用超临界CO_2制备微孔聚苯乙烯/热致液晶聚合物原位复合材料

微孔聚合物是80年代初发明的一种新型多孔材料,其特征为:泡孔直径1～10 μm,泡孔密度109～1012cells/cm3,相对密度0.05～0.95.具有缺口冲击强度高、韧性高、比强度高、疲劳寿命长、热稳定性高、介电常数低和导热系数低等优异性能.同时,制备微孔聚合物使用无公害、易回收的CO2和N2替代对臭氧层有害的氯氟烃(氟利昂)和易燃的碳氢化合物等作为发泡剂,是一种新型绿色材料[1].在微孔聚合物中使用超临界流体是90年代初提出的新方法[2～4],可缩短加工时间,同时制得泡孔直径更小、泡孔密度更大的微孔材料.目前研究中,对聚合物多相体系的研究报道很少,只有HIPS[5]、PE/iPP[6]和PVC/木纤维复合材料[7]等少数体系的报道,而聚合物多相体系的研究是材料科学的主要研究领域.可以预见,加入少量第二组分的共混物为基体的微孔材料可以达到更为优异的性能.本工作选择聚苯乙烯与热致液晶聚合物的原位复合材料为研究对象,采用超临界CO2快速降压法[3]制备微孔材料.在前期工作中,报道了该材料是一种综合了液晶聚合物的高强度和聚苯乙烯微孔材料轻质、高抗冲、保温隔音性能的具有仿生结构的新型复合材料[8].本文在此基础上,进一步研究热致液晶聚合物的加入对微孔结构的影响以及界面相容剂在微孔成型中的作用.     

轻度磺化聚苯乙烯与聚苯乙烯共混物的流变性能表征

采用DSR-200动态应力流变仪研究了磺化度为0.98%(摩尔分数)的轻度磺化聚苯乙烯(SPS)离聚物及其锌盐(ZnSPS)与聚苯乙烯(PS)的共混物(PS/SPS,PS/ZnSPS)的流变性能.由于离聚物中离子聚集的物理交联作用,使其流变性能与PS相比有明显差别.动态频率实验结果表明,所有样品均可采用时温等效处理.另外,在与分子链运动相关的低频区,由于离子聚集的作用使得离聚物的模量远大于PS的模量.离聚物在稳态剪切作用下,由于离子聚集的破坏而表现出明显的屈服现象,并能用Utracki的屈服应力公式表征其屈服应力和零切粘度.此外,离聚物的屈服现象还与温度相关.由于动态和稳态实验分别测试离子聚集存在和破坏的不同材料状态,因此对离聚物无法应用Cox-Merz规则.动态和稳态实验结果均表明,PS/SPS和PS/ZnSPS的性能与组成的变化规律不同,意味着二者之间存在不同的离子聚集结构或相互作用.     

Preparation of microcellular polypropylene/polystyrene blend foams with tunable cell structure

By using supercritical carbon dioxide (sc‐CO₂) as the physical foaming agent, microcellular foaming was carried out in a batch process from a wide range of immiscible polypropylene/polystyrene (PP/PS) blends with 10–70 wt% PS. The blends were prepared via melt processing in a twin‐screw extruder. The cell structure, cell size, and cell density of foamed PP/PS blends were investigated and explained by combining the blend phase morphology and morphological parameters with the foaming principle. It was demonstrated that all PP/PS blends exhibit much dramatically improved foamability than the PP, and significantly decreased cell size and obviously increased cell density than the PS. Moreover, the cell structure can be tunable via changing the blend composition. Foamed PP/PS blends with up to 30 wt% PS exhibit a closed‐cell structure. Among them, foamed PP/PS 90:10 and 80:20 blends have very small mean cell diameter (0.4 and 0.7 µm) and high cell density (8.3 × 10¹¹ and 6.4 × 10¹¹ cells/cm³). Both of blends exhibit nonuniform cell structure, in which most of small cells spread as “a string of beads.” Foamed PP/PS 70:30 blend shows the most uniform cell structure. Increase in the PS content to 50 wt% and especially 70 wt% transforms it to an irregular open‐cell structure. The cell structure of foamed PP/PS blends is strongly related to the blend phase morphology and the solubility of CO₂ in PP more than that in PS, which makes the PP serve as a CO₂ reservoir. Copyright © 2009 John Wiley & Sons, Ltd.     

