A series of thin films composed of liquid crystalline polymer (LCP) and low molecular weight liquid crystal (LMWLC) was prepared by a solventcasting method or by a bar—coating method. LCPs were of mesogenic side chain type with strong or weak polar terminalgroups in the side chain portion. A mixture of smectic LCP (LCP with side chain of strong polar end) and nematic LMWLC formed a smectic phase in a LCP weight fraction range above 50 %. Also, a mixture of nematic LCP (LCP with side chain of weak polar end) and nematic LMWLC with strong polar group induced a new smectic phase in a LCP molar fraction range of 20–80 %. Reversible and bistable electro-optical effects based on light scattering were recognized for a smectic phase of a binary composite composed of LCP and LMWLC. A light scattering state caused by many fragmented smectic lamellae appeared in the case of application of an a.c. electric field below a threshold frequency (∼l Hz). Furthermore, application of a 100 Vp—p a.c. field of 1 kHz made the transmission light intensity increased to 94 % within a few seconds. The optical heterogeneity in asmectic layer composed of the side chain group of LCP was caused by the difference of twoforces based on both dielectric anisotropy of the side chain and electrohydrodynamic motion of the main chain. Since application of a low frequency electric field causes an ioniccurrent throughout the mixture film, it is reasonable to consider that an induced turbulent flow of main chains by an ionic current collapsed a fairly well organized large smectic layer into many small fragments, resulting in an increase in light scattering. The response speed of LCP upon application of an electric field increased remarkably by mixingLMWLC. In the case of a smectic mesophase, turbid and transparent states remained unchanged as it was, even though after removing an electric field.1

Such abistable and reversiblelight switching driven by two different frequencies of electric field could be newly realized by both characteristics of turbulent effect of a wellorganized large smectic layer of LCP and rapid response of LMWLC. We believe that the LCP/LMWLC mixture system is promissing as a novel type of “light valve” exhibiting memory effect (bistable light switching).

The surface properties of symmetric microphase separated diblock copolymers of polystyrene (PS) and polymethylmethacrylate (PMMA) were investigated using X-ray photoelectron spectroscopy (XPS), the specular reflectivity of neutrons and secondary ion mass spectrometry (SIMS). PS, the lower surface energy component, exhibited a preferential affinity for the free surface. For copolymers that are far from the bulk microphase separation transition (MST), the surface consists of a layer of pure PS. When the system is close to the MST the surface is a mixture of PS and PMMA. The PS surface excess can be described bya N-1/2 dependence, where N is the number of segments that comprise the copolymer chain. It is shown that the surface undergoes an ordering transition at a temperature T2 that is above that of the bulk MST. The ordering of the bulk lamellar morphology is induced by an ordering at the surface. This is analogous to the ferromagnetic order observed in systems such as Gd at temperatures above the bulk Curie temperature. The results here are discussed in light of previous work on copolymer surfaces and in light of mean field theory.

A systematic approach has been applied to neutron reflectivity data to study interdiffusion across an interface. It is shown that with this technique it is possible to probe interface broadening from ∼10Å to upward of 200 Å, the upper limit being already within the range of observation of other techniques such as Rutherford backscattering spectrometry (RBS), forward recoil spectrometry (FRES) and secondary ions massspectroscopy (SIMS). As example is analyzed the interdiffusion of a bilayered polymer system: a deuterated polystyrene (d-PS) layer on protonated polystyrene (h-PS).

We have measured neutron reflectivities from the surface of films of deuterated polystyrene (d-PS) and protonated polystyrene (PS) blends before and after annealing, and used the results to determine the concentration versus depth profile of the films. After annealing, the surface is enriched in d-PS, with a surface excess proportional to the bulk concentration of d-PS, in agreement with previous measurements using forward recoil spectrometry[l]. The decay of the enhanced concentration into the bulk occurs over a length approximately equal to the bulk correlation length (∼200 A), in closeagreement with that predicted by current mean-field theoryometry[2]. However, the agreement between the experimental reflectivity curves and the fitted curves is not completely adequate. Figure 1, a plot of k4R against k, demonstrates thi point for a 15% d-PS sample. The dashed line is the best fit assuming the mean field profile. The inset shows the corresponding concentration profile and a trial profile, solidline, which fits the data much better. The small deviation between the theoretical and trial profiles may be due to the assumption of the theory that surface interactions leading to enrichment is short ranged.

