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1.
To mitigate the interface energies of block copolymers with high interaction parameters, a topcoat strategy has been experimentally proposed to produce perpendicular oriented domains on a length scale of sub‐10 nm. However, the origin of perpendicular oriented domains and the effect of topcoats on the self‐assembled nanostructures remain to be uncovered. Herein, we use the dynamic self‐consistent field theory to explore the self‐assembly behaviors of symmetric block copolymer films under homopolymer topcoats. It is clearly demonstrated that the introduction of homopolymer topcoats enables a wide formation range of perpendicular oriented lamellae, originating from the fluctuating diblock copolymer/homopolymer interfaces in the process of in‐plane microphase separation of block copolymer films. Our simulation results also demonstrate that the formation range of perpendicular oriented lamellae can be tuned by changing the wetting properties of homopolymer topcoats and the thickness of block copolymer films, but is weakly dependent upon the chain length of homopolymers. Our theoretical findings have wide implications for understanding the formation of perpendicular oriented domains of block copolymer films, which are important for the rational design of self‐assembled nanostructures with new horizons for block copolymer lithography. © 2020 Society of Chemical Industry  相似文献   

2.
This review summarizes recent advances in the preparation of hydrogen bonding block copolymer mixtures and the supramolecular structures they form through multiple hydrogen bonding interactions. Hydrogen bonding in block copolymer mixtures that form nanostructures and have unusual electronic, photonic and magnetic properties is a topic of great interest in polymer science. Combining the self‐assembly of block copolymers with supramolecular structures offers unique possibilities to create new materials with tunable and responsive properties. The self‐assembly of structures from diblock copolymer mixtures in the bulk state is readily controlled by varying the weight fraction of the block copolymer mixture and the copolymer composition; in solution, the morphologies are dependent on the copolymer composition, the copolymer concentration, the nature of the common solvent, the amount of the selective solvent and, most importantly, the hydrogen bonding strength. Copyright © 2008 Society of Chemical Industry  相似文献   

3.
The ability of block copolymers to self‐assemble into various nanostructures (such as micelles) has attracted significant attention over the years as these block copolymers provide a versatile platform that can readily be modified for a wide range of applications. As such, the solution behaviour of block copolymers has been at the forefront of the modern nanotechnology revolution. However, these novel block copolymer‐based self‐assemblies lack suitable characterisation techniques to determine size, molar mass and compositional distributions simultaneously. This mini‐review gives a short background on the current techniques used to determine important micelle properties as well as their limitations for characterising complex samples. Current column‐based fractionation techniques used for determining property distributions are addressed. As a result of the limitations of column‐based fractionations, a multidetector thermal field‐flow fractionation (ThFFF) approach is put forward as a powerful alternative for determining not only size and molar mass distributions, but also other micelle properties as a function of temperature. More importantly, ThFFF is highlighted as the only current characterisation platform capable of addressing the analytical challenges associated with compositional distributions of polymer self‐assemblies. © 2017 Society of Chemical Industry  相似文献   

4.
High molecular weight terpolymers based on L ‐lactide (LLA), trimethylene carbonate (TMC) and glycolide (GA) are synthesized and characterized with the aim of assessing their potential in the development of bioresorbable cardiovascular stents. The effect of the composition on the thermal and mechanical properties of terpolymers is investigated in comparison with the corresponding PLLA‐TMC copolymers as well as a PLLA homopolymer. Incorporation of GA units strongly decreases the crystallinity of PLLA‐TMC‐GA terpolymers due to its more random microstructure as evidenced by 13C NMR. Meanwhile, the toughness is greatly improved, with only a slight loss of tensile strength. Plasma‐treated poly[(L ‐lactide)‐co‐glycolide] (PLGA) fibers are used to reinforce the terpolymer matrix. Composite with 8 wt% fibers exhibits much higher tensile strength and modulus. A minitube is fabricated using a single‐screw extruder, and a stent prototype is successfully manufactured from a terpolymer by a CNC engraving machine, thus showing the feasibility of the terpolymers for the development of bioresorbable cardiovascular stents. POLYM. ENG. SCI., 54:1418–1426, 2014. © 2013 Society of Plastics Engineers  相似文献   