Miscible blends of zinc-neutralized sulfonated polystyrene and poly(2,6-dimethyl 1,4-phenylene oxide)

Zinc-neutralized sulfonated polystyrene ionomers (ZnSPS) and poly(2,6-dimethyl 1,4-phenylene oxide) homopolymer (PXE) form miscible blends up to at least 7.8 mol % sulfonation, as measured by thermal and mechanical criteria. The addition of an equal weight of PXE raises the glass transition temperature of ZnSPS by 40–50°C. However, this miscibility is not achieved by eradicating the microdomain structure present in ZnSPS, even though the PXE coils are considerably larger than the spacings between ionic aggregates. Small-angle x-ray scattering indicates that while the average interaggregate spacing is roughly the same in ZnSPS and its 50/50 blend with PXE at a given sulfonation level, the extent of phase separation is reduced upon PXE addition, indicating that more ionic groups are dispersed in the matrix. Factors influencing miscibility in the ZnSPS/PXE materials and related blends are discussed.     

Solution viscosity behavior of complexes of poly(γ-benzyl-L-glutamate) with lightly sulfonated polystyrene or its zinc salt

The rheological behavior of solutions containing blends of poly(γ-benzyl-L -glutamate) (PBLG) and either the free acid or the zinc salt of lightly sulfonated polystyrene (SPS) was studied as a function of blend composition, polymer concentration, degree of sulfonation of the SPS, and the polypeptide molecular weight. The zinc salt of SPS formed a transition metal complex with the amine-end groups of the PBLG, and this resulted in an enhancement of the solution viscosity relative to a weighted average of the viscosities of the individual polymer solutions. The ZnSPS/PBLG solutions showed no anomalous time or shear dependencies. In contrast, solutions containing PBLG and the sulfonic acid derivative of SPS also had enhanced viscosities, but in addition, they exhibited time-dependent viscosities (thixotropic behavior) and shear thickening (dilatant behavior). This was attributed to a nonequilibrium structure of the interpolymer complex due to a competition between acid-amine and acid-ester interactions. Although the acid-amine interaction is enthalpically favored, when sufficient sulfonic acid groups were available, interactions between the sulfonic acid and the glutamate ester side groups of PBLG developed and this interaction promotes a helix-to-coil transition of the PBLG. ©1995 John Wiley & Sons, Inc.     

Foaming behavior of polypropylene/polystyrene blends enhanced by improved interfacial compatibility

A series of polypropylene (PP)/polystyrene (PS) blends were prepared by solvent blending with PS‐grafted PP copolymers (PP‐g‐PS) having different PS graft chain length as compatibilizers. The interfacial compatibility was significantly improved with increasing PS graft chain length until the interface was saturated at PS graft chain length being 3.29 × 10³ g/mol. The blends were foamed by using pressure‐quenching process and supercritical CO₂ as the blowing agent. The cell preferentially formed at compatibilized interface because of low energy barrier for nucleation. Combining with the increased interfacial area, the compatibilized interface lead to the foams with increased cell density compared to the uncompatibilized one. The increase in interfacial compatibility also decreased the escape of gas, held more gas for cell growth, and facilitated the increase in expansion ratio of PP/PS blend foams. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1641–1651, 2008     

Competitive influence of atactic polystyrene and supercritical carbon dioxide on the conformation of syndiotactic polystyrene

