A variety of sub‐10 nm nanoparticles are successfully prepared by crosslinking of polystyrene‐b‐poly(1,3‐butadiene) (PS‐b‐PB) and polystyrene‐b‐poly(4‐vinyl pyridine) (PS‐b‐P4VP) block copolymer micelles and inverse micelles. Among them, the core‐crosslinked PS‐b‐PB micelles can self‐assemble into ultrathin (< 10 nm) macroporous (pore size <1 µm) membranes in a facile way, i.e., by simply drop‐coating the particle solution onto a mica surface. No continuous/porous membranes are produced from shell‐crosslinked PS‐b‐PB micelles and both forms of PS‐b‐P4VP micelles. This suggests that the unique structure of the block copolymer precursor, including the very flexible core‐forming block and the glassy corona‐forming block and the specific block length ratio, directly determines the formation of the macroporous membrane.
Hierarchical solution self‐assembly has become an important biomimetic method to prepare highly complex and multifunctional supramolecular structures. However, despite great progress, it is still highly challenging to prepare hierarchical self‐assemblies on a large scale because the self‐assembly processes are generally performed at high dilution. Now, an emulsion‐assisted polymerization‐induced self‐assembly (EAPISA) method with the advantages of in situ self‐assembly, scalable preparation, and facile functionalization was used to prepare hierarchical multiscale sea urchin‐like aggregates (SUAs). The obtained SUAs from amphiphilic alternating copolymers have a micrometer‐sized rattan ball‐like capsule (RBC) acting as the hollow core body and radiating nanotubes tens of micrometers in length as the hollow spines. They can capture model proteins effectively at an ultra‐low concentration (ca. 10 nm ) after functionalization with amino groups through click copolymerization. 相似文献
The hierarchical self‐assembly of an amphiphilic block copolymer, poly(N,N‐dimethylacrylamide)‐block‐polystyrene with a very short hydrophilic block (PDMA10‐b‐PS62), in large granular nanoparticles is reported. While these nanoparticles are stable in water, their disaggregation can be induced either mechanically (i.e., by applying a force via the tip of the cantilever of an atomic force microscope (AFM)) or by partial hydrolysis of the acrylamide groups. AFM force spectroscopy images show the rupture of the particle as a combination of collapse and flow, while scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of partly hydrolyzed nanoparticles provide a clear picture of the granular structure.
We employ dissipative particle dynamics (DPD) to examine the self‐assembly behavior of A2‐star‐(B‐alt‐C) molecules. We successfully observe various types of hierarchical structure‐within‐structures, such as A‐formed spheres in the matrix formed by B and C alternating layers, hexagonally packed A‐formed cylinders in the matrix with B and C segregated layers, B and C alternating layers‐within‐lamellae, coaxial B and C alternating domains within hexagonally packed BC‐formed cylinders in the A‐matrix, and co‐centric BC‐alternating domains within BC‐formed spheres in the A‐matrix, by increasing the A composition. Generally speaking, the small length‐scale B and C segregated domains are in parallel to the large length‐scale structures. This hierarchical periodicity along the same axis as well as the various characteristic structures, that the A2‐star‐(B‐alt‐C) copolymers display, are quite different from those in A‐block‐(B‐graft‐C) coil‐comb copolymers. Moreover, it is interesting to find that when the copolymer chain length increases, though the hierarchical structure type is maintained, the number of small length‐scale lamellae that can form within the large length‐scale structure increases. These hierarchical structures under various compositions are reported theoretically for the first time in the copolymer systems consisting of the alternating blocks, and are in good agreement with the most recent experimental work by Matsushita and co‐workers (Macromolecules 2007 , 40, 4023).相似文献
A coupling reaction is performed between polymeric nanoparticles and microparticles via the nucleophilic substitution of pendent β‐diketone groups with benzyl chloride. The coupling reaction results in the formation of hierarchical particles, through the nanoparticles being covalently linked onto the microparticles. The coupling reaction is tracked by TEM and SEM, and the formation of covalent C–C bonds through the coupling reaction between the polymeric nanoparticles and microparticles is confirmed by solid‐state 13C CP‐MAS NMR spectroscopy and XPS. The proposed coupling reaction between the nanoparticles and the microparticles is believed to be a promising strategy in particle‐surface modification. 相似文献
