FRINK Linked Data Fragments server

Matches in SemOpenAlex for { <https://semopenalex.org/work/W2024334895> ?p ?o ?g. }

• W2024334895 endingPage "589" @default.
• W2024334895 startingPage "584" @default.
• W2024334895 abstract "Multicomponent polymers have attracted considerable attention in the industrial field because these compounds combine a variety of functional components into a single material. In most multicomponent polymers, micro- or macrophase separation, which can directly affect the physical and chemical properties of the polymer,1-4 often takes place due to the very small entropy and positive heat of mixing. In the interest of developing a high-performance polymer, the morphology of polymer phase separation in multicomponent polymers has, therefore, been vigorously investigated.5-8 Based on this point of view, we have studied the relationship between the structure of multicomponent polymer membranes containing poly(dimethylsiloxane) (PDMS) and their permselectivity for aqueous ethanol solutions so as to develop excellent permselective membranes.9-16 However, there are many problems inherent in determining the quantitative relationship between their microphase separation and the subsequent membrane properties, because there is currently no simple method for the quantitative estimation of morphology in multicomponent polymer membranes due to the irregularities and intricacies of this problem. Fractal descriptions can be applied to systems that look the same over a limited range of magnification power; that is, self-similar systems. Mandelbrot17 advocated a fractal approach for the investigation of self-similarities in nature, and the fact that boundary lines of natural objects are fractals has similarly been reported in recent years.18-22 In this study, we focused on fractal geometry and quantified the microphase separation of block copolymer membranes containing PDMS by introducing a fractal dimension. This report describes the quantitative relationship between the microphase separation of block copolymer membranes and their permselectivity for aqueous ethanol solutions on the basis of their fractal geometry. In particular, the effects of annealing on the permselectivity of block copolymer membranes are discussed in detail by quantifying the morphological changes in their microphase separation using fractal dimension. The poly(dimethylsiloxane) (PDMS) macro-azo-initiator (PASA)23-25 (1), which has 59 units of the PDMS block subunit, was supplied by Wako Pure Chemical Industries, Ltd. Block copolymers containing a PDMS component (PMMA-b-PDMS) were synthesized by polymerizing methyl methacrylate (MMA) via a PDMS macro- azo-initiator (PASA, 1) according to previous articles.12-14, 23-25 The composition and average molecular weights of the resultant PMMA-b-PDMS have been summarized in a previous article.13 The prescribed amounts of the resultant PMMA-b-PDMS were dissolved in benzene at 25°C at a concentration of 4 wt % for the preparation of the casting solutions. The PMMA-b-PDMS membranes (original membranes) were prepared by pouring the casting solutions onto rimmed glass plates, and then allowing the solvent to evaporate completely at 25°C. Some of the resultant membranes were also annealed at 120°C for 2 h (annealed membranes). The resultant membranes were transparent, and their thickness was about 40 μm. The PMMA-b-PDMS membranes before and after the annealing were vapor stained with an aqueous solution of 5 wt % RuO4 in glass-covered dishes.26 The stained membranes were then embedded in epoxy resin and cross-sectioned into thin films (thickness: approximately 60 nm) with a microtome (Leica; Reichert Ultracut E). The morphological features that were highlighted by our staining procedure were observed with a transmission electron microscope (TEM) (JEOL JEM-1210) at an accelerating voltage of 80 kV. Pervaporation was performed using the apparatus described in previous articles9-15 under the following conditions: permeation temperature, 40°C; pressure on the permeate side, 1 × 10−2 Torr. The effective membrane area was 13.8 cm2. An aqueous solution of 10 wt % ethanol was used as the feed solution. The compositions of the feed solution and permeate were determined by a gas chromatography (Shimadzu GC-9A) equipped with a flame ionization detector (FID) and a capillary column (Shimadzu Co. Ltd.; Shimalite F) heated to 200°C. The permeation rates of an aqueous ethanol solution during pervaporation were determined from the weight of the permeate collected in a cold trap, the permeation time, and the effective membrane area. The results of the permeation of an aqueous ethanol solution by pervaporation were reproducible, and the errors inherent in the permeation measurements were of the order of a few percent. Figure 1 shows the effects of the DMS content on the ethanol concentration in the permeate and the normalized permeation rate through original and annealed PMMA-b-PDMS membranes by pervaporation. The normalized permeation rates of the original and annealed PMMA-b-PDMS membranes exhibited abrupt increases at a DMS content of about 60 and 40 mol %, respectively. The ethanol concentration in