Single Electron Transfer-living Radical Polymerization Research Articles

Controlled Magnetite Grafted Poly(glycidyl methacrylates) for Heavy Metal Absorption and Recovery via SET-LRP

A versatile magnetite based stringent polymer for effective metal capture was prepared by reacting iron oxide based initiator with glycidyl methacrylate monomer via single-electron transfer living radical polymerization (SET-LRP) technique. The versatile grafted polymer was successfully synthesized by metal catalyzed living radical polymerization using the catalyst system Cu/N,N,N',N'',N'''-pentamethyldiethylenetriamine as the ligand. The structural confirmation of the initiator and the grafted polymer was analyzed by using instrumentation methods such as proton nuclear magnetic resonance spectroscopy, UV-visible, TGA, SEM and gel permeation chromatography for molecular weight measurements. As the polymerization time increased, both the conversion and the molecular weight were observed to increase linearly with time. Narrow dispersed lower polydispersity index (PDI) and dispensable magnetite-g-PGMA was utilized for the extract of toxic lead from the wastewater. Sustained binding was observed due to the presence of epoxide ring in the repeating units of the polymer and recovered by magnetic effect. The material shows good stability as evident by TGA curves and better affinity to toxic lead as observed by UV-visible and SEM techniques.

SET-LRP - A Convenient Polymerization Method to Produce Rapid and Controlled Polymers

In this review study, the principles and evolution of Single Electron Transfer - Living Radical Polymerization (SET-LRP) together with the methodologies currently applied by researchers are discussed. It is considered that the techniques developed by Percec et al will be able to help the researchers and other industrial experts to practice, develop and invent new concepts and methodologies for SET-LRP. This renew deals with general mechanistic feature explained by Percec that undergoes a metal catalysed living radical polymerization by rapid activation and deactivation steps. In addition, the advantage of metal catalysed LRP, in mediating rapid polymerization and retain chain-end functionality necessary for reinitiating in block copolymerization can also be well explained.

Adsorption mechanism and interactions of coal particles modified with a novel hyperbranched dispersant

This account, a hyperbranched dispersant (Es-SAF-DBM-PSS) was assembled with the skeleton of Es-SAF-DBM (the functional modification of hydroquinone-based sulfonated acetone formaldehyde (SAF)) and numbers of linear polystyrene sodium sulfonate (PSS) chains by single electron transfer living radical polymerization (SET-LRP) in the system of PhBr2m4/Cu wire/PMDETA. The structure of the synthesized Es-SAF-DBM-PSS was detected by FTIR, 1H NMR, XPS, UV and GPC. Series of tests about the polymerization kinetics of Es-SAF-DBM-PSS were executed. Effects of temperatures and initiator concentration on the apparent polymerization rate were investigated, the results showed the low activation energy and higher initiation rate fitted the characteristic of SET-LRP. The rheological behaviors of Es-SAF-DBM-PSS as dispersant applied to coal water slurry (CWS) were tested. The following results were found as expected: the best usage of Es-SAF-DBM-PSS was only 0.3%, maximum coal content reached 63.7%, the viscosity dropped as low as 1000mPa·s. And the penetration ratio of slurry mixed with Es-SAF-DBM-PSS was still 100% even after 35days. Adsorption mechanism and interparticle interactions of coal particles modified with Es-SAF-DBM-PSS were investigated by Langmuir equation, dynamic equations and extended Derjaguin-Landau-Verwey-Overbeek (eDLVO) theory, the results showed the excellent dispersion and stability performance of Es-SAF-DBM-PSS were mainly related to the specific hyperbranched structure.

The Effect of Mixed Ligands on the Polymerization Rate of SET-LRP in Aqueous Solution

Abstract The mixed-ligand effect is investigated in single electron transfer-living radical polymerization (SET-LRP) of OEOMA in aqueous solution for the first time. Mediated by equimolar tris(2-aminoethyl)amine (TREN) and tris(dimethylaminoethyl)amine (Me6-TREN), SET-LRP exhibits the highest polymerization rate while maintaining living characteristics. The higher concentration of self-assembled micellar particles formed by amphiphilic initiator and monomer in aqueous solution under the influence of mixed ligands may be considered as one of factors for the mixed-ligand effect.

