Compatibility of some fluorosubstituted styrene polymers and copolymers in blends with poly(2,6-dimethyl-1,4-phenylene oxide) and with polystyrene

Blends of poly(p-fluorostyrene) (PpFS), poly(o-fluorostyrene) (PoFS), poly(styrene-co-p-fluorostyrene) (SP46), poly(styrene-co-o-fluorostyrene) (SO49), with poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and with polystyrene (PS), have been prepared by compression molding of coprecipitated polymers. Compatibility of these systems has been studied by differential scanning calorimetry. Detection of one or two glass transition regions was used to classify the blends as compatible or incompatible. Homopolymers of pFS and oFS were found to be incompatible with PPO and PS. The SP46 copolymer and SO49 copolymer were compatible with PPO in all proportions.     

Compatibility of poly(2,6-dimethyl-1,4-phenylene oxide)/poly(fluorostyrene-co-chlorostyrene) blends

The compatibility of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) with random copolymers of ortho- and para-fluorostyrene as well as with ortho- and para-chlorostyrene of various copolymer compositions was examined. The compatibility was studied by DSC and visual observation of film clarity. It was found that copolymers of ortho-fluorostyrene with para-chlorostyrene containing 15–74 mol % p-CIS are compatible with PPO in all proportions. Compatibility of the PPO/poly-(ortho-fluorostyrene-co-ortho-chlorostyrene) system was observed for copolymers containing between 15 and 36 mol % ortho-chlorostyrene. Copolymers of para-fluorostyrene with para-chlorostyrene, as well as copolymers of para-fluorostyrene with ortho-chlorostyrene appear to be incompatible with PPO at 210°C.     

Phase behavior of blends of poly(2,6-dimethyl-1,4-phenylene oxide)/polystyrene/poly(o-chlorostyrene-co-p-chlorostyrene) copolymer

The phase behavior of ternary blends of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), polystyrene (PS) and a 50/50 mole % statistical copolymer of o-chlorostyrene and p-chlorostyrene [p(oClS-pClS)] has been investigated by differential scanning calorimetry (DSC) and analyzed in terms of a Flory-Huggins mean-field segmental interaction parameter treatment. Both PS/PPO and PPO/p(oClS-pClS) binary blends exhibit single glass transition temperatures over the full composition range whereas the PS/p(oClS-pClS) system displays a substantial immiscibilty window which extends into the ternary phase diagram. In principle, ternary systems provide enhanced opportunities relative to binary systems for evaluating segmental interaction parameters χ_ijs from experimental data because of the high sensitivity of phase boundary locations to these parameters and to component molecular weights. In this system the effect of these parameters on the phase boundary was studied experimentally and compared to calculated values.     

Partial miscibility in the system poly(para-chlorostyrene-co-ortho-chlorostyrene)/poly(2,6-dimethyl-1,4-phenylene oxide)

The compatibility of random copolymers of para-chlorostyrene and ortho-chlorostyrene (PO copolymers) with poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) has been studied by differential scanning calorimetry (d.s.c.). Blends prepared by compression moulding of coprecipitated powders display either one or two glass transitions, dependent on the composition of the copolymer component of the blend. PO copolymers of para-chlorostyrene content from 23 to 64% are miscible with PPO in all proportions, using the customary criteria of a single calorimetric glass relaxation and optical clarity. Both homopolymers poly(para-chlorostyrene) (P_pClS) and poly(ortho-chlorostyrene) (P_oClS) are found to be incompatible with PPO; such blends exhibit two glass transitions at temperatures characteristic of the pure component phases. All compatible PO-PPO blends undergo phase separation upon annealing at elevated temperatures, indicating that a lower critical solution temperature (LCST) must exist. The phase separation is found to be reversible by annealing below the LCST, at temperatures which are still above the glass transitions of both blend components.     

Surface segregation of components in poly(vinyl chloride)–polydimethylsiloxane and polystyrene–poly(propylene oxide) solvent-cast blends

X-ray photoelectron spectroscopy and scanning electron microscopy are used to study the surface composition and morphology of poly(vinyl chloride)–polydimethylsiloxane (PVC–PDMS) and polystyrene–poly(propylene oxide) (PS–PPO) solvent-cast blends as a function of the blend composition and constituent molecular weights. The PVC–PDMS blends show a pronounced surface enrichment of PDMS, which is higher the lower the molecular weight of PDMS. The surface behavior ofthe PPO–PS blends is strongly dependent on the solvent used. Despite the much lower surface tension of PPO compared to that of PS, no surface segregation of PPO isobserved in the PPO–PS blends cast from tetrahydrofuran, while the blends cast from chloroform exhibit a high surface enrichment of PPO. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 517–522, 1998     