5.
The copolymers of ethylene/propylene as well as their terpolymers with polar monomers were prepared by Ni‐catalyst systems and their photodegradation behavior was studied by Fourier transform infrared spectroscopy. The polar monomers used to synthesize co‐ and terpolymers of ethylene/propylene/polar monomer were 5‐hexen‐1‐ol, 10‐undecen‐1‐ol, acrylamide, methylmethacrylate, acrylonitrile, and methylvinyl ketone. The morphological changes of the irradiated samples were determined by scanning electron microscopy. The photodegradation kinetics has also been studied. The surface damage caused by polychromatic irradiation (λ ≥ 290 nm) at 55 °C in atmospheric air is presented in different micrographs. The rate of photo‐oxidative degradation is very fast in terpolymers containing polar monomers as compared with copolymers and homopolymers. The morphological study of the photodegraded samples showed a very good correlation with the photodegraded results. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1783–1791, 2007  相似文献   

6.
DNA self‐assembly provides a powerful approach for preparation of nanostructures. It is often studied in bulk solution and involves only DNA–DNA interactions. When confined to surfaces, DNA–surface interactions become an additional, important factor to DNA self‐assembly. However, the way in which DNA–surface interactions influence DNA self‐assembly is not well studied. In this study, we showed that weak DNA–DNA interactions could be stabilized by DNA–surface interactions to allow large DNA nanostructures to form. In addition, the assembly can be conducted isothermally at room temperature in as little as 5 seconds.  相似文献   

7.
Block copolymers can form various ordered structures by self‐assembly, and their composites with inorganic materials may give surprising properties. This review summarizes recent developments in the preparation, mechanism and application of various types of self‐assembly of polystyrene‐block‐poly(2‐vinylpyridine) (PS‐b‐P2VP). The focus of the review is on how to control the self‐assembly of the dynamic and ordered structure of PS‐b‐P2VP based materials by applying effective factors such as thermal annealing, solvent annealing, block composition and blending. Moreover, the combination of the self‐assembly of PS‐b‐P2VP and various nanoparticles, with potentials in drug delivery, sensors and catalysis, is highlighted. © 2018 Society of Chemical Industry  相似文献   

8.
A series of biodegradable linear–hyperbranched barbell‐like poly(ethylene glycol) (PEG)‐supported poly(lactic‐ran‐glycolic acid) (PLGA) copolymers were synthesized with PEG, d ,l ‐lactic acid aqueous solution, glycolic acid and gluconic acid (Glu) under bulk conditions. The branching density of the hyperbranched section was varied by controlling the molar ratio of Glu to hydroxyl‐terminal groups of PEG ([Glu]/[OH] = 1, 3.5, 6.0, 8.5). Chemical structures of these copolymers were confirmed using NMR spectroscopy. The molecular weights were determined using 1H NMR group analysis and gel permeation chromatography, both results being consistent with one another. The results of hydrolytic degradation indicate that these copolymers can degrade completely in no more than three weeks. The thermal properties were evaluated using differential scanning calorimetry and thermogravimetric analysis. The results indicate that the glass transition temperatures and melt temperatures of these copolymers are not above 50 °C. The self‐assembly behavior of the copolymers on hydrophilic surfaces was also investigated. The morphology of self‐assembly films made of the copolymers was observed using atomic force microscopy, and the results indicate that these copolymers exhibit more inhomogeneous and rough structural orientated films on a silicon wafer substrate with increasing branching densities. Due to the favorable biodegradability and biocompatibility of the PLGA and PEG, the results suggest new possibilities for these novel structural amphiphilic linear–hyperbranched barbell‐like copolymers as potential biomaterials. © 2013 Society of Chemical Industry  相似文献   