The Effect of mPEGA/EHA Ratio and Copolymer Composition on the Solution Behavior of Amphiphilic, Comb‐Shape Copolymers Synthesized via Cu(0)‐Mediated SET‐LRP for Potential Drug Delivery Applications

AbstractComb‐shape, block copolymers from hydrophilic poly(ethylenglycol) monomethyl ether acrylate (mPEGA, A) and hydrophobic 2‐ethylhexyl acrylate (EHA, B) are synthesized by copper(0)‐mediated single‐electron transfer living radical polymerization (SET‐LRP) via sequential addition of the two monomers, resulting in different compositions (AB, ABA, BAB, BA), molar masses, and mPEGA/EHA ratios. All polymers show narrow molar mass distributions and molecular weights of 7.7–25.50 kg mol−1, demonstrating precise control over the polymerization and molecular weights through the utilization of SET‐LRP. Kinetic experiments are conducted to investigate the polymerization behavior of mPEGA and EHA in N,N‐dimethylformamide as a rather uncommon solvent for SET‐LRP further underlining a living‐type polymerization. Amphiphilic properties are investigated by critical micelle concentration (CMC) measurements and formation of micelles in water. A reverse relation between mPEGA/EHA ratio and CMC values reveals that an increased hydrophobicity leads to decreased CMC values. The self‐assembly behavior of polymers in water confirms the formation of uniform and stable micelles in water with a size between 12 and 184 nm depending on the composition of the polymers. With increased hydrophilicity, micelle sizes increase as well. In vitro tests of the obtained polymers show excellent biocompatibility even at high concentrations further affirming their suitability for drug delivery applications.

The synthesis of optically active poly(phenylethyl acrylate) via SET‐LRP

AbstractWe present the synthesis of optically active polymers derived from S‐phenylethyl acrylate and R‐phenylethyl acrylate for the first time. Cu(0) wire‐catalyzed single electron transfer‐living radical polymerization (SET‐LRP) methodology which provides a feasible platform makes its new application in designing and developing these two polymers. At various degrees of polymerizations (DPs) ranging from 100 to 400, first‐order kinetics is observed. In all cases, SET‐LRP demonstrates a rapid polymerization rate while maintaining excellent control over polymer's molecular weight, polydispersity and chain‐end functionality. These advantages facilitate the development of both homopolymers and block copolymers through in situ chain extensions. The circular dichroism measurement confirms that the SET‐LRP method yields optically active polymers derived from two enantiomeric monomers, which exhibit mirrored spectra.

Resolving the incompatibility between SET-LRP and non-disproportionating solvents

Cu(0)-catalyzed single-electron transfer-living radical polymerization (SET-LRP) has shown great potential for applications in which well-defined chain end-functionalized polymers are demanded as final products or as intermediates. However, the use of polar reaction media favoring the disproportionation of Cu(I)X species into Cu(0) and Cu(II)X2 was considered a limiting factor specially in the synthesis of complex hydrophobic polymers with functional chain ends. “Self-generated” biphasic systems, in which the polymer phase-separates from the homogeneous reaction mixture above a certain molecular weight, together with fundamental studies on the role of solvent, including catalytic solvent effect, and methodological developments such us the “mixed-ligand” concept served as inspiration, although sometimes in an unknown way, to solve this problem. Today, SET-LRP of both acrylic and methacrylic vinyl monomers is already feasible in both polar and non-polar non-disproportionating solvents using their corresponding bi(multi)phasic “programmed” mixtures with water. Under these conditions, SET-LRP is an interfacial process in which disproportionation and activation events occur independently in the aqueous and organic compartments, and the “self-controlled” reversible deactivation takes place at the interface. Consequently, this design entirely defeats the limiting requirement to exclusively use disproportionating solvents. After a brief discussion of the historical evolution of the field of LRP, starting with the landmark work of Otsu from 1950th, this feature article will describe the elaboration of “programmed” bi(multi)phasic SET-LRP systems starting from initial inspiration to development in laboratory large-scale experiments.

