Binary blends of poly(2,6–dimethyl–1,4–phenylene oxide) (PPE) with various styrene copolymers were investigated. Poly(styrene–co–acrylonitrile) (SAN), poly[styrene–co–(methyl methacrylate)] (SMMA), poly[styrene–co–(acrylic acid)] (SAA) and poly[styrene–co–(maleic anhydride)] (SMA) are only miscible with PPE when the amount of comonomer is rather small. From calculated binary interaction densities it can be concluded that the strong repulsion between PPE and comonomer limits miscibility. In blends of PPE with SAN, as well as with ABS, the inter-facial tension between the blend components is significantly reduced upon addition of polystyrene–block–poly–(methyl methacrylate) diblock copolymers (PS–b–PMMA) and polystyrene–block–poly (ethylene–co–butylene)–block–poly–(methyl methacrylate) triblock copolymers (PS–b–PEB–b–PMMA). They show a profound influence on morphology, phase adhesion and mechanical blend properties. 相似文献
A novel route to synthesize catenated macrocyclic PS–PMMA block copolymers is demonstrated via combination of supramolecular chemistry and controlled radical polymerization (CRP). Polymerization of styrene with bromopropionate ester initiator coupled with phenanthroline Cu(I) complex affords a four arm PS macroinitiator, which upon further chain extension by polymerization of MMA generates a four arm PS–PMMA block copolymer. Intramolecular coupling of PS–PMMA–Br arms via low temperature styrene‐assisted atom transfer radical coupling (ATRC) leads to the formation of PS–PMMA catenand, which generates the metal‐free catenated macrocyclic PS–PMMA block copolymer after removal of Cu metal. The interlocked structures of catenated block copolymers are confirmed by GPC, NMR, and AFM image analysis. 相似文献
Summary: PE‐block‐PS and P(E‐co‐P)‐block‐PS block copolymers were synthesised via sequential monomer addition during homogeneous polymerisation on various phenoxyimine catalysts. One phenoxyimine catalyst was tailored to produce high molecular weight block copolymers containing both, polyolefin and polystyrene segments. According to chromatographic analysis and TEM morphology studies, blends of block copolymers and PE homopolymers [or P(E‐co‐P), respectively] were formed. The direct olefin/styrene block copolymer synthesis on phenoxyimine catalysts represents an attractive, new one‐pot route to styrenic block copolymers which are commercially prepared by anionic styrene/diene block copolymerisation followed by hydrogenation.
The surface chemical structure development in solution-cast styrene(S)/butadiene(B) block copolymer films as a function of solvent evaporation time was investigated using sum frequency generation vibrational spectroscopy(SFG).The surface structure formation of the styrene(S)/butadien(B) block copolymer(30 wt% PS) films during the solution-to-film process was found to be controlled mainly by dynamic factors,such as the mobility of the PB block in solution.For SB diblock copolymers,a pure PB surface layer was formed only when the film was cast by dilute toluene solution.With increasing concentration of casting solution,PB and PS components were found to coexist on the film surface,and the morphology of the PB component on the film surface changed from cylindrical rods to spheres.For SBS triblock copolymers,a small amount of PS component existed on the surface even if the film was cast by 1.0 wt% toluene solution.In addition,PS components at the outermost layer of the film increased and the length of PB cylindrical rods on the surface decreased with increasing concentration of casting solution. 相似文献
A systematic investigation of the dynamic mechanical properties of high-density polyethylene (HDPE)/high-impact polystyrene (HIPS)/copolymer blends was carried out. Blends of 80/20 weight percent of HDPE/HIPS were prepared in the melt state at 180°C in a batch mixer. Synthesized pure diblock (H77) and tapered diblock (H35) copolymers of hydrogenated polybutadiene (HPB) and polystyrene (PS) were added at different concentrations (1, 3, and 5 wt %), and the dynamic mechanical properties were investigated. The results show that: (1) both the tapered and the pure diblock copolymers enhance the phase dispersion and the interphase interactions; (2) structure and molecular weight are both important parameters in the molecular design of copolymers; (3) important effects occur when only small amounts of copolymer are added (up to the interface saturation concentration SC); (4) a micellar structure formation is possible when the copolymer is in excess in the blend; (5) the effect of the copolymer structure on the SC and the critical micellar concentration (CMC) is more pronounced than the effect of molecular weight. These concentrations are found to be lower for the tapered diblock copolymer. The analysis of the dynamic mechanical thermal analysis (DMTA) results obtained for the 20/80 HDPE/HIPS blend leads to the conclusion that the copolymers also enhance the interactions between heterogeneous phases. Similar conclusions based on electron microscopy were reported in the literature. DMTA shows great potential to relate macroscopic observations to the state of a copolymer in an immiscible blend. 相似文献
