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1.
We demonstrate a simple methodology to incorporate interacting magnetic nanoparticles (mNPs) into cylinder forming block copolymer templates. Poly(styrene-block-isoprene) (PS-b-PI) with PI cylinders and poly(styrene-block-4vinylpyridine) (PS-b-P4VP) with PS cylinders were used as the block copolymer templates and γ-Fe2O3 NPs coated with oleic acids were pre-synthesized for the interacting mNPs. Regardless of the template block copolymers, the selective location of mNPs and the size of mNP aggregates are clearly altered by changing casting solvents. When good solvents for both blocks were used as casting solvents, mNPs are readily aggregated during the solvent evaporation. In contrast, under selective casting solvents for the minor blocks, the mNPs were selectively trapped into the cylinder domains through the facile inversion of micelles during solvent evaporation. The interplay between mNPs and block copolymers was also tested with different molecular weights of block copolymers.  相似文献   

2.
Deformation behavior of styrene-block-butadiene-block-styrene (SBS) triblock copolymers having different morphologies was investigated. Due to the combination of different methods which provide information on different deformation levels (macroscopic, microscopic and molecular) complex deformation mechanisms for each type of SBS block copolymer (including glassy-rubber alternating lamellae, rubber cylinders in glassy matrix and hard domains in soft matrix morphology) could be revealed. In combination with tensile tests, Fourier transform infrared (FTIR) spectroscopy was successfully applied to study the change of orientation in individual phases using the absorption bands at 1493 and 966 cm−1 for polystyrene (PS) and polybutadiene (PB) phases, respectively. For all the block copolymers investigated the PB phase always oriented stronger than the PS phase because of its lower Young's modulus. However, differences in orientation in both phases were influenced by an appropriate stress distribution within the specimens during deformation, which, in fact, depends on the morphology of the polymers. Additionally, atomic force microscopy revealed local morphological changes during uniaxial stretching, which, in fact, depend on the arrangement of the structural units.  相似文献   

3.
Composites based on microphase-separated diblock copolymers of styrene with vinylpyridine and gold nanoparticles, in which the block copolymers play simultaneously both the role of a stabilizer preventing the aggregation of nanoparticles and a matrix providing their selective arrangement within domains of the predefined type, are obtained for the first time. The suggested approach implies no use of additional stabilizers and is efficient for both initially organic dispersed small (~5 nm) spheres and hydrasols of larger (9 × 30 nm) rodlike nanoparticles. Nanospheres are introduced into the composites via replacement of a labile stabilizer used in synthesis with the diblock copolymer, while nanorods synthesized in aqueous media by the two-stage method are incorporated via phase transfer mediated by the diblock copolymer. Films capable of microphase separation leading to the formation of vinylpyridine cylindrical domains with a diameter of tens nanometers are spin-coated from the obtained composites. The content of nanoparticles in the composites is up to 5 wt %; they are dispersed and arranged predominantly within vinylpyridine domains, with nanospheres being localized near domain boundaries, while nanorods being mainly oriented perpendicularly to the axis of cylinders.  相似文献   

4.
Internal nanostructures in nanorods of polystyrene-poly(4-vinyl pyridine) (PS-PVP) diblock copolymers fabricated from pores having regular or irregular contours in AAO templates were investigated by cross-sectional transmission electron microscopy. When nanorods of PS-PVP copolymers were produced from pores with regular contours, a typical morphology of concentric cylinders was observed due to the strong affinity of the PVP block to the surface of the AAO pores. In the case of PS-PVP nanorods obtained from pores with irregular contours, a concentric cylindrical morphology was not induced. Instead, a nanostructure of lamellae mostly parallel to the axis of the nanorods was observed with a similar period of lamellae to the bulk lamellar period. In addition, nanorods having a functional coaxial nanostructure were fabricated by synthesizing Au nanoparticles in concentric cylinders of the nanorods to demonstrate the utilization of self-assembled internal nanostructures in nanorods.  相似文献   