Stiffening Polymer Brush Membranes for Enhanced Organic Solvent Nanofiltration Selectivity.

Membrane-based separations allow energy-efficient purification of organic solvents which are typically carried out by energy-intensive distillation. Polymer membranes are inexpensive and have obtained widespread industrial acceptance for water and biotech applications but not organic solvent nanofiltration due to relatively low selectivities. In this work, a new class of polymer brush membranes was prepared with high selectivities for methanol-toluene separation. Stiffening the brush structure by cross-linking with aromatic trimesic acid and aliphatic itaconic acid resulted in an increase in selectivity from 1.4 to 6.5-11.5. This was achieved by graft polymerization of a primary amine monomer (aminoethyl methacrylate) using single electron transfer-living radical polymerization (SET-LRP) followed by cross-linking. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and captive bubble contact angle measurements were used to characterize these membranes. The stiffness of the brush membranes was measured using a quartz crystal microbalance-dissipation (QCM-D) and correlated positively with selectivity for separating organic feed mixtures. This new class of membranes offers a tunable and scalable method for purification of organics.

Where is the induction from? Effect of disproportionation and comproportionation in Cu(0)-mediated reversible deactivation radical polymerization

There is a controversial debate about the mechanism of reversible deactivation radical polymerization (RDRP) in the presence of Cu(0). Two mechanism models have been proposed - supplemental activator and reducing agent atom transfer radical polymerization (SARA ATRP) and single-electron transfer living radical polymerization (SET-LRP), however, they are contradictory to each other, and neither of them are able to fully explain experimental phenomenon in the Cu(0)-mediated RDRP process, especially a period of slow addition i.e., induction period occurs under certain reaction conditions. In this work, the induction phenomenon and its underlying mechanism was explored and clarified by using different catalyst systems (CuI, Cu(0), Cu(0)&CuII) and different initiator systems i.e., EBriB (ethyl α-bromoisobutyrate), EBrP (ethyl 2-bromopropionate), MBrP (methyl 2-bromopropionate) and MClP (methyl 2-chloropropionate). New insights on the roles of different copper species and their mutual conversion kinetics were provided. It is proved that the appearance/absence of the induction period is due to the difference in the relative concentrations of CuI and CuII accumulated at the early stage of the reaction. Moreover, the disproportionation and comproportionation co-exist in the Cu(0)-mediated RDRP system and play an essential role in establishing the equilibrium among different copper species (Cu0, CuI and CuII) at the early reaction stage.

Highly tunable structure-by-design polymer brush membranes for organic solvent nanofiltration

Synthetic polymeric nanofiltration membrane processes offer an alternate low-energy option to energy-intensive distillation to fractionate similar size organic solvents for chemical, petroleum, food and biotechnology industries. Here, we synthesize and test a new class of structure-by-design hydrophilic polymeric brush membranes, that address the limitations of commercial polymer membranes, are tunable and exhibit commercially relevant filtration performance. Because these brush membranes are grafted by Single Electron Transfer-Living Radical Polymerization (SET-LRP) and replace statistically random phase inversion or interfacial polymerization used for synthesizing commercial polymer membranes, their porous structure can be remodeled by varying their morphology and chemistry. We graft hydroxyethyl methacrylate (HEMA) brush structures with short and long crosslinkers, demonstrate two competing phenomena - pore stiffening and opening - and obtain high selectivity at reasonable permeability for commercially relevant methanol/toluene separation. This new class of stable, tunable, and scalable membranes offers exciting opportunities to reduce energy for separation of organic solvents.

