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1.
The effect of the presence of different amounts of block copolymers [polystyrene-block-poly(methyl methacrylate)] on the morphology of polystyrene/poly (methyl methacrylate) composite latex particles was investigated. The block copolymers were produced in situ by controlled radical polymerization (CRP) through the addition of the second monomer to a seed prepared by miniemulsion polymerization with a certain amount of a CRP agent. With an increase in the amounts of the block copolymers, the particle morphology changed from a hemisphere morphology (for a latex without block copolymers, i.e., without the use of a CRP agent during the polymerization) to clear core–shell morphologies as a result of decreasing polymer–polymer interfacial tension © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2484–2493, 2007  相似文献   

2.
The surface and interface morphologies of polystyrene (PS)/poly(methyl methacrylate) (PMMA) thin‐film blends and bilayers were investigated by means of atomic force microscopy (AFM) and X‐ray photoelectron spectroscopy. Spin‐coating a drop of a PS solution directly onto a PMMA bottom layer from a common solvent for both polymers yielded lateral domains that exhibited a well‐defined topographical structure. Two common solvents were used in this study. The structure of the films changed progressively as the concentration of the PS solution was varied. The formation of the blend morphology could be explained by the difference in the solubility of the two polymers in the solvent and the dewetting of PS‐rich domains from the PMMA‐rich phase. Films of the PS/PMMA blend and bilayer were annealed at temperatures above their glass‐transition temperatures for up to 70 h. All samples investigated with AFM were covered with PS droplets of various size distributions. Moreover, we investigated the evolution of the annealed PS/PMMA thin‐film blend and bilayer and gave a proper explanation for the formation of a relatively complicated interface inside a larger PS droplet. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 9–21, 2006  相似文献   

3.
We investigate the surface-directed phase separation of spin-coated polystyrene/poly(methyl methacrylate) (PS/PMMA) blends on prepatterned octadecyltrichlorosilane (OTS)-glass substrates under various experimental conditions. As a result of tandem processes of spinodal decomposition and selective wetting of polymer components during spin-coating, low-energy OTS stripes and high-energy glass surfaces laterally arrange the phase-separated polymers according to the chemical pattern on the substrate. Optimal pattern replication was achieved when the length scale of phase separation, controlled via the polymer concentration of the spin-coating solution, matched the smallest feature dimension in a striped chemical pattern possessing two alternating distances between stripes. It was also shown that polymer blend patterns were most closely registered with the underlying substrate when the PS/PMMA composition ratio (30/70, w/w) matched the areal fraction of OTS on the glass surface (~30%). The influence of solvents demonstrated that a solvent with a relatively low volatility, such toluene, was required for patterning so that domain feature sizes were able to coarsen to the size of the patterned features before film vitrification. As well, we showed that the technique and optimized conditions developed in this study could be applied to pattern photoluminescent CdS quantum dots into microscale arrays of parallel lines via spin-coating onto transparent OTS-glass substrates.  相似文献   

4.
The fracture toughness between polystyrene (PS)/poly(methyl methacrylate) (PMMA) reinforced with reactive polymers, poly(glycidyl methacrylate) (PGMA) and dicarboxy or monocarboxy terminated PS (dcPS and mcPS), was measured by the asymmetric fracture test. Molecular weight effect of mcPS, although the molecular weight distribution is rather polydisperse, on the maximum achievable fracture toughness, Gmax qualitatively agreed with the results of the monodisperse case4,5). In the case of dcPS with Mw ≅ 142 K, Gmax reached ca. 170 J/m2 which is nearly 8 times higher than that of mcPS of molecular weight of about 150K. From the mechanical point of view, dcPS with a degree of polymerization (N) greater than the ratio of chain breaking force to monomeric friction force (fb/fmono) is more effective in enhancing the interfacial adhesion than mcPS since it provides two stitches to the interface. It was also shown by Monte Carlo simulation on reactive polymer system that the di‐endfunctional polymers are more effective than mono‐endfunctional polymers in reinforcing the week interface between immiscible polymers.  相似文献   

