Functional Block Copolymers Research Articles

Synthesis of Functional Block Copolymers Carrying One Poly(p-phenylenevinylene) and One Nonconjugated Block in a Facile One-Pot Procedure

Block copolymers composed of a MEH–PPV block and a nonconjugated functional block (molecular weights between 5 and 90 kg/mol) were synthesized in a facile one-pot procedure via ROMP. This one-pot procedure permits the synthesis of numerous block copolymers with little effort. Amphiphilic block copolymers were obtained via incorporation of oxanorbornene carrying a PEG side chain as well as via postpolymerization modification of a reactive ester carrying norbornene derivative with methoxypoly(ethylene glycol)amine. These amphiphilic block copolymers can be self-assembled into micelles exhibiting different sizes (60–95 nm), morphologies (micelles or fused, caterpillar-like micelles), and optical properties depending on the polymer composition and the micellization procedure. Furthermore, the reactive ester carrying block copolymers enabled the introduction of anchor groups which facilitated the preparation of nanocomposites with CdSe/CdZnS core–shell QDs. The obtained composites were studied using time-resolved photoluminescence measurements. The results revealed an increased interaction based on an accelerated decay of the QD emission for composites as compared to the mixture of the QDs with unfunctionalized polymers.

Design of stimuli-responsive nanoparticles with optoelectronic cores by post-assembly cross-linking and self-assembly of functionalized block copolymers

Temperature- and pH-sensitive nanoparticles having optoelectronic cores were synthesized by post-assembly cross-linking reaction of a block copolymer composed of poly(N-vinyl amine) and poly(N-isopropylacrylamide), which was prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization. The self-assembly of the block copolymer in a selective solvent, followed by the site-selective cross-linking of poly(vinyl amine) segment with anthracene and thiophene dialdehydes, afforded stable and uniform core cross-linked nanoparticles having pH-sensitive imine linkages. As comparisons, the poly(vinyl amine) segment in the block copolymer was modified selectively with monoaldehyde derivatives to yield anthracene- and thiophene-functionalized block copolymers, which can form self-assembled micelles with optoelectronic cores in aqueous solutions. Temperature-dependent morphological changes and optical properties of the core cross-linked nanoparticles and the functionalized block copolymers were compared in selective and non-selective solvents, which were characterized by DLS, UV–vis, fluorescence, and CV measurements. The core cross-linked nanoparticles also exhibited pH-triggered disintegration. To the best of our knowledge, this is the first report on the comparison of two series of stimuli-responsive nanoparticles, in which the optoelectronic cores are formed by post-assembly cross-linking reaction with the dialdehyde derivatives and self-assembly of the functionalized block copolymers prepared with the monoaldehyde derivatives.

Macromol. Rapid Commun. 1/2016.

Back Cover: RAFT polymerization yields reactive block copolymers bearing the pentafluorophenyl ester (PFPA) group, and subsequent Click amidation using 2,2,6,6-tetramethylpiperidine-N-oxyl- (TEMPO-) and imidazolium-functionalized primary amines produces the corresponding functional block copolymers, leading to installation of statistical radical and ionic- sites into the PFPA segment. The monolayered thin film devices fabricated using the obtained block copolymers exhibit repeatable switching (memory) characteristic of electric conductivity (on/off ratio > 103) under a bias voltage. Further details can be found in the article by T. Suga,* K. Aoki, T. Yashiro, and H. Nishide* on page 53.

Amphiphilic functional block copolymers bearing a reactive furfuryl group via RAFT polymerization; reversible core cross-linked micelles via a Diels–Alder “click reaction”

Amphiphilic BCPs, PFMA-b-PPEGMA were prepared via RAFT polymerization. They were self-assembled into micelles in aqueous medium with a hydrophobic PFMA core and hydrophilic PPEGMA corona. Core cross-linked micelles were prepared via the DA reaction.

Functional block copolymer nanocarriers for anticancer drug delivery

We present a synthetic strategy towards functional polymer-based nanocarriers for potential anticancer drug delivery.

"Click" Incorporation of Radical/Ionic Sites into a Reactive Block Copolymer: A Facile and On-Demand Domain Functionalization Approach toward Organic Resistive Memory.

Reversible addition-fragmentation chain transfer polymerization yields reactive block copolymers bearing the pentafluorophenyl ester (PFPA) group, and subsequent Click amidation using 2,2,6,6-tetramethylpiperidine-N-oxyl- and imidazolium-functionalized primary amines produces the corresponding functional block copolymers, leading to installation of statistical radical- and ionic sites into the PFPA segment. The monolayered thin film devices fabricated using the obtained block copolymers exhibit repeatable switching of electric conductivity (on/off ratio > 103 ) under a bias voltage, which reveals that the coexistence of radicals and ions in the same spherical domain of the copolymer layer is a prerequisite for repeatable switching memory.

Directing Hybrid Structures by Combining Self-Assembly of Functional Block Copolymers and Atomic Layer Deposition: A Demonstration on Hybrid Photovoltaics.

The simplicity and versatility of block copolymer self-assembly offers their use as templates for nano- and meso-structured materials. However, in most cases, the material processing requires multiple steps, and the block copolymer is a sacrificial building block. Here, we combine a self-assembled block copolymer template and atomic layer deposition (ALD) of a metal oxide to generate functional hybrid films in a simple process with no etching or burning steps. This approach is demonstrated by using the crystallization-induced self-assembly of a rod-coil block copolymer, P3HT-b-PEO, and the ALD of ZnO. The block copolymer self-assembles into fibrils, ∼ 20 nm in diameter and microns long, with crystalline P3HT cores and amorphous PEO corona. The affinity of the ALD precursors to the PEO corona directs the exclusive deposition of crystalline ZnO within the PEO domains. The obtained hybrid structure possesses the properties desired for photovoltaic films: donor-acceptor continuous nanoscale interpenetrated networks. Therefore, we integrated the films into single-layer hybrid photovoltaics devices, thus demonstrating that combining self-assembly of functional block copolymers and ALD is a simple approach to direct desired complex hybrid morphologies.