X-ray fluorescence using synchrotron radiation at glancing angles of incidence was used to measure interface widths for the highly immiscible polymer blend system polystyrene/polybromostyrene (PS/PBrxS, with bromination level x = 0.8 bromine atoms per monomer). The interfacial widths are for bilayers annealed for 4 hours and 24 hours at 141±1C are found to be 100± 20Å and 110±20Å respectively.

Secondary Ion Mass Spectroscopy (SIMS) has been used to study the surface and interfacial segregation of diblock copolymers in mixtures of the copolymer in the homopolymer. Symmetric, diblock copolymers of polystyrene (PS) and poly(methyl methacrylate) (PMMA), in either the PS or the PMMA homopolymers were investigated. In mixtures of the copolymer with the PS homopolymer, systematic surface enrichment of the copolymer as well as segregation of the copolymer to the polymer/Si interface or in the case of bilayered filmsto the polymer/polymer interface occurs with annealing treatments. These segregation effects persist over a large range of homopolymer molecular weights with changes in the kinetics of the segregation process being predominant.

Use of a Fourier—transform interferometer integrated with a variable incidence angle ellipsometer extends the spectral range and the capabilities of spectroscopic ellipsometry into the infrared. With a spectral range of 600 to 6600 cm—1, thick layers, such as epitaxial doped layers and polymers can be analysed.

A full description of this novel instrument will be given. Incidence angle can be variedautomatically to enhance signal/noise and the ellipsometric data can be obtained together with vibrational absorption bands information to give a characteristic “fingerprint ” of the layers.

Examples of spectra of HCN polymer on nickel, DMHS on aluminium and PMMA on silicon willbe presented for various incidence angles and layer thickness.

The behavior of polymer molecules at interfaces is an essential aspect of a wide variety of physical-chemical phenomena. For example, polymer molecules in the fiber-polymer interface play an important role in determining the mechanical properties of composites, and polymer molecules at the liquid-solid interface are critical in the stabilization of colloidal dispersions. In some cases polymer molecules are physically adsorbed at the interface and in other cases they are chemically bonded to the surface at one or more positions along the chain. To simplify the terminology, however, both cases will be referred to as polymer adsorption. The chains in the second case are said to be grafted to the surface. It is an example of this second case that we are concerned with in this paper, and in particular with polymer grafted to a finely divided substrate dispersed in a liquid.

Properties specific to silica—siloxane mixtures are analysed and discussed. The effect of polymer adsorption is interpreted from the Gaussian statistics of chains: the amount of adsorbed polymer Qr is proportional to the square root of the chain molecular weight. The kinetics of adsorption is described as a process of surface saturation. It is discussed as a function of the silica concentration. The effect of swelling of the mixtures is interpreted within the statistical framework proposed by Flory for ordinary gels.

The mechanical properties of epoxy resins and epoxy resin/graphite fiber composites are adversely affected by moisture absorption. Incorporation of masked isocyanates that unmask to release isocyanates in situ at the cure temperatures (150-177ºC) reduce the equilibrium absorption up to ∼70%. Dynamic mechanical analyses and stress-strain properties of epoxy resins containing masked isocyanates were examined to determine their effect on mechanical properties. The ultimate Tg of the epoxy is reduced by incorporation of masked isocyanate, but the actual Tg is comparable to the “as cured” Tg of the epoxy. The dynamic moduli up to the Tg are relatively unaffected. Ina number of cases, the initial modulus, elongation at break and peak stress are equal or better than the unmodified resins.