The crystallization behavior of miscible syndiotactic polystyrene (sPS) and atactic polystyrene (aPS) blends with different sPS/aPS weight ratios was investigated in supercritical CO₂ by using Fourier‐transform infrared spectroscopy, differential scanning calorimetry, and wide‐angle X‐ray diffraction. Supercritical CO₂ and aPS exhibited different effects on the conformational change of sPS and competed with each other. Increasing the content of amorphous aPS in the blends made its effect on the conformational change of sPS gradually surpass that of supercritical CO₂. Supercritical CO₂ favored the formation of the helical conformation of sPS in lower temperature range and the all trans planar conformation in higher temperature range, instead of forming the latter one only in higher temperature range in ambient atmosphere. However, increasing aPS content in the blends pushed the range for forming the helical conformation to lower temperature and made the all trans planar conformation dominant in aPS/sPS 25/75 blend after treating in supercritical CO₂ above 60 °C. The all trans planar zigzag conformation was more favorable than the helical conformation after mixing aPS in sPS in supercritical CO₂. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1755–1764, 2007     

Sorption and diffusion of carbon dioxide in wood‐fiber/polystyrene composites

In this study, sorption and diffusion of carbon dioxide (CO₂) in wood‐fiber/polystyrene composites were investigated. The effects of gas pressure and fiber content on the solubility and diffusion coefficients were evaluated. A statistical analysis indicated that pressure is more important than fiber content in determining the solubility and diffusivity of CO₂. An increase in saturation pressure causes an increase in the solubility and diffusion coefficients, whereas inclusion of the fibers decreases both of these properties. Models were developed to predict the uptake and diffusion coefficients of CO₂ in the composite samples as functions of pressure and fiber content. A theoretical model based on Henry's law and the Langmuir equation compared favorably to the experimental data for CO₂ solubility. This dual mode model also described both the transient sorption and desorption data, but only if the concentration‐dependent value of diffusivity was treated as a history‐dependent parameter. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 723–735, 2002     

The compatibilization effect of ethylene/styrene interpolymer on polystyrene/polyethylene blends

In this study, ethylene/styrene interpolymer (ESI) was used as compatibilizer for the blends of polystyrene (PS) and low‐density polyethylene (LDPE). The mechanical properties including impact, tensile properties, and morphology of the blends were investigated by means of uniaxial tension, instrumented falling‐weight impact measurements, and scanning electron microscopy. Impact measurements indicated that the impact strength of the blends increases slowly with LDPE content up to 40 wt %; thereafter, it increases sharply with increasing LDPE content. The impact energy of the LDPE‐rich blends exceeded that of pure LDPE, implying that the LDPE polymer can be further toughened by the incorporation of brittle PS minor phase in the presence of ESI. Tensile tests showed that the yield strength of the PS/LDPE/ESI blends decreases considerably with increasing LDPE content. However, the elongation at break of the blends tended to increase significantly with increasing LDPE content. The compatibilization efficiency of ESI and polystyrene‐hydrogenated butadiene‐polystyrene triblock copolymers (SEBS) for PS/LDPE 50/50 was further compared. Mechanical properties show that ESI is more effective to achieve a combination of LDPE toughness and PS rigidity than SEBS. The correlation between the impact property and morphology of the ESI‐compatibilized PS/LDPE blends is discussed. The excellent tensile ductility of the LDPE‐rich blends resulted from shield yielding of the matrix. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2136–2146, 2007     

离聚物在液晶聚合物与聚碳酸酯共混体系中的增容作用

离聚物在液晶聚合物与聚碳酸酯共混体系中的增容作用刘杰何嘉松（中国科学院化学研究所工程塑料国家重点实验室北京１０００８０）关键词增容作用，离聚物，热致液晶聚合物原位复合材料（Ｉｎ ｓｉｔｕｃｏｍｐｏｓｉｔｅ）是一种新兴的复合材料，是由热致液晶聚合...     

