New polyisobutylene-based model elastomeric ionomers. VIII. Thermal-mechanical analysis

A series of well-characterized telechelic polyisobutylene-based sulfonated metal-neutralized ionomers have been studied using thermal-mechanical analysis (TMA). These ionomers serve as models in the sense that the ionic groups are located exclusively at the chain ends and hence the ionomeric character is well defined. The chemical parameters varied are (i) molecular weight, (ii) molecular architecture (linear or triarm products), (iii) addition of excess neutralizing agent, and (iv) type of cation. The effect of the above parameters on the glass transition temperature and the softening temperature (after the rubbery plateau region) is presented. It is observed that the glass transition temperature is only slightly affected by the above parameters due to the very low ionic content in these ionomers (< 2 mol %). In the case of the triarm ionomer with excess neutralizing agent, the softening temperature following the rubbery plateau is much higher than that of the linear difunctional species. Linear monofunctional species do not show a rubbery plateau behavior and readily flow above their T_g in the absence or presence of excess neutralizing agent. The excess salt is most likely located at the ionic sites rather than being uniformly distributed throughout the matrix. Zinc-neutralized ionomers were found to have the lowest softening temperatures as compared to the corresponding calcium and potassium-neutralized ionomers. The covalent character of zinc is believed to be primarily responsible for this behavior. Thermal stability of these metalneutralized ionomers is not significantly different from the sulfonated hydrocarbon precursor polymer. However, the unneutralized acid precursor polymers start to discolor at relatively lower temperatures, thereby suggesting poorer thermal stability.     

New polyisobutylene-based model ionomers

Mechanical properties of tri-arm polyisobutylene based ionomers have been investigated. Number average molecular weights (¯M_n's) of the polymers were varied from 8,300 to 34,000. The ionomer of lowest ¯M_n (8,300) exhibits very low extension at break (～ 150%) while the others with ¯M_n's of 11,000, 14,000 and 34,000 show very high extensions, often exceeding 1,000%, and display relatively low permanent set and low hysteresis behavior. Since the ionic bonding is located exclusively at the chain ends, end-linked pseudo networks are formed due to coulombic attractions.At higher temperatures the coulombic interactions are weakened and the networks can be compression molded (～150°C).     

New polyisobutylene-based model ionomers

Strain induced crystallization has been observed at 25°C in low molecular weight three-arm star polyisobutylene ionomers at elongations exceeding about 550%. The sulfonated form of the polymer was neutralized with calcium hydroxide. The number average molecular weight of the polymer was only 9,000 with a dispersity ratio of about 1.7. This molecular weight is at the edge of the critical molecular weight for entanglements. Strain induced crystallization has been reported in the literature for very high molecular weight linear polyisobutylene. However, no such effects have been observed for linear, low molecular weight polyisobutylene and it has been stated it could not be induced. The cause for this strain induced crystallization in our materials is due to the presence of three ionic terminal groups per molecule which results in sufficient coulombic forces for maintenance of molecular orientation with strain without significant relaxation.     

New polyisobutylene-based model elastomeric ionomers. VI. The effect of excess neutralizing agents on solid-state mechanical properties

The role of excess neutralizing agents on the mechanical properties of three-arm star polyisobutylene-based model ionomers is discussed. The stress level, particularly at high elongations, is significantly affected by the presence of excess neutralizing agents, and these effects are observed with different cations such as potassium, calcium, and zinc. A morphological model is proposed that can account for the observed mechanical behavior.     

Melt rheology of ion-containing polymers. I. Effect of molecular weight and excess neutralizing agent in model elastomeric sulfonated polyisobutylene-based ionomers

