A novel route towards the synthesis of well‐defined linear–dendronized diblock copolymers is reported. Precursor alkyne containing diblock copolymers were modified in a highly efficient cycloaddition reaction with dendritic azides of different generation. The dendronization has been shown to be selective and could be driven to completion under ambient conditions. The phase separation of such dendronized diblock copolymers was investigated in dependence of the generation size being attached. Compared to a linear–linear diblock copolymer as starting material the dendronization yielded in a pronounced phase separation. The nanoscaled features observed in thin films strongly depended on the dendron size and a variety of morphologies could be identified. Hence, the unique combination of controlled radical polymerization and click chemistry allows for the triggering of structured surfaces in the nanometer‐regime.
Atom transfer radical polymerization (ATRP) and copper‐catalyzed azide–alkyne cycloaddition (CuAAC) reactions, both utilizing copper(I) (Cu(I)) complexes, make a tremendous progress in synthetic polymer chemistry. Independently or in combination with other polymerization processes, they give access to the synthesis of polymers with well‐defined structures, desired molecular architectures, and a wide variety of functionalities. Here, a novel in situ photoinduced formation of block copolymers is described by simultaneous ATRP and CuAAC processes. This approach relies on the direct reduction of initially charged copper(II) complexes to Cu(I) complexes to trigger both ATRP and CuAAC reactions coinciding under UV light at ambient temperature in one pot. Its synthetic utility is demonstrated on a model block copolymerization process by photoinduced ATRP of methyl methacrylate (MMA) using an initiator possessing acetylene functionality and concomitant click reaction between thus formed α‐acetylene‐poly(methyl methacrylate) (Ac‐PMMA) and independently prepared azide functional polystyrene (PS‐N3). Successful formation of PS‐b‐PMMA block copolymer is confirmed by FT‐IR and 1H NMR spectral analysis and gel permeation chromatography (GPC) measurements.
Polymers and copolymers with complex, yet well-defined architectures are drawing significant attentions in the search for materials with excellent properties. Of these macromolecular structures, dendritic-linear block copolymers consisting of covalently bound linear and dendritic segments have shown interesting solution, solid-state, and interfacial properties. As a novel polymerization approach, atom transfer radical polymerization (ATRP) has been attracting increasing interest recently, sin… 相似文献
Well‐defined figure‐of‐eight‐shaped (8‐shaped) polystyrene (PS) with controlled molecular weight and narrow polydispersities has been prepared by the combination of atom transfer radical polymerization (ATRP) and click chemistry. The synthesis involves two steps: 1) Preparation of a linear tetrafunctional PS with two azido groups, one at each end of the polymer chain, and two acetylene groups at the middle of the chain. 2) Intramolecular cyclization of the linear tetrafunctional PS at a very low concentration by a click reaction to produce the 8‐shaped polystyrenes. The resulting intermediates and the target polymers were characterized by 1H NMR and FT‐IR spectroscopy, and gel permeation chromatography. The glass transition temperatures (Tgs) were determined by differential scanning calorimetry and it was found that the decrease in chain mobility by cyclization resulted in higher Tgs for 8‐shaped polystyrenes as compared to their corresponding precursors.