Near infrared analysis of blends of sulfonated polystyrene ionomers and poly(ε‐caprolactam)

Near infrared spectroscopy (NIR) was used to characterize the nature of specific interactions in blends of lightly sulfonated polystyrene ionomers (M‐SPS where M = Zn⁺², Mn⁺², or Li⁺) and polycaprolactam (PA6). The assignments of the NIR overtone bands that arise due to the interactions between the cation of the ionomer, and the amide groups were made using spectra of model compounds. The relative populations of the different environments of the N? H groups were qualitatively determined by deconvoluting the NIR spectra into five absorbances representing hydrogen‐bonded N? H in crystalline and amorphous phases and an ion‐amide complex. The ion‐amide complex was specific for the blends. The interpolymer interactions were sensitive to composition and temperature, but qualitatively the behavior was the same for all three ionomer salts investigated. © 2008 Wiley Periodicals, Inc. JPolym Sci Part B: Polym Phys 46: 1602–1610, 2008     

Sulfonation of polystyrene: Toward the “ideal” polyelectrolyte

Sulfonation of narrow polydispersity polystyrene, PS, standards remains the method of choice for generating polystyrene sulfonate, PSS, samples with defined composition. Although a variety of sulfonation techniques have been described, relatively little is reported on the material obtained, which is used for so many studies on the fundamental behavior of polyelectrolytes. Here, we show that powdered polystyrene treated with concentrated sulfuric acid (96%) at 90 °C without catalyst yields fully sulfonated PSS. Extensive characterization with ¹H and ¹³C NMR as well as size exclusion chromatography coupled with static and dynamic light scattering shows no evidence of sulfone crosslinking or chain degradation under the conditions used. Though mono‐sulfonated as soon as it dissolves in the acid, the PSS contains about 6% meta substitution. Sulfonation kinetics for this heterogeneous reaction depend strongly on particle size, sulfuric acid content and temperature. For preparing perdeuterated PSS from the corresponding PS it is essential to employ D₂SO₄, as about half of the aromatic units undergo H/D exchange during sulfonation. The remaining ortho H/D may be exchanged with extended exposure to the concentrated sulfuric acid, but the meta site is deactivated. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2416–2624     

Morphology,structure, and properties of in situ compatibilized linear low‐density polyethylene/polystyrene and linear low‐density polyethylene/high‐impact polystyrene blends

Blends of linear low‐density polyethylene (LLDPE) with polystyrene (PS) and blends of LLDPE with high‐impact polystyrene (HIPS) were prepared through a reactive extrusion method. For increased compatibility of the two blending components, a Lewis acid catalyst, aluminum chloride (AlCl₃), was adopted to initiate the Friedel–Crafts alkylation reaction between the blending components. Spectra data from Raman spectra of the LLDPE/PS/AlCl₃ blends extracted with tetrahydrofuran verified that LLDPE segments were grafted to the para position of the benzene rings of PS, and this confirmed the graft structure of the Friedel–Crafts reaction between the polyolefin and PS. Because the in situ generated LLDPE‐g‐PS and LLDPE‐g‐HIPS copolymers acted as compatibilizers in the relative blending systems, the mechanical properties of the LLDPE/PS and LLDPE/HIPS blending systems were greatly improved. For example, after compatibilization, the Izod impact strength of an LLDPE/PS blend (80/20 w/w) was increased from 88.5 to 401.6 J/m, and its elongation at break increased from 370 to 790%. For an LLDPE/HIPS (60/40 w/w) blend, its Charpy impact strength was increased from 284.2 to 495.8 kJ/m². Scanning electron microscopy micrographs showed that the size of the domains decreased from 4–5 to less than 1 μm, depending on the content of added AlCl₃. The crystallization behavior of the LLDPE/PS blend was investigated with differential scanning calorimetry. Fractionated crystallization phenomena were noticed because of the reduction in the size of the LLDPE droplets. The melt‐flow rate of the blending system depended on the competition of the grafting reaction of LLDPE with PS and the degradation of the blending components. The degradation of PS only happened during the alkylation reaction between LLDPE and PS. Gel permeation chromatography showed that the alkylation reaction increased the molecular weight of the blend polymer. The low molecular weight part disappeared with reactive blending. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1837–1849, 2003     