5.
Sum frequency generation (SFG) vibrational spectroscopy has been applied to study the molecular surface structures of polystyrene (PS)/poly(methyl methacrylate) (PMMA) blends and the copolymer between PS and PMMA (PS-co-PMMA) in air, supplemented by atomic force microscopy (AFM) and contact angle goniometer. Both the blend and the copolymer have equal weight amounts of the two components. SFG results show that both components, PS and PMMA, can segregate to the surface of the blend and the copolymer before annealing, although PMMA has a slightly higher surface tension. Upon annealing both SFG results and contact angle measurements indicate that the PS segregates to the surface of the PS/PMMA blend more but no change occurs on the PS-co-PMMA surface. AFM images show that the copolymer surface is flat but the 1:1 PS/PMMA blend has a rougher surface with island like domains present. The annealing effect on the blend surface morphology has also been investigated. We collected amide SFG signals from interfacial fibrinogen molecules at the copolymer or blend/protein solution interfaces as a function of time. Different time-dependent SFG signal changes have been observed, showing that different surfaces of the blend and the copolymer mediate fibrinogen adsorption behavior differently.  相似文献   

6.
Nonspherical polystyrene (PS)/poly(methyl methacrylate) (PMMA) composite particles having a dent were prepared by releasing toluene from PS/PMMA/toluene droplets dispersed in a poly(vinyl alcohol) aqueous medium. An ex-centered PS-core/PMMA-shell morphology, in which a part of the PS core contacted with the aqueous medium and toluene partitioned more in the PS core than in the PMMA shell, was formed in the polymers/toluene droplet in the process of phase separation therein with releasing toluene. The volume of the dent became bigger with an increase in the PS content and in the toluene content partitioned in the PS core.Part CCLXI of the series Studies on Suspension and Emulsion.  相似文献   

7.
The effect of glass beads (GB) on morphology of polystyrene (PS)/poly(methyl methacrylate) (PMMA) blends has been studied by scanning electron microscopy (SEM) at different shear rates and during quiescent annealing. For the viscosity ratio of PMMA to PS greater than unity, the dispersed viscous PMMA phase in the blend coalesced during the shear flow or quiescent annealing. However, the domain size of the PMMA phase decreased significantly under shear even though a small amount of GB was added. The PMMA domain size further decreased and the size distribution became narrower with increasing GB content. According to SEM images, the quiescent coalescence of the PMMA phase was effectively inhibited by adding large amounts of GB, and the breakup of PMMA domains in shear flow was greatly favored by the high local shear prevailed between GB. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 25–35, 2009  相似文献   

8.
The low vapor pressure solvent 1‐chloropentane was used to directly spincast polystyrene (PS) films onto poly(methyl methacrylate) (PMMA) with smooth surfaces and sharp interfaces. Interface roughness after removal of the PS layer with cyclohexane was determined with scanning force microscopy to be <1 nm. Dynamic secondary mass spectroscopy revealed an interfacial width below the resolution limit of ~10 nm. Large area bilayers with smooth surfaces could be created. In addition, direct spincasting with 1‐chloropentane allows the production of thin PS films (<15 nm) and films of low molecular weight (<5 kDa) PS, all of which would be impossible to produce for this important model system by the traditional water‐transfer method. 1‐chloropentane was confirmed to be a sufficiently selective solvent for PS by measuring the Flory–Huggins χ parameters of 1‐chloropentane with PS and PMMA, respectively, with inverse gas chromatography. In the search for a suitable selective solvent, the authors have also examined the role of vapor pressure in spin casting smooth films over a wider molecular weight (4.3–190 kDa) and thickness range (~5–500 nm) than previously reported. Only solvents with low vapor pressure produced high quality PS films. Methylcyclohexene can also be used to produce excellent, directly cast PS/PMMA bilayers, but with a smaller molecular weight and thickness window compared with 1‐chloropentane. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3234–3244, 2006  相似文献   

