Synthesis and characterization of ABA triblock copolymers containing poly(2,6-dimethyl-1,4-phenylene oxide) as A blocks and tetramethyl bisphenol-A polysulfone as B blocks

α, β-Bis(hydroxyphenol) tetramethyl bisphenol-A polysulfone (PSUT) was synthesized by two different methods, one using a strong base, the other using a weak base. The bifunctional polysulfone containing tetramethyl bisphenol-A chain ends was exploited as a model telechelic that can be used for the preparation of ABA triblock copolymers containing poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) as A segments and PSUT as B segments. PSUT and PPO were incorporated into triblock copolymers by an oxidative coupling copolymerization of PSUT with 2,6-dimethylphenol or by the redistribution of PPO in the presence of PSUT. The mechanism of block copolymerization is discussed. DSC studies indicate that short immiscible PPO and PSUT segments incorporated into a triblock copolymer do not exhibit phase separation. Polymer blends of the PPO–PSUT–PPO triblock copolymers with PPO homopolymer were analyzed by DSC. Both miscible and phase-separated blends can be prepared depending on the molecular weight of both PPO homopolymer and of the PPO segment present in the triblock copolymer. Polymer blends of the PPO–PSUT–PPO triblock copolymer with PSUT were miscible at all compositions.     

Blends of poly(2,6–dimethyl–1,4–phenylene oxide) with styrene copolymers

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.     

Surface segregation in blends of miscible amorphous polymers

The isothermal luminescence decay kinetics in near-surface nanolayers of plasma-activated bulk samples of amorphous polystyrene (PS) and poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and their miscible blends with weight ratios PS/PPO of 75/25 and 50/50 has been studied at 77 K. The intensities of isothermal luminescence (I) of homopolymer and blend surfaces have been compared. It has been found that the ratio between the luminescence intensities for PS and PPO (I(PS)/I(PPO)) may be as high as 50, while the luminescence intensities for the PS–PPO blends are close to I(PPO). The results obtained indicate that the PPO concentration in the surface layers of the blends is higher than that in the bulk.     

On the macro- and microphase separation of compatibilizers in immiscible polymer blends

Macro- and microphase separation of compatibilizing graft copolymers in melt-mixed polystyrene/polyamide-6 blends was studied by transmission electron microscopy and thermal analysis. Three different graft copolymers with main chains of polystyrene and side chains of poly(ethylene oxide) were used as additives at various concentrations. The polyamide-6 domain sizes decreased with increasing amounts of compatibilizing graft copolymers in the blends up to a saturation concentration, after which no further reduction was noted. Macrophase separation of the graft copolymers into discrete macrodomains 20–200 nm in size occurred at concentrations equal to or slightly lower than the saturation concentration. The macrodomains of the graft copolymers were microphase separated, and the sizes and shapes of the microdomains were found to largely depend on the graft copolymer structure and composition. As a consequence of microphase separation, poly(ethylene oxide) crystallinity was noted in blends with sufficiently high macrophase contents. Observations of a graft copolymer interphase between the polystyrene matrix and the polyamide-6 domains confirmed that the graft copolymer was present at the blend interfaces in some of the compatibilized blends. © 1996 John Wiley & Sons, Inc.     

Local compositional fluctuations in PPO/HIPSand PPO/SBS blends

Solid-state NMR relaxation has been used to explore the distribution of components in poly(phenylene oxide) (PPO) high impact polystyrene (HIPS) and PPO/poly(styrene-b-butadiene-b-styrene) (SBS) blends. The nuclear relaxation of PPO in the former system is single exponential for all compositions, but the relaxation of PS in the blend is simple exponential only when the PPO content is low but is otherwise nonexponential. The nuclear magnetization decay curves were analyzed in terms of statistical compositional fluctuation at the scale of spin diffusion distances of several nm. Distribution functions for nuclear relaxation and for blend composition have been derived. Extraction of low molecular weight occluded PS from HIPS resulted in blends having reduced homogeneity. Addition of low molecular weight PS enhanced homogeneity in both the PPO/HIPS and PPO/SBS blends. © 1994 John Wiley & Sons, Inc.     

