Ilan Duvdevani

Synthesis and rheological properties of low charge density polyampholytes in nonaqueous solvents

Abstract The synthesis and rheological properties of a family of styrene-based polyampholytes are described. These polymers are composed mainly of styrene with relatively low levels of 4-vinylpyridine (4VP) and zinc neutralized sulphonated styrene (Zn-SS). Although these materials resemble in some instances the homogeneously-charged sulphonated polystyrene ionomers, marked differences in solution properties are noted. For example, in a single component nonaqueous solvent (such as xylene), the ampholytic ionomers are completely soluble, while the sulphonated ionomer requires the use of soluble polar cosolvents. Moreover, viscosity measurements over a broad shear rate range shows that these polyampholytes are effective viscosifiers possessing pronounced dilatant characteristics. This interesting behaviour can be varied over a broad shear gradient through minor changes in the polymer structure. The results show that through the interactions of 4VP and Zn-SS, a degree of control over physical properties is established which is not readily attained in other ionomeric materials. In an attempt to understand this particular rheological behaviour, an equation is proposed which summarizes on a molecular level the observed shear thickening behaviour. In its derivation, it is assumed that due to the shear gradient, intramolecular associations are transformed into intermolecular linkages. If the lifetime of these associations are longer than the relaxation time of the chain, an increase in the apparent molecular weight of the polymer will occur resulting in a rise in the viscosity of the polymer solution. Further implications of this equation are discussed with regard to associating-type polymer solutions.

Co-Continuity and Ozone Resistance of Bims Compounds

A co-continuous blend of a high ozone resistant rubber with high diene rubbers, or with a mixture of high diene rubbers, can provide a rubber blend that is both ozone resistant and wear and scuff resistant. High diene rubbers have excellent wear and scuff resistances, but are prone to ozone damage. The high ozone resistant rubbers are rubbers that have saturated backbone after vulcanization, such as BIMS. However, depending on the co-continuos morphology, not all co-continuous blends of an ozone resistant rubber with other rubbers are ozone resistant. In this study, a co-continuity index was proposed to measure the co-continuity morphology of 50/50 BIMS/GPR blends. GPR represents a general-purpose rubber and is a mixture of NR and BR in this study. It was found that BIMS compounds having their co-continuity indices greater than 0.7 are ozone resistant. These ozone-resistant compounds were prepared by first adding GPR followed by adding small N351 CB fillers, as compared with the other large N660 CB used in this work. Thus, smaller CB filler first presence in GPR appears to enhance GPR/BIMS phase compatibility during mixing with later added BIMS leading to strong intermixing between co-continuous phases.

Functional Water Soluble Polymers

Functional polymers are macromolecules containing functional groups (e.g. -OH, -COOH, hydrophobes) which have polarity/reactivity differences from backbone chains. Alternatively, functional polymers may be viewed as materials that have a function or a use. Functional polymers often show unusual or improved properties by virtue of enhancements in phase separation, reactivity or associations.