9.
A series of well‐defined amphiphilic poly[(2‐hydroxyethyl methacrylate)‐block‐(N‐phenylmaleimide)] diblock copolymers containing hydrophilic and hydrophobic blocks of different lengths were synthesized by atom transfer radical polymerization. The properties of the diblock copolymers and their ability to form large compound spherical micelles are described. Their optical, morphological and thermal properties and self‐assembled structure were also investigated. The chemical structure and composition of these copolymers have been characterized by elemental analysis, Fourier transform infrared, 1H NMR, UV–visible and fluorescence spectroscopy, and size exclusion chromatography. Furthermore, the self‐assembly behavior of these copolymers was investigated by transmission electron microscopy and dynamic light scattering, which indicated that the amphiphilic diblock copolymer can self‐assemble into micelles, depending on the length of both blocks in the copolymers. These diblock copolymers gave rise to a variety of microstructures, from spherical micelles, hexagonal cylinders to lamellar phases. © 2013 Society of Chemical Industry  相似文献   

10.
The aim of the work reported was to synthesize a series of double‐hydrophilic poly(methacrylic acid)‐block‐poly(ethylene glycol)‐block‐poly(methacrylic acid) (PMAA‐b‐PEG‐b‐PMAA) triblock copolymers and to study their self‐assembly behavior. These copolymeric self‐assembly systems are expected to be potential candidates for applications as carriers of hydrophilic drugs. Bromo‐terminated difunctional PEG macroinitiators were used to synthesize well‐defined triblock copolymers of poly(tert‐butyl methacrylate)‐block‐poly(ethylene glycol)‐block‐poly(tert‐butyl methacrylate) via reversible‐deactivation radical polymerization. After the removal of the tert‐butyl group by hydrolysis, double‐hydrophilic PMAA‐b‐PEG‐b‐PMAA triblock copolymers were obtained. pH‐sensitive spherical micelles with a core–corona structure were fabricated by self‐assembly of the double‐hydrophilic PMAA‐b‐PEG‐b‐PMAA triblock copolymers at lower solution pH. Transmission electron microscopy and laser light scattering studies showed the micelles were of nanometric scale with narrow size distribution. Solution pH and micelle concentration strongly influenced the hydrodynamic radius of the spherical micelles (48–310 nm). A possible reason for the formation of the micelles is proposed. Copyright © 2010 Society of Chemical Industry  相似文献   

11.
Polyacetal copolymers were prepared by cationic ring‐opening copolymerizations of 1,3,5‐trioxane (TOX) with 1,3‐dioxolane (DOX), and polyacetal terpolymers were prepared by terpolymerizations of TOX, DOX, and 2‐ethylhexyl glycidyl ether (EHGE). Polyacetal polymers with three different structures such as polyacetal homopolymers, polyacetal copolymers, and polyacetal terpolymers were compared in the mechanical properties and the creep characteristics, and discussed from the view point of the polymer structure. The polyacetal copolymers and the polyacetal terpolymers were determined by 1H‐MNR measurement. About 80 mol % of DOX and EHGE amounts in feed were incorporated randomly into the each polymer. From the plots of the degree of crystallinity (Xc) versus the tensile strength, the tensile strength and crystallintiy of the polyacetal homopoymers are higher than those of the polyacetal copolymers and the polyacetal terpolymers. However, the tensile strength does not decrease linearly with a decrease in the crystallinity among the polyacetal polymers with three different structures, the polyacetal homopolymer, the polyacetal copolymers, and the polyacetal terpolymers. Creep rupture was characterized by the activation volume, υc, value in Zhurkov's equation, which can be estimated from the slope in the plots of load versus log (rupture time) at 80°C. The polyacetal polymers with higher molecular weight have larger values of the activation volume than those with lower molecular weight. When the activation volume values are compared among the polyacetal polymers with the same molecular weights, they increase in the following order: the polyacetal homopolymers < the polyacetal copolymers < polyacetal terpolymers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

