Physicomechanical and dielectric properties of magnesium and barium ionomers based on sulfonated maleated styrene‐ethylene/butylene‐styrene block copolymer

Ionomers, containing both carboxylate and sulfonate anions on the polymer backbone, based on metal cations like Mg⁺² and Ba⁺² were prepared by sulfonating maleated styrene‐ethylene/butylene‐styrene block copolymer, hereafter referred to as m‐SEBS, followed by its neutralization by metal acetates. Infrared spectroscopic studies reveal that sulfonation reaction takes place in the para position of the benzene rings of polystyrene blocks and metal salts are formed on neutralization of the precursor acids. Dynamic mechanical thermal analyses show that sulfonation causes increase in T_g of the rubbery phase of m‐SEBS and decrease in tan δ at T_g of the hard phase, along with formation of a rubbery plateau. The changes become more pronounced on neutralization of the sulfonated maleated SEBS, and the effect is greater in the case of Ba salt. Dielectric thermal analyses (DETA) show that incorporation of ionic groups causes profound changes in the dielectric constant (ϵ′) of m‐SEBS. In addition to the low temperature glass–rubber transition, the plot of ϵ′ vs. temperature shows occurrence of a high‐temperature transition, also known as the ionic transition. Activation energy for the dielectric relaxation could be determined on the basis of frequency dependence of the ionic transition temperature. Two values of the activation energy for the dielectric relaxation refer to the presence of two types of ionic aggregates, namely multiplets and clusters. Incorporation of the ionic groups causes enhancement in stress–strain properties as well as retention of the properties at elevated temperatures (50° and 75°C), and the effect is more pronounced in the case of Ba ionomer. Although sulfonated ionomers show greater strength than the carboxylated ionomers, the sulfonated maleated ionomers show higher stress–strain properties in comparison to both sulfonated and carboxylated ionomers. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 816–825, 2000     

Some properties of styrene‐based ionomers. I

Some properties of styrene‐based ionomers containing alkali metal salts of acrylic acid or methacrylic acid have been investigated. A study has been conducted to examine the influence of the acidic content and nature (acrylic or methacrylic) and the nature of the alkali metal salt on the glass transition temperature, density, melt index and activation energy of a flow of the styrene‐based ionomers. The present studies have indicated that the temperature of glass transition (T_g) of sodium ionomers increases as the sodium content rises and the region of the glass transition broadens. The T_g's of the styrene‐acrylic acid (S‐AA) ionomers do not depend on the nature of the alkali metal introduced into the copolymer. The density of films rises with the content of acid or salt introduced to the polystyrene chain. The melt index of the investigated ionomers depends on the amount and type of the introduced acid and salt as well as on the molecular weight of the initial copolymer. The energy of activation of the flow is independent of the polymer molecular weight; however, the energy of activation of flow of the ionomers increases with larger ionic radii of the introduced alkali metal. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 55–62, 2003     

Synthesis and mechanical properties of poly(styrene-b-lsobutylene-b-styrene) block copolymer lonomers

Linear and three-arm star poly(styrene-b-isobutylene-b-styrene) (PS-PIB-PS) block copolymer ionomers possessing various counterions and levels of sulfonation were synthesized by sulfonating the polystyrene blocks of PS-PIB-PS block copolymers. Analysis of compression-molded films of the ionomers showed that the incorporation of sulfonate groups into the polystyrene blocks of these materials resulted in an increase in tensile strength, a decrease in elongation at break, and a persistence of elastic properties to much higher temperatures as compared with unsulfonated precursors. Among all counterions studied, zinc resulted in the strongest ionomers and potassium yielded the most easily processed ionomers. Dynamic mechanical analysis showed that the block copolymer ionomers possessed a phase-separated morphology; however, anomalous relaxations observed during the first heating cycle, but that were substantially reduced or completely absent in subsequent cycles, implied that strong ionic interactions were causing reduced processability and the formation of nonequilibrium morphologies. The observed relaxations were interpreted to be domain rearrangements brought about by the thermal energy supplied by the dynamic experiment. Annealing of films of relatively low ionic contents yielded viscoelastic behavior that was consistent with an equilibrium morphology characterized by phase-separated, partially sulfonated polystyrene domains of the same density and size as the polystyrene domains of the unsulfonated precursor. Compression molded films of high ionic content yielded a higher rubbery plateau modulus than the unsulfonated precursor, suggesting a different morphology. Solution-cast films of zinc ionomers exhibited two values for the rubbery modulus, a higher values at temperature below the T_g of polystyrene and a lower value at temperature above the T_g of polystyrene. Thermogravimetric analysis revealed the major mass-loss process of the parent, linear block copolymer at 417°C (mid-point) and of the tetramethyl ammonium ionomer at 431°C.     