Redox-Responsive Comparison of Diselenide and Disulfide Core-Cross-Linked Micelles for Drug Delivery Application.

In this study, diselenide (Se-Se) and disulfide (S-S) redox-responsive core-cross-linked (CCL) micelles were synthesized using poly(ethylene oxide)2k-b-poly(furfuryl methacrylate)1.5k (PEO2k-b-PFMA1.5k), and their redox sensitivity was compared. A single electron transfer-living radical polymerization technique was used to prepare PEO2k-b-PFMA1.5k from FMA monomers and PEO2k-Br initiators. An anti-cancer drug, doxorubicin (DOX), was incorporated into PFMA hydrophobic parts of the polymeric micelles, which were then cross-linked with maleimide cross-linkers, 1,6-bis(maleimide) hexane, dithiobis(maleimido) ethane and diselenobis(maleimido) ethane via Diels-Alder reaction. Under physiological conditions, the structural stability of both S-S and Se-Se CCL micelles was maintained; however, treatments with 10 mM GSH induced redox-responsive de-cross-linking of S-S and Se-Se bonds. In contrast, the S-S bond was intact in the presence of 100 mM H2O2, while the Se-Se bond underwent de-crosslinking upon the treatment. DLS studies revealed that the size and PDI of (PEO2k-b-PFMA1.5k-Se)2 micelles varied more significantly in response to changes in the redox environment than (PEO2k-b-PFMA1.5k-S)2 micelles. In vitro release studies showed that the developed micelles had a lower drug release rate at pH 7.4, whereas a higher release was observed at pH 5.0 (tumor environment). The micelles were non-toxic against HEK-293 normal cells, which revealed that they could be safe for use. Nevertheless, DOX-loaded S-S/Se-Se CCL micelles exhibited potent cytotoxicity against BT-20 cancer cells. Based on these results, the (PEO2k-b-PFMA1.5k-Se)2 micelles can be more sensitive drug carriers than (PEO2k-b-PFMA1.5k-S)2 micelles.

Grafting of poly(stearyl acrylate) on cellulose fibers as 3D-printable HDPE composites

This paper aimed to produce a bio-based filament, suitable for 3D printing (fused deposition modeling), made of surface modified cellulose fiber and high density polyethylene. The cellulose fibers (CF) were first surface modified and transformed into a CF-based macroinitiator through an esterification reaction with the 2-bromoisobutyric acid. We finally studied the ability of this CF-based macroinitiator to initiate a single electron transfer-living radical polymerization (SET-LRP) with an hydrophobic monomer: the stearyl acrylate. The grafting of poly(stearly acrylate) onto the cellulose fibers did strongly increased the adhesion, compatibility of the modified fibers with the hydrophobic host matrix (HDPE). Finally, the resulting hydrophobic fibers were extruded with the high density polyethylene (HDPE) through a counter-rotating twin-screw extruder, yielding a bio-based filament suitable for FDM 3d printing. The successful surface modification, such as the correct incorporation of the modified fibers into the thermoplastic matrix, were characterized through ATR-FTIR, 13C CP-MAS NMR, FE-SEM, and mechanical testing. Throughout those characterization techniques, it was concluded that the fiber surface modification significantly improved the compatibility of the fibers with HDPE. Finally, the 3D printing properties of the composite were tested and compared to those of pure HDPE through the 3d printing of simple objects. It was concluded that the printability of the composite made with poly(stearyl acrylate)-grafted cellulose overcomes the problem (shrinkage, warpage, print fidelity) encountered with the printing of pure HDPE.Graphical abstract

In vitro anti-prostate adenocarcinoma and lung cancer studies of phenoxyaniline-block-poly(methyl methacrylate) based nanocomposites via controlled radical polymerization.

