Preparation of a blocked isocyanate compound and its grafting onto styrene-b-(ethylene-co-1-butene)-b-styrene triblock copolymer

The ε-caprolactam was used to block the isocyanate group to enhance the storage stability of allyl (3-isocyanate-4-tolyl) carbamate. The spectra of FTIR and NMR showed that blocked allyl (3-isocyanate-4-tolyl) carbamate (BTAI) possesses two chemical functions, an 1-olefin double bond and a blocked isocyanate group. The FTIR spectrum showed BTAI could regenerate isocyanate group at elevated temperature. DSC and TG/DTA indicated the minimal dissociation temperature was about 135 °C and the maximal dissociation rate appeared at 226 °C. Then the styrene-b-(ethylene-co-1-butene)-b-styrene triblock copolymer (SEBS) was functionalized by BTAI via melt free radical grafting. The effect of temperature, monomer and initiator concentrations on the grafting degree and grafting efficiency was evaluated. The highest grafting degree was obtained at 200 °C. The grafting degree and grafting efficiency increased with the enhanced concentration of BTAI or initiator. The weight-average molecular weight (M_w) increased greatly at higher initiator concentration and lower ratio of the monomer/initiator. And the molecule weight distribution (MWD) of the modified SEBS became wider than that of pure SEBS. It is obvious that shearing thinning behavior of grafted SEBS is more profound than pure SEBS.     

Microstructure of triblock copolymers in asphalt oligomers

A model asphalt has been separated into two parts, asphaltene and maltene, through solvent extraction by n-heptane. The interactions of asphaltene and maltene with the triblock copolymer poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) were investigated by transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), dynamic mechanical analysis (DMA), and differential scanning calorimetry (DSC). Asphaltene was found to be essentially immiscible with both blocks of SEBS, while maltene was miscible with SEBS. An unusual sequence of morphological transformations of SEBS microstructure with respect to the addition of maltene was observed. The morphology transformed from hexagonal cylinder, to perforated layers, to lamellae and then back to the original hexagonal cylinder. The observed transformation reflects a limited solubility for both S and EB domains: at lower concentration maltene is a preferential additive for S domains, while increasing concentration the swelling of EB-rich microdomains by maltene becomes significant. The basic understanding of the interactions of the components of asphalt with SEBS gives a simple path to characterize and predict the microstructure of triblock copolymers in asphalt oligomers. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2857–2877, 1997     

“Living” free radical copolymerization of styrene and N-vinylcarbazole

Poly[styrene-co-(N-vinylcarbazole)] copolymers with controlled molecular weights and narrow polydispersities were synthesized by nitroxide-mediated “living” free radical copolymerization using an initiator/capping agent system consisting of benzoyl peroxide (BPO) and the stable nitroxyl radical 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO). The copolymerization behaves in a “living” fashion and allows the synthesis of poly[styrene-co-(N-vinylcarbazole)]/polystyrene block copolymers via a controlled chain-extension reaction of the prepared copolymers with styrene.     

Synthesis of amphiphilic block–graft copolymers [poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene)‐g‐poly(acrylic acid)] and their aggregation in water

Novel block–graft copolymers [poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene)‐g‐poly(tert‐butyl acrylate)] were synthesized by the atom transfer radical polymerization (ATRP) of tert‐butyl acrylate (tBA) with chloromethylated poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene) (SEBS) as a macromolecular initiator. The copolymers were composed of triblock SEBS as the backbone and tBA as grafts attached to the polystyrene end blocks. The macromolecular initiator (chloromethylated SEBS) was prepared by successive hydrogenation and chloromethylation of SEBS. The degree of chloromethylation, ranging from 1.6 to 36.5 mol % according to the styrene units in SEBS, was attained with adjustments in the amount of SnCl₄ and the reaction time with a slight effect on the monodispersity of the starting material (SEBS). The ATRP mechanism of the copolymerization was supported by the kinetic data and the linear increase in the molecular weights of the products with conversion. The graft density was controlled with changes in the functionality of the chloromethylated SEBS. The average length of the graft chain, ranging from a few repeat units to about two hundred, was adjusted with changes in the reaction time and alterations in the initiator/catalyst/ligand molar ratio. Incomplete initiation was detected at a low conversion; moreover, for initiators with low functionality, sluggish initiation was overcome with suitable reaction conditions. The block–graft copolymers were hydrolyzed into amphiphilic ones containing poly(acrylic acid) grafts. The aggregation behavior of the amphiphilic copolymers was studied with dynamic light scattering and transmission electron microscopy, and the aggregates showed a variety of morphologies. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1253–1266, 2002     