12.
Amphiphilic copolymers with cationic hydrophilic moieties and different ratios of hydrophobic portion to hydrophilic portion were designed and synthesized via the combination of hydrosilylation reactions and quaternization reactions. The structures were characterized through Fourier transform infrared spectroscopy, 1H NMR , 13C NMR and gel permeation chromatography. The measurements of critical micelle concentrations, electrical conductivities and zeta potentials indicated that the copolymers could self‐assemble into nanoparticles with charges around the surface in aqueous solution. The sizes of the micelles were between 67 nm and 104 nm detected by dynamic light scattering. The self‐assembled micelles were used as drug carriers to encapsulate a model drug (tocopherol), and their drug‐loading content (DLC ) and efficiency (DLE ) were determined by UV ?visible spectra, resulting in considerable drug‐loading capacity to a tocopherol maximum up to 17.2% (DLC ) and 80.3% (DLE ) with a size of 90 nm. The blank micelles and drug‐loaded micelles displayed a spherical shape detected by transmission electron microscopy, which demonstrated not only the self‐assembly behaviors but also the drug‐loading performances of the cationic amphiphilic copolymers. All the results demonstrated that the cationic amphiphilic copolymers could be used as potential electric‐responsive drug carriers. © 2017 Society of Chemical Industry  相似文献   

13.
Low‐charge‐density amphoteric copolymers and terpolymers composed of AM, the cationic comonomer (3‐acrylamidopropyl)trimethyl ammonium chloride, and amino acid derived monomers (e.g., N‐acryloyl valine, N‐acryloyl alanine, and N‐acryloyl aspartate) have been prepared via free‐radical polymerization in aqueous media. These terpolymers with random charge distributions have been compared to terpolymers of like compositions containing the anionic comonomer sodium 3‐acrylamido‐3‐methylbutanoate. Terpolymer compositions determined by 13C‐ and 1H‐NMR spectroscopy, terpolymer molecular weights and polydispersity indices obtained via size exclusion chromatography/multi‐angle laser light scattering, and hydrodynamic dimensions determined via dynamic light scattering have allowed a direct comparison of the fundamental parameters affecting the behavioral characteristics. The solution properties of low‐charge‐density amphoteric copolymers and terpolymers have been studied as functions of the solution pH, ionic strength, and polymer concentration. The low‐charge‐density terpolymers display excellent solubility in deionized water with no phase separation. The charge‐balanced terpolymers exhibit antipolyelectrolyte behavior at pH values greater than or equal to 6.5 ± 0.2. As the solution pH decreases, these charge‐balanced terpolymers become increasingly cationic because of the protonation of the anionic repeat units. The aqueous solution behavior (i.e., globule‐ to‐coil transition at the isoelectric point in the presence of salt and globule elongation with increasing charge asymmetry) of the terpolymers in the dilute regime correlates well with that predicted by the polyampholyte solution theories. An examination of the comonomer charge density, hydrogen‐bonding ability, and spacer group (e.g., the moiety separating the ionic group from the polymer chain) indicates that conformational restrictions of the sodium 3‐acrylamido‐3‐methylbutanoate and N‐acryloyl valine segments result in increased chain stiffness and higher solution viscosities in deionized water and brine solutions. On the other hand, the terpolymers with N‐acryloyl alanine and N‐acryloyl aspartate segments are more responsive to changes in the salt concentration. An assessment of the effects of the terpolymer structure on the viscosity under specified conditions of the ionic strength and pH from these studies should allow for rational design of optimized systems for enhanced petroleum recovery. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007.  相似文献   