聚苯醚离聚体/聚(苯乙烯-co-4-乙烯吡啶)共混体系的溶液行为

聚（２，６ 二甲基 １，４ 苯醚）（ＰＰＯ）离聚体（磺化或羧化聚苯醚）／聚（苯乙烯 ｃｏ ４ 乙烯吡啶（ＰＳＶＰ）共混物的溶液行为研究表明，与对应的ＰＰＯ／ＰＳＶＰ共混物相比，这两个系列的共混物都表现出较高的比浓粘度．这是由于聚苯醚离聚体上的酸基发生质子转移，产生了酸根阴离子和吡啶基阳离子，两组分间的酸 碱相互作用导致了分子间的缔合，从而使比浓粘度提高．     

Clouding Behavior of Ethylene Oxide‐Propylene Oxide Block Copolymer P85: The Effect of Additives

The characteristic feature of nonionic poly(ethylene oxide)‐poly(propylene oxide)‐poly(ethylene oxide) (PEO‐PPO‐PEO) triblock copolymers is that at higher temperatures they undergo clouding and liquid‐liquid phase separation. The clouding temperature of such block copolymers can be profoundly altered in the presence of various additives. In this work the effect of various additives on the clouding phenomenon of triblock copolymer P85[(EO)₂₆(PO)₃₉(EO)₂₆] is discussed.     

聚氧化乙烯-聚苯乙烯-聚氧化乙烯三嵌段共聚物/聚苯醚共混物的相容性和结晶行为

本工作对聚氧化乙烯-聚苯乙烯-聚氧化乙烯(PEO-PS-PEO)三嵌段共聚物与聚苯醚(PPO)均聚物共混物的相容性及结晶行为进行了研究。结果表明,共混体系的相容性与嵌段共聚物中苯乙烯段的含量有关,PS含量越高,PPO与共聚物PS段的相容性越好。共混体系的结晶行为也明显不同于一般均聚物共混体系。在DSC降温结晶过程中最多可出现三个结晶峰。     

聚氧化乙烯-聚苯乙烯-聚氧化乙烯三嵌段共聚物/聚苯醚共混物的相容性和结晶行为

 本工作对聚氧化乙烯-聚苯乙烯-聚氧化乙烯(PEO-PS-PEO)三嵌段共聚物与聚苯醚(PPO)均聚物共混物的相容性及结晶行为进行了研究。结果表明,共混体系的相容性与嵌段共聚物中苯乙烯段的含量有关,PS含量越高,PPO与共聚物PS段的相容性越好。共混体系的结晶行为也明显不同于一般均聚物共混体系。在DSC降温结晶过程中最多可出现三个结晶峰。     

环氧化聚丁二烯-聚苯乙烯嵌段共聚物对聚苯醚/环氧体系反应诱导相分离行为的影响

采用扫描电镜、光学显微镜和光散射仪研究了环氧化聚丁二烯一聚苯乙烯嵌段共聚物(EBs)对聚苯醚(PPO)/双酚A 型环氧树脂(DGEBA)/4,4二(2,6-二甲基苯胺基)甲烷(DIM-DDM)体系反应诱导相分离行为的影响.实验结果表明,EBS的加入对PPo/DGEBA/DIM-DDM体系反应诱导相分离的演化过程有阻滞作用.随着EBS加入量的增加,体系形成双连续相结构所需的PPO含量范围变宽,而对于相同PPO含量、形成双连续相的体系则相结构尺寸减小.     

Energy transfer in connection with the photo-oxidation of polystyrene and its blends with poly(2,6-dimethyl-1,4-phenylene oxide)

By fluorescence spectroscopy it is possible to investigate some of the photophysical processes, particularly the energy transfer, that occur during the photo-oxidative degradation of polystyrene (PS), poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), and homogeneous blends of these. In connection with the irradiation, a part of the absorbed energy is transferred from excited phenyl groups in PS to PPO. The decrease in PS excimer fluorescence at 319 nm by admixture of PPO is greater than expected from the absorption of PPO at the excitation wavelength. A radiative energy transfer is suggested from PS to PPO which absorbs at 319 nm. Energy transfer also occurs to groups formed during photo-oxidation. The quenching of PS excimer fluorescence during the process has been studied for both the homopolymer and the blends, and in all cases the reactions occurring during photo-oxidation result in marked quenching at 319 nm.     