Effect of pressure on phase behavior in polymer blends of poly(2,6-dimethyl-1,4-phenylene oxide) and poly(o-fluorostyrene-co-p-fluorostyrene) copolymers

The effect of pressure on miscibility and phase separation in blends of random copolymers of ortho- and para-fluorostyrene, P(o-FS-co-p-FS) and poly(2,6-dimethyl-1,4-phenylene oxide), PPO, has been studied by differential thermal analysis (DTA) at pressures up to 300 MPa. At 200 MPa the copolymers containing from 10 to 38 mol% p-FS are miscible with PPO below 230°C using the customary criterion of a single calorimetric glass transition temperature (T_g). Each blend undergoes phase separation upon annealing at higher temperatures at both atmospheric and elevated pressures indicating the presence of a lower critical solution temperature (LCST). When the phase behaviors of the 50/50 wt% blends are examined as a function of temperature and copolymer composition, a symmetric miscibility “window” can be observed in the resulting temperature-composition diagram with a maximum at about 22 mol% p-FS. In a complementary set of experiments, the pressure dependence of the phase boundary for the blend of PPO and P(o-FS-co-p-FS) in which the copolymer contained 29 mol% p-FS was studied. The temperature minimum of the phase boundary is at about 50 wt% PPO and is independent of pressure. The consolute temperature, T_c, increases at about 0.1₀°C/MPa up to 200 MPa and then becomes independent of pressure to reach an asymptotic value at around 270°C. Similar behavior is also observed for blends in which the copolymer composition contains either 16 or 23 mol% p-FS. In these blends the decrease of dT_c/dP at higher pressures may indicate that the negative volume of mixing approaches zero above 200 MPa. This study shows therefore, that pressure no longer plays a role in increasing the miscibility above 200 MPa.     

Orientation and relaxation in uniaxially stretched poly(vinyl methyl ether)-atactic polystyrene blends

Infrared measurements of the dichroic ratio of polystyrene and poly(vinyl methyl ether) absorption bands allow us to determine chain orientation for each component in their compatible blends. Influence of strain rate and temperature of stretching on orientation of both polymer chains in blends containing up to 25% PVME has been studied. Mechanical relaxation master curves at a reference temperature T=T_g+40°C have also been determined. Results are compared to previous results obtained in PS-PPO compatible blends. Although PPO and PVME chains behave differently PS chains behaviour is similar in the two types of blends and interpreted in terms of a hindrance of relaxation of PS chains induced by a modification of friction coefficients due to the molecular interactions which are at the origin of compatibility.     

Thermally induced phase separation in homogeneous blends of poly(2,6-dimethyl-1,4-phenylene oxide) with poly(o-fluorostyrene-co-p-chlorostyrene) and with poly(o-fluorostyrene-co-o-chlorostyrene)

The phase separation behavior of initially compatible blends of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) with poly(o-fluorostyrene-co-p-chlorostyrene) [poly(oFS-co-pCIS)] and with poly(o-fluorostyrene-co-o-chlorostyrene) [poly(oFS-co-oCIS)] was studied by DSC. It was found that copolymers of poly(oFS-co-pCIS) containing between 15 and 62 mol % pCIS have shown no phase separation after annealing at temperatures up to 320°C. It was also observed that blends containing this copolymer with 74 mol % pCIS show phase separation at 250°C, which depended on blend composition. Additionally, all PPO/poly(oFS-co-oCIS) blends exhibit phase separation after annealing to a temperature of 230°C. Thermal degradation of the polymer blends was not observed at the temperatures studied.     

Phase behavior for blends of styrene containing triblock copolymers with poly(2,6-dimethyl-1,4-phenylene oxide)

The extent to which the styrene end-blocks of three commercially available triblock copolymers can mix with a particular poly(2,6-dimethyl-1,4-phenylene oxide) (M_n = 22,600 and M_w = 34,000) or PPO has been examined by investigation of the glass transition behavior of the PPO and polystyrene (PS) portions of the blends using differential scanning calorimetry. Each block copolymer has a butadiene-based mid-block which was hydrogenated for two of these materials, but not the third. The three copolymers differ substantially in overall molecular weight and in molecula weight of the blocks. However, in analogy with the literature on blends of homopolymer polystyrene with styrene-based block copolymers, the molecular weight of the PS block should be the principal factor affecting the phase behavior in the present blends. Mixtures of the PPO with the block copolymers having PS blocks with M = 14,500 (nonhydrogenated midblock) and with M = 29,000 (hydrogenated mid-block) exhibited single composition-dependent T_gs for the hard phase, indicating complete mixing of PS segments with the PPO, for all proportions. On the other hand, the block copolymer having a PS block with M = 7,500 and a hydrogenated mid-block exhibited two separate hard phase T_gs corresponding to an essentially pure PPO phase and a PS-rich phase. For blends of homopolymer PS with styrene-based block copolymers, the similar two-phase behavior of the glassy portion can be readily explained by entropic considerations. For the present case, the favorable enthalpic contribution for mixing PPO and PS is an additional factor which seems to influence the restrictions on molecular weight for complete mixing; however, additional work is needed to develop a more quantitative assessment of this new issue.     