Melt rheology of elastomeric triarm sulfonated polyisobutylene model ionomers has been studied. The molecular weights (M _n) of the polymers have been varied from 8300 to 34,000. The sulfonated materials were neutralized with potassium hydroxide either to the exact stoichiometric equivalence point or to twice this amount, i.e., 100% excess neutralizing agent was added. For comparison one nonsulfonated precursor of M _n = 8300 was also studied. It was observed that the introduction of one sulfonate group at each chain end of the triarm poly-isobutylene molecule changes the state of matter at room temperature. Specifically, the unsulfonated materials are viscous liquids while the sulfonated ionomers are solid elastomers at room temperature. The zero-shear melt viscosity of the unsulfonated precursor is 900 poise (90 Pa·s), at room temperature while for those materials neutralized with potassium hydroxide to the exact stoichiometric point it is above 9 × 10³ poise (900 Pa·s) at 180°C. As expected, the zero shear viscosity increases with an increase in the molecular weight. Significant ionic interactions still persist at 180°C as evident by the high viscosity of the ionomers. However, at higher frequencies (～600 rad/s), the melt viscosity decreases to about 5 × 10³ poise for the different molecular weight materials. The melt viscosity of ionomers containing 100% excess neutralizing agent shows a dramatic increase. The excess KOH is speculated to be incorporated into the ionic domains rather than uniformly distributed throughout the matrix. This results in an increased strength of the ionic aggregates, thereby increasing the melt viscosities. Thus, due to the very pronounced effect on rheological properties it is important to know not only the extent of neutralization (up to full neutralization) but also the amount of excess neutralizing agent, if any, which is present in the sample.     

弹性离聚体的研究进展

总结及评述了近年来弹性离聚体的研究进展,包括羧基离聚体、磺化离聚体及遥爪离聚体等,介绍了最近用新方法合成的新型离聚体.     

New polyisobutylene based model ionomers

Three-arm star polyisobutylene ionomers (¯M_n=8800) with terminal SO₃ M (M=K or Ca²) groups were synthesized and their mechanical properties investigated. Compression molded films displayed high elongations, i.e., -1000% for Ca² ionomers with lower values for the K counterions. Strain induced crystallinity was observed at higher elongations. Mechanical properties in general compared favorably with conventional covalently linked rubbery networks and were comparable and in some cases superior to EPDM-based ionomers carrying randomly distributed SO₃ M groups.For the first two parts see Proceedings, 28th IUPAC Macromolecular Symposium, Amherst, MA, July 11–16, 1982, p. 905 and 906     

Quaternary ammonium elastomeric ionomers by melt-state conversion

Quaternizations of benzyl bromide units in brominated poly(isobutylene-co-p-methylstyrene), or BIMS, elastomers with tertiary amines can be readily accomplished either by solution techniques or by melt reactive mixing. At temperatures of 130 °C and above, the nucleophilic substitution of benzyl bromide with ammonium bromide occurs instantaneously in an internal mixer. The conversion is around 95% for both dimethyl alkyl and dialkyl methyl amines. Suppressions in loss tangent measured in dimethyl alkyl amine melt quaternized BIMS indicate that molecular weight amplifications as a result of ionic association in these ionomers are in line with that obtained from solution quaternized BIMS. These melt quaternized BIMS ionomers become gels when their molecular weight amplification factors are greater than 1.5. Viscosity of BIMS can be raised significantly through quaternization to facilitate its mixing with thermoplastics. BIMS ionomers can also be added into bromobutyl innerliner compounds to enhance their green strengths. The efficiency in promoting ionic associations during melt mixing of BIMS with only 0.1 mol equiv. of dimethyl alkyl amines allows residual benzyl bromide units for subsequent curing.     

New polyisobutylene-based UV-curable flexible coatings

Summary New UV-curable solventless flexible transparent coatings have been prepared of acrylate- and methacrylate-capped linear or three-arm star polyisobutylenes PIB in the presence of conventional reactive diluents (multifunctional acrylate or methacrylate esters) and a UV-sensitizer. Solvent extraction studies show essentially complete network formation. The swelling ratios were surprisingly small indicating highly crosslinked gels. Films cast on glass, Teflon, stainless steel and aluminum and UV cured very strongly adhere to these surfaces and could not be removed without destroying the films. Films obtained by casting on aluminum, UV curing and subsequently dissolving the support by concentrated NaOH, contain no pinholes. DSC traces show a low and a high temperature transition characteristic of a domain separated morphology of soft PIB and hard acrylate or methacrylate segments. The exact positions of the transitions in the range from –57 to –45°C, and from 62 to 78°C are affected by the overall film composition. Tensile and elongation data have been obtained. The water absorption of these highly hydrophobic coatings is negligible.     