引入离子基团改善聚苯乙烯和热致液晶聚合物的相容性 Ⅰ热性能和形态

ＤＳＣ和ＳＥＭ研究结果表明聚苯乙烯（ＰＳ）与一种热致液晶聚合物（ＬＣＰ）（ＰＨＢ／ＰＥＴ（６０／４０）共聚酯）完全不相容．共混体系具有与组分无关的Ｔｇ，并且表现出明显的两相结构．将ＰＳ进行化学改性（引入磺酸基团）制备成磺化聚苯乙烯（ＳＰＳ），随中和盐离子的变化有：酸式、Ｌｉ、Ｎａ、Ｚｎ和Ｍｎ盐五种形式．用ＤＳＣ和ＳＥＭ对ＬＣＰ与ＳＰＳ共混物的热性能和形态进行了分析和表征．共混体系有一个与组成相关，且明显低于纯ＳＰＳ的Ｔｇ．这表明了ＰＳ与ＬＣＰ的相容性因为磺酸基团的引入而得到了改善．同时用Ｆｏｘ方程计算了ＬＣＰ的Ｔｇ．当ＳＰＳ含量较低时（不大于５０％）在各个共混体系中，所估算的ＬＣＰ的Ｔｇ相互吻合．表明共混体系满足Ｆｏｘ方程的前提条件，即ＬＣＰ与ＳＰＳ形成相容体系．当ＳＰＳ含量较低时（２５％），ＬＣＰ／ＳＰＳ的共混物为较均一体系，断面光滑；而ＳＰＳ含量较高时，在脆断面可以观察到纳米级的颗粒．电子能谱分析证明了这些颗粒是ＳＰＳ负离子的聚集体．     

Solubility of polystyrene in selectively deuterated methyl acetate

Cloud point measurements were made for binary systems of polystyrene (PS) + methyl acetate (MA) and polystyrene (PS) + selectively deuterated MA: CD₃COOCH₃ and CH₃COOCD₃ with three PS samples of M_w = 4.0 × 10⁵, 2.0 × 10⁶, and 13.2 × 10⁶. All systems are characterized by the phase diagrams with upper and lower critical temperature. H/D isotope effects on miscibility for both selectively deuterated acetates are very large and appeared to be independent of the site of deuterium substitution. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47:2140–2143, 2009     

Effects of organoclays on morphology and thermal and rheological properties of polystyrene and poly(methyl methacrylate) blends

Morphology, thermal and rheological properties of polymer‐organoclay composites prepared by melt‐blending of polystyrene (PS), poly(methyl methacrylate) (PMMA), and PS/PMMA blends with Cloisite® organoclays were examined by transmission electron microscopy, small‐angle X‐ray scattering, secondary ion mass spectroscopy, differential scanning calorimetry, and rheological techniques. Organoclay particles were finely dispersed and predominantly delaminated in PMMA‐clay composites, whereas organoclays formed micrometer‐sized aggregates in PS‐clay composites. In PS/PMMA blends, the majority of clay particles was concentrated in the PMMA phase and in the interfacial region between PS and PMMA. Although incompatible PS/PMMA blends remained phase‐separated after being melt‐blended with organoclays, the addition of organoclays resulted in a drastic reduction in the average microdomain sizes (from 1–1.5 μm to ca. 300–500 nm), indicating that organoclays partially compatibilized the immiscible PS/PMMA blends. The effect of surfactant (di‐methyl di‐octadecyl‐ammonia chloride), used in the preparation of organoclays, on the PS/PMMA miscibility was also investigated. The free surfactant was more compatible with PMMA than with PS; the surfactant was concentrated in PMMA and in the interfacial region of the blends. The microdomain size reduction resulting from the addition of organoclays was definitely more significant than that caused by adding the same amount of free surfactant without clay. The effect of organoclays on the rheological properties was insignificant in all tested systems, suggesting weak interactions between the clay particles and the polymer matrix. In the PS system, PMMA, and organoclay the extent of clay exfoliation and the resultant properties are controlled by the compatibility between the polymer matrix and the surfactant rather than by interactions between the polymer and the clay surface. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 44–54, 2003     

