Dennis G. Peiffer

RHEOLOGY OF HYDROPHOBICALLY MODIFIED POLYMERS WITH SPHERICAL AND ROD-LIKE SURFACTANT MICELLES

Abstract Rheological measurements are used to probe the interactions between hydrophobically modified polymers and surfactant micelles. Hydrophobically modified hydroxyethylcellulose (hmHEC) with substitution levels of C12 and C16 hydrophobes between 0.9 and 7.3 mol% and hydrophobically modified polyacrylamide (hmPAM) with a sulfonated C12 hydrophobe at 1 mol% show the effects of hydrophobe type and content on interactions. Sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), and cetyldimethylamine oxide (CDMAO) surfactants show the effect of anionic, cationic, and nonionic surfactant interactions, respectively. Two patterns of association are observed: strong cooperative interaction and non-cooperative interaction. For the systems displaying cooperativity (e.g. SDS/hmHEC and CTAB/hmPAM), a large increase in viscosity is seen as a function of surfactant concentration, and the increase begins about a decade in concentration below the critical micelle concentration (cmc). For the non-cooperative interactions, the viscosity maximum occurs at concentrations higher than the cmc. For CTAB the addition of KBr and for CDMAO the addition of hexanol induce a sphere-to-rod transition in the surfactant phase. Whereas, the polymer-surfactant interaction is completely masked at high surfactant concentrations for spherical micelles, in the case of rod-like micelles high viscosity levels are maintained at high surfactant concentrations.

Bonding between precipitated silica and epoxidized natural rubber in the presence of silane coupling agent

Results of Monsanto rheometic studies and measurements of physical properties reveal that precipitated silica interacts chemically with epoxidized natural rubber (ENR) during high temperature (180°C) molding and the extent of chemical interaction increases in the presence of silane coupling agent, namely N-3(N-vinyl benzyl amino) ethyl-γ-amino propyl trimethoxy silane monohydrogen chloride. Fourier transform infrared spectroscopic studies show that silica is bonded to ENR through formation of Si—O—C bond, whereas in the presence of silane coupling agent, silica is bonded to the coupling agent through Si—O—Si bond, and ENR is bonded to the coupling agent through C—N—C bond formation.

Effect of silane coupling agent on the chemorheological behaviour of epoxidised natural rubber filled with precipitated silica

Abstract Results of measurements of physical properties and solvent swelling of the extrudates indicate that epoxidised natural rubber (ENR) interacts chemically with precipitated silica when the mix of the two was extruded at 150–170°C in a Monsanto Processability Tester (MPT). The extent of interaction between the rubber and the filler depends on the extrusion time, the volume fraction of the filler, the shear rate and the addition of the silane coupling agent, namely N-3-(N-vinyl benzyl amino) ethyl-γ-amino propyl trimethoxy silane monohydrochloride. The activation energy of the chemical interaction between ENR and silica decreases on the addition of the silane coupling agent.

Miscibility and immiscibility in functionalized associating polymer systems : polystyrene-poly(phenylene oxide) blends

Abstract The thermal properties of several families of polystyrene-poly(phenylene oxide), sulphonated polystyrene-poly(phenylene oxide), polystyrene-sulphonated poly(phenylene oxide), and sulphonated polystyrene-sulphonated poly(phenylene oxide) blends were studied by differential scanning calorimetry. The appearance of a single glass transition temperature, i.e. blend miscibility, depended on the level of sulphonation of one or both components of the blend. Even though blends formed from the unfunctionalized components were miscible over the complete composition range, miscibility was reduced as the sulphonation level increased in either component. A substantially broader range of miscibility was observed when both blend components were functionalized. Compared with blends containing one sulphonated component, where immiscibility could occur within a relatively modest sulphonation range (typically 2–4 mol%), blends with two sulphonated components retained miscibility over a substantially broader sulphonation range (typically 10 mol%). The results are interpreted in terms of the mean field theory involving interaction parameters for the individual monomer segments.

An investigation into the behaviour of SPBT and SPBT/PC blends

Thermal, wide angle X-ray scattering and light microscopy studies have been carried out on sulphonated poly(butylene terephthalate) (SPBT) and its blends with polycarbonate (PC). A better understanding of the morphology and behaviour of the ionomer SPBT as well as initial information on the miscibility and level of crystallinity of the new family of ionomer blends, SPBT/PC, has been obtained. The samples with a degree of sulphonation above 7 mol.% showed the partial miscibility as well as improved optical clarity with respect to blends of non-sulphonated PBT/PC.