9.
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  相似文献   

10.
Blends of monodisperse polystyrene and poly(vinyl-methyl-ether) of various compositions were prepared from solution in benzene. Dynamic rheological properties of these blends were studied at different temperatures below, near, and above Ts, the temperature of phase separation, and in a frequency range from 0.05 to 100 rad/s. A flattening in the storage modulus and an initial plateau for the complex viscosity were observed near and above Ts in the low-frequency region; in contrast, below Ts the behavior of the blends was similar to that of the homopolymers. The WLF superposition principle applies only at temperatures below Ts, i.e., in the miscible and homogeneous region. G″ versus G′ representations for the blends were found to be independent of temperature and to vary with composition in the miscible region but are temperature and composition-dependent in the immiscible region. It is also shown that the η″ versus η′ representation is a useful tool for characterizing phase separation of blends and is more sensitive than the classical frequency dependence of the material functions.  相似文献   

11.
Two methacrylate‐modified clays have been prepared and used to produce nanocomposites of polystyrene and poly(methyl methacrylate) by in situ polymerization. These nanocomposites have been characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), cone calorimetry and the evaluation of mechanical properties. When the clay contains only a single methacrylate unit, the styrene system is exfoliated but methacrylate is intercalated. When two methacrylate units are present on the cation of the clay, both systems are exfoliated. TGA data show that the thermal stability of all the nanocomposites is improved, as expected. The relationships between the fire properties and nanostructure of the nanocomposites are complicated, as shown by cone calorimetry. The conclusions that one may reach using cone calorimetry do not completely agree with those from XRD and TEM. The evaluation of mechanical properties shows an increase in Young's modulus for all nanocomposites along with a decrease in elongation; tensile strength is decreased for methacrylate nanocomposites but increased for styrenics systems. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

12.
The cloud points for the co-nonsolvent systems (i) pyridine (PY) + formic acid (FA) towards poly(?-caprolactone) (PCL) or poly(methyl methacrylate) (PMMA) and (ii) pyridine + acetic acid (AA) towards PCL have been experimentally determined as a function of solvent composition at fixed polymer concentrations. Heats of mixing for the (FA + PY) system have also been measured. The single liquid approximation model correctly predicts for the (PY + FA) system the solvent composition at which the solvent power of the mixture is the poorest, provided it is recognized that the solvent system is comprised of pyridinium formate (PYFA) as one component and either PY or FA (depending on which is present in excess over 1:1 mole ratio) as the other. With the other co-nonsolvent system, the prediction is not as good. A possible reason for the discrepancy has been given.  相似文献   

13.
This work reports the preparation and characterization of Buriti (Mauritia flexuosa L.) oil/polystyrene (PS) and Buriti oil/poly(methyl methacrylate) blends. The Buriti is an abundant palm tree of the Amazon region. This oil was used because of its chemical composition (high concentrations of oleic acid, tocopherols and carotenoids, especially β-carotene) and interesting optical properties, such as absorption and photoluminescence. The incorporation of the vegetable oil in the PS and PMMA matrices renders orange-colored blends, which were verified to absorb UV-Vis radiation and emit light in the green region. The intensity of these properties is proportional to the oil content in the samples. Micrographs of the blends showed that the oil is located in cavities distributed in the polymeric matrices. This work shows that it is possible to employ the Buriti oil, a cheaper and abundant natural resource, to improve absorption and light emission properties of PS and PMMA polymers.  相似文献   

