Preparation Of Block Copolymers Research Articles

One‐pot synthesis of block copolymers by ring‐opening polymerization and ultraviolet light‐induced ATRP at ambient temperature

ABSTRACTWe successfully synthesized poly(l‐lactide)‐b‐poly (methyl methacrylate) diblock copolymers at ambient temperature by combining ultraviolet light‐induced copper‐catalyzed ATRP and organo‐catalyzed ring‐opening polymerization (ROP) in one‐pot. The polymerization processes were carried out by three routes: one‐pot simultaneous ATRP and ROP, one‐pot sequential ATRP followed by ROP, and one‐pot sequential ROP followed by ATRP. The structure of the block copolymers is confirmed by nuclear magnetic resonance and gel permeation chromatography, which suggests that the polymerization method is facile and attractive for preparing block copolymers. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 699–704

Main-chain benzoxazine precursor block copolymers

A novel strategy for one-pot preparation of block copolymers of benzoxazine precursors with polyetheramines is described.

Living Anionic Polymerization – Part II: Further Expanding the Synthetic Versatility for Novel Polymer Architectures

Living Anionic Polymerization – Part II: Further Expanding the Synthetic Versatility for Novel Polymer Architectures

Effective macrophage delivery using RAFT copolymer derived nanoparticles

We use reversible addition fragmentation chain transfer (RAFT) polymerisation to prepare block copolymers that are subsequently assembled into nanoparticles. The prepared nanoparticles were extensively taken up by primary murine macrophages and are effective in the delivery of a cell impenetrable cargo.

Tadpole-shaped magnetic block copolymer: Self-assembly induced increase of magnetic susceptibility

Self-assembly induced increase of magnetic susceptibility for the tadpole-shaped block copolymer based on paramagnetic FeCl4 pyridinium was reported in this work. The tadpole-shaped block copolymer was prepared by sequential reversible addition-fragmentation chain transfer polymerization of styrene (St) and 4-vinylpyridine (4VP) at the presence of chain transfer agent-modified polyhedral oligomeric silsesquioxanes (POSS). The corresponding magnetic block copolymer (POSS-PSt-b-QP4VP(FeCl4)) was obtained by quternization of 4VP and complexation with FeCl3. The prepared block copolymer was paramagnetic with magnetic susceptibility of 15.4 × 10−6 emu g−1, as investigated by superconducting quantum interference device. Surprisingly, the magnetic susceptibility of the block copolymer was almost doubled (27.5 × 10−6 emu g−1) after self-assembly in thin film. Since the composition of the block copolymer is unchanged, the increase of the susceptibility should be generated by the self-assembly, which makes the magnetic FeCl4− more ordered. And, self-assembly will be an efficient and convenient method in improving magnetic properties of such polymers.

Polymersomes with high loading capacity prepared by direct self-assembly of block copolymers in drugs

We develop a new method to prepare block copolymer vesicles with high loading capacity of drugs which can then be released in a controlled manner. The block copolymers, including PS-b-PAA, PS-b-PEO, and biocompatible PCL-b-PEO, can directly self-assemble into vesicles in aspirin and encapsulate aspirin by solvent annealing with ethanol which imparts mobility to the originally solid block copolymers and aspirin molecules. Aspirin associates with the hydrophilic blocks after premixing, firstly leading to the formation of bilayer structures. During solvent annealing, the bilayers are wrapped into vesicles to enclose aspirin that fills the cores of the vesicles. The interactions between block copolymers and aspirin were probed by FT-IR, and the formation of aspirin-loaded vesicles were confirmed by transmission electron microscopy and dynamic light scattering. The loading content of aspirin in the extracted vesicles is 59 ± 5%, higher than that of conventional vesicles formed in liquid systems with dilute drugs. The release rate and final release amount of aspirin from vesicles in aqueous solutions can be controlled by addition of different amount of n-dioxane or by changing pH values.

Exclusive Synthesis of Poly(3-hexylthiophene) with an Ethynyl Group at Only One End for Effective Block Copolymerization.

