Comparisons of styrene ionomers prepared by sulfonating polystyrene and copolymerizing styrene with styrene sulfonate

As part of a continuing study of ion-containing polymers, a comparison has been made on styrene-based sulfonate ionomers obtained by two different processes. Copolymers of styrene with sodium styrene sulfonate (SSS) have been compared with corresponding polymers obtained by the sulfonation/neutralization of preformed polystyrene (S–PS). The former system covered a range of sulfonate level from 1 to 30 mol %, while the latter ranged from about 1 to 7 mol %. The characterization of these materials has been conducted using solubility behavior, dilute solution viscometry, thermal mechanical analysis, density measurements, and water adsorption studies. At low (ca. 1%) levels the solubility behavior of the SSS copolymers and the sulfonated polystyrenes were similar. However, at higher sulfonate levels the solubility behavior in different solvents and the dilute solution viscometry were significantly different for the two systems. Similarly, thermal analysis studies (DSC) showed that the glass transition of the sulfonated polystyrene increased linearly with sulfonate level, while the T_g for the SSS copolymer increased modestly, up to about 7 mol % sulfonate content, and then remained constant. Significant differences in the softening behavior and water absorption characteristics were also observed for these two classes of ionomers. Although molecular weights and molecular weight distributions are not now available for these ionomers, the differences in their behavior does not appear to be due simply to differences in molecular weight. It is postulated that the differences in the copolymer and the S–PS ionomers may originate with differences in sulfonate distribution. It is suggested that the SSS monomer units are incorporated as blocks in the copolymer as opposed to a more random distribution in the S–PS ionomer. Indirect evidence in support of his argument is found, for example, in the case of the copolymer in the solubility behavior, the relative independence of T_g on sulfonate concentration and the apparent existence of a second, high temperature transition tentatively attributable to an ion-rich phase. Additional studies are required to confirm this hypothesis.     

Synthesis of poly(styrene sulfonate) brushes.

Dense poly(styrene sulfonate sodium salt) brushes were prepared on silicone wafers using a two-step procedure: polystyrene (PS) chains, terminated by a reactive trichlorosilane group, were first covalently grafted, and then the PS brush was converted to a poly(styrene sulfonate) brush by a soft sulfonation reaction. Ellipsometry and infrared spectroscopy in ATR were used to characterize the samples and to optimize the procedure: in particular, the sulfonation was shown to be homogeneous along the chain backbone and the neutralization complete. In some cases, the polymer layer revealed to be quite fragile: the chains were pulled out of the brush. A consolidation treatment which consisted in grafting oligomers inbetween the long PS chains significantly increased the robustness of the layer. This might be relevant for industrial applications.     

The emulsion copolymerization of styrene and sodium styrene sulfonate

The emulsion copolymerization of styrene and sodium styrene sulfonate has been shown to be a feasible preparative route to ionomeric sulfonated polystyrene. The properties of these copolymers are reported elsewhere. The copolymerization rate was found to be dramatically enhanced when compared to that for the emulsion copolymerization of styrene under identical conditions. This copolymerization was studied in detail and two mechanisms were proposed to account for these rate differences. An increase in the number of polymerizing particles in the copolymerization with consequent rate enhancement was substantiated by electron microscopy. However, the data indicate that the rate differences cannot be fully accounted for by this effect. In addition, a gel effect is proposed as a second contributor to the enhanced rate. This gel effect is believed to result from the intermolecular association of the incorporated metal sulfonate units in the growing polymer particles. When a third monomer that plasticizes the ionic interactions is used the polymerization rate decreases. This supports the gel effect hypothesis.     