A phenoxyaniline-based macroinitiator is utilized for the first time in order to produce phenoxyaniline-block-poly(methyl methacrylate) composites through single electron transfer-living radical polymerization (SET-LRP) under mild conditions. A different weight percentage of Cloisite 93A is added into the polymer mixtures in order to increase their biochemical properties. The prepared block copolymer nanocomposites are characterized using ATR-IR, UV-vis-spectroscopy, XRD, Raman, TGA, DSC, a particle size analyzer, contact angle measurements and SEM in order to characterize their structural, thermal, surface and morphological properties. Further, the developed polymeric nanocomposites are successfully applied in two different cancer cell lines (prostate adenocarcinoma and lung cancer), which show excellent anticancer properties. Also, acridine orange/ethidium bromide (AO/EtBr) dual staining is performed, which causes drastic cell death by apoptosis in both A549 and PC-3 cell lines, which indicated that the prepared polymeric nanocomposites effectively inhibit the cell proliferation and induce the apoptosis in both the cancer cells. Here nanoclay is used for cancer treatment because of its complete water solubility, which essentially causes the formation of a cationic complex between the clay and drug through electrostatic interactions. Hence, the exchange of ions between the clay and other ions in the biological environment leads to inhibition of the proliferation of prostate adenocarcinoma and lung cancer cells in the system.

Polymer-Modified Cellulose Nanofibrils Cross-Linked with Cobalt Iron Oxide Nanoparticles as a Gel Ink for 3D Printing Objects with Magnetic and Electrochemical Properties

This paper presents a strategy to convert hydrophilic cellulose nanofibrils (CNF) into a highly cross-linked hydrophobic network with inorganic nanoparticles to develop a gel ink suitable for gel 3D printing. The CNF were chemically modified initially through a single-electron transfer-living radical polymerization (SET-LRP) of stearyl acrylate (SA) in the presence of the surface-modified cobalt iron oxide (CoFe2O4, CFO) nanoparticles. The modified CFO nanoparticles provide their multifunctional properties, such as magnetic and electrochemical, to the CNF hybrid network and, at the same time, act as cross-linking agents between the nanocellulose fibrils, while the grafted poly-stearyl acrylate (PSA) introduces a strong hydrophobicity in the network. A suitable gel ink form of this CNF–PSA–CFO material for gel 3D printing was achieved together with a certain solvent. Some test structure prints were directly obtained with the CNF–PSA–CFO gel and were used to evaluate the consolidation of such 3D objects through solvent exchange and freeze-drying while also keeping the magnetic and electrochemical properties of CFO in the CNF-based composite intact. The pristine CNF and CFO particles and the CNF–PSA–CFO were characterized by FTIR, SEM, XPS, TGA, VSM, and CV measurements.

Preparation of a magnetocaloric dual-response SiO2-based green nano-emulsifier by an SET-LRP method and evaluation of its properties

In recent years, intelligent nano-emulsifiers have received extensive attention in various fields. In this study, core–shell–shell nanoparticles (Fe3O4@SiO2@PNIPAM) showing magnetic and thermal responsiveness have been successfully prepared as a green nano-emulsifier by single-electron-transfer living radical polymerization (SET-LRP). The emulsifying properties of Fe3O4@SiO2@PNIPAM with different PNIPAM contents in toluene/water systems and the magnetic and thermal responsiveness of Pickering emulsions have been mainly investigated. The research shows that when the content of PNIPAM is higher, Fe3O4@SiO2@PNIPAM has the strongest emulsifying power and the Pickering emulsion is the most stable. After applying a magnet field outside the emulsion, Fe3O4@SiO2@PNIPAM nanoparticles can be separated rapidly, which leads to emulsion demulsification. When the temperature is above the low critical solution temperature (LCST), the PNIPAM chain shrinks and the Pickering emulsion is demulsified. When the temperature returns below the LCST, the emulsion is emulsified again, and a stable emulsion can still be formed. Therefore, the Pickering emulsion made by Fe3O4@SiO2@PNIPAM as an intelligent and efficient green nano-emulsifier can be converted between emulsified state and demulsified state by the control of magnetic field and temperature. These provide a wide range of ideas for Pickering emulsion recycling, industrial oil-containing wastewater separation and enhanced oil recovery.