Characterization of polyisobutylene-based model urethane networks

Polyisobutylene-based model urethane networks have been prepared by crosslinking liquid α, ω-di(hydroxyl)polyisobutylenes, i.e., PIB-diols carrying exactly two ? CH₂OH functions, F _n = 2.0 ± 0.1, and rather narrow molecular weight distributions, M _w/M _n = 1.5?1.6, with tritriphenylmethyl isocyanate \documentclass{article}\pagestyle{empty}\begin{document}$$\rm{HC}\ (\hskip-6pt\hbox{---}p\rm{C}_6\rm{H}_4\hbox{---}\rm{NCO})_3$$\end{document}. Networks prepared with M _n = 1400 and 7500 PIB-diols, and with 90/10 and 80/20 mixtures of these PIB-diols (bimodal networks), have been characterized by extraction, by the Flory–Rehner swelling method, and by the Mooney–Rivlin equilibrium modulus method, and tested by stress–strain measurements. M _c values of the M _n = 1400 PIB-diol network obtained by swelling (1550) and by equilibrium modulus studies (1500) were in excellent agreement with the M _n of the prepolymer. Also the C₂ parameter was negligible in comparison to C₁, suggesting the absence of interchain entanglements. This is the first hydrocarbon-based polyurethane network that exhibits a negligible C₂ value by stress–strain measurements of unswollen samples. The M _c values of the M _n = 7500 PIB-diol were also in good agreement with the M _n of the prepolymer; however, C₂ was larger than C₁, indicating interchain entanglements. Evidence for strain-induced toughening was observed with both networks prepared with the M _n = 1400 and 7500 PIB-diols. The ultimate properties of the two bimodal networks did not show improvement over those of the individual constituents; however, the M _n's of the constituents were not very different.     

Imidazolium bromide derivatives of poly(isobutylene-co-isoprene): A new class of elastomeric ionomers

New imidazolium bromide ionomers are prepared by halide displacement from brominated poly(isobutylene-co-isoprene) (BIIR) with a variety of imidazole-based nucleophiles. N-alkylation of butylimidazole (BuIm) by the allylic halide functionality within BIIR provides stable imidazolium bromide functionality in high yields. Characterization of the resulting thermoformable ionomer by dilute solution viscosity and solid-state rheology shows the effects of ion-pair aggregation on material properties over a range of ionomer composition. Knowledge of BuIm alkylations is extended to produce thermoset ionomer derivatives through solvent-free reactions of BIIR with 1,1′(1,4-butanediyl)bis(imidazole) and imidazole, whose physical properties stem from both a covalent network and a network of ion-pair aggregates. A novel method of preparing these thermosets is described, wherein a poly(isobutylene-co-isoprene) derivative bearing pendant imidazole functionality is prepared, and heated with BIIR parent material to yield covalent crosslinks comprised of dialkylated imidazole moieties.     

Investigation of the structure and properties of polyisobutylene-based telechelic ionomers of narrow molecular weight distribution. I.

The solid state morphology of recently developed sulfonated polyisobutylene (PIB) telechelic ionomers with narrow molecular weight distribution (MWD) (M¯_w/M¯_n ≈ 1.15) was investigated. A small angle X-ray scattering (SAXS) peak often associated with the aggregation of the ionic species in the bulk, as well as a secondary peak, have been observed in the narrow distribution sulfonated PIB telechelic ionomers for the first time. Ionomers of difunctional and tri-arm architecture at several number average molecular weights (M¯_n) with one of several counterions were investigated and the preparation method was also considered in terms of observed SAXS behavior. Compression-molded films made from these narrow MWD telechelics were examined in detail using SAXS. Primary and secondary peaks were observed in the slit-smeared SAXS profiles up to an M¯_n of 27 kg/mol. The ratio of the interdomain spacings derived from these peaks (ca. 2 : 1) suggests cylindrical or lamellar ordering in the morphology in both difunctional and tri-arm ionomers. Pinhole SAXS images showed no azimuthal dependence in the scattering pattern and thus, this ordering is on a local scale. It was found that the counterion has an inconsistent effect on the smeared interdomain spacing associated with the SAXS peak. The smeared interdomain spacings were systematic with respect to architecture and M¯_n for solution cast Cs⁺ ionomers. The difunctional telechelics exhibited higher smeared interdomain spacings than tri-arms of comparable M¯_n and unlike the compression-molded films, the smeared interdomain spacings of the solution cast Cs⁺ telechelic ionomers increased systematically with increasing M¯_n. Even a broad MWD (M¯_n/M¯_n ≈ 1.8) tri-arm telechelic ionomer M¯_n of 20.6 kg/mol exhibited a diffuse primary peak in SAXS when solution-cast. However, it exhibited no peak when compression-molded. © 1997 John Wiley & Sons, Inc.     