Effects of SEBS-g-BTAI on the morphology, structure and mechanical properties of PA6/SEBS blends

Styrene-b-(ethylene-co-1-butene)-b-styrene (SEBS) triblock copolymer functionalized with ε-caprolactam blocked allyl (3-isocyanate-4-tolyl) carbamate (SEBS-g-BTAI) was used to toughen polyamide 6 (PA6) via reactive blending. Compared to the PA6/SEBS blends, mechanical properties such as tensile strength, Young’s modulus, especially Izod notched strength of PA6/SEBS-g-BTAI blends were improved distinctly. Both rheological and FTIR results indicated a new copolymer formed by the reaction of end groups of PA6 and isocyanate group regenerated in the backbone of SEBS-g-BTAI. Smaller dispersed particle sizes with narrower distribution were found in PA6/SEBS-g-BTAI blends, via field emitted scanning electron microscopy (FESEM). The core-shell structures with PS core and PEB shell were also observed in the PA6/SEBS-g-BTAI blends via transmission electron microscopy (TEM), which might improve the toughening ability of the rubber particles.     

Chemiluminescence from poly(styrene-b-ethylene-co-butylene-b-styrene) (SEBS) block copolymers

A detailed analysis of the chemiluminescence emission (CL) from poly(styrene-b-ethylene-co-butylene-b-styrene), SEBS, was carried out. A phenol-phosphite stabilization system based on Irgafos 168 and Irganox 1330, was studied. The kinetic analysis of the CL profile under nitrogen shows a first-order reaction for the decay of chemiluminescence. The activation energy shows different values as a function of temperature, showing that different reactions are involved in the thermal degradation of the SEBS. The CL decay rate correlates well with the amount of the phosphite, Irgafos 168, and confirms the activity of this stabilizer as radical chain-breaking antioxidant in these copolymers.The isothermal analysis of CL under oxygen allows evaluation of the oxidation state, as well as the efficiency of the antioxidants. Good correlations are found between the CL parameters and concentration of Irgafos 168. Several factors suggest that oxidation begins in the interfacial region. Spectral analysis of the chemiluminescence shows the presence of different types of hydroperoxides.Finally, the characterization of the SEBS copolymers by differential scanning calorimetry reveals an order-disorder transition, assigned to aggregates that behave as paracrystalline regions.     

Synthesis,characterization, and properties of block and bigraft copolymers

The syntheses of poly(styrene-b-isobutylene), poly[(ethylene-co-propylene-co-1,4-hexadiene)-g-styrene-g-α-methylstyrene], and poly[(ethylene-co-propylene-co-1,4-hexadiene)-g-styrene-g-isobutylene] have been accomplished by using the principle of selective sequential initiation. This method makes use of the large differences in initiation rates that exist between labile organic chlorides and bromides when these halides interact with alkylaluminum compounds. Synthesis conditions have been worked out which allow composition control. These new AB blocks and bigrafts exhibit unusual mechanical and solubility properties, some of which will be described. For example, the Nordel-g-PSt-g-PIB bigraft exhibits only one low temperature transition (DSC, Rheovibron), suggesting an intimate aggregation of Nordel and polyisobutylene phases.     

SEBS的间接氯甲基化研究

研究了以二甲氧基甲烷和氯化亚砜为原料实现氢化聚苯乙烯-乙烯丁烯无规共聚物-聚苯乙烯三嵌段共聚物(SEBS)苯环对位上的间接氯甲基化. 通过红外光谱和核磁氢谱表征了氯甲基化SEBS的化学结构; 采用佛尔哈德法测定了氯甲基化程度. 通过对比研究几种催化剂的催化效果, 表明氯化锌催化效果最佳, 在氯化锌浓度仅为0.056 mol/L, 45 ℃, 12 h内即可使SEBS的苯环对位氯甲基化程度达到28.94%. 本文还探讨了催化剂用量、反应温度、反应时间对接氯甲基化程度的影响.     

Application of FTIR Microscopy in Combinatorial Experimentation on Polymer Blends

Summary: A novel combinatorial, high-throughput experimentation (HTE) setup has been developed, which allows for rapid mapping of the phase behavior of blends of homopolymers and block copolymers. The principle is based on the preparation of composition (ϕ)-temperature (T) gradient films. Linear ϕ gradients were obtained over a large composition range, as shown by FTIR microscopy. The applicability of this combinatorial approach was demonstrated by studying the phase behavior of a poly(styrene-co-acrylonitrile) (SAN)/poly(methyl methacrylate-co-ethyl acrylate) (PMMA-EA) blend with varying EA content and a poly(styrene-b-butadiene-b-methyl methacrylate) (SBM) triblock copolymer.     

