Introducing a second component is an effective way to manipulate polymerization behavior. However, this phenomenon has rarely been observed in colloidal systems, such as polymeric nanoparticles. Here, we report the supramolecular polymerization of polymeric nanorods mediated by block copolymers. Experimental observations and simulation results illustrate that block copolymers surround the polymeric nanorods and mainly concentrate around the two ends, leaving the hydrophobic side regions exposed. These polymeric nanorods connect in a side-by-side manner through hydrophobic interactions to form bundles. As polymerization progresses, the block copolymers gradually deposit onto the bundles and finally assemble into helical nanopatterns on the outermost surface, which terminates the polymerization. It is anticipated that this work could offer inspiration for a general strategy of controllable supramolecular polymerization. 相似文献
Controlled free-radical polymerization has been monitored with great interest in recent years since it offers an opportunity to combine the advantages of conventional free-radical polymerization with those of living ionic polymerization. We present the 1,1-diphenylethene (DPE) method which enables us to produce block copolymers on an industrial scale by a free-radical mechanism. This DPE process enables industrially relevant monomers, such as styrene, methacrylates, acrylates, methacrylic acid, acrylic acid and N-vinyl compounds, to be converted into block copolymers. The synthesis can be carried out in organic solvents, without solvents or in water. We have been able to demonstrate, that the addition of 1,1-diphenylethylene to a normal free-radical polymerization results in polymers whose molar mass, after a short uncontrolled phase, increases in a linear manner with conversion. The amount of 1,1-diphenylethylene added also determines the order of magnitude of the final molar mass. It was also possible to employ the polymers isolated during this polymerization as initiators for the polymerization of a further monomer, resulting in the formation of block copolymers. With possibly somewhat reduced claims on the perfection of the structures, a wide variety of possibilities arise with the known advantages of free-radical polymerization. The one-pot synthesis is carried out by simple successive addition of the desired monomers and has already been used successfully on an industrially relevant scale. 相似文献
Summary: This article deals with recent progress including the authors' work concerning the application of block copolymers as polymeric surfactants in heterophase polymerizations. The synthesis methods for preparing block copolymers by emulsion and dispersion techniques are outlined, with emphasis on recently developed controlled free radical polymerizations in aqueous media. Specific characteristics of amphiphilic block copolymers are described, for example, micellization and emulsifying effects. A general overview of emulsion and dispersion polymerization in an aqueous and organic medium with ionic and nonionic block copolymers is presented for the preparation of electrosteric and sterically stabilized latex particles. Typical examples of microemulsion, miniemulsion, oil‐in‐oil emulsion, and micellar polymerizations are provided. Current and potential developments of so‐called “hairy latexes”, inverse‐, multiple‐, and solid emulsions, as well as of nonaqueous polymeric dispersions are also discussed.
PS foam obtained by free radical polymerization of water‐in‐styrene, stabilized with a PS–PEO diblock copolymer. 相似文献
The contribution refers to the possibility of using emulsion polymerization of styrene, initiated by a heterogeneous initiator Chydroperoxide of isotactic powdered polypropylene) in the presence of a complex type activator, for the synthesis of block copolymers. Vinylmonomers with various water-solutibility, i.e. methyl methacrylate (MMA), acrylonitrile (AN) and maleic anhydride (MA), were utilized as comonomers of styrene. It was found that at the used conditions, the composition of block copolymers PS-b-P(S/AN) and PS-b-PCS/MA) can be varied by the time of polymerization of the first or second comonomer. The block copolymers were characterized by their molecular weight, and their thermal stability was also investigated. 相似文献
The field of cationic polymerization has moved center stage with the recent discovery of living polymerization that lead to the design of polymers with controlled molecular architecture. This report will provide a brief introduction of living cationic polymerization of isobutylene (IB) by tertiary ethers, and new cationic initiating systems based on peroxides and hydroperoxides. This paper will also briefly review some our recent work on the design of block copolymers via multi-mode polymerization (cationic–radical transformation) including the synthesis of star-blocks. The application of polyisobutylenes (PIBs) in the design of “beaded molecular strings,” a new class of molecular assembly will be discussed as well. 相似文献
Atom transfer radical polymerization of methyl methacrylate initiated by a poly(oxyethylene) macroinitiator by the esterification of PEG 1500 with 2-chloro propionyl chloride was synthesized. These polymerization proceeds both in bulk and solution with a quantitative initiation efficiency, leading to A-B-A triblock copolymers. The macroinitiators and their block copolymers were characterized by FT-IR, FT-NMR and GPC analyses. In bulk polymerization, the kinetic study showed that the relationship between ln[M]0/[M] vs time was linear showing that there is a constant concentration of active species throughout the polymerization and follow the first order kinetics with respect to monomer. Moreover, the experimental molecular weight of the block copolymers increased linearly with the monomer conversion and the polydispersity index remained between 1.3 and 1.5 throughout the polymerization. No formation of homo poly(methyl methacrylate) could also be detected, and all this confirms that the bulk polymerization proceeds in a controlled/“living” manner. 相似文献