Correlation between morphology and micromechanical deformation behaviour of blends consisting of a lamellae-forming linear styrene/butadiene block copolymer and polystyrene homopolymer (hPS) was studied by different microscopic techniques (transmission electron microscopy and scanning electron microscopy) and rheo-optical Fourier transformed infrared spectroscopy. Attributable to a change in morphology from well-ordered lamellae to a distorted one, a transition in deformation mechanism from homogeneous plastic flow of the lamellae to formation of local craze-like deformation zones was observed on addition of hPS. The latter led to a drastic reduction in elongation at break. An abrupt depression in the degree of orientation of the polystyrene (PS) and the polybutadiene (PB) phases in the blends suggested that the failure occurs at the interface between the added hPS and PS blocks of the block copolymer. 相似文献
This paper reports on the interfacial behaviour of block and graft copolymers used as compatibilizers in immiscible polymer blends. A limited residence time of the copolymer at the interface has been shown in both reactive blending and blend compatibilization by preformed copolymers. Polystyrene (PS)/polyamide6 (PA6), polyphenylene oxide (PPO)/PA6 and polymethylmethacrylate (PMMA)/PA6 blends have been reactively compatibilized by a styrene-maleic anhydride copolymer SMA. The extent of miscibility of SMA with PS, PPO and PMMA is a key criterion for the stability of the graft copolymer at the interface. For the first 10 to 15 minutes of mixing, the in situ formed copolymer is able to decrease the particle size of the dispersed phase and to prevent it from coalescencing. However, upon increasing mixing time, the copolymer leaves the interface which results in phase coalescence. In PS/LDPE blends compatibilized by preformed PS/hydrogenated polybutadiene (hPB) block copolymers, a tapered diblock stabilizes efficiently a co-continuous two-phase morphology, in contrast to a triblock copolymer that was unable to prevent phase coarsening during annealing at 180°C for 150 minutes. 相似文献
Polystyrene–poly(ethylene oxide) PS–PEO di- and triblock copolymers have been used as stabilizers in the emulsion polymerization of styrene and styrene–butylacrylate for the preparation of “hairy latexes”. The polymerization kinetics and the efficiency of these polymeric surfactants were correlated with the molecular characteristics of the block copolymer. It was shown that the efficiency decreased with increasing molecular weight and PS content of the block copolymer. The PEO frige, with a thickness of 4–25 nm, on the latex particle surface could be characterized and it was shown by differential scanning calorimetry (DSC) that water is strucured in that PEO layer. Film formation with “hairy latexes” was also examined both by DSC and thermomechanical analysis. The properties and application possibilities, such as in controlled latex flocculation, have been reviewed. 相似文献
Dilute solution viscosity and osmotic pressure measurements were performed on polystyrene (PS), polybutadiene (PB), polystyrene–polybutadiene (SB) diblock and polystyrene–polybutadiene (SBS) triblock copolymers. Anionic polymerization was used in such a way that the molecular weight of the PS block was kept constant (ca. 10 000), while the molecular weight of the PB block varied from 18000 to 450000. The measurements were carried out at a fixed temperature of 34.20°C in three solvents, namely toluene, a good solvent for PS as well as for PB, dioxane, which is a good solvent for PS and almost a theta solvent for PB, and cyclohexane, which is nearly a theta solvent for PS and a good solvent for PB. The compositions of SB and SBS, as derived from kinetic data agree with ultraviolet measurements in CHCl3 solutions. The viscosity and osmotic pressure results indicate that the properties of SB and SBS are similar. Their intrinsic viscosities and second virial coefficients can be calculated from their chemical compositions, molecular weight, properties of parent polymers, and values of the interaction parameter \documentclass{article}\pagestyle{empty}\begin{document}$\bar \beta _{{\rm SB}}$\end{document} between styrene and butadiene units, for molecular weights not exceeding approximately 105. The magnitude of \documentclass{article}\pagestyle{empty}\begin{document}$\bar \beta _{{\rm SB}} $\end{document} varies with the solvent. The results suggest that the domains of the PS and PB blocks overlap to a great extent. 相似文献