14.
Poly(ethylene glycol)‐block‐poly(N‐isopropylacrylamide) (PEG‐b‐PNIPAM) block copolymers were synthesized by atom transfer radical polymerization, and the α‐cyclodextrin (α‐CD) induced self‐assembly characteristics of the system were elucidated. Below the lower critical solution temperature (LCST) of PNIPAM, CD threaded onto the PEG segments and induced micellization to form rod‐shaped nanostructures comprising of a PEG/α‐CD condensed phase and a PNIPAM shell. Increasing the temperature of system above the LCST caused the PNIPAM segments to collapse, which resulted in the dethreading of the CD. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013  相似文献   

15.
《Polymer》2014,55(26):6664-6671
A series of imidazolium-based noncharged-charged diblock copolymers (1) was synthesized by the direct, sequential ATRP of styrene and styrenic imidazolium bis(trifluoromethyl)sulfonamide monomers with methyl, n-butyl, and n-decyl side-chains. Small-angle X-ray scattering studies on initial examples of 1 with a total of 50 repeat units and styrene:imidazolium-styrene repeat unit ratios of 25:25, 20:30, and 15:35 showed that their ability to form ordered nanostructures (i.e., sphere and cylinder phases) in their neat states depends on both the block ratio and the length of the alkyl side-chain on the imidazolium monomer. To our knowledge, the synthesis of imidazolium-based BCPs that form ordered, phase-separated nanostructures via direct ATRP of immiscible co-monomers is unprecedented.  相似文献   

16.
The modification of epoxy composites through the construction of nanostructures via the self‐organization of block copolymers in epoxy has become a hot topic. In this research, polystyrene‐b‐poly(?‐caprolactone)‐b‐polydimethylsiloxane‐b‐poly(?‐caprolactone)‐b‐polystyrene (PS‐PCL‐PDMS‐PCL‐PS) block copolymers with different lengths of PS subchains were synthesized and incorporated into epoxy thermoset. Due to the difference in the length of PS subchains, two different sizes of core‐shell nanostructures were obtained. When these two block copolymers were incorporated into epoxy, the tensile strength, elongation at break, damping temperature in range (tan δ > 0.2), and storage modulus of the epoxy thermoset below 105 °C were simultaneously improved. Meanwhile, the effects of the lengths of PS subchains on the size of nanostructures and the relationship between microstructure and macroscopic properties of epoxy composites were systematically investigated. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46362.  相似文献   

17.
The discovery of stereocomplexation, secondary interaction between enantiomeric poly(l ‐lactide) (PLLA) and poly(d ‐lactide) (PDLA) provides a method for the creation of novel biomaterials with distinctive chemical and physical stability. Stereocomplexation opens a new way for the preparation of diverse micro‐ and nanostructures such as uniform microspheres, hollow particles, micelles, nanocrystals, nanofibres, nanotubes and polymerosomes. Herein, we describe the design of stereocomplex assemblies for specific applications and methods for their preparation. This review focuses primarily on the use of stereocomplex assemblies in biomedical applications due to the improved stability and physicochemical properties in comparison to enantiomeric polylactides. To make the polylactide stereocomplexes soluble in water and, as a consequence, to improve compatibility with the human body, various amphiphilic copolymers with PLLA and PDLA enantiomeric segments can be prepared. Stereocomplexation can facilitate their self‐assembly into micro‐ and nanoparticles, stabilize the particle size and morphology and can also have an influence on the in vivo degradation rate and cytotoxicity of these materials. Stimuli‐responsiveness in stereocomplex assemblies can be achieved by copolymerization of lactide with, for example, thermoresponsive N‐isopropylacrylamide or amino acids with pH‐sensitive pendant groups. Stereocomplex micro‐ and nanoparticles are used for encapsulation of various bioactive compounds: anticancer drugs, antibiotics and proteins. Finally, examples of materials in which high thermal and mechanical stabilities delivered as a result of stereocomplexation play a crucial role, i.e. hydrogels, nanofibres, microcellular foams and artificial skin, are described. The preparation of biomaterials and biomedical systems based on polylactide stereocomplex assemblies opens new opportunities in this field. © 2015 Society of Chemical Industry  相似文献   