Well-controlled synthesis of ethynyl-functionalized poly(3-hexylthiophene) (P3HT) is crucial for preparation of block copolymers containing the P3HT segment by means of click coupling reaction. A well-known chain end modification method, in which Kumada-Tamao catalyst-transfer polymerization is quenched with ethynylmagnesium chloride, under various conditions is re-examined, but in all cases not only P3HT with an ethynyl group at one end but also P3HT di-ethynylated at both ends is obtained. Accordingly, Sonogashira coupling reaction of P3HT having H/Br ends with trimethylsilylacetylene is tried, followed by removal of the trimethylsilyl group, and it is found that this protocol affords exclusively P3HT with an ethynyl group at one end. This post end-modification method is applied to the synthesis of an amphiphilic diblock copolymer of P3HT and poly(2-ethyl-2-oxazoline) (PEtOx) by means of click reaction between ethynylated P3HT and PEtOx with an azide group at one end, and the product is confirmed to be free from contamination with triblock copolymer. Micellization of this block copolymer is confirmed in tetrahydrofuran (THF)/water and THF/methanol mixtures.

Preparation of block copolymers via metal‐free visible‐light‐induced ATRP for the detection of lead ions

ABSTRACTPolyacrylamide‐b‐poly(methacrylic acid) was prepared on the surface of Au electrode (Au/PAM/PMAA) for Pb2+ ion electrochemical sensing via metal‐free visible‐light‐induced atom transfer radical polymerization, which was very simple, convenient, and environmentally friendly. Au/PAM/PMAA was carefully examined by cyclic voltammetry, electrochemical impedance spectroscopy, and X‐ray photoelectron spectroscopy. Further, Au/PAM/PMAA was successfully used for the determination of Pb2+ ion by differential pulse anodic stripping voltammetry. Under the optimal conditions, a linear response from 1.0 × 10−11 to 1.0 × 10−4 mol/L with detection limit of 2.5 × 10−12 mol/L (S/N = 3) was achieved from the results of experiments. Comparing with similar Pb2+ sensors, the broader linear range and lower detection limit suggested the promising prospect of Au/PAM/PMAA. In a word, the work of this article had an important significance for the polymer‐modified electrodes and the sensitive detection of Pb2+. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45863.

Ferrocene-Modified Block Copolymers for the Preparation of Smart Porous Membranes.

The design of artificially generated channels featuring distinct remote-switchable functionalities is of critical importance for separation, transport control, and water filtration applications. Here, we focus on the preparation of block copolymers (BCPs) consisting of polystyrene-block-poly(2-hydroxyethyl methacrylate) (PS-b-PHEMA) having molar masses in the range of 91 to 124 kg mol−1 with a PHEMA content of 13 to 21 mol %. The BCPs can be conveniently functionalized with redox-active ferrocene moieties by a postmodification protocol for the hydrophilic PHEMA segments. Up to 66 mol % of the hydroxyl functionalities can be efficiently modified with the reversibly redox-responsive units. For the first time, the ferrocene-containing BCPs are shown to form nanoporous integral asymmetric membranes by self-assembly and application of the non-solvent-induced phase separation (SNIPS) process. Open porous structures are evidenced by scanning electron microscopy (SEM) and water flux measurements, while efficient redox-switching capabilities are investigated after chemical oxidation of the ferrocene moieties. As a result, the porous membranes reveal a tremendously increased polarity after oxidation as reflected by contact angle measurements. Additionally, the initial water flux of the ferrocene-containing membranes decreased after oxidizing the ferrocene moieties because of oxidation-induced pore swelling of the membrane.

Tunable Fluorescence of a Semiconducting Polythiophene Positioned on DNA Origami.

A novel approach for the integration of π-conjugated polymers (CPs) into DNA-based nanostructures is presented. Using the controlled Kumada catalyst-transfer polycondensation, well-defined thiophene-based polymers with controllable molecular weight, specific end groups, and water-soluble oligoethylene glycol-based side chains were synthesized. The end groups were used for the easy but highly efficient click chemistry-based attachment of end-functionalized oligodeoxynucleotides (ODNs) with predesigned sequences. As demonstrated by surface plasmon resonance spectroscopy, the prepared block copolymers (BCPs), P3(EO)3T-b-ODN, comprising different ODN lengths and specific or repetitive sequences, undergo specific hybridization with complementary, thiol-functionalized ODNs immobilized on a gold surface. Furthermore, the site-specific attachment of the BCPs to DNA origami structures is studied. We demonstrate that a nanoscale object, that is, a single BCP with a single ODN handle, can be directed and bound to the DNA origami with reasonable yield, site-specificity, and high spatial density. On the basis of these results, we are able to demonstrate for the first time that optical properties of CP molecules densely immobilized on DNA origami can be locally fine-tuned by controlling the attractive π-π-stacking interactions between the CPs. In particular, we show that the fluorescence of the immobilized CP molecules can be significantly enhanced by surfactant-induced breakup of π-π-stacking interactions between the CP's backbones. Such molecular control over the emission intensity of the CPs can be valuable for the construction of sophisticated switchable nanophotonic devices and nanoscale biosensors.

