectra indicate that phase IV has the same chain conformation (TGTG′) as phase II. The reflections of phase IV can be indexed to an orthorhombic unit cell with lattice constants similar to the phase II lattice constants, a=0.496 nm, b=0.964 nm, and c (chain axis)=0.462 nm. There are two chains in this unit cell. The two chains pack with the chain dipole moments parallel. Three different ways of packing the chains were investigated: both chains up, one up and one down, and a statistical up‐down packing. It was found that to within a 97% confidence level, the chains pack with a statistical up‐down packing.

The polymerization and structure of mixed multilayers of ethyl and vinyl stearate

Abstract This study is a continuation of previous work done in this laboratory which has demonstrated the possibility of polymerizing multilayers of vinyl stearate to a controlled extent; thus, paving the way for the preparation of thin polymeric films. In the present work, the formation of mixed multilayers of various compositions of vinyl and ethyl stearate was studied. The polymerization reaction was initiated by cobalt-60 γ-radiation. The extent of polymerization was followed by internal reflection infrared spectroscopy (ATR), while the structure and orientation of the multilayers before and after the reaction were determined by polarized ATR infrared spectroscopy and by X-ray diffraction. It was found that the ethyl stearate creates a homogeneous solid solution with the vinyl stearate in monolayers and multilayers and lowers the extent of polymerization when it is present in a significant concentration. There is a high degree of order in the original monomeric film, which is proved to be made of many crystallites oriented normal to the film but randomly around the normal to the surface. Considerable order is maintained after the polymerization reaction.

ELECTRON BEAM RESISTS PRODUCED FROM MONOMER–POLYMER LANGMUIR–BLODGETT FILMS

Abstract Recent technological advances in very-large-scale integration are beginning to outstrip the technology used to produce these circuits. UV and optical lithography techniques are producing resist patterns with resolutions approaching the expected minimum. Application needs demand that this minimum be improved to achieve more features per unit area of circuit. We have achieved improved resolution of resist patterns. Through the use of monomer-polymer multilayers, fine line resolution, produced by way of a novel computer-controlled electron beam technique, is now possible. The relative ease and high reliability of multilayer formation ensures uniform films of a thickness an order of magnitude less than that of spin-cast films. The high electron sensitivities of these films enables excellent degradation (or polymerization) upon exposure to an electron beam. Final pattern resolution, for both positive and negative resists, is an order of magnitude higher than conventional resist resolution, offering possible improvement in circuit capability. Morphological studies of these multilayer films provide unique information on domain size and structure. The ultimate morphology of these films is shown to be dependent on deposition conditions as well as the substrate used.

The polymorphism of poly(vinylidene fluoride) IV. The structure of high-pressure-crystallized poly(vinylidene fluoride)

Abstract A detailed study of high-pressure-crystallized poly(vinylidene fluoride) has indicated that a mixture of low-melting phase II and high-melting phase I is present, rather than a new crystalline phase (phase III) as originally suggested. The relative amounts of phase I and phase II resulting from crystallization under pressure are a function of pressure and the degree of supercooling. Pressure crystallization at 285°C and 5500 atm results in samples which were pure phase I with an increased melting point of 187°C.

Polymerization of oriented monolayers of vinyl stearate

Abstract Oriented monolayers of vinyl stearate were photolytically polymerized with uv radiation at the air-water and nitrogen-water interfaces. Experiments were conducted on a film balance. Measurements of surface pressure, surface potential, relative surface viscosity, and infrared internal reflectance spectra provided means for characterizing reactants and products, and determining reaction kinetics. Complete conversion of monomer was achieved. The monolayer polymerization was found to be best fit by a second-order rate expression. The reaction rate constant increased as the irradiation area was increased.

Langmuir-Blodgett films as barrier layers in Josephson tunnel junctions☆

Abstract We report the observation of the Josephson current in tunnel diodes in which the barrier is a monolayer of poly(vinyl stearate) deposited by the Langmuir-Blodgett technique. The fabrication of these diodes is described and the resulting current-voltage characteristic is given. A critical current density of 140 A cm −2 was obtained at 4.2 KK, the energy gap of the superconducting electrode was observed, and hysteretic switching behavior was obtained. The characteristic time constant was estimated and was found to be very attractive for very high speed logic applications.

POLYMERIZATION OF TWO AMPHIPHILIC DIACETYLENES IN MULTILAYER FILMS

The mechanism of solid state polymerization of multilayers of heptadecadiyne-4,6-ol-1 and heptadecadiyne-4,6-acid-1 were studied. In each case the multilayers showed the same type of phase transition on polymerization as is observed in the bulk crystals. The crystalline packing of the multilayers was found to be the same as in the corresponding bulk materials. Finally a comparison of the behavior of the alcohol and the acid was made. Unlike in the alcohol polymer, the greater volume change on phase transition leads to crack formation in the acid polymer.

The polymorphism of poly(vinylidene fluoride) V. The effect of hydrostatic pressure on the melting behavior of copolymers of vinylidene fluoride

Abstract The high-pressure melting behavior of samples of vinylidene fluoride copolymerized with vinyl fluoride, trifluoroethylene, or tetrafluoroethylene indicate that the copolymers have a lower entropy of melting than the poly(vinylidene fluoride) homopolymers in the same phase. As the comonomer size increases, the entropy of melting decreases. High-pressure crystallization of copolymers of 91-9 mole% vinylidene fluoride-trifluoroethylene and 93-7 mole% vinylidene fluoride-tetrafluoroethylene results in a high-melting form of phase I (planar zig-zag).