Studies on interactions between amphiphilic block copolymers and lipid membranes have been focused traditionally on ABA triblock copolymers of poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide), widely due to their commercial availability. However, new architectures of amphiphilic block copolymer have been synthesized in recent years partially taking advantage of new polymerization techniques. This review focuses on amphiphilic block copolymers with potential biological activity and on model membrane systems used for studying interactions with such block copolymers. Experimental methods to study block copolymer–phospholipid interactions in Langmuir monolayers, liposomes, and planar bilayers are summarized. This work is intended to convey a better understanding of amphiphilic block copolymers used for in vitro and in vivo experiments in medicine and pharmacy. Recent developments and open questions are addressed. 相似文献
The formation of inorganic structures in nature is commonly controlled by biogenic macromolecules. The understanding of mineralization phenomena and the nucleation and growth mechanisms involved is still a challenge in science but also of great industrial interest. This article focuses on the formation and mineralization of two archetypical inorganic materials: zinc oxide and amorphous calcium carbonate (ACC). Zinc oxide is selected as a model compound to investigate the role that polymers play in mineralization. Most of the effort has been devoted to the investigation of the effects of double-hydrophilic block and graft copolymers. Recent work has demonstrated that latex particles synthesized by miniemulsion polymerization, properly functionalized by various chemical groups, have similar effects to conventional block copolymers and are excellently suited for morphology control of ZnO crystals. Latex particles might serve as analogues of natural proteins in biomineralization. The second example presented, ACC, addresses the issue of whether this amorphous phase is an intermediate in the biomineralization of calcite, vaterite, or aragonite. Conditions under which amorphous calcium carbonate can be obtained as nanometer-sized spheres as a consequence of a liquid-liquid phase segregation are presented. Addition of specific block copolymers allows control of the particle size from the micrometer to the submicrometer length scale. The physical properties of novel materials synthesized from concentrated solution and their potential applications as a filler of polymers are also discussed. 相似文献
This Article describes a simple two-step synthesis of comb block copolymers with molecular weights exceeding 1,000,000 g mol(-1) and their assembly into ordered morphologies in the solid state. This work is exciting because these polymers assembled into morphologies with domain sizes exceeding 100 nm and, in some examples, 200 nm without the use of additives. These materials reflected selected wavelengths of visible light, and these wavelengths could be affected by swelling with methylene chloride vapor. A comparison between the structures of comb block copolymers and linear block copolymers is presented with a discussion of important parameters affecting their assembly in the solid state. This Article will first describe the synthesis of comb block copolymers using ring opening metathesis polymerization and atom transfer radical polymerization and their subsequent characterization. The comb block copolymers, backbone polymers, and polystyrene arms were all characterized independent of each other and had low polydispersities. The comb block copolymers were assembled by dissolving in methylene chloride and allowing the solvent to evaporate. After thermal annealing, the polymers were characterized by scanning electron and optical microscopy. These polymers assembled into spherical, lamellar, and cylindrical arrays with domain sizes from 132 to 258 nm. This work extends the molecular architectures of polymers that can be assembled in the solid state, the molecular weights of block copolymers that were assembled, and the domain sizes that can be realized without the use of additives. 相似文献
Conjugated block copolymers have gained increasing interests in recent years. Development of a novel method for facile synthesis of conjugated block copolymers with desired structures and functions is greatly desired. In this mini review, we summarized the recent advances in one-pot synthesis of conjugated block copolymers containing π-conjugated polythiophene and helical polyisocyanide segments by using a nickel(Ⅱ) complex as single catalyst. The sequential living polymerization of the two monomers proceeded in a controlled manner, affording expected block copolymers in high yields with controlled molecular weights(Mns) and narrow molecular weight distributions(Mw/Mns). By using this method, a family of block copolymers with expected structure and tunable compositions can be facilely prepared. Introducing functional groups onto the pendant, these block copolymers can exhibit interesting self-assembly property, tunable light emission and multi-responsiveness. 相似文献
A new initiating/catalytic system for atom transfer radical polymerization (ATRP) is reported. This system starts with alkyl halides as initiators and transition metal complexes in their oxidatively stable state (e.g., Cu(II)Br2/ligand) as catalysts. The activators are generated by electron transfer (AGET) without involvement of initiating organic radicals. AGET ATRP has a significant advantage over simultaneous reverse and normal initiation (SR&NI) ATRP, because it provides a simple route for synthesizing pure polymers with complex architectures such as star copolymers, block copolymers, etc. Furthermore, AGET ATRP can be also successfully carried out in miniemulsion. Homopolymers and pure block copolymers were successfully synthesized via ATRP in miniemulsion using AGET ATRP. The final products were analyzed via two-dimensional chromatography, which combines high performance liquid chromatography (HPLC) and gel permeation chromatography (GPC). The resulting chromatograms showed that pure linear block copolymers and star block copolymers were prepared without the presence of any homopolymers. 相似文献