Production and 3D Printing of a Nanocellulose-Based Composite Filament Composed of Polymer-Modified Cellulose Nanofibrils and High-Density Polyethylene (HDPE) for the Fabrication of 3D Complex Shapes

This work aims to produce a 3D-printable bio-based filament composed of high-density polyethylene (HDPE) and chemically modified cellulose nanofibrils. Printing using HDPE as a raw material is challenging due to its massive shrinkage and warping problems. This paper presents a new method to overcome those difficulties by enhancing the mechanical properties and achieving better print quality. This was achieved using modified cellulose nanofibrils (CNFs) as fillers. Firstly, CNF was converted to a CNF-based macroinitiator through an esterification reaction, followed by a surface-initiated single-electron transfer living radical polymerization (SI-SET-LRP) of the hydrophobic monomer stearyl acrylate. Poly stearyl acrylate-grafted cellulose nanofibrils, CNF-PSAs, were synthesized, purified and characterized with ATR-FTIR, 13C CP-MAS NMR, FE-SEM and water contact angle measurements. A composite was successfully produced using a twin-screw extruder with a CNF-PSA content of 10 wt.%. Mechanical tests were carried out with tensile testing. An increase in the mechanical properties, up to 23% for the Young’s modulus, was observed. A morphologic analysis also revealed the good matrix/CNF compatibility, as no CNF aggregates could be observed. A reduction in the warping behavior for the composite filament compared to HDPE was assessed using a circular arc method. The 3D printing of complex objects using the CNF-PSA/HDPE filament resulted in better print quality when compared to the object printed with neat HDPE. Therefore, it could be concluded that CNF-PSA was a suitable filler for the reinforcement of HDPE, thus, rendering it suitable for 3D printing.

Construction of pH-responsive nanoplatform from stable magnetic nanoparticles for targeted drug delivery and intracellular imaging

Currently, developing responsive hydrophobic drug delivery systems centered on magnetic nanoparticles is a promising approach for the efficient delivery of hydrophobic drugs to living cells. Here, an efficacious designed strategy was proposed to construct pH-responsive nanoplatform for targeted hydrophobic drug delivery based on the formation of surface-anchored targeting molecules on the surface of Fe3O4 @C via single electron transfer living radical polymerization (SET-LRP) method. First, we prepared polymer-modified Fe3O4 @C using 4-vinylphenylboronic acid (VB) and polyethylene glycol methyl ether methacrylate (PEGMA) as polymerized monomers and confirmed that Fe3O4 @C-VB-PEGMA had high biocompatibility and low cytotoxicity. Next, we prepared curcumin-containing Fe3O4 @C-VB-PEGMA-Cur nanoplatform with an encapsulation efficiency for Cur as high as 67.7%. Furthermore, the nanoplatform not only displayed pH-responsive release behaviors of Cur under different pH values (pH=7.2, 6.5, 5.4), but also can be effectively targeted into HepG2 cells. More importantly, the nanoplatform also exhibited effectively inhibiting the growth of HepG2 cells and continuously intracellular imaging by the targeted releasing of loaded Cur. It is envisaged that these findings are a step forward in the construction of pH-responsive platform as a tool for clinical hydrophobic drug delivery.

Association Behavior of Amphiphilic ABA Triblock Copolymer Composed of Poly(2-methoxyethyl acrylate) (A) and Poly(ethylene oxide) (B) in Aqueous Solution.