5.
Chang-Hong Ho  Yu-Der Lee 《Polymer》2010,51(7):1639-1647
This investigation characterizes the molten morphologies following isothermal crystallization of poly(l-lactide-block-dimethyl siloxane-block-l-lactide) triblock copolymers, which were synthesized by ring-opening polymerization of l-lactide using hydroxyl-telechelic PDMS as macroinitiators, via small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The break-out and preservation of the nanostructure of the triblock copolymer depended on the segregation strength, which was manipulated by varying the degree of polymerization. The crystallization kinetics of these semicrystalline copolymers and the effect of isothermal crystallization on their melting behaviors were also studied using DSC, FT-IR and WAXS. The exclusive presence of α-phase PLLA crystallite was verified by identifying the absence of the WAXS diffraction signal at 2θ = 24.5° and the presence of IR absorption at 1749 cm−1 when the PLLA segment of the block copolymers was present as a minor component. The dependence of the crystallization rate (Rc) on the chemical composition of the triblock copolymers reveals that the Rc of the triblock copolymers was lower than that of PLLA homopolymer and the Rc were substantially reduced when the minor component of the crystallizable PLLA domains was dispersed in the PDMS matrix.  相似文献   

6.
AAO template is highly recommended to nanostructure polymers and to study polymer properties under confinement. The dynamic properties of polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) under confinement using broadband dielectric spectroscopy are investigated in this work and the results compared to those of the bulk. Anodized aluminum oxide (AAO) membranes, having pore diameters from tens to hundreds of nanometers in size, were used to confine PS-b-P4VP. Moreover, the influence of gold nanoparticles (AuNPs) in the copolymer matrix was also studied. The morphology and structure of the bulk copolymer and the copolymer confined in the AAO templates were characterized by transmission electron microscopy, scanning electron microscopy and Small Angle X-Ray Scattering. For PS-b-P4VP in bulk, dielectric relaxation techniques allowed studying selectively the P4VP segmental dynamics within the diblock. At high temperature this copolymer presents a dominant peak (MWS relaxation), most likely originated by the relatively high conductivity combined with the presence of interfaces emerging in the nanostructured samples. Moreover, a pronounced β-relaxation is observed for the copolymer compared with that of pure P4VP. This is likely due to a non-negligible contribution from the α-relaxation of the PS component. The γ-relaxation is markedly different in the copolymer, which is evidenced by a distinct temperature dependence of the resulting relaxation times. When the copolymer is embedded in alumina nanopores with small pore diameters (25 and 35 nm) there are significant changes, where the tendency is going to a faster dynamics when the pore diameter decreases more likely related to the relevance of surface effects. The presence of the AuNPs in the system enhances this effect. These results are in agreement with segregated structures found in the block copolymer by TEM and SAXS.  相似文献   

7.
Linli He  Hongping Chen 《Polymer》2009,50(14):3403-2721
Mixtures of cylindrical forming diblock copolymers (DBCPs) and mobile nanorods (NRs) are systematically investigated via dissipative particle dynamics (DPD) simulations. Final morphology of such composites depends not only on the characteristics of the copolymers, but also on the physical or chemical features of NRs, such as NR number, length, and surface adsorption (neutral, A and B attractive). A consideration of enthalpic and entropic interactions is necessary when physically or chemically distinct NRs are introduced into the copolymer/nanorod composites. For the short NRs, the phase behavior is similar to that of spherical nanoparticles (NPs). For the long NRs, the self-assembly of NRs can influence both the orientation and morphology of diblock/nanorod mixtures. If more NRs are incorporated, under stronger confinement from the host phase separated domains, the long NRs will aggregate and self-assemble into a certain spatial organization, inducing the morphological transitions of the composites from one phase to another. This behavior is not encountered for a similar system doped with spherical particles, emphasizing the role of particle shape in the interaction between doping particles and the host phase.  相似文献   