Photoinitiating capabilities of vinyl polyperoxides and metamorphosis of block-into-block copolymer

This article describes the first comprehensive study on the use of a vinyl polyperoxide, namely poly(styrene peroxide) (PSP), an equimolar alternating copolymer of oxygen and styrene, as a photoinitiator for free radical polymerization of vinyl monomers like styrene. The molecular weight, yield, structure and thermal stability of polystyrene (PS) thus obtained are compared with PS made using a simple peroxide like di-t-butyl peroxide. Interestingly, the PS prepared using PSP contained PSP segments attached to its backbone preferably at the chain ends. This PSP–PS–PSP was further used as a thermal macroinitiator for the preparation of another block copolymer PS-b-PMMA by reacting PSP–PS–PSP with methyl methacrylate (MMA). The mechanism of block copolymerization has been discussed. © 1996 John Wiley & Sons, Inc.     

Anionic copolymerization of styrenic‐tipped macromonomers: A route to novel triblock–comb copolymers of styrene and isoprene

The following triblock–comb copolymers of isoprene (I) and styrene (S)—PS‐b‐(PI‐g‐PI)‐b‐PS, PS‐b‐[PI‐g‐(PI‐b‐PS)]‐b‐PS, and (PS‐g‐PS)‐b‐(PI‐g‐PI)‐b‐(PS‐g‐PS) (where PS is polystyrene and PI is polyisoprene)—with PS contents of 20–30% were synthesized with high‐vacuum techniques and the anionic copolymerization of styrenic‐tipped macromonomers with I and S. The macromonomers, prepared by the reaction of living PI or PS with 4‐(chlorodimethylsilyl) styrene, were used without isolation. Molecular characterization by size exclusion chromatography, size exclusion chromatography/two‐angle laser light scattering, and NMR spectroscopy indicated that the triblock–comb copolymers had high molecular and compositional homogeneity. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4030–4039, 2005     

苯乙烯-苯乙烯磺酸钠共聚物的制备及其流变性能

采用乳液聚合合成了一种可作为聚丙烯(PP)纤维可染改性添加剂的苯乙烯-苯乙烯磺酸钠共聚物P(St-co-NaSS)。通过傅里叶转换红外光谱仪(FT-IR)和核磁共振氢谱仪(~1 H-NMR)对共聚物的苯乙烯磺酸钠结构单元进行了表征,研究了反应条件对共聚物磺化度的影响;通过差示扫描量热仪(DSC)和热重分析仪(TG)研究了磺酸基团的引入对共聚物的玻璃化转变温度和起始分解温度的影响;通过旋转流变仪研究了磺化度对共聚物剪切黏度的影响;初步探讨了PP/P(St-co-NaSS)共混体系的染色性能。结果表明:当反应时间为2h,反应温度为70℃,引发剂质量分数为0.6%,苯乙烯磺酸钠的摩尔分数为0.01时,共聚物的磺化度f=6.68%(零切黏度η0=19 620Pa·s,属牛顿流体);在10~(-2)~10~(-1) s~(-1)的剪切速率范围内,P(St-co-NaSS)表现出假塑性流体的特征,具有较好的加工流动性。对于PP/P(St-co-NaSS)共混体系,使用阳离子染料染色时,染色深度(K/S值)为2.603 2,使用分散染料染色时,K/S值为10.168 8。P(St-co-NaSS)适合作为聚丙烯纤维的可染改性添加剂。     

Emulsifier-free emulsion copolymerization of styrene and sodium styrene sulfonate

The kinetics of the emulsifier-free emulsion copolymerization of styrene and sodium styrene sulfonate have been examined over a range of comonomer compositions. The rate of polymerization was found to increase dramatically in the presence of small amounts of sodium styrene sulfonate. This increase is attributed to the increased number of particles formed when sodium styrene sulfonate was present and to a gel effect enhanced by ion association. At low concentrations of functional comonomer, where a monodisperse product was obtained, a homogeneous nucleation mechanism of particle generation is proposed. At higher concentrations, broader and then bimodal size distributions were obtained, and this is ascribed to significant aqueous phase polymerization of sodium styrene sulfonate. The water-soluble homopolymer is supposed to act as a locus of polymerization. The occurrence of this aqueous phase side reaction and the generation of secondary particles makes impossible the preparation of highly sulfonated polystyrene latexes by batch or seeded batch emulsion copolymerization.     