14.
左敏  郑强 《高分子科学》2013,31(11):1470-1483
The effect of clay on the morphology and phase-separation behavior of poly(methyl methacrylate)/poly(styreneco-acrylonitrile)(PMMA/SAN) blends and the variation of clay dispersion have been investigated. With the evolution of phase separation in PMMA/SAN, most of the clays are first located at the boundaries between PMMA and SAN, and then gradually move to the PMMA-rich domain, owing to the affinity of clay to PMMA. The introduction of clay causes the increase of binodal and spinodal temperatures of PMMA/SAN and enlarges their metastable region, indicating the phase stabilizing effect of clay on the matrix. But the influence of clay on the cloud points obviously depends on the composition of PMMA/SAN. The selective adsorption of PMMA on the clay results in the difference between the composition of surface layer and that of polymer matrix. Hence, the clay plays the role of an agent changing the conditions of phase structure formation.  相似文献   

15.
Persistence vectors a ≡ 〈 r 〉 are calculated for polypropylene, polystyrene, and poly(methyl methacrylate) chains as functions of chain length and stereochemical constitution. Differences between the progressions of a with chain length for these vinyl polymers are related to their conformational characteristics. The preferences of the syndiotactic chains for the tt dyad conformation are manifested most strikingly in the behavior of this vector.  相似文献   

16.
Melting processes and thermal decompositions of [Ca(H2O)4](ClO4)2 and [Ca(NH3)6](ClO4)2 were studied by thermogravimetry analysis (TG) and differential scanning calorimetry (DSC). The gaseous products of the decomposition were on-line identified by a quadruple mass spectrometry (QMS). In both compounds the processes of loss of the ligands start at ca. 340–350 K and continue up to ca. 600 K. Tetraaquacalcium perchlorate dissolves in own coordination water (melts) at T m=350 K. The decomposition of the sample proceeds in three main stages. In stage I (351–602 K) dehydration of [Ca(H2O)4](ClO4)2 to anhydrous Ca(ClO4)2 undergoes in two steps, in which consecutively 2/4 and 2/4 of all H2O molecules are liberated. In stage II (602–701 K) anhydrous Ca(ClO4)2 has one solid-solid phase transition at T c=619 K and then melts at T m=689 K. Stage III (above 700 K) is connected with decomposition of melted Ca(ClO4)2 to oxygen and solid CaCl2. The decomposition of the [Ca(NH3)6](ClO4)2 proceeds also in three main stages. In stage I (341–601 K) deamination of [Ca(NH3)6](ClO4)2 to Ca(ClO4)2 undergoes in two steps, in which consecutively 3/6 and 3/6 of all NH3 molecules are liberated. Stages II and III (601–868 K) are exactly the same as they were observed for [Ca(H2O)4](ClO4)2.  相似文献   

17.
Inelastic helium atom scattering has been used to investigate the vibrational dynamics at the polymer vacuum interface of poly(methyl methacrylate), polystyrene, and polybutadiene thin films on SiO(x)Si(100). Experiments were performed for a large range of surface temperatures below and above the glass transition of these three polymers. The broad multiphonon feature that arises in the inelastic scattering spectra at surface temperatures between 175 and 500 K is indicative of the excitation of a continuum of surface vibrational modes. Similarities exist in the line shapes of the scattering spectra, indicating that helium atoms scatter from groups of similar mass on the surface of these polymer thin films. The line shapes obtained were further analyzed using a semiclassical scattering model. This study has shown that quite different polymer thin films can have similar interfacial dynamics at the topmost molecular layer.  相似文献   

18.
19.
The fracture behavior of blends of poly(vinylidene fluoride) and poly(methyl methacrylate) was investigated all over the composition range. A detailed analysis of the net stress versus crack opening displacement curves was performed. Fracture surface observations allowed statements on the process zone characteristics ahead of the crack tip. For the amorphous blends, the crack initiation energy is well related to the glass transition temperature. For the semicrystalline blends, the fracture energy is correlated with the degree of crystallinity. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012  相似文献   

20.
Poly(ethyl methacrylate) and poly(methyl methacrylate) prepared by benzoyl peroxide-catalyzed polymerization were fractionated. The Fox-Flory constant K was determined for these polymers by viscometry in several good and bad solvents. Application of some empirical methods for evaluation of K are also briefly discussed in relation to our results.  相似文献   

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