Phase behavior in mixtures of a homopolymer and a block copolymer 1. FTIR and DSC studies

Miscibility in blends of three styrene-butadiene-styrene and one styrene-isoprene-styrene triblock copolymers containing 28%, 30%, 48%, and 14% by weight of polystyrene, respectively, with poly(vinyl methyl ether) (PVME) were investigated by FTIR spectroscopy and differential scanning calorimetry (DSC). It was found from the optical clarity and the glass transition temperature behavior that the blends show miscibility for each kind of triblock copolymers below a certain concentration of PVME. The concentration range to show miscibility becomes wider as the polystyrene content and molecular weight of PS segment in the triblock copolymers increase. From the FTIR results, the relative peak intensity of the 1100 cm^-1 region due to COCH₃ band of PVME and peak position of 698 cm^-1 region due to phenyl ring are sensitive to the miscibility of SBS(SIS)/PVME blends. The results show that the miscibility in SBS(SIS)/PVME blends is greatly affected by the composition of the copolymers and the polystyrene content in the triblock copolymers. Molecular weights of polystyrene segments have also affected the miscibility of the blends. ©1995 John Wiley & Sons, Inc.     

Glass‐formation kinetics of miscible blends of atactic polystyrene and poly(2,6‐dimethyl‐1,4‐phenylene oxide)

We present a detailed investigation of the kinetics associated with the glass transitions of miscible blends composed of atactic polystyrene (a‐PS) and poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO). According to both dynamic mechanical analysis and differential scanning calorimetry, relaxation times displayed an enhanced temperature dependence (i.e., more fragile or more cooperative behavior) for the blends compared with additive behavior based on the responses of neat a‐PS and PPO. This is consistent with the notion that specific interactions between the blend components heighten the intermolecular cooperativity. The compositional dependence of fragility provided insight into physical aging results for the properties of volume and enthalpy. The combination of our research and a previously reported pressure–volume–temperature study by Zoller and Hoehn (J Polym Sci Polym Phys Ed 1982, 20, 1385) provided evidence that the observation of increased glassy densities for the blends compared with those of the pure polymers was kinetic in origin and was not a feature of the thermodynamics of miscibility. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2118–2129, 2001     

Glass transition temperature of low molecular weight styrene–isoprene block copolymers

Different series of poly(styrene–isoprene) diblock and poly(styrene–isoprene–styrene) triblock copolymers were prepared. In each series, the low molecular weight polystyrene block was kept constant, and the molecular weight of the polyisoprene block varied. The glass transition behavior of these polymers was studied and their glass transition temperatures compared with those of the random copolymers of styrene and isoprene. It is concluded that some low molecular weight styrene-isoprene block copolymers form a single phase. Krause's thermodynamic treatment of phase separation in block copolymers was applied to the data. One arrives at a polystyrene–polyisoprene interaction parameter χ1,2 ≈ 0.1. The experimental and theoretical limitations of this result are discussed.     

环氧化聚丁二烯-聚苯乙烯嵌段共聚物对聚苯醚/环氧体系反应诱导 相分离行为的影响

采用扫描电镜、光学显微镜和光散射仪研究了环氧化聚丁二烯-聚苯乙烯嵌段共聚物(EBS)对聚苯醚(PPO)/双酚A型环氧树脂(DGEBA)/4,4’-二(2,6-二甲基苯胺基)甲烷(DIM-DDM)体系反应诱导相分离行为的影响. 实验结果表明, EBS的加入对PPO/DGEBA/DIM-DDM体系反应诱导相分离的演化过程有阻滞作用. 随着EBS加入量的增加, 体系形成双连续相结构所需的PPO含量范围变宽, 而对于相同PPO含量、形成双连续相的体系则相结构尺寸减小.     