ASAXS study of styrene‐grafted sulfonated poly(vinylidene fluoride) membranes

Small‐angle and wide‐angle X‐ray scattering and anomalous small‐angle X‐ray scattering were used to investigate proton‐conducting membranes prepared by radiation‐induced styrene grafting and sulfonation of commercial poly(vinylidene fluoride) (PVDF‐g‐PS) films. The membranes retain the lamellar and highly oriented structure of the original PVDF films even through excessive grafting and sulfonation. The sulfonate groups aggregate in the central part of the amorphous layers, where they form a weakly ordered structure that does not show any preferred orientation. This structure is suggested to be lamellar with alternate metal‐sulfonated hydrate and PVDF‐g‐PS layers. The lamellar period is 15.1 Å. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1734–1748, 2000     

Polymerization and copolymerization of styrene by Ph2Zn‐metallocene‐MAO initiator systems.

Combined systems including diphenylzinc, Ph₂Zn, a metallocene, and methylaluminoxane, MAO, have been employed to initiate styrene polymerization. These initiator systems have been also used to initiate the copolymerization of styrene with p‐alkylsubstituted styrenes and with α‐olefins. Both polymerization and copolymerization processes depend on the nature of the metallocene included in the initiator system, the presence of Ph₂Zn, the temperature and the solvent used. Titanocenes produced syndiotactic polystyrene, s‐PS, while zirconocenes gave atactic polystyrene, a‐PS, with a certain content, less the 20% of s‐PS. For copolymerizations the conversion to polymer was also influenced by the comonomer nature and its molar proportion in the initial feed, as well as the sort of metallocene, titanocene or zirconocene included.     

The synthesis of sulfonated polymers by free radical copolymerization. Poly(butadiene-co-sodium styrene sulfonate)

The copolymerization of butadiene with sodium styrene sulfonate was studied and the copolymer products characterized. In general these copolymers contain 0.5–4 mole% of sulfonated monomer. The effects of the following reaction variables are described: emulsifier type and concentration, monomers feed ratio, chain transfer agent concentration, and reaction conversion. The products were heterogeneous with regard to composition, molecular weight, and solubility behavior. Copolymers prepared under certain conditions exhibited strong intermolecular interactions derived from associations of the ionic species as observed in other ionomers.     

Synthesis and transport properties of proton-conducting membranes based on polyvinylidene fluoride films with introduced and sulfonated polystyrene

Thermal polymerization of styrene sorbed into a polyvinylidene fluoride (PVdF) film from a toluene solution followed by sulfonation of the resulting material was performed. The kinetics of polystyrene (PS) accumulation in the PVdF film during thermal polymerization was studied. Samples with 6–30 wt % PS and ∼100% PS sulfonation were obtained. Proton-exchange membranes wsith an ion-exchange capacity of up to 2 mg-eq/g and proton conductivity of up to 0.008 S/cm at 75% relative humidity were prepared. The permeability coefficients of water, methanol, and hydrogen and their dependences on the amount of introduced PS, ion-exchange capacity, and water uptake of membranes were measured. The synthesized materials proved similar to MF-4SK membranes in their basic transport characteristics and can be used as proton-exchange membranes in hydrogen-air and alcohol fuel cells.     

Model filled polymers. IX. Synthesis of uniformly crosslinked polystyrene microbeads

Monodisperse sized crosslinked polystyrene (PS) beads prepared by reaction of styrene (S) and divinylbenzene (DVB), in batch emulsion copolymerization in the absence of emulsifiers, are not uniformly crosslinked, because DVB is more reactive than S. For copolymerization of 1 to 10 mol % DVB and S, within each crosslinked PS microbead, the crosslink density varies by a factor exceeding two and decreases with increased conversion. A semicontinuous copolymerization, involving incremental additions of DVB, produces uniformly crosslinked PS beads. For both copolymerization techniques, T_g correlates well with crosslink density and PS beads are spherical and monodisperse in size. © 1992 John Wiley & Sons, Inc.     