Elastic and durable multi-cation-crosslinked anion exchange membrane based on poly(styrene-b-(ethylene-co-butylene)-b-styrene)

Anion exchange membranes (AEMs), as the core component of the new generation anion exchange membrane fuel cells (AEMFCs), directly determine the performance and the lifetime of this energy conversion device. Here, AEMs with pendant multiple quaternary ammonium anchored onto the poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) backbone are synthesized. The comb-shaped copolymer SEBS-C16 is synthesized with N,N-dimethyl-1-hexadecylamine and chloromethylated SEBS to improve solubility, then the multi-cation crosslinker is prepared and grafted on the above backbone to fabricate a series of flexible multi-cation crosslinked SEBS-based AEMs (SEBS-C16-xC4, where x% is the ratio of the crosslinker to polystyrene block) with practical properties. The obtained SEBS-C16-20C4 membrane exhibits a microphase separated morphology with an interdomain spacing of 18.87 nm. Benefited from the ion channels, SEBS-C16-20C4 shows high conductivity of 77.78 mS/cm at 80°C. Additionally, the prepared SEBS-C16-20C4 membrane with ion exchange capacity of 2.35 mmol/g also exhibits enhanced alkaline stability (5.87% hydroxide conductivity decrease in 2 M NaOH solution at 80°C after 1,700 hr) and improved mechanical properties, compared with the non-crosslinked SEBS-C16 sample. Furthermore, AEMFC single cell performance is evaluated with the SEBS-C16-20C4 membrane, and a maximum power density of 182 mW/cm² is achieved at 80°C under H₂/O₂ conditions.     

Bilayer nanocomposite molecular coatings from elastomeric/rigid polymers: fabrication,morphology, and micromechanical properties

We fabricated bilayered nanocomposite coatings composed of a hard polymer layer placed on top of an elastomeric layer. The primary layer of poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] (SEBS) was attached to the surface by grafting to a chemically reactive silicon surface functionalized with epoxy‐terminated SAM. The SEBS layer served as the compliant interlayer in the bilayered polymer coating. The topmost hard layer was a high performance polymer made of epoxy resin (EP) and an amino functionalized poly(paraphenylene) (PPP). We built the bilayered structure by spincoating the EP/PPP mixture on top of the grafted SEBS layer. The solidification of the topmost layer was initiated at low temperatures (40‐50°C) to avoid dewetting. The curing of the film was finished at 110°C (15 hours) and the EP/PPP layer was strongly attached to the SEBS layer. It was found that the EP/PPP layer did not penetrate inside the elastic primary layer during the solidification. The elastic response of the hard polymer layer was affected significantly by the underlying elastomeric layer. The SEBS layer served as a compliant interlayer capable of dissipating the interfacial stresses originating from dissimilarities in the physical properties between the polymer coating and the inorganic substrate.     

Polystyrene–Polyperfluorooctylethyl acrylate Diblock Copolymers: The Effect of Dilution of the Fluorinated Mesogenic Chains on Bulk and Surface Properties

Summary : Three smectic poly(styrene-b-perfluorooctylethyl acrylate) block copolymers (S-b-AF8) with different degrees of polymerization (n, m) of the relative blocks were synthesized by atom transfer radical polymerization (S, n = 25; AF8 m = 2, 6, 23). The mesophase structure and transition temperatures were investigated by DSC and WAXD. The block copolymer having the shortest fluorinated block was blended with a thermoplastic elastomer SEBS in different proportions, in order to look at the effect of a further dilution of the perfluorinated groups on non-wetting properties. Thin films of the block copolymers as well as the blends exhibited large contact angles with both water and n-hexadecane, which resulted in low solid surface tensions. XPS findings at different photoemission angles confirmed the effective surface segregation of the mesogenic chains of the fluorinated polymer block.     

Iodine-Transfer Polymerization (ITP) of Ethylene and Copolymerization with Vinyl Acetate

Controlled radical polymerization of ethylene using different commercially available, cheap, and non-toxic iodo alkyls is performed by iodine transfer polymerization (ITP) under mild conditions (≤100 °C and ≤200 bar). The formed well-defined iodo end-capped polyethylene (PE−I) species is very stable upon storage. Narrow molar-mass distributions (dispersities around 1.6) were obtained up to number average molar masses of 7300 g mol⁻¹. The ethylene copolymerization by ITP (ITcoP) with vinyl acetate allowed to form a broad range of poly(ethylene-co-vinyl acetate) (EVA) containing from 0 to 85 mol % of VAc unit. In addition, EVA-b-PE block copolymers or EVA-b-EVA gradient block copolymers with different content of VAc in the blocks were obtained for the first time using ITP. Finally, reactivity trends were explored by a theoretical mechanistic study. This highly versatile synthetic platform provides a straightforward access to a diverse range of well-defined PE based polymer materials.     