核壳结构微纳橡胶粒子的可控合成及对PPO/PS共混体系的增韧

采用乳液聚合方法在粒径为100 nm的聚丁二烯(PB)胶乳上接枝聚合苯乙烯(St),合成了核壳比为70/30(PB/PS)的PB-g-PS接枝共聚物,将其与聚苯醚(PPO)、聚苯乙烯(PS)树脂熔融共混,制备出一系列橡胶含量、基体组成不同的PPO/PS/PB-g-PS共混物,并考察了共混物的相容性、力学性能及形态结构。结果发现:PPO与PS为完全相容体系,且PB-g-PS在PPO/PS基体中的均匀分散程度随体系中PPO引入量的增大而明显改善,共混物的冲击强度及屈服强度也随之逐渐增大,进而促使共混物发生脆-韧转变所需的橡胶含量逐渐降低;随着共混体系中橡胶含量的增加,共混物的冲击强度逐渐提高,而屈服强度却逐渐降低,共混物的韧性断裂特征越发显著。     

Phase behavior of binary and ternary blends of poly(styrene‐co‐methacrylic acid), poly(styrene‐co‐4‐vinylpyridine), and poly(2,6‐dimethyl‐1,4‐phenylene oxide)

Poly(styrene‐co‐methacrylic acid) (PSMA) and poly(styrene‐co‐4‐vinylpyridine) (PS4VP) of different compositions were prepared and characterized. The phase behavior of these copolymers as binary PSMA/PS4VP mixtures or with poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) as PPO/PSMA or PPO/PS4VP and PPO/PSMA/PS4VP ternary blends was investigated by differential scanning calorimetry (DSC). This study showed that PPO was miscible with PS4VP containing up to 15 mol % 4‐vinylpyridine (4VP) but immiscible with PS4VP‐30 (where the number following the hyphen refers to the percentage 4VP in the polymer) and PSMA‐20 (where the number following the hyphen refers to the percentage methacrylic acid in the polymer) over the entire composition range. To examine the morphology of the immiscible blends, scanning electron microscopy was used. Because of the hydrogen‐bonding specific interactions that occurred between the carboxylic groups of PSMA and the pyridine groups of PS4VP, chloroform solutions of PSMA‐20 and PS4VP‐15 formed interpolymer complexes. The obtained glass‐transition temperatures (T_g's) of the PSMA‐20/PS4VP‐15 complexes were found to be higher than those calculated from the additivity rule. Although, depending on the content of 4VP, the shape of the T_g of the PPO/PS4VP blends changed from concave to S‐shaped in the case of the miscible blends, two T_g were observed with each PPO/PS4VP‐30 and PPO/PS4VP‐40 blend. The thermal stability of the PSMA‐20/PS4VP‐15 interpolymer complexes was studied by thermogravimetry. On the basis of the obtained results, the phase behavior of the ternary PPO/PSMA‐20/PS4VP‐15 blends was investigated by DSC. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis, thermal properties, and specific interactions of high Tg increase in poly(2,6-dimethyl-1,4-phenylene oxide)-block-polystyrene copolymers

We have synthesized a series of block copolymers of poly(2,6-dimethyl-1,4-phenylene oxide) and polystyrene (PPO-b-PS copolymer) by atom transfer radical polymerization. The PS content in these copolymer systems was determined by using infrared spectroscopy, thermal gravimetric analysis, and solution and solid-state NMR spectroscopy; good correlations exist between these characterization methods. DSC analyses indicated that the PPO-b-PS copolymers have higher glass transition temperatures than do their corresponding PPO/PS blends. Our FTIR and solid-state NMR spectroscopic analyses suggest that the PPO-b-PS copolymers possess stronger specific interactions that are responsible for the observed relatively higher values of T_g. We found one single dynamic relaxation from the dynamic mechanical analysis, which implies dynamic homogeneity exists in the PPO-b-PS copolymer; this result is consistent with the one single proton spin-lattice relaxation time observed in the rotating frame [T_1ρ(H)] during solid state NMR spectroscopic analysis. In addition, the 2D FTIR spectroscopy reveals evidence for the stronger interactions between segments of PPO and PS through the formation of π-cation complexes.     