Over the years, the conventional involvement of short fiber reinforced composites in electrical applications has been as electrical insulation. Contrary to this approach, with the increasing need of better electromagnetic interference (EMI), radio—frequencyinterference (RFI) shielding and control of electrostatic charge distribution (ESD) for computer, defense, space exploration and some high—tech structural components, itis expected that the development of conductive polymeric composite materials will grow strongly and significantly.

An experimental investigation is designed to systematically evaluate the mechanical properties and electrical properties of metal fiber reinforced composites subjected to various loading conditions. In this study, chopped Inconel 601 (nickel base) metal fiber witha fixed fiber aspect ratio (length/diameter ratio) is used to reinforce commercially available thermoset polyester resin. Mechanical testing of custom made samples, failure analyses using visual inspection, light microscopy and SEM are conducted to understand the fracture behaviors and possible failure causes in such composites. The feasibility of using metal fiber polymeric composites in structural/electrical applicationsis discussed in this paper.

The deformation of poly(acrylic acid)—co—(acrylamide) gels and poly(vinyl alcohol)—poly(acrylic acid) gels under an electric field was investigated. Bending of these ionic gels was induced by an electic field. Using this deformation, we constructed a prototype of a robot hand having soft fingers, and an artificial fish able to swim.

Biaxial films of polyimide LARC—TPI and LARC—TPI/liquid crystal polymer Xydar® were extruded directly from the melt for the first time via an innovative new extrusion technique. Three types of films, neat LARC—TPI, LARC—TPI/lO wt percent and 30 wt percent blends were processed as a part of this NASA funded program. This new process offers an alternative technique to costly post—processing stretching of both solution cast and sheet extruded films. The post—processing step is often required to enhance certain properties. Processability was greatly enhanced by incorporating Xydar. The coefficient of thermal expansion was reduced from 34 ppm/ºC for the neat LARC—TPI to 15 ppm/º C for the 10 wt percent Xydar blend and ultimately down to I to 3 ppm/º C for the 30 wt percent blend films in the direction of extrusion. The maximum improvementin stiffness was realized by incorporating 10 wt percent Xydar (2.8 GPa up to 4.9 GPa). Tensile strength, however, experienced a drop as a result of Xydar addition, probably caused by inefficient mixing of the two phases.

The molecular structure of a series of perfluoroalkane oligomers having two F(CF2)n chains attached to a phenyl group in the para position has beenstudied by Fourier Transform and conventional Raman spectroscopy at ambient and low temperatures. From comparison with model compounds bands attributable to both the substituted phenyl ring and the perfluoroalkane chains could be assigned. In particular, the low frequency region was investigated as a function of temperature and pressure in order to assess the impact of the rigid aromatic core on the bandshapes and frequencies.

The effect of low power nitrogen and ammonia plasmas on carbon fibre surfaces has been studied using X-ray photoelectron spectroscopy(XPS) and scanning electron microscopy (SEM). A comparison is made between two polyacrylonitrile based fibres and a pitch based fibre. Grazing angle techniques have been exploited to probe only the first 12-15A of the fibre surface. Plasma treatments were carried out in an insitu plasma treatment cell which was attached to a PHI 5400 X-ray photoelectron spectrometer enabling the immediate effects of the plasma to be studied before the treated surface was exposed to air.

A method for determining particle diameters up to ca 500 rnm is described. X-ray data are obtained with an ultra-high resolution Bonse-Hart diffractometer and subsequently desmeared. The resultant data, viewed as the invariant argument h l(h), are interpreted as arising from a log-normal distribution of independent spherical particles. The distribution is characterized by its median value and breadth.

Several research projects in our laboratory have used an LCP based on 4,4'-dihydroxy,a-a' dimethylbenzalazine, that was first synthesized by Roviello and Sirigu 1.2 Copolymers with the following qeneral structure,

have been used in self-reinforcing polymer blends3 and are currently being used in small angle neutron scattering studies of the molecular conformation of an LCP in a nematic field. In this latter study, it is imperative that the polymer be well characterized, especially with respect to molar mass and thermal stability. This paper describes the effect of molar mass and thermal history on the thermal stability and transitions of this particular LCP.