SYNOPSISBlends of poly(styrene)-bloch-poly(ethene-co-but-l-ene)-bloch-poly(styrene) (SEBS) with isotactic polypropylene (PP) and syndiotactic PP, respectively, were investigated. The morphology was observed by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The cryofracture surfaces studied by SEM did not show any particles that were pulled out, so that a good compatibility between SEBS and different PPs could be assumed. The multiphase character of the blends could be well detected by TEM of RuO, stained samples. TEM micrographs of two-layer specimens revealed that SEBS tends to diffuse into the PP phase under formation of micelles. The block copolymer shows a reorientation phenomenon of large domains at the interface before the diffusion into the PP phase occurs. The interfacial strength as a function of annealing time was measured by a peel test of two-layer specimens. Mechanical properties are studied and related to the blend morphology.

No abstract

The effect of magnetic fields on the orientation and properties of 4,4'-bis(2,3-epoxypropoxy)-alpha-methylstilbene cured with sulfanilamide has been studied. This epoxy system is initially isotropic and forms a smectic A phase upon curing. A magnetic field was applied during the cure reaction, resulting in alignment of the molecules along the direction of the applied field. Measurement of the orientation parameter of the fully cured material by wide-angle X-ray scattering (WAXS) showed that orientation improved with an increase in field strength. The orientation parameters of the smectic layer normals calculated from the inner reflection of the WAXS pattern attained a maximum level of approximately 0.8 at a field strength of approximately 12 T. The orientation parameters calculated from the outer reflection of the WAXS pattern were considerably lower, possibly due to the presence of amorphous regions associated with domain boundaries or the loss of molecular alignment within the smectic layers due to topological restrictions of the cross-linking sites. Orientation resulted in an anisotropic linear thermal expansion coefficient after curing, although the overall volumetric expansion was constant. The elastic tensile modulus increased with the square of the orientation parameter, attaining a maximum value of 8.1 GPa, compared to 3.1 GPa for the unoriented material. The change in modulus with orientation could be fit with a simple model for the modulus of anisotropic materials.

Using the Langmuir Blodgett (LB) technique, monolayers of spherical polymer particles were investigated at the air-water interface. In this study, LB methods were used to examine particle interactions, packing, morphology, and viscosity of polymer films. Films composed of polymer microgels (diameters of 113-427 nm) having a block-copolymer dispersant were investigated through isotherm, atomic force microscopy imaging, and two-dimensional (2D) viscosity studies. During monolayer formation, the effect of the dispersant and particle size on the behavior of the isotherms was examined. The contact cross-sectional area of the isotherms for these spheres was compared to the ideal hexagonal close packing (hcp) model. Initial investigations concerning the flow properties of the particles in 2D slurries were also performed. In addition, spherical hyperbranched polymer particles (≈60 nm) with and without a modified hydrophilic surface were also studied using isotherm and hysteresis experiments and the hcp model. Both of these studies may show the influence of surface composition and particle size on the interaction of polymer particles at the airwater interface.

A C60 derivatized triarm poly(ethylene oxide) copolymer was synthesized and characterized. The soluble polymer produced spread at aqueous interfaces to form highly expanded fluid Langmuir monolayers. The onset area of 1300 Å2/arm is likely due to the polymer disrupting cohesion between C60 units. Compression/expansion studies revealed a significant elastic region, beyond which the C60 units condensed, and a compact rigid and irreversible monolayer formed.