Miscibility of poly(butyl methacrylate-CO-methacrylic acid) or poly(styrene-CO-methacrylic acid) with poly(styrene-CO-4-vinylpyridine) or poly(butyl methacrylate-CO-4-vinylpyridine)

The miscibility of blends of copolymers of different compositions of butyl methacrylate-co-methacrylic acid or styrene-co-methacrylic acid with styrene-co-4-vinylpyridine or butyl methacrylate-co-4-vinylpyridine was studied by differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy. It was found that these blends were miscible in part as a result of specific favorable interactions between the carboxylic acid and pyridine groups within the polymer chains. Evidence of such interactions was obtained from the single composition-dependent glass transition temperature and the FTIR results.     

Novel emulsion graft copolymerization onto the silylmethyl group of poly(dimethylsiloxane)

The influence of radical initiators upon the emulsion graft copolymerization of styrene and acrylonitrile onto poly(dimethylsiloxane) (PDMS) was studied. As initiators, a series of peroxides and hydroperoxides were coupled with ferrous sulfate, among which the tert-butyl peroxylaurate system gave the highest grafting efficiency (30%). The tert-butyl peroxylaurate initiator fulfills the criteria for efficient radical grafting by generating only the tert-butoxy radical, which is reluctant to form a carbon radical via β-scission, being highly hydrophobic, and not carrying a tertiary hydrogen that may be abstracted by a radical. ¹³C-NMR analysis of the products showed that the grafting occurred on the silylmethyl groups of PDMS to give 10–25 grafts per polymer and graft ratio in the range 44–140%. The PDMS graft copolymers thus obtained could be used as surface-modifying agents to improve the lubricity and water-repellency of ABS [poly(styrene-co-acrylonitrile)-graft-polybutadiene]. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2607–2617, 1997     

Random and block styrenic copolymers bearing both ammonium and fluorinated side‐groups

1H,1H,2H,2H‐Perfluorooctyloxymethylstyrene (FS) was prepared and copolymerized with chloromethylstyrene (CMS). Conventional radical copolymerization of both these aromatic monomers led to poly(CMS‐co‐FS) random copolymers for which CMS was shown to be more reactive than the fluorinated comonomer. Their controlled radical copolymerization based on degenerative transfer, namely iodine transfer polymerization (ITP), led to various poly(CMS)‐b‐poly(FS) block copolymers. Molecular weights of poly(CMS‐co‐FS) copolymers reached 33,000 g mol^?1 while those of poly(CMS)‐b‐ poly(FS) block copolymers were 22,000 g mol^?1. Their composition ranged from 18 to 61 mol.% in FS. These copolymers were modified via a cationization step, aiming at replacing the chlorine atom in CMS unit by a trimethylammonium group, leading to the formation of cationic sites. The resulting functionalized copolymers exhibited different solubilities. If both copolymerization techniques led to water‐insoluble copolymers, the block architecture enabled incorporating lower FS proportion, resulting in more cationic sites. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Correlation of Morphology Evolution with Superior Mechanical Properties in PA6/PS/PP/SEBS Blends Compatibilized by Multi-phase Compatibilizers