Effect of surface oxidation of filler and silane coupling agent on the chemorheological behavior of epoxidized natural rubber filled with ISAF carbon black

On the basis of results of measurements of physical properties and solvent swelling of the extrudates, it has been observed that epoxidized natural rubber (ENR) interacts chemically with intermediate super abrasion furnace (ISAF) carbon black when the mix of the two was extruded at 130-160°C in a Monsanto Processability Tester (MPT). The extent of interaction between the rubber and filler depends on the following factors: extrusion time, carbon black loading, shear rate, and the extent of oxidation on the carbon black surface. Addition of the silane coupling agent, namely, N-3-(N-vinyl benzyl amino) ethyl-γ-amino propyl trimethoxy silane monohydrochloride, enhances the rate of the interaction.

Small-angle neutron scattering and neutron reflectometry study of a model graft copolymer

Abstract A model graft copolymer material consisting of polystyrene (PS) chains grafted onto a poly(ethyl acrylate) backbone was studied by small-angle neutron scattering (SANS) and neutron reflectivity. This 28 wt% PS graft material exhibited a lamellar phase morphology; it also produced abnormal butterfly isointensity patterns in SANS when uniaxially strained. It is believed that the polydispersity in structure of the copolymers is critical in producing the unexpected lamellar morphology.

Intramolecular mobility and its role in the glass transition temperature of ionic polymers

The glass transition temperature of ionic polymers is found to depend on the molar ionic cohesive energy, the universal gas constant and a factor (n) that is related to intramolecular interactions. The polyphosphates, polyacrylates and X, Y-ethylene ionenes polymer families are shown to follow the equation interrelating the above-mentioned variables. The significance of n can be understood by deriving various rules of constant specific heat at Tg (ΔCp). The results of this analysis show that approximately 23 of ΔCp is attributable to intersegmental interactions, while 13 of ΔCp is related to intramolecular forces. Similar relationships were established between the degrees of freedom of the polymer repeat unit and ΔCp. These rules are shown to be related to Wunderlichs ‘bead’ concept.

Study of polystyrene monolayers in two dimensions

Abstract The surface pressure of a series of monodisperse polystyrene monolayers covering a wide range of molecular weights was measured as a function of surface concentration and polymer molecular weight on an aqueous, i.e. hydrophilic, substrate. The determined experimental surface pressure-polymer surface concentration relationship corresponds closely to the theoretical scaling concepts. Interestingly, these relationships are dependent on the delivery solvent used in the formation of a polymer monolayer. An important implication of these studies is that the properties of the chains as observed in a particular solvent system (a three dimensional system) is retained, to a large extent, when the chains are placed onto an aqueous substrate and the solvent is evaporated. The solvent quality of the surface, in this particular instance, is poor. Therefore, it appears that the solvent qualith of the delivery solvent has a profound influence on the chain properties at the interfacial region.

Self-organization of graft copolymers at surfaces, interfaces and in bulk

The morphology in bulk and thin film of high-integrity graft copolymers has been investigated by small-angle neutron and light scattering, neutron reflectity and transmission electron microscopy. The model graft copolymers are based on two chemically incompatible blocks composed of an elastomeric poly(ethyl acrylate)(PEA) backbone onto which pendant monodisperse thermoplastic polystyrene (PS) are statistically placed. Two different levels of graft corresponding to an average of one and three per chain were investigated. In the bulk phase, the low graft-level shows irregular fractal-like structures while the high graft-level exhibits lamellar microdomains. In thin film, ordered structures were observed also in both compositions. The interphase adhesion between the PS and the PEA microdomain was investigated by elongating the copolymer films uniaxially. The low graft-level material exhibits normal behaviour characteristic of filler-reinforced rubber: the isotropic scattering pattern deforms in an anisotropic manner, i.e. ellipsoid-shaped with the long axis perpendicular to the stretching direction. An ‘abnormal butterfly’ pattern was observed with the high graft-level. The butterfly pattern is attributed to the deformation of the lamellar morphology of the copolymer.