Crystallization and melting of the system isotactic polystyrene + poly(2,6-dimethyl phenylene oxide)

From glass transition T_g measurements on isotactic polystyrene (IPS)–poly(2,6-dimethyl phenylene oxide) (PPO) blends, it was concluded that thoroughly annealed, freeze-dried samples, or samples evaporated from solution at high temperature, are homogeneous. Without annealing, the freeze-dried blends show two to three T_g's characteristic of the presence of different phases. The overall crystallization rate of these samples is much higher than that observed with annealed samples. The presence of dissolved PPO in annealed samples reduces the overall crystallization rate and the spherulitic growth rate, compared to IPS. The melting behavior of the blends is influenced by the extent of mixing of both polymers. Without annealing, isothermally crystallized, freeze-dried blends show the same melting behavior as IPS (i.e., multiple melting). In homogeneous annealed samples the rate of reorganization is strongly reduced and multiple melting only occurs at low scanning rate (e.g., 1°C/min). This behavior is influenced by the crystallization temperature and by the composition of the blends. The addition of PPO has no influence on the relation between melting point and crystallization temperature and the same equilibrium melting point is found by extrapolation.     

Reactive compatibilization of poly(styrene-Co-maleic anhydride)/poly(phenylene oxide) blends

Primary amine terminated polystyrene (PS-NH₂), with Mn=12,000 g/mol and Mw=23,000 g/mol, was applied as a reactive compatibilizer for poly(styrene-co-maleic anhydride)/poly(phenylene oxide) (SMA/PPO) blends, in which both an impact modifier for the continuous SMA phase, viz. ABS, and the dispersed PPO phase, viz. SEBS, was incorporated. During melt blending, SMA-g-PS copolymers are generated at the interface between the SMA/ABS and the PPO/SEBS phases. The addition of 10 wt % of the reactive PS-NH₂ compatibilizer to a SMA/ABS/PPO/SEBS 30/30/30/10 blend results in a more significant refinement of the dispersed PPO/SEBS particles than 10 wt % of a commercially available, bulky PS-graft-PMMA copolymer with Mn=45,300 and Mw=293,400 g/mol. In addition, PS-NH₂ gives a more pronounced enhancement of the yield stress, the stress at break and the notched Izod Impact than the PS-g-PMMA. On the other hand, the elongation at break is higher in the case of the non-reactive PS-g-PMMA. It was demonstrated that surface imperfections, probably introduced by an observed strongly elastic character due to partial crosslinking of the SMA/ABS phase by difunctional H₂N-PS-NH₂, are responsible for the lower elongation at break for the PS-NH₂ based blends.     

Orientation and relaxation study of polystyrene: Polystyrene/poly(phenylene oxide) blends

Polarization modulation infrared linear dichroism has been used to study the molecular orientation and relaxation of polystyrene/poly(2,6‐dimethyl 1,4‐phenylene oxide) (PS/PPO) miscible blends, containing up to 20% PPO, during and after a rapid uniaxial deformation above T_g. In general, it is found that both the PS and PPO chain orientation functions increase with stretching rate and PPO content, and decrease with temperature. For all blends investigated, between T_g + 5 and T_g + 13 °C, the relaxation occurs at the same rate for PS and PPO and, therefore, the relaxation times calculated are similar indicating, under those conditions, a strong relaxation coupling between the two polymers at both short and long times. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1405–1415, 2000     

Miscibility and volume changes of mixing in the polystyrene/poly(2-chlorostyrene) blend system

The specific volume-temperature relationships of polystyrene, poly(2-chlorostyrene), and their polymer blends as well as the volume change of mixing Δv_m of the blends were obtained in the liquid state by dilatometry. The equation of state parameter and the molecular parameter of each homopolymer and blends were determined according to the lattice fluid theory of Sanchez and Lacombe. The experimental Δv_m obtained agreed quite well with that predicted from theory, and the enthalpy of mixing ΔH_m was also predicted using the pair molecular parameter. These two values were negative, indicative of miscibility of polystyrene and poly(2-chlorostyrene) in the liquid state. The absolute values of Δv_m and ΔH_m were about twice those for polystyrene and poly(phenylene oxide) blend, suggesting a specific interaction between the two polymers.     

嵌段共聚物傅里叶变换拉曼光谱

用傅里叶变换拉曼光谱(FT-Paman)研究了聚环氧乙烷-聚环氧丙烷-聚环氧乙烷(PEO-PPO-PEO)嵌段共聚物的无水样品,发现某些谱带对PEO0-PPO-PEO嵌段共聚物的结构和构象变化敏感,其中某些峰的相对强度的PPO/PEO比率和共聚物的构象有关,研究表明PluronicF68和F88具有一些反式构象的螺旋结构,PluronicP103(P123)是无规则结构,其它的嵌段共聚物处于二者之间.