In this study,the maleic anhydride(MAH)and styrene(St)dual monomers grafted polypropylene(PP)and poly[styrene-b-(ethylene-co-butylene)-b-styrene](SEBS),i.e.PP-g-(MAH-co-St)and SEBS-g-(MAH-co-St)are prepared as multi-phase compatibilizers and used to compatibilize the PA6/PS/PP/SEBS(70/10/10/10)model quaternary blends.Both PS and SEBS are encapsulated by the hard shell of PP-g-(MAH-co-St)in the dispersed domains(about 2μm)of the PA6/PS/PP-g-(MAH-co-St)/SEBS(70/10/10/10)quaternary blend.In contrast,inside the dispersed domains(about 1μm)of the PA6/PS/PP/SEBS-g-(MAH-co-St)(70/10/10/10)quaternary blend,the soft SEBS-g-(MAH-co-St)encapsulates both the hard PS and PP phases and separates them.With increasing the content of the compatibilizers equally,the morphology of the PA6/PS/(PP+PP-g-(MAH-co-St))/(SEBS+SEBS-g-(MAH-co-St))(70/10/10/10)quaternary blends evolves from the soft(SEBS+SEBS-g-(MAH-co-St))encapsulating PS and partially encapsulating PP(about 1μm),then to PS exclusively encapsulated by the soft SEBS-g-(MAH-co-St)and then separated by PP-g-(MAH-co-St)inside the smaller domains(about 0.6μm).This morphology evolution has been well predicted by spreading coefficients and explained by the reaction between the matrix PA6 and the compatibilizers.The quaternary blends compatibilized by more compatibilizers exhibit stronger hierarchical interfacial adhesions and smaller dispersed domain,which results in the further improved mechanical properties.Compared to the uncompatibilized blend,the blend with both 10 wt%PP-g-(MAH-co-St)and 10 wt%SEBS-g-(MAH-co-St)has the best mechanical properties with the stress at break,strain at break and impact failure energy improved significantly by 97%,71%and 261%,respectively.There is a strong correlation between the structure and property in the blends.     

Preparation of micelles with azo dye and UV absorbent at their cores or coronas using non-amphiphilic block copolymers

Micelles with azo dye and UV absorbent at their cores or coronas were prepared from non-amphiphilic random diblock copolymers by α,ω-diamine. Poly[4-(phenylazophenoxymethyl)styrene-ran-4-(2-hydroxybenzophenoxymethyl)styrene-ran-vinylphenol]-block-polystyrene (P(AS-r-HBS-r-VPh)-b-PSt) and poly(vinylphenol)-block-poly[4-(phenylazophenoxymethyl)styrene-ran-4-(2-hydroxybenzophenoxymethyl)styrene-ran-styrene] (PVPh-b-P(AS-r-HBS-r-St)) diblock copolymers were prepared by living radical polymerization mediated by 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl. The former copolymer had a molecular weight of Mn[P(AS-r-HBS-r-VPh)-b-PSt] = 10,000-b-250,000 by ¹H NMR and a molar ratio of AS:HBS:VPh = 0.01:0.01:0.98, while the latter had a molecular weight of Mn[PVPh-b-P(AS-r-HBS-r-St)] = 10,000-b-111,000 and a molar ratio of AS:HBS:St = 0.02:0.03:0.95. The copolymers showed no self-assembly in 1,4-dioxane because this solvent was non-selective to the copolymers. Dynamic light scattering demonstrated that the copolymers formed micelles in the solvent in the presence of α,ω-diamine. The hydrodynamic radii of the micelles slightly increased with the copolymer concentration decrease, while the aggregation numbers were almost independent of the copolymer concentration. It was found that P(AS-r-HBS-r-VPh)-b-PSt formed smaller micelles with a lower aggregation number than PVPh-b-P(AS-r-HBS-r-St) because of the steric hindrance of the AS and HBS units present at the micellar coronas.     

Synthesis of polypropene-block-poly(ethylene-co-propene) by short-period polymerization with MgCl2-supported Ziegler catalyst

The short-period polymerization method was successfully applied to the synthesis of a novel diblock copolymer, polypropene-block-poly(ethylene-co-propene). The polymerization was carried out for ca. 0,1 s with a MgCl₂-supported Ziegler catalyst. The copolymers obtained showed unimodal curves in gel-permeation chromatography without any peak in the low-molecular-weight region. After extraction with heptane, the fraction of poly(ethylene-co-propene) remained unchanged in the copolymer but disappeared in a commercial so-called block-type copolymer. All the results the formation of polypropene-block-poly(ethylene-co-propene), in which poly(ethylene-co-propene) is chemically linked with polypropene.     

High-temperature creep resistant ternary blends based on polyethylene and polypropylene for thermoplastic power cable insulation

The impact of a small amount of polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS) on the thermomechanical and electrical properties of blends comprising low-density polyethylene (LDPE) and isotactic polypropylene (PP) is investigated. SEBS is found to assemble at the PP:LDPE interface as well as within isolated PP domains. The addition of 10 wt% SEBS significantly increases the storage modulus between the melting temperatures of the two polyolefins, 110 and 160°C, and results in improved resistance to creep during both tensile deformation as well as compression. Furthermore, the ternary blends display a very low direct-current (DC) conductivity as low as 3.4 × 10⁻¹⁵ S m⁻¹ at 70°C and 30 kV mm⁻¹, which is considerably lower than values measured for neat LDPE. The here presented type of ternary blend shows potential as an insulation material for high-voltage direct current power cables.