In situ grazing incidence small‐angle X‐ray scattering study of solvent vapor annealing in lamellae‐forming block copolymer thin films: Trade‐off of defects in deswelling

ABSTRACTSolvent vapor annealing (SVA) is one route to prepare block copolymer (BCP) thin films with long‐range lateral ordering. The lattice defects in the spin‐coated BCP thin film can be effectively and rapidly reduced using SVA. The solvent evaporation after annealing was shown to have a significant impact on the in‐plane ordering of BCP microdomains. However, the effect of solvent evaporation on the out‐of‐plane defects in BCPs has not been considered. Using grazing‐incidence x‐ray scattering, the morphology evolution of lamellae‐forming poly(2‐vinlypyridine)‐b‐polystyrene‐b‐poly(2vinylpyridine) triblock copolymers, having lamellar microdomains oriented normal to substrate surface during SVA, was studied in this work. A micelle to lamellae transformation was observed during solvent uptake. The influence of solvent swelling ratio and solvent removal rate on both the in‐plane and out‐of‐plane defect density was studied. It shows that there is a trade‐off between the in‐plane and out‐of‐plane defect densities during solvent evaporation. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 980–989

Improvement of Sludge Dewaterability by Ultrasound-Initiated Cationic Polyacrylamide with Microblock Structure: The Role of Surface-Active Monomers

Cationic polyacrylamides have been employed widely to improve sludge dewatering performance, but the cationic units are randomly distributed in the molecular chain, which restricts the further enhancement of dewaterability. Common template technology to prepare block copolymers requiring a huge number of templates reduces the polymer purity and molecular weight. Here, we adopted the surface-active monomer benzyl dimethyl 2-(methacryloyloxy)ethyl ammonium chloride (BDMDAC) to synthesize cationic microblocky polyacrylamide initiated by ultrasound. The reactivity ratio of monomers suggested that novel cationic monomer BDMDAC had higher homopolymerization ability, and was thus more prone to forming a microblock structure. The statistical analysis of sequence-length distribution indicated that the number and length of cationic segments increased in the PAB molecules. In addition, the characteristic results of Fourier transform infrared (FTIR), proton nuclear magnetic resonance (1H NMR), and thermogravimetric analysis (TGA) provided evidence for the synthesis of copolymer with cationic microblocks. Finally, the results of dewatering tests demonstrated that sludge dewaterability was greatly improved by adding the synthesized novel flocculants, and the sludge-specific resistance to filtration, filter cake moisture content and residual turbidity all reached a minimum (68.7%, 5.4 × 1012 m·kg−1, and 2.6 NTU, respectively) at 40 mg·L−1. The PAB flocs were large, compact, difficult to break, and easy to regrow. Furthermore, PAB was more effective in the removal of protein from soluble extracellular polymeric substances (SEPSs). In summary, this study provides a novel solution to synthesize cationic microblock polyacrylamide for improving sludge dewatering.

Design and synthesis of gold-loaded micelles based on poly (ethylene glycol) and poly (4-vinyl pyridine) triblock copolymers for biomedical applications

Gold-loaded micelles were prepared using triblock copolymers based on poly (ethylene glycol) and poly (4-vinyl pyridine) (P4VP-b-PEG-b-P4VP) obtained via atom transfer radical polymerization (ATRP). This was achieved using novel dichloro-terminated PEG as a macroinitiator. Further, ATRP was performed using 4-VP as a second forming block in the presence of CuCl/PMDETA as a catalyst system. The successful formation of P4VP-b-PEG-b-P4VP block copolymers was proved by FT-IR and 1H NMR with the presence of all characteristic signals arising from PEG and 4-VP units. The self-assembling behavior of thus prepared block copolymer in an aqueous media was investigated. Further, gold nanoparticles were embedded into the P4VP core of the micelles. Cell viability of the gold-loaded micelles was proven by MTT test as they showed no cytotoxicity on cancerous and non-cancerous cells.

Correction: Dual-initiator alkoxyamines with an N-tert-butyl-N-(1-diethylphosphono-2,2-dimethylpropyl) nitroxide moiety for preparation of block co-polymers

Correction for ‘Dual-initiator alkoxyamines with an N-tert-butyl-N-(1-diethylphosphono-2,2-dimethylpropyl) nitroxide moiety for preparation of block co-polymers’ by Gérard Audran et al., RSC Adv., 2017, 7, 4993–5001.