Proton conducting materials based on thermoplastic elastomers silica composites

In this research, ionomeric composites based on organophilized silica (SIL) and a thermoplastic elastomer (HSBR), were prepared and characterized from a microstructural and electrical point of view. DSC was used to confirm silica sulfonation and FTIR to characterize the polymer before and after sulfonation reaction. DSC and DMA analysis show that T_g^HPB remains constant in all the samples studied. T_g^PS measured through DMA presents an increase of about 40°C in the sample containing both the sulfonated filler and the sulfonated polymer matrix. The resulting materials can be easily processed to yield thin films (thickness 0.2–0.4 mm) with outstanding proton conducting properties (10^?2 S · cm^?1). The suitability for film formation and good electrical properties is indicative of their potential use as electrolytes in polymer fuel cells. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2715–2720, 2003     

Characterization and properties of sPS/PET/SsPS‐K engineering plastic alloys

The compatibility, crystallization behavior, and mechanical properties of syndiotactic polystyrene (sPS)/polyester (PET)/potassium salt of sulfonated syndiotactic polystyrene (SsPS‐K) were investigated. DMA results showed that all the alloys showed one T_g and the half‐peak width of the sPS/PET/SsPS‐K alloys became narrower compared with that of sPS/PET alloys, which decreased with an increasing content of the SsPS‐K ionomer. The results of DSC showed that the T_m of sPS and PET of the alloys was similar to those of the pure materials and did not change with the content of the SsPS‐K ionomer, while the initial crystallization temperature (T₀) and crystallization temperature at peak (T_p) increased. The crystallization velocity of PET increased with an increasing content of SsPS‐K. The TMA results showed that the alloys could retain the perfect heat proof property of sPS. SEM micrographs showed that the addition of SsPS‐K could reduce the PET domain dimension and enhance the adhesion between the PET domains and the matrix. With an increasing content of SsPS‐K, the PET domain dimension was reduced continuously and dispersed more evenly. The ternary alloys had better mechanical properties and significantly higher unnotched Izod impact strength than those of the alloys without SsPS‐K. When the weight ratio of sPS/PET/SsPS‐K was 85/15/4, the impact strength reached a maximum of 11.5 kJ/m², which was about three times that of pure sPS, and still had a higher tensile strength, flexural strength, and storage modulus, which were 38.8, 54.2, and 1.55 × 10⁴ MPa, respectively. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 656–661, 2002     

Some properties of styrene‐based ionomers II

Some properties of styrene‐based ionomers obtained from copolymers styrene (S) and acrylic acid (AA) or methacrylic acid (MA) obtained in emulsion containing alkali metal salts have been investigated. A study has been conducted to examine the influence of the acid content and nature (acrylic or methacrylic) and nature of alkali metal salt on the glass transition temperature, density, melt index, and activation energy of flow of the styrene‐based ionomers. The present studies have indicated that the temperature of glass transition (T_g) of sodium ionomers increases as the sodium content rises, but the increase is lower than in the case of the ionomers based on copolymers obtained in bulk. The density of films rises with the content of alkali metal salt introduced to the polystyrene chain, and it is higher than in the case of the ionomers based on copolymers obtained in bulk containing almost the same content of alkali metal salts. Styrene ionomers containing alkali metal acrylates have higher densities than those containing alkali metal methacrylates. The melt index of the investigated ionomers depends on the amount and type of introduced acid and salt, as well as on the molecular weight of the initial copolymer. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 268–275, 2005     

Mechanical and chemical properties of poly(styrene‐isobutylene‐styrene) block copolymers: Effect of sulfonation and counter ion substitution

In this study, the mechanical and chemical properties of a series of sulfonated poly(styrene‐isobutylene‐styrene) (SIBS) block copolymers were evaluated using a combination of nanoindentation, dynamic mechanical analysis (DMA), elemental analysis (EA), Fourier transform infrared spectroscopy (FTIR), water absorption, and small angle X‐ray scattering studies (SAXS). The materials properties were characterized as a function of the sulfonation percent in the block copolymers, as well as a result of the counter‐ion substitution with Mg²⁺, Ca²⁺, and Ba²⁺. Nanoindentation studies revealed that the elastic modulus (E) and hardness (H) increase with sulfonation up to a certain level, at which point, the effect of water content further hinders any mechanical reinforcement. The incorporation of counter‐ions increases E and H, but the results are dependent upon the size of the counter‐ion. DMA results showed that the polymer maintained the glass transition temperature (T_g) of the polyisobutylene (PIB) segment (?60°C) regardless of the sulfonation level or counter‐ion substituted. However, both the shoulder of the PIB T_g (?30°C), which was probably caused by a Rouse‐type motion, as well as the T_g of polystyrene (105°C) disappeared upon sulfonation. Counter‐ion substitution increased the storage modulus of the rubbery plateau, which is indicative of a stronger and more thermally stable crosslinked complex formation. Additional unique relaxations were observed with the counter‐ions, and could be attributed to the stretching/rotation of the S? O bond and the interaction of the cations with the oxygen in the sulfonic group. FTIR results also revealed a unique shifting of the asymmetric S? O band when counter‐ions were added. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40344.     