18.
We report on the synthesis and self‐assembly in water of well‐defined amphiphilic star‐block copolymers with a linear crystalline polyethylene (PE) segment and two or three poly(ethylene glycol) (PEG) segments as the building blocks. Initially, alkynyl‐terminated PE (PE‐?) is synthesized via esterification of pentynoic acid with hydroxyl‐terminated PE, which is prepared using chain shuttling ethylene polymerization with 2,6‐bis[1‐(2,6‐dimethylphenyl) imino ethyl] pyridine iron (II) dichloride/methylaluminoxane/diethyl zinc and subsequent in situ oxidation with oxygen. Then diazido‐ and triazido‐terminated PE (PE‐(N3)2 and PE‐(N3)3) are obtained by the click reactions between PE‐? and coupling agents containing triazido or tetraazido, respectively. Finally, the three‐arm and four‐arm star‐block copolymers, PE‐b‐(PEG)2 and PE‐b‐(PEG)3, are prepared by click reactions between PE‐(N3)2 or PE‐(N3)3 and alkynyl‐terminated PEG. The self‐assembly of the resultant amphiphilic star‐block copolymers in water was investigated by dynamic light scattering, transmission electron microscopy, and atomic force microscopy. It is found that, in water, a solvent selectively good for PEG blocks; these star‐block copolymer chains could self‐assemble to form platelet‐like micelles with insoluble PE blocks as crystalline core and soluble PEG blocks as shell. The confined crystallization of PE blocks in self‐assembled structure formed in aqueous solution is investigated by differential scanning calorimetry. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013  相似文献   

19.
BACKGROUND: Hollow microspheres, especially biodegradable polymeric microspheres, have attracted considerable attention due to their particular characteristics. Up to now, microspheres have been prepared via various strategies, for instance the template synthesis method and the self‐assembly process. However, economic, novel and simple methods to prepare hollow microspheres are still being sought. RESULTS: Phosphazene‐containing microspheres, which contain self‐assembled core‐shell structures, were prepared at high colloid contents using an ultrasonic bath via a self‐template approach. Along with the controlled self‐degradation of the internal core, the corresponding hybrid inorganic–organic hollow microspheres appeared. The mechanism was evidenced by means of transmission and scanning electron microscopy, cross‐polarization with magic angle spinning NMR, Fourier transform infrared spectroscopy, X‐ray diffraction and thermogravimetric analysis. CONCLUSION: It was clarified that the phosphazene‐containing microspheres could be formed and stably dispersed without aggregation even at high colloid contents using the ultrasonic bath method and the microspheres contain self‐assembled core–shell structures. Along with the controlled self‐degradation of the internal core, the corresponding hollow microspheres appeared. The mechanism of this preparation is of great significance because it is completely different from the conventional template synthesis method and the self‐assembly process. The absence of any stabilizing agent and special templates might inspire creative imagination in the design of new morphologies of micro‐ and nanostructures. Copyright © 2007 Society of Chemical Industry  相似文献   

20.
In molecular self‐assembly, molecules interact with each other by non‐covalent interactions to form larger structures. The process occurs in‐equilibrium, which means that molecules can leave the assembly and reassemble elsewhere, but that occurs on average with equal rates. For self‐assembly, peptides have proven to be a particularly useful building block, in part because of their versatility. Biology also uses self‐assembly to create functional materials. For example, components of the cytoskeleton, like actin filament and microtubules, are self‐assembled proteins. In other words, biology uses the same building blocks and design rules as supramolecular chemists to create functional structures. However, biological assemblies are vastly more complex than their synthetic counterparts. The discrepancy is in part because proteins are more complex than the peptides we use as building blocks. Another contributing factor to the difference in complexity is that most assemblies in living systems exist out of equilibrium. To use peptides for complex functions as biology does, we should understand and be able to create peptide assemblies out of equilibrium. In this work, we review recent advances towards the creation of peptide assemblies that exist out of equilibrium driven by an external energy source.  相似文献   

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