Compatibilising action of random and triblock copolymers of poly(styrene-butadiene) in polystyrene/polybutadiene blends: A study by electron microscopy, solid state NMR spectroscopy and mechanical measurements

Scanning electron microscopy, solid-state proton NMR spectroscopy and static mechanical analysis have been performed in order to evaluate the compatibilising action of random copolymers of polystyrene and polybutadiene and triblock copolymers of poly(styrene-butadiene-styrene) in incompatible polystyrene/polybutadiene (PS/PB) blends. Scanning electron microscopic examination of the cryofractured and etched surfaces showed high degree of compatibilising action of the triblock copolymers as evidenced by the very sharp decrease of the domain size of the dispersed phase followed by an increase at higher concentrations. This is a clear indication of interfacial saturation. These results were in agreement with the theoretical predictions of Noolandi and Hong. The random copolymer was not effective in compatibilising the system. Solid-state proton NMR experiments were performed on the uncompatibilised and compatibilised blends. The proton spin-lattice relaxation times in the laboratory frame, T₁(H), and in the rotating frame, T_1ρ(H), and spin-spin relaxation times, T₂(H), were carefully measured for the systems. Significant changes were observed for the systems compatibilised with triblock copolymers due to the preferential localisation of the copolymers at the PS/PB interface. However, the random copolymer did not have any compositional drift and is not an effective interface modifier in agreement with microscopy study. The static mechanical properties of the blends have also been analysed. The addition of triblock copolymers increased the mechanical properties of the blends. Finally, attempts have been made to correlate the NMR results with the microstructure and mechanical properties of the blends.     

Orientation and relaxation in uniaxially-stretched poly(2,6-dimethyl 1,4-phenylene oxide) — atactic polystyrene blends

Infra-red measurements of the dichroic ratio of atactic polystyrene and poly(2,6-dimethyl 1,4-phenylene oxide) absorption bands provide a valuable method for the determination of orientation as well as relaxation of chains of both polymers during stretching of their compatible blends. Influence of strain rate, temperature of stretching, and molecular weight of the polymers on orientation of both polymer chains in blends containing up to 35% PPO has been studied. Orientation relaxation for both polymers has been analysed using Lodge's constitutive equation. Master curves have been obtained for PPO and PS in the blends at a reference temperature T₀ = T_g + 10°C. Results are interpreted in terms of an hindrance of relaxation of PS chains induced by interaction with a highly-oriented PPO network which slowly relaxes.     

Miscibility and specific interactions in blends of poly(4-vinylphenol-co-methyl methacrylate)/poly(styrene-co-4-vinylpyridine)

The miscibility and phase behavior of poly(4-vinylphenol-co-methyl methacrylate) (PVPhMMA50) containing 50% of methyl methacrylate with random copolymers of poly(styrene-co-4-vinylpyridine) (PS4VPy) containing 5, 15, 30, 40, and 100% of 4-vinylpyridine, respectively, were investigated by differential scanning calorimetry, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). It was shown that for a composition of 4-vinylpyridine less than 30%, all blends of PVPhMMA50/PS4VPy are immiscible, characterized by the apparition of two glass transitions (T_g) over their entire composition range. However, above this composition, a single T_g has been observed in all the blends of PVPhMMA50 and PS4VPy. When the amount of vinylpyridine exceeds to 40% in PS4VPy, the obtained T_gs of PVPhMMA50/PS4VPy blends were found to be significantly higher than those observed for each individual component of the mixture indicating that these blends are able to form interpolymer complexes. FTIR analysis reveals the existence of preferential specific interactions via hydrogen bonding between the hydroxyl and pyridyl groups and intensifies when the amount of 4VPy is increased in PS4VPy copolymers. Furthermore, the quantitative FTIR study carried out for PVPhMMA50/PS4VPy blends was also performed for the vinylphenol and vinylpyridine functional groups. These results were also confirmed by SEM study. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Influence of diblock copolymer on the morphology and properties of polystyrene/poly(dimethylsiloxane) blends