A fascinating nanoobject, hydrophobic polymer brushes with a hard core of silica nanoparticles and a relatively soft shell of polystyrene-block-poly(? -caprolactone) (PS-b-PCL), was easily constructed by surface-initiated atom transfer radical polymerization (ATRP) of styrene, ring-opening polymerization (ROP) of ?-caprolactone and click reaction. The structure and morphology of the as-prepared hybrid nanomaterials were characterized and confirmed by FTIR, 1H-NMR, TGA and TEM. We believe that the breakthrough associated with formation of such a complex nanoobject would open a door for the fabrication of novel functional nanomaterials or nanodevices with designable structure and tailor-made properties. 相似文献
A functionalized compound, 4‐(2‐bromoisobutyryl)‐2,2,6,6‐tetra‐methylpiperidine‐1‐oxyl (Br‐TEMPO), was synthesized and used to synthesize block copolymers through tandem nitroxide‐mediated radical polymerization (NMRP) and atom transfer radical polymerization (ATRP). First, Br‐TEMPO was used to mediate the polymerization of styrene. The kinetics of polymerization proved a typical “living” nature of the reaction and the effectiveness in the mediation of polymerization of Br‐TEMPO. Then the PS‐Br macroinitiator was used to initiate atom transfer radical polymerization (ATRP). A series of acrylates were initiated by PS‐Br macroinitiators in typical ATRP processes at various conditions. The controlled polymerization of ATRP was also confirmed by molecular weight and kinetic analysis. Several cleavable block copolymers of PS‐b‐P(t‐BA), PS‐b‐P(n‐BA), and PS‐b‐PMA, with different molecular weights, were synthesized via this strategy. Relatively low polydispersities (<1.5) were observed and the molecular weights were in agreement with the theoretical ones. Hydrolysis of PS‐b‐P(t‐BA) was carried out, giving amphiphilic block copolymer PS‐b‐PAA without the cleavage of C‐ON bond or ester bond. All the block copolymers have two Tgs as demonstrated by DSC. A typical cleavable block copolymer of PS‐b‐PMA was cleaved by adding phenylhydrazine at 120°C to produce homopolymers in situ. 相似文献
Synthesis of hydroxy‐functionalized cyclic olefin copolymer (COC) is achieved with remarkably high activity (up to 5.96 × 107 g‐polymer mol‐Ti−1 h−1) and controlled hydroxy group in a wide range (≈17.1 mol%) by using ansa‐dimethylsilylene (fluorenyl)(amido)titanium complex. The catalyst also promotes living/controlled copolymerization to afford novel diblock copolymers consisting of hydroxy‐functionalized COC and semicrystalline polyolefin sequence such as polyethylene and syndiotactic polypropylene, where the glass transition temperature of the norbornene/10‐undecen‐1‐ol segment and each block length are controlled by comonomer composition and copolymerization time, respectively.
We report a new method for the synthesis of block copolymers with a pentasilane core by the polymerization of alkyl methacrylate monomers using the pentasilyl dianion as an initiator. The polymerization proceeded with living features and yielded the corresponding block copolymers with controlled molecular weights. The amphiphilic block copolymer was obtained by the polymer reaction, and it formed sphere‐like aggregates in MeOH/H2O solution.
Summary: The free‐radical addition of ω‐functional mercaptans to the vinyl double bonds of 1,2‐polybutadiene‐block‐poly(ethylene oxide) copolymers was used for modular synthesis of well‐defined functional block copolymers. The modification reaction proceeds smoothly and yields quantitatively functionalized block copolymers (1H NMR and FT‐IR spectroscopy) without disturbing the molecular‐weight distribution of the parent copolymer (PDI < 1.09, size exclusion chromatography).
The modular synthetic pathway towards the functional block copolymers reported here. 相似文献
Due to the topological effect, cyclic polymers demonstrate different and unique physical and biological properties in comparison with linear counterparts having the same molecular-weight range. With advanced synthetic and analytic technologies, cyclic polymers with different topologies, e.g. multicyclic polymers, have been reported and well characterized. For example, various cyclic DNA and related structures, such as cyclic duplexes, have been prepared conveniently by click chemistry. These types of DNA have increased resistance to enzymatic degradation and have high thermodynamic stability, and thus, have potential therapeutic applications. In addition, cyclic polymers have also been used to prepare organic–inorganic hybrids for applications in catalysis, e.g. catalyst supports. Due to developments in synthetic technology, highly pure cyclic polymers could now be produced in large scale. Therefore, we anticipate discovering more applications in the near future. Despite their promise, cyclic polymers are still less explored than linear polymers like polyolefins and polycarbonates, which are widely used in daily life. Some critical issues, including controlling the molecular weight and finding suitable applications, remain big challenges in the cyclic-polymer field. This review briefly summarizes the commonly used synthetic methodologies and focuses more on the attractive functional materials and their biological properties and potential applications. 相似文献
Covalently attaching lanthanide complexes to the polymer backbone can effectively reduce the clustering of lanthanides and thus become an important strategy to fully unleash their potential. In this Communication, a metal‐free click reaction is used for the first time to link a lanthanide complex to the polymer matrix. A diene‐bearing copolymer with anthracenylmethyl methacrylate as a monomer and a dienophile‐bearing lanthanide complex with 5‐maleimido‐1,10‐phenanthroline as the second ligand are synthesized and coupled together through a Diels–Alder cycloaddition (DA). A comparative investigation demonstrates that the composite material prepared by DA click reaction shows the highest quantum yields in the same lanthanide concentration as compared to materials prepared by widely used “directly doping” and “in situ coordinating lanthanide ions with macromolecular ligand” approaches. This work suggests that the “metal‐free” DA click reaction can be a promising tool in the synthesis of high efficient lanthanide functionalized polymeric materials.