Grafting of methacrylates and styrene on to polystyrene backbone via a “grafting from” ATRP process at ambient temperature

Well defined graft copolymers are prepared by “grafting from” atom transfer radical polymerization (ATRP) at room temperature (30 °C). The experiments were aimed at grafting methacrylates and styrene at latent initiating sites of polystyrene. For this purpose, the benzylic hydrogen in polystyrene was subjected to allylic bromination with N‐bromosuccinimide and azobisisobutrylnitirle to generate tertiary bromide ATRP initiating sites (Br? C? PS). The use of Br? C? PS with lesser mol % of bromide initiating groups results in better control and successful graft copolymerization. This was used to synthesize a series of new graft copolymers such as PS‐g‐PBnMA, PS‐g‐PBMA, PS‐g‐GMA, and PS‐g‐(PMMA‐b‐PtBA) catalyzed by CuBr/PMDETA system, in bulk, at room temperature. The polymers are characterized by GPC, NMR, FTIR, TEM, and TGA. Graft copolymerization followed by block polymerization enabled the synthesis of highly branched polymer brush, in which the grafting density can be adjusted by appropriate choice of bromide concentration in the polystyrene. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3818–3832, 2007     

Radiation-initiated homogeneous grafting of styrene to benzylcellulose

Graft copolymers of benzylcellulose and styrene were prepared by direct irradiation of benzylcellulose–styrene solutions with ⁶⁰Co γ-radiation. The solutions remained homogeneous during irradiation. The amount of styrene grafted to benzylcellulose increased in dilute solutions and was dose-dependent up to 4.0 MR. The graft copolymer consisted of both branched and linear structures with one in every 140–1020 benzylated anhydroglucose units carrying a grafted polystyrene chain. Grafted polystyrene was isolated from the graft copolymer by hydrolysis of the benzylcellulose substrate. The number-average molecular weight and molecular weight distribution of the grafted polystyrene were the same as those for hompolymer formed in the same solution, indicating that the substrate is fully accessible to the monomer and polymerization conditions are uniform throughout the solution during the grafting procedure. The existence of a true graft copolymer was proved by the solubility behavior, intrinsic viscosity, number-average molecular weight, and density-gradient sedimentation of the product of the grafting procedure. Column elution fractionation of the gross products of the grafting procedure failed to isolate the benzylcellulose–styrene copolymer which was eluted with ungrafted benzylcellulose.     

用含偶氮基的聚苯乙烯大分子引发剂合成两亲性嵌段共聚物

采用含偶氮基的聚苯乙烯预聚物（ＰＳ ＡＣＰＣ）作为引发剂，合成了苯乙烯（Ｓｔ）分别与甲基丙烯酸（ＭＡＡ）、甲基丙烯酸（β 羟丙酯）（ＨＰＭＡ）的嵌段共聚物，考察了ＰＳ ＡＣＰＣ引发第二单体的聚合反应行为，以及影响第二单体转化率和均聚物含量、共聚物组成的因素．用溶解性、凝胶渗透色谱（ＧＰＣ）、红外光谱（ＩＲ）、核磁共振（ＮＭＲ）、动态接触角（ＤＣＡ）等表征了嵌段共聚物．     

Preparation of polystyrene/silica nanocomposites by radical copolymerization of styrene with silica macromonomer