Blending of styrene‐block‐butadiene‐block‐styrene copolymer with sulfonated vinyl aromatic polymers

Different polymers containing sulfonic groups attached to the phenyl rings were prepared by sulfonation of polystyrene (PS) and styrene‐block‐(ethylene‐co‐1‐butene)‐block‐styrene (SEBS). The sulfonation degree (SD) was varied between 1 and 20 mol% of the styrene units. Polyphase materials containing sulfonated units were prepared by blending styrene‐block‐butadiene‐block‐styrene (SBS), with both sulfonated PS and sulfonated SEBS in a Brabender mixer. Such a procedure was performed as an alternative route to direct sulfonation of SBS which is actually not selective towards benzene rings because of the great reactivity of the double bonds in polybutadiene (PB) blocks to sulfonation agents. Thermal and dynamic‐mechanic analysis, together with morphology characterization of the blends, is consistent with obtaining partially compatible blends characterized by higher T_g of the polystyrene domains and improved thermal stability. © 2001 Society of Chemical Industry     

Synthesis and thermal properties of telechelic poly(lactic acid) ionomers

Telechelic poly(lactic acid) (PLA) ionomers were synthesized using a chemical recycling process. A transesterification reaction between a commercial PLA and 2-hydroxyethyl methacrylate or ethylene glycol was used to produce a hydroxy-terminated PLA. The hydroxy-terminated PLA was then reacted with itaconic anhydride to produce terminal carboxylic acid groups, which were neutralized with appropriate metal acetates to produce Na-, Li-, K-, Zn-, Ca- and Y-ω- and α,ω-telechelic PLA ionomers. ¹H NMR spectroscopy was used to confirm the presence of the itaconic acid end-groups and FTIR spectroscopy was used to quantify the extent of neutralization. The addition of the ionic groups increased the glass transition (T_g), and T_g increased as the strength of the ion-pair increased. The ionic groups suppressed crystallinity, especially when multivalent cations were used.     

Pre‐melting temperature effect on the isothermal melt crystallization and multiple melting behavior of syndiotactic polystyrene

This work examined how pre‐melting temperature (T_max) affects the isothermal melt crystallization kinetics, the resulting melting behavior and crystal structure of syndiotactic polystyrene (sPS) by using differential scanning calorimetry (DSC), polarized light microscopy (PLM) and the wide angle X‐ray diffraction (WAXD) technique. Experimental results indicated that raising T_max decreased the nucleation rate and the crystal growth rate of sPS. The Avrami equation was also used to analyze the overall crystallization kinetics. The Avrami exponent n and rate constant K were determined for different T_max specimens at various crystallization temperatures (T_c's). Our results indicated that the nucleation type of sPS is T_max and T_c dependent as well. Evaluation of the activation energy for the isothermal crystallization processes revealed that it increases from 375 kJmol^?1 to 485 kjmol ^?1 with an increase of T_max. From the melting behavior study, we believe that the T_max and T_c‐dependent multiple melting peaks are associated with different polymorphs as well as recrystallized crystals formed during heating scans. Moreover, the percentage content of α form in the crystals formed under different crystallization conditions was estimated through WAXD experiments.     

Sulfonation degree determination of polystyrene ionomers by using adiabatic bomb calorimeter

Sulfonation degree determination of sulfonated polystyrene and the corresponding ionomers are performed by adiabatic bomb calorimeter. The theoretical calculations from the band energies for the combustion enthalpy values (calorific values) and the experimental values are compared, and a linear relation between the values is found. Sulfonation and neutralization processes are examined by elemental sulfur analysis and atomic absorption spectroscopy (AAS). It was obvious that increasing sulfonation degree yields a decrease in the combustion enthalpy values, as it is expected from the theoretical calculations. In addition, metal ion incorporation to the structure deviates the experimental combustion enthalpy values especially for the ionomers which have higher sulfonation degrees. This is due to the formation of a higher degree aggregation. © Wiley Periodicals, Inc. J Appl Polym Sci 100: 4684–4688, 2006     