Dual-initiator alkoxyamines with an N-tert-butyl-N-(1-diethylphosphono-2,2-dimethylpropyl) nitroxide moiety for preparation of block co-polymers

Novel SG1-based alkoxyamines were used as initiators for preparation of block-copolymers both, by sequential NMP and by graft-polymerization.

A novel copper catalyst containing a hydroxyl functional group: a facile strategy to prepare block copolymers of vinyl monomer and ε-caprolactone via tandem reverse ATRP and ROP

A facile hydroxyl-functionalized catalyst was first accessed to prepare block copolymers of vinyl and cyclic ester monomers via tandem reverse ATRP/ROP.

Closed‐System One‐Pot Block Copolymerization by Temperature‐Modulated Monomer Segregation

AbstractA biphasic one‐pot polymerization method enables the preparation of block copolymers from monomers with similar and competitive reactivities without the addition of external materials. AB diblock copolymers were prepared by encapsulating a frozen solution of monomer B on the bottom of a reaction vessel, while the solution polymerization of monomer A was conducted in a liquid layer above. Physical separation between the solid and liquid phases permitted only homopolymerization of monomer A until heating above the melting point of the lower phase, which released monomer B, allowing the addition of the second block to occur. The triggered release of monomer B allowed for chain extension without additional deoxygenation steps or exogenous monomer addition. A method for the closed (i.e., without addition of external reagents) one‐pot synthesis of block copolymers with conventional glassware using straightforward experimental techniques has thus been developed.

Closed-System One-Pot Block Copolymerization by Temperature-Modulated Monomer Segregation.

A biphasic one-pot polymerization method enables the preparation of block copolymers from monomers with similar and competitive reactivities without the addition of external materials. AB diblock copolymers were prepared by encapsulating a frozen solution of monomer B on the bottom of a reaction vessel, while the solution polymerization of monomer A was conducted in a liquid layer above. Physical separation between the solid and liquid phases permitted only homopolymerization of monomer A until heating above the melting point of the lower phase, which released monomer B, allowing the addition of the second block to occur. The triggered release of monomer B allowed for chain extension without additional deoxygenation steps or exogenous monomer addition. A method for the closed (i.e., without addition of external reagents) one-pot synthesis of block copolymers with conventional glassware using straightforward experimental techniques has thus been developed.

Porous proton exchange membranes based on sulfonated poly (arylene ether ketone)/polylactide block copolymers for enhanced proton conductivity and dimensional stability

Sulfonated poly(arylene ether ketone) (SPAEK) with hydroxyl end group was synthesized and used as a precursor for the ring-opening polymerization of lactide to afford sulfonated poly(arylene ether ketone)/polylactide block copolymers. The proton exchange membranes based on the prepared block copolymers were fabricated by the solvent casting method for direct methanol fuel cell (DMFC) application. The pores with different average diameters from 50nm to 2.6μm were established by the selective removal of polylactide (PLA) molecules from the self-assembled copolymers in a variety of composition. The morphology of the prepared porous membranes was examined by scanning electron microscopy. A variety of membrane properties for DMFC application such as water uptake, dimensional swelling, thermal and mechanical stability, methanol permeability, and proton conductivity were investigated. Although the proton conductivity of the porous membranes was much higher than that of the non-porous ones at the same degree of sulfonation, it decreased with increasing pore size. In this study, the SPAEK with the smallest pore diameter of 50nm showed the highest proton conductivity and the lowest methanol permeability. The porous SPAEK membranes exhibited excellent mechanical and dimensional stability, although the water uptake was significantly increased by the presence of pores.

One-Pot Synthesis of Block Copolymers by Orthogonal Ring-Opening Polymerization and PET-RAFT Polymerization at Ambient Temperature.

Well-defined poly(ε-caprolactone)-b-poly(methyl acrylate) (PCL-b-PMA) block copolymers were synthesized at ambient temperature by one-pot combination of diphenyl phosphate (DPP)-catalyzed ring-opening polymerization (ROP) and photoinduced electron/energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization. Full orthogonality of PET-RAFT polymerization and DPP-catalyzed ROP was confirmed by kinetic studies, which allowed facile synthesis of PCL-b-PMA block copolymers without a specific polymerization sequence. The resulting PCL-b-PMA block copolymers synthesized by either sequential or simultaneous ROP and PET-RAFT polymerization showed remarkably low molecular weight distributions (≤1.15), indicating that both ROP and PET-RAFT polymerizations proceeded in a controlled manner. In contrast to previous synthetic methods to prepare block copolymers, this facile one-pot method allows for rapid synthesis of block copolymers controlled via visible light.