the permeate through the original membrane with a DMS content of less than 60 mol % was much less than in the feed (10 wt %). However, increasing the DMS content to over 60 mol % brought about a steep increase in the ethanol concentration in the permeate. This means that original membranes with a DMS content of less than 60 mol % are water permselective, whereas those of over 60 mol % are ethanol permselective. On the other hand, the annealed membranes changed suddenly from water to ethanol permselectivity at a DMS content of about 40 mol %. Consequently, in the PMMA-b-PDMS membranes with a DMS content between 40 and 60 mol %, annealing leads to an abrupt change from water to ethanol permselectivity. This means that the permselectivity of pervaporation membranes can be controlled by a variety of after treatments even if the composition of the membranes is kept constant. Effects of the DMS content on the ethanol concentration in the permeate (○) and the normalized permeation rate (•) through (a) original and (b) annealed PMMA-b-PDMS membranes by pervaporation. An aqueous solution of 10 wt % ethanol was used as the feed solution. The dashed line represents the feed composition. Previous studies have demonstrated that the morphology of phase separation strongly influences the permselectivity of multicomponent polymer membranes.9-13 Therefore, PMMA-b-PDMS membranes were stained with RuO4, and then embedded in epoxy resin and cross-sectioned into thin films with a microtome. The morphological features of the thin sections were then observed using a transmission electron microscope (TEM). As shown in Figure 2, all of the PMMA-b-PDMS membranes had a microphase separation consisting of a PMMA phase (unstained region) and a PDMS phase (stained region). In the original PMMA-b-PDMS membranes with a DMS content of less than 60 mol %, the PMMA and PDMS components formed continuous and discontinuous phases, respectively, in the direction of the membrane thickness. However, original membranes with a DMS content of 62 mol % had a bicontinuous microphase separation, in which both the PMMA and PDMS components formed continuous phases. In the original membranes, the fact that the PDMS component changes from a discontinuous phase to a continuous phase at a DMS content of 60 mol % was more noticeable. On the other hand, annealed membranes with a DMS content of 29 mol % were composed of a continuous PMMA phase and a discontinuous PDMS phase, but increasing the DMS content to over 40 mol % caused the PDMS phase to form a continuous phase. Therefore, the morphology of the annealed membranes changed from a discontinuous PDMS phase to a continuous phase at a DMS content of about 40 mol %. In the membranes with a DMS content between 40 and 60 mol %, annealing gives rise to dramatic changes in their morphology from a discontinuous PDMS phase to a continuous phase. These morphological changes are responsible for the effects of annealing on the permselectivity of the PMMA-b-PDMS membranes. Transmission electron micrographs of cross-sections from the original and annealed PMMA-b-PDMS membranes composed of various DMS contents. The dark regions stained by RuO4 represent the PDMS component. The main purpose of this study was to determine the quantitative relationship between microphase separation in block copolymer membranes and their permselectivity for aqueous ethanol solutions. Therefore, a quantitative estimation of the morphology of the microphase separation in the block copolymer membranes is required to quantitatively relate the microphase separation to its permselectivity for aqueous ethanol solutions. However, it is difficult to clearly and quantitatively describe the morphological changes in microphase separation because of their disordered systems. In this study, we introduced fractal dimensions into the analysis of the phase separation for the shape of PDMS phases. Fractal dimensions can quantify the shape of the phase separation.16-22 During the phase separation, there are many domains of various sizes that have intricate shapes. The interface roughness between their phases can be described by fractal geometry. Method used to determine the fractal dimension, D, for microphase separation in PMMA-b-PDMS membranes. The TEM image of the microphase separation is magnified to such an extent that each domain (dark region) can be discriminated. Because domains of different sizes are self-similar, investigating the relationship between the boundary lines and the areas of domains of different sizes gives a fractal dimension for the shape of the microphase separation. The length of the boundary line of the nth domain, X(n), and its area, S(n) were obtained by image analysis using a personal computer. Therefore, D can be determined from the slope of a plot of log X(n) vs. log S(n)1/2 on the basis of eq. 1. For example, the relationship between X(n) and S(n)1/2 for an original PMMA-b-PDMS with a DMS content of 41 mol % is shown in this figure. Figure 4 shows the relationship between the DMS content and the fractal dimensions for the microphase separation in original and annealed PMMA-b-PDMS membranes. The fractal dimension of the PDMS