Synthesis of tellurium containing syndiotactic polymethyl methacrylate using diphenyl ditelluride as a novel initiator

The synthesis of syndiotactic polymethyl methacrylate containing tellurium by using diphenyl ditelluride in the dioxan at (60 ± 0.1)°C for 2 h has been carried out. The presence of tellurium in the polymer has been confirmed qualitatively as well as by induced coupled plasma mass spectroscopy (ICP‐MS). The electron spin resonance spectrum shows the presence of T?Ph, and value of gyromagnetic constant g has been calculated as 2.2203. The T_g of the polymer, measured by DSC, is 105°C. The syndiotactic nature has been confirmed by FTIR and NMR spectroscopy and DSC. The system follows ideal kinetics with activation energy 66 kJ mol^?1. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1017–1022, 2006     

Dynamic mechanical properties of lightly sulfonated polystryrene ionomers

The effects of counterion type and addition of plasticizers on the dynamic mechanical properties of sulfonated atactic polystyrene (SaPS) containing 2.1 mole percent ionic groups have been investigated. For SaPS neutralized with alkali metal counterions at temperatures below 180°C, the matrix T_g and elastic modulus were not significantly affected by counterion type. However, above 180°C, the breadth of the rubbery plateau significantly decreased with increasing counterion size. Neutralization of SaPS with alkyl ammonium counterions decreased both the matrix T_g and the breadth of the rubbery plateau with increasing counterion size. By incorporating an ionic plasticizer in Na⁺ neutralized SaPS, dynamic mechanical properties were observed to be intermediate of systems neutralized with the alkali metal and alkyl ammonium counterions.     

Non‐isothermal crystallization and multiple melting behavior of syndiotactic polystyrene—pre‐melting temperature effects

This work investigated how pre‐melting temperature (T_max) and cooling rate (C) affected the non‐isothermal melt crystallization, melting behavior and crystal structure of syndiotactic polystyrene (sPS) by using differential scanning calorimetry (DSC) and wide angle X‐ray diffraction (WAXD) techniques. Experimental results indicated that raising T_max or C decreased the crystallization peak temperature (T_p) and crystallization initiating temperature (T_i). The crystallization kinetics was analyzed through the Ozawa equation. Although the Ozawa exponent n and cooling function K(T) were determined for T_max = 340°C and T_max = 315°C specimens, for T_max = 290°C specimens, the Ozawa equation was not applicable. Activation energies for the non‐isothermal crystallization processes of different T_max specimens were estimated to be approximately 418 kJ/mol. As T_max was raised the nucleation rate of sPS became slower. The multiple melting peaks were associated with different polymorphs as well as recrystallized crystals that formed during heating scans. The percentage content of α polymorph formed in the crystals under various crystallization conditions was estimated through WAXD experiments.     

Effects of nucleating agent on nonisothermal crystallization of syndiotactic polystyrene

The effects of nucleating agent on nonisothermal crystallization were examined for syndiotactic polystyrene (SPS) using Differential Scanning Calorimetry (DSC). The crystallization peak temperature T_c, the crystallization rate parameter (CRP), the enthalpy of crystallization and melting, and the recrystallization behavior were compared between organic (DMBS, 1,3,2,4-dis-5-(3,4-dimethyl benzylidene) sorbitol) and inorganic (talc) nucleating agents. Both of the nucleation agents promoted the crystallization rate of SPS until some critical concentration of about 3,000 ppm. DMBS worked more effectively as a nucleating agent than talc, although the T_c showed lower level in SPS/DMBS than SPS/talc.     

Utilization of wastes of foam polystyrene as sorbents

Wastes of foam polystyrene were dissolved in styrene and copolymerized with DVB and the final product was sulfonated with H₂SO₄ (group B). Group A of cross-linked polystyrene was synthesized using styrene and divinylbenzene (DVB) in the presence of n-heptane (macroporous ion exchangers) and then was sulfonated with H₂SO₄. The chemical structure of the cross-linked polymers before and after sulfonation was determined by infrared spectroscopy. The ion-exchange capacity was higher for the polymers of group A. The poresize distribution for polymers of group A was determined and the average pore diameter (4V/A) of 39.9 nm for a representative polymer resulted. The degree of swelling of the polymers and their adsorption for methylene blue and alizarin yellow were also determined. The degree of swelling in toluene is decreased by increasing the ratio of DVB in the initial mixture and by sulfonation. The adsorption of methylene blue and alizarin yellow is strongly increased by the sulfonated polymers in comparison with the unsulfonated. As far as group B is concerned, the adsorption of alizarin yellow on the sulfonated polymers, which have higher cross-linking and lower sulfonation, increased more, especially at the initial time. The networks of both groups examined are different. The polystyrene wastes were incorporated into the whole network to an extent of 15–35%. Such investigations could contribute to the utilization of wastes of polystyrene in the direction of sorbents and especially if the polystrene wastes are contaminated with other polymers. © 1995 John Wiley & Sons, Inc.     