磺化聚苯乙烯离聚体水基微乳液乳化过程中相反转机理的研究

将聚苯乙烯改性制成磺化聚苯乙烯离聚体，溶解在甲苯／甲醇混合溶剂中，缓慢加水将聚苯乙烯乳化成稳定的水包油的水基微乳液。本文通过研究在乳化过程中体系粘度和导电性的变化，研究了聚苯乙烯离聚体溶液乳化过程的相反转机理和离子含量对乳化过程和相反转机理的影响。     

The effect of polyethylene addition on the morphology of polystyrene/polyamide blends

The effect of a small admixture of high‐density polyethylene (HDPE) with a high or low viscosity to polystyrene/polyamide (PS/PA) blends of various compositions was studied. PS/PA blends with composition near 50/50 form sheet‐like or fiber‐like morphology at mixing that passes to the cocontinuous structure during compression molding. Ternary PS/PA/HDPE blends with PS/PA ratio about 50/50 show similar behavior. Generally, neither continuity nor shape of PS and PA phases was changed qualitatively by the addition of a small amount of HDPE. In agreement with existing rules for ternary blends, HDPE particles prefer a contact with PS phase to PA phase. On the other hand, none of these rules explains why a number of small HDPE subinclusions were dispersed into PS particles instead of HDPE‐PS core‐shell structure with a lower Gibbs free energy. Quantitative evaluation of the size of PA particles in blends with PS matrix showed that the previously proposed rule stating, that the addition of a small amount of a third immiscible component leads to a strong decrease in the size of dispersed particles, was not valid for the blends studied in this work. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2158–2170, 2009     

Effect of aromatic substitution on phase behavior of blends of halogenated polystyrene and conventional polystyrene

Miscibility phase behavior in blends of poly(bromostyrene) with polystyrene (PS) has been investigated by means of time‐resolved light scattering, optical microscopy, and DSC. Cloud point phase diagrams of blends of conventional PS with poly‐(2‐bromostyrene) (P2BrS), poly‐(3‐bromostyrene), and poly‐(4‐bromostyrene) of comparable molecular weights were established by light scattering. Of particular interest is the fact that ortho, meta, and para substitutions in the styrenic aromatic rings of poly(bromostyrene) show profound effects on the composition–temperature phase diagrams of their blends with PS, exhibiting a lower critical‐solution temperature (LCST), an upper critical solution temperature (UCST), and combined LCST/UCST diagrams, respectively. Poly‐(2‐chlorostyrene) exhibits an LCST behavior very close to that of the P2BrS blend, suggesting that these types of halogen atoms may be inconsequential to phase behavior. A similar study has been extended to a PS blend containing commercial brominated PS (66 mol % bromine substitution) to determine what location of bromine substitution is crucial for miscibility enhancement in the flame‐retardant brominated PS blends. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1605–1615, 2001     

Investigation of the micromechanical deformation behavior of styrene–butadiene star block copolymer/polystyrene blends with high‐voltage electron microscopy

The deformation behavior of blends consisting of a styrene–butadiene star block copolymer and a polystyrene homopolymer was studied by high‐voltage electron microscopy with a tensile device. The mechanical properties and micromechanical deformation mechanisms in the star block copolymer/polystyrene blends were directly influenced by their morphology. Although the pure block copolymer deformed in a very unequal manner (because of a thin‐layer‐yielding mechanism) and revealed no local deformation zones, a transition to the formation of crazelike zones was observed in the blends. This transition in the deformation mechanisms was correlated to the abrupt change in the macroscopic strain at break of the injection‐molded specimens. At lower contents of added polystyrene, a craze‐stopping mechanism was observed, whereas the blends with higher polystyrene contents demonstrated crazing like that in pure polystyrene. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1157–1167, 2003