clusters in the original membranes decreased dramatically from 1.60 to 1.45 at a DMS content of 60 mol %. On the other hand, the annealed membranes show an abrupt decrease in their fractal dimension at a DMS content of about 40 mol %. This suggests that the DMS clusters in the microphase separation of original and annealed membranes change from a more intricate shape to a less intricate shape at DMS contents of about 60 and 40 mol %, respectively. At a DMS content of over 60 mol %, the fractal dimension of the annealed membrane is in agreement with the original membrane. This means that their membranes have the same morphology in the microphase separation. The fractal dimensions for an original membrane with a DMS content of less than 40 mol % were also similar to the annealed membranes with the same DMS content. This suggests that the annealing process results in little morphological change in the microphase separation of PMMA-b-PDMS membranes with a DMS content of less than 40 mol %. It is worth noting that the DMS content at which the fractal dimension decreases dramatically corresponds to the DMS content at which the PMMA-b-PDMS membrane changes from water to ethanol permselectivity. In other words, PMMA-b-PDMS membranes having a fractal dimension of 1.60 are water permselective, whereas those with a fractal dimension of 1.45 are ethanol permselective. This is valid for both original and annealed membranes. The fact that the fractal dimension decreases following annealing is probably due to the fact that the annealing produces a smoother interface between the PDMS and PMMA phase for lowering the interfacial free energy. Although the interface becomes smoother following annealing, the PDMS component forms a continuous phase with a less intricate outline in the direction of the membrane thickness. Consequently, PMMA-b-PDMS membranes with a continuous PDMS phase and a less intricate outline show ethanol permselectivity because an aqueous ethanol solution is permeated predominantly through the continuous PDMS phase that is ethanol permselective. This is the reason why increasing the DMS content and annealing make the PMMA-b-PDMS membranes more ethanol permselective. It is quite noticeable that there is a close relationship between the fractal dimension of the microphase separation and the membrane permselectivity. Even though determining a definitive relationship between the fractal dimension for microphase separation and permselectivity of multicomponent polymer membranes will require further research work for other membranes, it is likely to become clear in the future based on the results of this study. Our method of estimating the microphase separation by evaluating the fractal dimension is useful for quantitatively relating microphase separation in multicomponent polymer membranes to the membrane properties. This novel approach makes it possible to study the relationship between microphase separation and membrane properties, thus facilitating a more detailed comparison of microphase-separated structure in multicomponent polymer membranes. Effects of the DMS content on the fractal dimension of the PDMS cluster in original (○) and annealed (•) PMMA-b-PDMS membranes. This report described the relationship between microphase separation in block copolymer membranes and their permselectivity for aqueous ethanol solutions on the basis of their fractal geometry. The permselectivities of the original and annealed poly(methylmethacrylate)-block-poly(dimethylsiloxane) (PMMA-b-PDMS) membranes were strongly influenced by the morphology of their microphase separation, which was dependent upon the copolymer composition. The fractal dimensions for the microphase separation in the block copolymer membranes were obtained from the analysis of transmission electron microscopy (TEM) images. The annealing of the membranes at 120°C for 2 h resulted in a decreased fractal dimension for microphase separation in the membranes. This is due to the fact that the annealing produces a smoother interface between the PDMS and PMMA phases, thus lowering the interfacial free energy. There was a close relationship between the fractal dimensions for the microphase separation and the membrane permselectivity. PMMA-b-PDMS membranes with a fractal dimension of 1.60 were water permselective, and those with a fractal dimension of 1.45 were ethanol permselective. This was valid for both the original and the annealed PMMA-b-PDMS membranes. Membranes with a continuous PDMS phase and a less intricate outline exhibited ethanol permselectivity, because aqueous ethanol solutions are permeated predominantly through the continuous PDMS phase which is ethanol permselective." @default.
• W2024334895 created "2016-06-24" @default.
• W2024334895 creator A5039946998 @default.
• W2024334895 creator A5042571232 @default.
• W2024334895 creator A5074189456 @default.
• W2024334895 date "2000-02-15" @default.
• W2024334895 modified "2023-09-27" @default.
• W2024334895 title "Relationship between fractal microphase separation and permselectivity of block copolymer membranes containing poly(dimethylsiloxane)" @default.
• W2024334895 cites W1966166072 @default.