A two-stage process has been developed to generate the silica-based macromonomer through surface-modification of silica with polymerizable vinyl groups. The silica surfaces were treated with excess 2,4-toluene diisocynate (TDI), after which the residual isocyanate groups were converted into polymerizable vinyl groups by reaction with hydroxypropylacrylate (HPA). Thus, polystyrene/silica nanocomposites were prepared by conventional radical copolymerization of styrene with silica macromonomer. The main effecting factors, such as ratios of styrene to the macromonomer, together with polymerization time on the copolymerization were studied in detail. FTIR, DSC and TGA were utilized to characterize the nanocomposites. Experimental results revealed that the silica nanoparticles act as cross-linking points in the polystytene/silica nanocomposites, and the glass transition temperatures of the nanocomposites are higher than that of the corresponding pure polystyrene. The glass transition temperatures of nanocomposites increased with the increasing of silica contents, which were further ascertained by DSC.     

Polymers-Copolymer as Flow Improvers for Fuel Oils and Their Electrical Conductivity

In order to find efficient cold flow improvers for fuel oil, polymethylmethacrylate (PMMA), polystyrene (PS), and a copolymer [styrene (S)–methylmethacrylate (MMA) were prepared. The structure of these polymers and the copolymer were characterized by infrared spectral analysis and their molecular weights were measured. These polymers-copolymer were used as additives for fuel oils in order to lower their pour point. Accordingly, they were evaluated as flow improvers for fuel oil. The results indicated that PMMA possesses less performance as pour point depressant. While the addition of PS and the copolymer (S–MMA) yield excellent pour point depressants for fuel oil. Upon studying the prepared additives and their properties, it was found that the electrical properties of the copolymer were changed due to the presence of polar ion in MMA effect on the electrical properties. The highest electrical conductivity was found when styrene:MMA molar ratio was 1:1.     

Preparation of esters of styrene sulfonic acid and their emulsion copolymerization with isoprene

Sulfonate-containing rubbers were prepared by emulsion copolymerization of isoprene and the secondary butyl ester of styrene sulfonic acid. Substantially gel-free copolymers of relatively high sulfonate content were prepared. It was shown that hydrolysis of the ester copolymers with a suitable base can lead to the formation of ionically crosslinked elastomers.     

Isospecific homo- and copolymerization of styrene with ethylene in the presence of VCl3, AlCl3 as catalyst

The homopolymerization of styrene and its copolymerization with ethylene in the presence of a vanadium-based supported catalyst, {VCI₃, 1 AICI₃}, associated to triethylaluminium is examined. As indicated by means of ¹³C nuclear magnetic resoance and differential scanning calorimetry analysis, the homopolystyrenes obtained present a highly isotactic microstructure and are semicrystalline (melting temperature 220°C). In the case of styrene/ethylene random copolymerization, the formation of both, polyethylene blocks and isotactic polystyrene sequences was identified by analysis of the crude polymer. Solubility characteristics and structural characteristics from nuclear magnetic resonance spectra of these products support the formation of copolymers with ethylene and isotactic styrene blocks rather than that of two distinct homopolymers.     

Synthesis of polymer nanocomposite ion-exchange membranes from sulfonated polystyrene and study of their properties

Methods for the preparation of composite ion-exchange membranes from polymer (polyvinylidene fluoride (PVDF), ultrahigh molecular weight polyethylene (UHMWPE), and polypropylene (PP)) matrices were considered. Polystyrene (PS) was introduced in the matrices by thermal polymerization of the monomer followed by sulfonation of the implant. The fundamentals of membrane synthesis from industrial polytetrafluoroethylene (PTFE, Teflon F-4) films by thermal polymerization of styrene in a film stretched in a monomer solution followed by sulfonation of incorporated PS were described. The literature on radiation- chemical synthesis of composite ion-exchange membranes based on polymer matrices with embedded polystyrene and its subsequent sulfonation was analyzed. Some problems of the kinetics and mechanism of thermal implantation of PS into various polymer matrices under different conditions were discussed. The physicochemical characteristics, structure, and transport properties of the membranes synthesized by thermal implantation of PS were reported. The obtained membranes were tested in low-temperature fuel cells.