8.
We investigated, via small angle X-ray scattering, depolarized light scattering, rheometry, and transmission electron microscopy, the phase behavior of the mixture of a symmetric polystyrene-block-poly(n-pentyl methacrylate) copolymer (PS-b-PnPMA) showing the closed-loop phase behavior and excellent baroplasticity, and dodecanol, a PnPMA-selective solvent. We found that the addition of a selective solvent is simple, but very effective to obtain various microdomains including hexagonally packed cylinders and gyroids. Also, with increasing temperature, the mixtures showed multiple ordered-to-ordered transitions (OOTs) in addition to upper ordered-to-disordered transition (UODT). The first observation of gyroid microdomains in PS-b-PnPMA is very important, although they have been widely reported in many block copolymers, for instance, PS-block-polyisoprene copolymer (PS-b-PI) and PS-block-poly(d,l-lactide) copolymer (PS-b-PLA). Since the gyroid microdomains of PS-b-PnPMA show excellent baroplasticity, external pressure instead of temperature could easily change the microdomains.  相似文献   

9.
We investigated the effect of an anisotropic silicate layer on the alignment and orientational proliferation of hexagonally packed cylinder microdomains of a block copolymer in the presence of a clay by using synchrotron small angle X-ray scattering (SAXS), rheology, and transmission electron microscopy (TEM). The block copolymer employed in this study was polystyrene-block-polyisoprene-block-polystyrene copolymer (SIS). The degree of intercalation of the clay in the presence of SIS was examined by wide angle X-ray diffraction (WAXD).Almost all of the HEX cylinders in neat SIS are aligned toward the flow direction after large amplitude oscillatory shearing is applied to the specimens. However, some tactoids in nanocomposites are not aligned, although most tactoids are also aligned to the flow direction. Due to HEX cylinders near tactoids, which are not aligned to the flow direction, the orientational factor of HEX cylinders in SIS/clay nanocomposites is smaller than that of neat SIS. However, once HEX cylinders in SIS/clay nanocomposites are degenerated after experiencing body-centered cubic microdomains, the decrease in the orientational factor from original aligned HEX is smaller compared with neat SIS.  相似文献   

10.
Jiyoung Hwang  Bumsuk Jung  Min Park 《Polymer》2005,46(21):9133-9143
Microstructures of hundreds of micron thick poly(styrene-block-isoprene) copolymer films solution-cast in a cylindrical tube with the solvent evaporation controlled were investigated by transmission electron microscope (TEM), small angle X-ray scattering (SAXS) and optical microscope (OM). In a block copolymer with cylindrical polyisoprene microdomains, the orientation of the cylinders was varied along radial direction of the cylindrical tube. Highly aligned hexagonal arrays of in-plane polyisoprene cylinders were formed with their cylindrical axis parallel to the circumference of the tube in the regimes close to the wall edge. In contrast randomly ordered microdomains were observed at the center of the tube. We have also found that the orientation depends on the solvent evaporation rate and an intermediate rate (∼2.3 nL/s) provides the best orientation. In the case of a block copolymer with a bicontinuous double gyroid structure, we obtained a globally ordered microstructure where [111] crystallographic direction was parallel to the circumference of the tube. For both block copolymers, the area of highly ordered arrays of nanoscopic domains is over 1 mm2. Development of the orientation was explained by coupling two orthogonal fields: (1) The flow of a solution induced by strong capillary force at a meniscus between the cylindrical tube wall and the block copolymer solution and (2) the solvent evaporation.  相似文献   

11.
A polymer blend system consisting of polystyrene grafted onto poly (p-phenylene ethynylene) (PS-g-PPE) and poly (styrene-block-isoprene-block-styrene) triblock copolymer (SIS) yields highly polarized emission due to the unidirectional alignment of the PPE molecules. During the roll casting, the triblock copolymer microphase separates and creates unidirectionally aligned PS cylindrical microdomains in the rubbery PI matrix. PPE, a fluorescent conjugated polymer, was grafted with polystyrene (PS) side chains that enabled sequestration and alignment of these rigid backbone emitter molecules into the PS microdomains of the SIS triblock copolymer. Deforming the thermoplastic elastomer in a direction perpendicular to the orientation direction of the cylinders causes rotation of the PS cylinders and the PPE emitter molecules and affords tunable polarized emission due to re-orientation of the PPE containing PS cylinders as well as film thinning from Poisson effect.  相似文献   