• W2024334895 cites W1967953371 @default.
• W2024334895 cites W1969558457 @default.
• W2024334895 cites W1984314729 @default.
• W2024334895 cites W1999684450 @default.
• W2024334895 cites W2018198161 @default.
• W2024334895 cites W2026824122 @default.
• W2024334895 cites W2047108398 @default.
• W2024334895 cites W2053746708 @default.
• W2024334895 cites W2070066123 @default.
• W2024334895 cites W2079741064 @default.
• W2024334895 cites W2083225902 @default.
• W2024334895 cites W2085774985 @default.
• W2024334895 cites W2403622547 @default.
• W2024334895 cites W2506831584 @default.
• W2024334895 cites W4210949720 @default.
• W2024334895 doi "https://doi.org/10.1002/(sici)1099-0488(20000215)38:4<584::aid-polb10>3.0.co;2-x" @default.
• W2024334895 hasPublicationYear "2000" @default.
• W2024334895 type Work @default.
• W2024334895 sameAs 2024334895 @default.
• W2024334895 citedByCount "15" @default.
• W2024334895 countsByYear W20243348952012 @default.
• W2024334895 countsByYear W20243348952016 @default.
• W2024334895 countsByYear W20243348952017 @default.
• W2024334895 crossrefType "journal-article" @default.
• W2024334895 hasAuthorship W2024334895A5039946998 @default.
• W2024334895 hasAuthorship W2024334895A5042571232 @default.
• W2024334895 hasAuthorship W2024334895A5074189456 @default.
• W2024334895 hasBestOaLocation W20243348951 @default.
• W2024334895 hasConcept C126348684 @default.
• W2024334895 hasConcept C127313418 @default.
• W2024334895 hasConcept C127413603 @default.
• W2024334895 hasConcept C151730666 @default.
• W2024334895 hasConcept C15920480 @default.
• W2024334895 hasConcept C159985019 @default.
• W2024334895 hasConcept C185592680 @default.
• W2024334895 hasConcept C188027245 @default.
• W2024334895 hasConcept C192562407 @default.
• W2024334895 hasConcept C41625074 @default.
• W2024334895 hasConcept C42360764 @default.
• W2024334895 hasConcept C499950583 @default.
• W2024334895 hasConcept C521977710 @default.
• W2024334895 hasConcept C55493867 @default.
• W2024334895 hasConceptScore W2024334895C126348684 @default.
• W2024334895 hasConceptScore W2024334895C127313418 @default.
• W2024334895 hasConceptScore W2024334895C127413603 @default.
• W2024334895 hasConceptScore W2024334895C151730666 @default.
• W2024334895 hasConceptScore W2024334895C15920480 @default.
• W2024334895 hasConceptScore W2024334895C159985019 @default.
• W2024334895 hasConceptScore W2024334895C185592680 @default.
• W2024334895 hasConceptScore W2024334895C188027245 @default.
• W2024334895 hasConceptScore W2024334895C192562407 @default.
• W2024334895 hasConceptScore W2024334895C41625074 @default.
• W2024334895 hasConceptScore W2024334895C42360764 @default.
• W2024334895 hasConceptScore W2024334895C499950583 @default.
• W2024334895 hasConceptScore W2024334895C521977710 @default.
• W2024334895 hasConceptScore W2024334895C55493867 @default.
• W2024334895 hasIssue "4" @default.
• W2024334895 hasLocation W20243348951 @default.
• W2024334895 hasOpenAccess W2024334895 @default.
• W2024334895 hasPrimaryLocation W20243348951 @default.
• W2024334895 hasRelatedWork W1564088826 @default.
• W2024334895 hasRelatedWork W1984015401 @default.
• W2024334895 hasRelatedWork W2024349192 @default.
• W2024334895 hasRelatedWork W2082971079 @default.
• W2024334895 hasRelatedWork W2090105468 @default.
• W2024334895 hasRelatedWork W2093846035 @default.
• W2024334895 hasRelatedWork W2123676998 @default.
• W2024334895 hasRelatedWork W2180716370 @default.
• W2024334895 hasRelatedWork W2396972712 @default.
• W2024334895 hasRelatedWork W3198492087 @default.
• W2024334895 hasVolume "38" @default.
• W2024334895 isParatext "false" @default.
• W2024334895 isRetracted "false" @default.
• W2024334895 magId "2024334895" @default.
• W2024334895 workType "article" @default.