Blends of polystyrene (PS) and poly(dimethylsiloxane) (PDMS), with and without diblock copolymers (PS‐b‐PDMS), were prepared by melt mixing. The melt rheology behavior of the blends was studied with a capillary rheometer. The morphology of the blends was examined with scanning electron microscopy. The miscibility of the blends was studied with differential scanning calorimetry. The morphology of PS/PDMS blends was modified by the addition of PS‐b‐PDMS copolymers and investigated as a function of the molar mass of the diblock copolymers, viscosity ratios and the processing conditions. As investigated, the observed morphology of the melt‐blended PS/PDMS pair unambiguously supported the interfacial activity of the diblock copolymers. When a few percent of the diblock copolymers blended together with the PS and PDMS homopolymers, the phase size was reduced and the phase dispersion was firmly stabilized against coalescence. The compatibilizing efficiency of the copolymers was strongly dependent on its molar mass. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2747–2757, 2004     

Blends of SBS triblock copolymer with poly(2,6‐dimethyl‐1,4‐phenylene oxide)/polystyrene mixture

Blends of styrene–butadiene–styrene (SBS) or styrene–ethylene/1‐butene–styrene (SEBS) triblock copolymers with a commercial mixture of polystyrene (PS) and poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) were prepared in the melt at different temperatures according to the chemical kind of the copolymer. Although solution‐cast SBS/PPO and SBS/PS blends were already known in the literature, a general and systematic study of the miscibility of the PS/PPO blend with a styrene‐based triblock copolymer in the melt was still missing. The thermal and mechanical behavior of SBS/(PPO/PS) blends was investigated by means of DSC and dynamic thermomechanical analysis (DMTA). The results were then compared to analogous SEBS/(PPO/PS) blends, for which the presence of a saturated olefinic block allowed processing at higher temperatures (220°C instead of 180°C). All the blends were further characterized by SEM and TGA to tentatively relate the observed properties with the blends' morphology and degradation temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2698–2705, 2003     

Plastification of poly(vinyl chloride) by polymer blending

Blends of poly(vinyl chloride) (PVC) with different copolymers have been studied to obtain a plasticized PVC with improved properties and the absence of plasticizer migration. The copolymers used as plasticizers in the blends were acrylonitrile butadiene rubber, ethylene vinyl acetate (EVA), and ethylene-acrylic copolymer (E-Acry). Blends were studied with regard to their processing, miscibility, and mechanical properties, as a function of blend and copolymer composition. The results obtained were compared with those of equivalent compositions in the PVC/dioctyl phthalate (DOP) system. Better results than PVC/DOP were obtained for PVC/acrylonitrile butadiene rubber blends. The plasticizing effect on PVC of EVA and E-Acry copolymers was similar to that of DOP. It is shown that crosslinking PVC/E-Acry blends or increasing the vinyl acetate content in PVC/EVA blends, are alternatives that can increase the compatibility and mechanical properties of these blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1303–1312, 2000     

XPS and DSC Studies of Solution Cast Polystyrene/Poly(organophosphazene) Blends. I. Polystyrene/Poly(phenoxy)phosphazene

Blends of polystyrene (PS) with poly(phenoxy)phosphazene (PPN) were studied by differential scanning calorimetry (DSC) and X-ray photoelectron spectroscopy (XPS). A third component, poly(2,6-dimethyl-1,4-phenylene ether) (PPE), was added with the aim of increasing compatibility of the blends. T _g values did not vary in the PS/PPN blends, indicating that the components are substantially incompatible. The addition of PPE did not change the situation much even though some compatibility between PPN and PPE was detected. XPS on the cast films showed that only PPN was present at the surface. The surface composition of the blends was found to be dependent on the preparation technique.     

Craze microstructure and molecular entanglements in polystyrene-poly(phenylene oxide) blends

Polystyrene and poly(phenylene oxide) are miscible over the entire range of compositions. Thin films of five blends of high molecular weight polystyrene (PS) with high molecular weight poly(phenylene oxide) (PPO), and four blends of low molecular weight PS (whose molecular weight lies below its entanglement molecular weight M_e) with the same PPO have been prepared. Following bonding of these films to copper grids, crazes were grown by uniaxial straining in air. Suitable crazes were then observed by transmission electron microscopy. From microdensitometry of the image plates it is possible to measure the extension ratio λ_craze within crazes in the nine blends. These measured values are compared with predicted values of λ_max, computed from λ_max = I_ed, where I_e is the chain contour length between entanglements and d is the root mean square end-to-end distance for a chain of molecular weight M_e. For the high molecular weight PS blends λ_max depends on the entanglement properties of both PS and PPO chains. For the low molecular weight PS blends, the PS chains cannot form part of the entanglement network and the correct value of λ_max is obtained from appropriate scaling of the pure PPO value. Comparison of λ_craze and λ_max for both types of blends shows excellent agreement, demonstrating the importance of the entanglement network in determining craze parameters and hence the toughness of a given polymer.