Aggregation behavior of halato-telechelic ionomers in a low-polarity solvent

Summary The solution behavior of halato-telechelic ionomers (polybutadiene with carboxylate end groups) in a low-polarity solvent (tetrahydrofuran (THF)) was studied. It was shown that the degree of aggregation can be expressed as a function of polymer concentration by an empirical equation, DA - 10_c, where DA is the degree of aggregation, c is polymer concentration, and is a constant relating to the rate of aggregation with polymer concentration. It was also shown that the aggregation effect of the Na salt was larger than that of the Cs salt, which was reflected in the value of .     

Synthesis,characterization, and properties of novel polyisobutylene-based urethane model networks

This paper concerns the synthesis, characterization, and physical properties of novel polyisobutylene (PIB)-based urethane model networks prepared from diphenylmethane diisocyanate (MDI) and three-arm star PIBs capped with ? CH₂OH end groups (PIB(CH₂OH)₃). The PIB(CH₂OH)₃ starting materials were produced by the inifer method in the M?_n = 13,550–27,000 range. The best networks were obtained with NCO : OH = 1. Solvent extractions showed uncatalyzed network formation to be essentially complete and swelling studies indicated the expected architecture, i.e., M?_c = 2M?_n/3 and virtual absence of dangling chains. Stannous octoate was found to increase the rate of network formation in the absence of side reactions (i.e., allophanate formation), while other catalysts also accelerated undesirable reactions. The effect of molecular weight between crosslinks (M?_c) on network physical properties has been studied in the M?_c = 900–18,500 range. The tensile strength increases with decreasing M?_c up to a limiting value after which it sharply declines. Elongations at break decrease monotonously with decreasing M?_c. Low temperature tensile studies show higher tensile data at ?20°C, and, surprisingly, a retention of elongations at break. The T_g's decrease with increasing M?_c's until a plateau is reached at ?73°C. Hysteresis is fairly constant and permanent set is constant and low. The PIB-based urethane networks exhibit excellent hydrolytic stability, negligible moisture absorption, and outstanding heat-aging stability, far beyond what is expected for a polyurethane. Conceivably the thermal deblocking of the urethane group may be reversible (? NH? COO? CH₂? ? ? NCO + HOCH₂? ) because the isocyanate that arises in the highly hydrophobic PIB matrix recombines with the alcohol, and cannot react with moisture as in conventional urethane networks.     

Solution behavior of ionomers. III. Sulfo-EPDM-modified hydrocarbon solutions

The solution viscosity of polymer thickened hydrocarbons normally decreases markedly as temperature is increased. It has been observed that metal sulfonate ionomers, such as sulfonated ethylene propylene terpolymer, or sulfo-EPDM, when dissolved in a mixed solvent behave much differently. Specifically, sulfonated ionomers, dissolved in xylene or paraffinic oils with low levels of a polar cosolvent, can provide solutions whose viscosities are either relatively constant or can actually increase with increasing temperature. This isoviscosity effect can be manifested over broad temperature ranges and is mechanistically different from the behavior of conventional polymer solutions. This unusual behavior is explained on the basis of a simple equilibrium involving solvated ion pairs and is shown to be a specific example of a general phenomenon.     