12.
Morphologies of polymer blends based on polystyrene‐b‐ polybutadiene‐b ‐poly(methyl methacrylate) (SBM) triblock copolymer were predicted, adopting the phase diagram proposed by Stadler and co‐workers for neat SBM block copolymer, and were experimentally proved using atomic force microscopy. All investigated polymer blends based on SBM triblock copolymer modified with polystyrene (PS) and/or poly(methyl methacrylate) (PMMA) homopolymers showed the expected nanostructures. For polymer blends of symmetric SBM‐1 triblock copolymer with PS homopolymer, the cylinders in cylinders core?shell morphology and the perforated lamellae morphology were obtained. Moreover, modifying the same SBM‐1 triblock copolymer with both PS and PMMA homopolymers the cylinders at cylinders morphology was reached. The predictions for morphologies of blends based on asymmetric SBM‐2 triblock copolymer were also confirmed experimentally, visualizing a spheres over spheres structure. This work presents an easy way of using PS and/or PMMA homopolymers for preparing nanostructured polymer blends based on SBM triblock copolymers with desired morphologies, similar to those of neat SBM block copolymers. © 2017 Society of Chemical Industry  相似文献   

13.
Temperature responsive or bactericidal coatings with poly(n-butyl methacrylate) (PBMA) as bulk material and surface segregated poly(n-butyl acrylate)-block-poly-(N-isopropylacrylamide) (PBA-b-PNIPAAm) or poly(n-butyl acrylate)-block-quaternized poly(2-(dimethylamino)ethyl methacrylate) (PBA-b-PDMAEMAq) as additive were prepared via sequential solvent evaporation of polymer solutions in a solvent mixture. The degree of enrichment at the air surface of the coating and the functionality were examined for different molecular weight additives with different block ratios obtained via Atom Transfer Radical Polymerization (ATRP). The design of the block copolymers with an anchor block (PBA) which is compatible with the bulk polymer (PBMA) and water-compatible functional blocks (PNIPAAm and PDMAEMAq) along with the selection of suited solvent mixtures based on pre-estimation of the selective solubility and sequential evaporation via the Hansen solubility parameters and vapor pressures, respectively, were found to work very well. A small fraction of water in the solvent mixture had been crucial to obtain surface segregation of the functional block, e.g., a PNIPAAm surface with temperature-switchable wettability. Reversible temperature dependent wettability and long term stability of the functionalization, based on contact angle data, were obtained for an optimized PBA-b-PNIPAAm additive. Surface charge density, estimated from dye binding and zeta potential measurements, and killing efficiency against Staphylococcus aureus were investigated for PBA-b-PDMAEMAq as additive. Both block copolymer additives were found to dominate the surface properties and the functionality of the PBMA coating.  相似文献   

14.
Qipeng Guo  Ralf Thomann 《Polymer》2007,48(14):3925-3929
Mesostructurally ordered inorganic-organic hybrid composite materials were successfully synthesized by utilizing a low-molecular-weight amphiphilic polyethylene-block-poly(ethylene oxide) (PE-PEO) diblock copolymer as the directing agent. The hybrid composites were formed via the sol-gel reaction of inorganic precursor tetraethoxysilane (TEOS) in an acidic ethanol/water solution with various amounts of PE-PEO. In these composite materials, the hydrophobic PE block of the PE-PEO copolymer forms separate microphase on the nanoscales within the rigid matrix of silica network. The crystallization of the PE block is strictly restricted within the microphase by the rigid silica matrix and takes place through homogeneous nucleation under the nanoscale confinement environment.  相似文献   

