Structure-property comparison of sulfonated and carboxylated telechelic ionomers based on polyisoprene

Abstract

The structure and properties of polyisoprene-based telechelic ionomers having neutralized terminal sulfonate and carboxylate groups have been compared. In general, the mechanical properties of these materials suggest that metal sulfonates form stronger aggregates than the aggregates formed by metal carboxylates. This agrees with the results of previous workers who made similar comparisons for randomly substituted ionomers. Small-angle X-ray scattering data indicate that the periodic spacings between metal sulfonate aggregates are consistently higher than for the carboxylate ionomers, suggesting that the metal sulfonate aggregates may contain more ion pairs per aggregate than the metal carboxylate aggregates. The phase boundary between the ionic and nonionic regions is very sharp for both sulfonate and carboxylate ionomers.

Synthesis and characterization of poly (styrene‐co‐vinyl phosphonate) ionomers

“…Lundberg and Makowski6 showed that for a fixed level of functionality, the melt viscosities of the sulfonated ionomers were two to three orders of magnitude higher than those of the carboxylate analogs. Other investigations7–9 also observed similar differences in the properties of carboxylate and sulfonate ionomers. The differences are due to the fact that sulfonic acid (pK a ∼1) is a much stronger acid than carboxylic acid (pK a ∼4–5), which results in stronger electrostatic attractions between the sulfonate ion‐pairs than the carboxylate ion‐pairs.…”

Hybrid ionic/covalent polymer networks derived from functional imidazolium ionomers

“…At low elongations, the tensile strength of the two ionomers was superiour to that of IIR‐Acrylate‐XL, with Young's modulus values of 0.97 MPa for IIR‐BuImBr and 0.95 MPa for IIR‐VImBr‐XL, versus just 0.45 MPa for IIR‐Acrylate‐XL. This data demonstrates the ability of ionic aggregation at 25 °C to provide exceptional tensile strength, given that IIR‐BuImBr performed well while lacking a covalent network …”

“…Figure provides static modulus measurements recorded as a function of time for samples held at 100°C and a fixed shear strain. The non‐crosslinked polymers, IIR‐Acetate and IIR‐BuImBr, relaxed extensively, since they lacked the covalent network needed to prevent polymer chains from moving through their entanglements . The static modulus of IIR‐Acetate declined continuously, reaching zero stress in less than one minute.…”

Matched Random Ionomers: Carboxylate vs Sulfonate

“…Because of the difficulty in synthesizing "matched" ionomers, this work still represents the only direct comparison of the melt rheology for randomly functionalized ionomers with different anion type; the conclusion that sulfonation yields stronger associations and higher viscosities (vs carboxylation) has become essentially axiomatic. 2,5,6 Recently, we 7 have applied Lundberg and Makowski's 4 sulfonation procedure to styrene-ethylenebutene (SEB) random terpolymers of narrow molecular weight distribution, synthesized by anionic polymeri-zation and catalytic hydrogenation; that work demonstrated and quantified the influence of both chain length and degree of sulfonation on the melt dynamics. 7 Lundberg and Makowski's parallel carboxylation procedure employed the complex between n-butyllithium (n-BuLi) and tetramethylethylenediamine (TMEDA) to lithiate the aromatic ring, 8 followed by reaction with CO 2 .…”