The glass transition,crystallization, and melting characteristics of a class of polyester ionomers

The glass transition temperature (T_g), crystallization, and melting character of a class of random polyester ionomers (polymer containing < 10 mol % ionic groups) were investigated. The nonlinear change of the T_g and crystallization and melting behavior were characterized using differential scanning colorimetry (DSC). The ionomers are derived from polyethylene terephathalate (PET) modified through copolycondensation with a fully neutralized sulfonate moiety (sodiosulfo) isophthalate (Na‐SIP). Significant and systematic changes in the glass transition temperature and thermal characteristics upon addition of Na‐SIP on the PET backbone were observed, indicating strong association and interaction on the ionic species. At Na‐SIP levels ≥ 4 mol %, the turn of the the glass transition temperature was found, and the same results were obtained for the samples treated either by quenching or dissolution, suggesting the presence of reversible crosslink and aggregation of the ionic species within the organic matrix. When crystallized from the healing or cooling the samples during the DSC nonisothermal crystallization run at a 10°C/min, the enthalpy of the cold crystallization and melting showed an obvious decrease with the increase of Na‐SIP content, and changes of the crystal temperature had an analogy to those of the T_g. A tune of the crystal temperature was found at Na‐SIP levels ≥ 3 mol % (see Figs. 4 , 5 , and 7 ). The experimental data were discussed in the context of the restricted mobility model of the aggregation in the ionomers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3660–3666, 2002     

Isothermal and nonisothermal melt‐crystallization kinetics of syndiotactic polystyrene

Analyses of the isothermal and nonisothermal melt kinetics for syndiotactic polystyrene have been performed with differential scanning calorimetry, and several kinetic analyses have been used to describe the crystallization process. The regime II→III transition, at a crystallization temperature of 239°, is found. The values of the nucleation parameter K_g for regimes II and III are estimated. The lateral‐surface free energy, σ = 3.24 erg cm^?2, the fold‐surface free energy, σ_e = 52.3 ± 4.2 erg cm^?2, and the average work of chain folding, q = 4.49 ± 0.38 kcal/mol, are determined with the (040) plane assumed to be the growth plane. The observed crystallization characteristics of syndiotactic polystyrene are compared with those of isotactic polystyrene. The activation energies of isothermal and nonisothermal melt crystallization are determined to be ΔE = ?830.7 kJ/mol and ΔE = ?315.9 kJ/mol, respectively. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2528–2538, 2002     

离聚体对PA1010／PS共混体系相形态及结晶的影响

采用ＳＥＭ,ＤＳＣ和偏光显微镜等方法研究了磺化聚苯乙烯及其锂盐,锌盐和钠盐（ＰＳ－ＮａＳ）;四种离聚体对ＰＡ１０１０／ＰＳ共混体系相形主结晶性能的影响。结果表明,对于ＰＡ１０１０／ＰＳ（８０／２０）共混体系,四种离聚体的增容效果依次按ＰＳ－ｎａＳ〈ＰＳ－ＺｎＳ〈ＰＳ〈ＺｎＳ〈ＰＳ－ＬｉＳ〈ＰＳ－ＨＳ的顺序递增,表明离聚体的离子交联能力越弱,其增容效果越好。四种离聚体中只有ＰＳ－ＺｎＳ对ＰＡ１０１０     

High styrene–rubber ionomers,an alternative to thermoplastic elastomers

High styrene rubber ionomers were prepared by sulfonating styrene–butadiene rubber of high styrene content (high styrene rubber) in 1,2‐dichloroethane using acetyl sulfate reagent, followed by neutralization of the precursor acids using methanolic zinc acetate. The ionomers were characterized using X‐ray fluorescence spectroscopy, Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), dynamic mechanical analysis (DMA), and also by the evaluation of mechanical properties. The FTIR studies of the ionomer reveal that the sulfonate groups are attached to the benzene ring. The NMR spectra give credence to this observation. Results of DMA show an ionic transition (T_i) in addition to glass–rubber transition (T_g). Incorporation of ionic groups results in improved mechanical properties as well as retention of properties after three cycles of processing. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2294–2300, 2002