15.
Effects of polystyrene block content on adhesion property and phase structure of polystyrene block copolymers were investigated. Polystyrene-block-polyisoprene-block-polystyrene triblock and polystyrene-block-polyisoprene diblock copolymers with different polystyrene block contents in the range from 13 to 35 wt% were used. In the case of the low polystyrene block content (below 16 wt%), a sea-island structure was observed: near-spherical polystyrene domains having a mean diameter of about 20 nm were dispersed in polyisoprene matrix. The phase structure changed from a sea-island structure to a cylindrical structure with an increase of polystyrene block content (over 18 wt%). Peel strength decreased with an increase of polystyrene block content and the pure triblock copolymers had lower peel strength than their blends with the diblock copolymers. Pulse nuclear magnetic resonance studies indicated that molecular mobility of polyisoprene phase decreased with an increase of polystyrene block content, and the molecular mobility was lower in the pure triblock than in the blend. Thus, the peel strength was found to be related to molecular mobility. The adhesion strength of the block copolymer depended on the molecular mobility: high molecular mobility can promote interfacial adhesion.  相似文献   

16.
Exfoliated nanocomposites based on polystyrene-block-polyisoprene-block-poly(2-vinylpyridine) (SI2VP triblock) copolymer were prepared by solution blending and melt blending. Their dispersion characteristics were investigated using transmission electron microscopy, X-ray diffraction, and small-angle X-ray scattering (SAXS). For the study, SI2VP triblock copolymers with varying amounts of poly(2-vinylpyridine) (P2VP) block (3, 5, and 13 wt%) and different molecular weights were synthesized by sequential anionic polymerization. In the preparation of nanocomposites, four different commercial organoclays, treated with a surfactant having quaternary ammonium salt, were employed. It was found from SAXS that the microdomain structure of an SI2VP triblock copolymer having 13 wt% P2VP block (SI2VP-13) transformed from core-shell cylinders into lamellae when it was mixed with an organoclay. It was found further that the solution-blended nanocomposites based on a homogeneous SI2VP triblock copolymer having 5 wt% P2VP block (SI2VP-5) gave rise to an exfoliated morphology, irrespective of the differences in chemical structure of the surfactant residing at the surface of the organoclays, which is attributable to the presence of ion-dipole interactions between the positively charged N+ ion in the surfactant residing at the surface of the organoclay and the pyridine rings in the P2VP block of SI2VP-5 and SI2VP-13, respectively. Both solution- and melt-blended nanocomposites based on microphase-separated SI2VP-13 having an order-disorder transition temperature (TODT) of approximately 210 °C also gave rise to exfoliated morphology. However, melt-blended nanocomposite based on a high-molecular-weight SI2VP triblock copolymer having a very high TODT (estimated to be about 360 °C), which was much higher than the melt blending temperature employed (200 °C), gave rise to very poor dispersion of the aggregates of organoclay. It is concluded that the TODT of a block copolymer plays a significant role in determining the dispersion characteristics of organoclay nanocomposites prepared by melt blending.  相似文献   

17.
Three random and three block copolymers of methyl methacrylate (MMA) and octadecyl acrylate (ODA) were synthesized by atom transfer radical polymerization. These copolymers were assessed for their application as stabilizers in the one-step non-aqueous dispersion (NAD) polymerization of MMA and of acrylonitrile (AN) in a non-polar solvent mixture of hexane and dodecane. In all cases stable spherical micro-particle colloidal dispersions were formed with particle diameters in the range of 62-2725 nm for PMMA. Uniform monodisperse PMMA particles with standard deviations in size distributions of less than 5% were obtained in two cases demonstrating the utility of ODA:MMA copolymers as replacement preformed stabilizers in the one-step synthesis of MMA micro-spheres. Overall the block copolymer PMMA64-block-PODA36 gave greater control over size when varying the solvent:monomer ration than a related gradient PMMA-PODA copolymer. These copolymers were further used as stabilizers in the one-step NAD polymerization of MMA with ethylene glycol dimethacrylate (EGDMA) under similar conditions allowing for the preparation of monodisperse cross-linked PMMA particles with diameters ranging from 110 to 1700 nm. The general utility of the copolymers as stabilizers was demonstrated by the NAD polymerization of acrylonitrile (AN) in non-polar solvent mixture of hexane and dodecane giving ‘crumpled’ latex dispersions with particle diameters in the range 85-483 nm.  相似文献   