Hydrophobic recovery behavior of PMMA and PEA ionomers treated with PSII

The surfaces of poly(methyl methacrylate) (PMMA)‐based and poly(ethyl acrylate) (PEA)‐based ionomers were treated either with plasma or with plasma source ion implantation (PSII), and their hydrophobic recovery behavior was studied by measuring water contact angles. It was found that the hydrophobic recovery of the plasma‐treated and PSII‐treated surfaces of PMMA ionomers was much slower than that of the acid‐form copolymers. This was due to the presence of hydrophilic ionic groups on the ionomer surface. In addition, in the case of the PMMA ionomers, a slow hydrophobic recovery behavior for a long period of time was observed. In the case of the PEA ionomer, the water contact angle values were found to be larger than those for the PMMA ionomers. When the contact angle values of the PMMA and PEA ionomers were compared to those of polystyrene (PS) ionomers, it was found that the order of ionomers showing higher angle value at comparable aging time was as follows: PS ionomer > PEA ionomer > PMMA ionomer. This was due to the difference in polarity and matrix glass transition temperature of the ionomers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3100–3106, 2003     

Influence of two-phase behavior of ethylene ionomers on diffusion of water

In this study, diffusion of water into ethylene ionomers neutralized with sodium or zinc cations (Na-ionomer and Zn-ionomer, respectively) was studied by in situ Fourier transform near infrared (NIR) spectroscopy. Water ingress was measured by NIR from the edge of the laminated glass toward the center and the measured water concentration profiles were analyzed by Fick's second law or the modified Jacobs–Jones model, which describes diffusion into a two-phase system of different density and polarity. It was found that the modified Jacobs–Jones model agrees well with the measured water concentration profiles of ionomers, while the Fickian model fits well to the poly(vinyl-butyral) (PVB) results. The modified Jacobs–Jones model was also confirmed to apply to water vapor transmission rate (WVTR) data of another sodium ionomer (Na-ionomer-HTM) with a higher melting temperature than Na-ionomer. The water diffusion coefficient for Na-ionomer, Zn-ionomer, and PVB are compared, and the diffusion parameters are discussed considering the higher-ordered structures of ionomers studied by small-angle X-ray scattering (SAXS). Simulating conditions that PV modules encounter in field applications, model projections show that Zn-ionomer and Na-ionomer-HTM give significantly lower water permeation than PVB, and due to its low diffusion coefficient, Na-ionomer will have significantly less water ingress than PVB. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48929.     

Simulation of the fracture behavior of elastomeric composites: Mechanical interactions at material interfaces

The fracture mechanics of multilayered elastomeric composites was simulated by the Blister Test using a polyurethane (PU)/A1 base plate interfacial assembly. In the various systems studies, and hard or soft intrposed layer (∼50 μm) separated the bulk matrix (∼ 1000 μm) from the metal counterface, with a hard-to-soft modules ratio of 1.70. Debonding was performed at a constant pressurization rate 1 × 10⁻⁸ m³/s corresponding to an average delamination rate of 0.25 m/s. Lateral hardening of the composite modules (negative transversal gradient of modulus) improved the fracture resistance (by 35%) at the material interface, in conformance with analytical predictions. Particle-dispersed and liquid-doped systems exhibited a sharp attenuation (40 to 90%) in the debond pressure. The latter results were substantiated by subjective assessement using optical microscopy, and were found consistent with stress concentration and weak conhesive fracture at the resin-substrate interface, respectively.     

Study of the behavior of polyester concretes containing ionomers as curing agents

Polyester concretes have been used in constructions for more than 20 years. This type of polymer concrete can advantageously replace traditional Portland concrete in situations that require fast consolidation of the material. Otherwise, polyester concretes are usually more expensive than Portland concretes. Part of the high cost of the polyester concretes is due to the fact that the aggregates used in the formulation of the concretes need to be dried prior to their incorporation into the polymer matrix. In this work, the use of different curing systems (methacrylic acid and maleic anhydride) was investigated to test the hypothesis that the introduction of acid functionalities into unsaturated polyesters based on isophthalic acid could both restrict the detrimental effect of moisture in the curing process and also improve interfacial interactions even in polyester concretes containing wet aggregates. In this work, as there was no search for ways to reduce cost of polyester concretes and also to contribute to the environmental preservation, unsaturated polyesters were synthesized from PET bottles and tested in the fabrication of concretes by reacting them with a conventional curing agent (styrene). Gel permeation chromatography, infrared spectroscopy, and electron microscopy were used to monitor and analyze the production of unsaturated polyester resins and concretes. Mechanical properties were also evaluated by compression tests. Results showed that methacrylic acid and maleic anhydride, when used as curing agents, led to the production of polyester concretes having higher mechanical properties in both dry and wet states than conventional polyester (based on isophthalic acid) concretes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008