Multiresponsive amphiphilic poly(N,N‐dimethylaminoethyl methacrylate)‐b‐poly(N‐isopropylacrylamide) (PDMAEMA‐b‐PNIPAM) was successfully synthesized by reversible addition‐fragmentation chain transfer polymerization. Poly(N,N‐dimethylaminoethyl methacrylate)‐b‐poly(N‐isopropylacrylamide) has thermal and pH stimuli responsiveness. Their lower critical solution temperature and hydrodynamic radius can be adjusted by varying the copolymer composition, block length, solution pH, and temperature. In addition, a convenient method has been established to prepare cross‐linked silica‐coated nanoparticles with PDMAEMA‐b‐PNIPAM micelles as a template, resulting in good organic/inorganic hybrid nanoparticles defined as 175 to 220 nm. The structure and morphology were characterized by proton nuclear magnetic resonance (1HNMR), Fourier‐transform infrared spectroscopy (FT‐IR), transmission electron microscopy (TEM), and transmission electron microscopy‐energy dispersive X‐ray spectroscopy (TEM‐EDS). 相似文献
A novel method for the in situ synthesis of dual‐phase thermosensitive ultrasmall gold nanoparticles (USGNPs) with diameters in the range of 1–3 nm was developed by using poly(N‐isopropylacrylamide)‐block‐poly(N‐phenylethylenediamine methacrylamide) (PNIPAM‐b‐PNPEDMA) amphiphilic diblock copolymers as ligands. The PNPEDMA block promotes the in situ reduction of gold precursors to zero‐valent gold and subsequently binds to the surface of gold nanoparticles, while PNIPAM acts as a stabilizing and thermosensitive block. The as‐synthesized USGNPs stabilized by a thermosensitive PNIPAM layer exhibit a sharp, reversible, clear–opaque transition in aqueous solution between 30 and 38 °C. An unprecedented finding is that these USGNPs also show a reversible soluble–precipitate transition in nonpolar organic solvents such as chloroform at around 0 °C under acidic conditions. 相似文献
The interaction of PEGylated poly(amino acid)s with their biological targets depends on their chemical nature and spatial arrangement of their building blocks. The synthesis, self‐assembly, and DNA complexation of ABC terblock copolymers consisting of poly(ethylene glycol), (PEG), poly(l ‐lysine), and poly(l ‐leucine), are reported. Block copolymers are produced by a metal‐free, living ring‐opening polymerization of respective amino acid N‐carboxyanhydrides using amino‐terminated PEG as macroinitiator: (PEG‐b‐p(l ‐Lys)x‐b‐p(l ‐Leu)y, PEG‐b‐p(l ‐Leu)x‐b‐p(l ‐Lys)y, and PEG‐b‐p((l ‐Lys)x‐co‐p(l ‐Leu)y). Sizes of self‐assembled nanoparticles depend on the formation method. The nanoprecipitation method proves useful for copolymers with the poly(l ‐lysine) block protected as trifluoroacetate, effective diameters range between 92 and 132 nm, while direct dissolution in distilled water is suitable for the deprotected copolymers, yielding effective diameters between 52 and 173 nm. Critical micelle concentration (CMC) analyses corroborate particle size analyses and show a distinct impact of the molecular architecture; the lowest CMC (8 µg mL−1) is observed when the poly(l ‐leucine) segment forms the C‐block and the hydrophilic, disassembly driving poly(l ‐lysine) segment is short. DNA complexation, evaluated by gel motility and RiboGreen analyses, depends strongly on the molecular architecture. A more efficient DNA complexation is observed when poly(l ‐lysine) and poly(l ‐leucine) form individual blocks as opposed to them forming a copolymer. 相似文献
A novel biocompatible polymer was prepared by grafting the derivate of β ‐cyclodextrin (6‐SH ‐β ‐CD ) onto poly(3,4‐dihydroxycinnamic acid) (PDHCA ) via Michael addition. PDHCA ‐β ‐CD nanoparticles were prepared by the self‐assembly of amphiphilic PDHCA ‐β ‐CD polymer with N,N ‐dimethylformamide (DMF ) as good solvent and water as poor solvent. The PDHCA ‐β ‐CD nanoparticles were monodispersed with spherical morphology as shown in the scanning electron microscopic (SEM ) images in accord with the result of dynamic light scattering (DLS ) measurement. The size of the nanoparticles could be controlled from 60 to 180 nm by tuning the grafting degree (GD ) of PDHCA ‐β ‐CD polymer and also significantly influenced by the amount of water used during the process. These as‐prepared nanoparticles were stable without any significant change in the particle size after six‐months’ storage and even after being irradiated by UV at λ >280 nm for hours. The formation mechanism of PDHCA ‐β ‐CD nanoparticles was explored. The content of doxorubicin (DOX ) loaded onto the nanoparticles was up to 39% with relatively high loading efficiency (approximately 78.8% of initial DOX introduced was loaded). In vitro release studies suggested that DOX released slowly from PDHCA ‐β ‐CD nanoparticles. These features strongly support the potential of developing PDHCA ‐β ‐CD nanoparticles as carriers for the controlled delivery of drug. 相似文献