Poly(2-methoxyethyl acrylate) (PMEA) and poly(ethylene oxide) (PEO) have protein-antifouling properties and blood compatibility. ABA triblock copolymers (PMEAl-PEO11340-PMEAm (MEOMn; n is average value of l and m)) were prepared using single-electron transfer-living radical polymerization (SET-LRP) using a bifunctional PEO macroinitiator. Two types of MEOMn composed of PMEA blocks with degrees of polymerization (DP = n) of 85 and 777 were prepared using the same PEO macroinitiator. MEOMn formed flower micelles with a hydrophobic PMEA (A) core and hydrophilic PEO (B) loop shells in diluted water with a similar appearance to petals. The hydrodynamic radii of MEOM85 and MEOM777 were 151 and 108 nm, respectively. The PMEA block with a large DP formed a tightly packed core. The aggregation number (Nagg) of the PMEA block in a single flower micelle for MEOM85 and MEOM777 was 156 and 164, respectively, which were estimated using a light scattering technique. The critical micelle concentrations (CMCs) for MEOM85 and MEOM777 were 0.01 and 0.002 g/L, respectively, as determined by the light scattering intensity and fluorescence probe techniques. The size, Nagg, and CMC for MEOM85 and MEOM777 were almost the same independent of hydrophobic DP of the PMEA block.

Redox-responsive properties of core-cross-linked micelles of poly(ethylene oxide)-b-poly(furfuryl methacrylate) for anticancer drug delivery application

The design and fabrication of smart delivery systems that can efficiently deliver a payload to a targeted site in a controlled manner are immensely desirable in chemotherapy. We report the redox-responsive drug delivery property of core-cross-linked (CCL) micelles of poly(ethylene oxide)5k-b-poly(furfuryl methacrylate)2k (PEO5k-b-PFMA2k). The PEO5k-b-PFMA2k was prepared by using single electron transfer-living radical polymerization of furfuryl methacrylate (FMA) with a PEO-Br macro-initiator. Doxorubicin (DOX) was loaded into hydrophobic PFMA cores of the polymeric micelles, which were subsequently cross-linked with a diselenide-containing cross-linker, bis(maleimidoethyl) 3,3′-diselanediyldipropionoate via Diels-Alder reaction. Under physiological conditions, CCL micelles displayed increased structural stability, whereas the micelles showed a redox-responsive behavior when treated with 100 mM hydrogen peroxide (H2O2) and 10 mM glutathione (GSH). The CCL micelles were de-cross-linked due to the breaking of diselenide bonds present in the core-cross-linkages. DOX-loaded CCL micelles were stable at pH 7.4, while a higher DOX release was achieved at acidic pH 5.0 owing to the protonation of DOX. The DOX release was significantly enhanced in presence of 10 mM GSH or 100 mM H2O2 at pH 5.0 (which is a similar environment in tumor cells). The non-CCL and CCL micelles were found non-toxic to HFF-1 normal cells. However, DOX encapsulated CCL micelles showed remarkable cytotoxicity in HeLa cells. The confocal images showed that the DOX-loaded CCL micelles can quickly be internalized and efficiently deliver DOX into the HeLa cells.

Withdrawal: Quantitative Synthesis of Temperature-responsive Polymersomes by Multiblock Polymerization.

The current challenge for polymersomes is to prepare amphiphilic block polymers with not only well-defined molecular weight, but also precisely high-order multiblock structure in terms of the distribution of monomeric units along the chain. Here, we describe a synthesis of temperature-responsive polymersomes with precisely defined membrane structures using high-precision amphiphilic multiblock polymer via aqueous single electron transfer living radical polymerization (SET-LRP) in which poly(ethylene glycol) (PEG) macromolecules are used as initiators. We develop a one-pot, rapid and multistep sequential polymerization process with yields >99% within 30 min for each block, giving access to a wide range of high-precision multiblock polymers with very narrow molecular weight distributions (Ð ≤ 1.14). Synthesized multiblock polymers are used to form nano-sized polymersomes which are highly promising as smart carriers for high loading and triggered release of biopharmaceutics such as pharmaceutical proteins and peptides. This synthesis approach is environmentally friendly, fully translation and thus represents a significant advance in the design and synthesis of a new generation of polymer nanomaterials with precisely defined structures, which is highly attractive for applications in nanotechnology.