18.
Poly(ε-caprolactone)-block-poly[2-(dimethylamino)ethyl methacrylate] (PCL-b-PDMAEMA) block copolymers were applied to fabricate elongated polymer platelets with axial length of 5–20 μm and thickness of ca. 10 nm by crystallization-driven self-assembly (CDSA). The block copolymer platelets composed of a crystallized PCL layer sandwiched between two PDMAEMA layers were obtained spontaneously by adding methanol, a selective solvent of PDMAEMA, into the block copolymer solution of THF at 25 °C. Therefore, this is a facile approach to generate lamellar nanoobjects of block copolymers. Effects of the block copolymer compositions on the morphologies of platelets were investigated. The presence of PDMAEMA segments along the lamellar surfaces was further confirmed by loading gold nanoparticles. Moreover, PEO-b-PCL-b-PDMAEMA triblock terpolymer could form spindle platelets by this approach. The crystalline platelets were characterized by the transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD).  相似文献   

19.
Chia-Fen Lee  Lee-Yih Wang 《Polymer》2005,46(15):5514-5523
The purpose of this study was to modify the surface characteristics of CB so as to prevent the aggregation of CB to provide the dispersibilities in either H2O or organic solvent. In this study, five kinds of hydrophilic TEMPO-terminated polymer, hydrophobic TEMPO-terminated polymer and amphiphilic TEMPO-terminated block copolymer were synthesized. The five kinds of TEMPO-terminated polymers were: (1) poly(4-acetoxystyrene) (PAS-T), (2) poly(4-hydroxystyrene) (PHS-T), (3) polystyrene (PS-T), (4) poly(4-acetoxystyrene)-block-polystyrene (PAS-b-PS-T), (5) poly(4-hydroxystyrene)-block-polystyrene (PHS-b-PS-T). These TEMPO-terminated polymers with desired molecular weights and specific structures were synthesized by using the method of living radical polymerization in the presence of 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO). These TEMPO-terminated polymers and TEMPO-terminated block copolymers were grafted onto the surface of CB through a reaction of polymer radicals trapped by CB, so as to obtain the TEMPO-terminated polymer/CB and TEMPO-terminated block copolymer/CB composite nanoparticles. Various variables such as reaction time, reaction temperature, amount of TEMPO-terminated polymer, molecular weight of TEMPO-terminated polymer and amount of CB all of which influenced the grafting efficiency were investigated. Besides, the stability of the composite nanoparticles, which dispersed in H2O or organic solvent, was investigated by laser light scattering. The amphiphilic composite nanoparticles, PHS-T/CB and PHS-b-PS-T/CB, which dispersed well in both H2O and organic solvent, were synthesized successfully in this work.  相似文献   

20.
The ordering behavior of polymer nanocomposites composed of gold nanoparticles confined in the polystyrene (PS) domains of PS based block copolymers was investigated. The results reveal that the self‐assembly of nanoparticles in the PS domains improved the ordering of microdomains. This is attributed to the presence of nanoparticles that reduced the degree of segregation of the system, causing slow phase separation. This facilitates the packing of the cylindrical microdomains, leading to a well‐ordered structure of the composite. When particles were incorporated into the major domains of cylindrically ordered block copolymer, the connectivity of the domains allowed particles to move to the top of the film to gain additional entropy of the system. In contrast, when particles were organized in parallel cylinders in the block copolymer, they were confined in the cylinders which prevented them from diffusing in the depth direction. The aggregation of nanoparticles was amplified when the composite was annealed in air. We believe that the results from this study will enable more understanding of the effects of nanoparticles on the ordering of block copolymer/nanoparticle composite thin films and will provide a tool in the fabrication of composite thin films. Copyright © 2012 Society of Chemical Industry  相似文献   

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