Thymine-functionalized amphiphilic biodegradable copolymers for high-efficiency loading and controlled release of methotrexate

In this study, a novel thymine-functionalized six-membered cyclic carbonate monomer (TAC) was synthesized by the Michael-addition reaction between thymine and acryloyl carbonate (AC). The corresponding functional amphiphilic block copolymer mPEG-b-PTAC was further successfully synthesized by ring-opening polymerization using immobilized porcine pancreas lipase (IPPL) as the catalyst and mPEG as the macroinitiator. Meanwhile, mPEG-b-P(TAC-co-DTC) and mPEG-b-PDTC were also synthesized by the same enzymatic methods for comparison on different TAC contents. The structures of monomer and copolymers were characterized by 1H-NMR, 13C-NMR and FTIR. All the amphiphilic block copolymers could self-assemble to form nano-sized micelles in aqueous solution. Transmission electron microscopy (TEM) observation showed that the micelles dispersed in spherical shape with nano-size before and after MTX loading. 1H-NMR and FTIR results confirmed the successful formation of multiple hydrogen-bonding interactions between exposed thymine groups of hydrophobic PTAC segments and 2,6-diaminopyridine (DAP) groups of MTX molecules, which resulting in the higher drug loading capacity and the pH-sensitive drug release behavior. MTT assays also indicated lower toxicity of copolymer but higher potent cytotoxic activity of MTX-loaded copolymer against HeLa cells.

Controlled Architecture of Dual-Functional Block Copolymer Brushes on Thin-Film Composite Membranes for Integrated "Defending" and "Attacking" Strategies against Biofouling.

We report a new macromolecular architecture of dual functional block copolymer brushes on commercial thin-film composite (TFC) membranes for integrated "defending" and "attacking" strategies against biofouling. Mussel-inspired catechol chemistry is used for a convenient immobilization of initiator molecules to the membrane surface with the aid of polydopamine (PDA). Zwitterionic polymer brushes with strong hydration capacity and quaternary ammonium salt (QAS) polymer brushes with bactericidal ability are sequentially grafted on TFC membranes via activators regenerated by electron transfer-atom transfer radical polymerization (ARGET-ATRP), an environmentally benign and controlled polymerization method. Measurement of membrane intrinsic transport properties in reverse osmosis experiments shows that the modified TFC membrane maintains the same water permeability and salt selectivity as the pristine TFC membrane. Chemical force microscopy and protein/bacterial adhesion studies are carried out for a comprehensive evaluation of the biofouling resistance and antimicrobial ability, demonstrating low biofouling propensity and excellent bacterial inactivation for the modified TFC membrane. We conclude that this polymer architecture, with complementary "defending" and "attacking" capabilities, can effectively prevent the attachment of biofoulants and formation of biofilms and thereby significantly mitigate biofouling on TFC membranes.

차체 구조용 에폭시 접착제의 접합강도에 미치는 나노 기능성 블록공중합체 첨가의 영향

The structural epoxy adhesive used in car body assembly needs the highest level of joint mechanical strength under lap shear, T-peel and impact peel conditions. In this study, the effect of nano functionalized block copolymer addition on the impact peel strength of epoxy adhesive was investigated. DSC analysis showed that the addition of nano functionalized block copolymer did not affect the curing reaction of epoxy adhesive. From single lap shear test, it was found out that the addition of nano functionalized block copolymer slightly decreased the cohesive strength of cured adhesive layer. The addition of nano functionalized block copolymer showed beneficial effect on T-peel strength by changing the adhesive failure mode to the mixed mode. However, the addition of nano functionalized block copolymer just decreased the room temperature impact peel strength. It was considered that the addition of nano functionalized block copolymer could have effect on disturbing the crack propagation only for the case of slow strain rate.

Functional block copolymers from controlled radical and ring opening polymerization

Three techniques of controlled radical polymerization, namely nitroxide-mediated radical polymerization (NMRP), atom transfer radical polymerization (ATRP), and reversible addition-fragmentation chain transfer (RAFT) polymerization in combination with ring opening polymerization (ROP) were employed to prepare functional block-copolymers with controllable molecular weight and narrow molecular weight distribution. The structure, molecular weight, and PDI of block-copolymers were characterized by various techniques. The synthesis routes of NMRP-ROP, ROP-ATRP, and ROPRAFT exhibited excellent controllable features in the preparation of functional block-copolymers.

Continuous and patterned deposition of functional block copolymer thin films using electrospray

We report the use of electrospray to continuously deposit thin films, including patterned films, of a block copolymer (BCP). High substrate temperatures led to vertically oriented cylindrical microdomains at the film surface independent of the solvent composition and deposition rates utilized. Conversely, low substrate temperatures resulted in morphologies that were more sensitive to these parameters, with poorly ordered films of globular structures observed at the lowest temperatures considered. The deposition pattern is defined by spatially varying the electric field at the substrate using an underlying charged grid. These results open up new possibilities for patterned deposition of BCP films with morphological control.

Bacterial phospholipases C as vaccine candidate antigens against cystic fibrosis respiratory pathogens: The Mycobacterium abscessus model

BackgroundVaccine strategies represent one of the fighting answers against multiresistant bacteria in a number of clinical settings like cystic fibrosis (CF). Mycobacterium abscessus, an emerging CF pathogen, raises difficult therapeutic problems due to its intrinsic antibiotic multiresistance. MethodsBy reverse vaccinology, we identified M. abscessus phospholipase C (MA-PLC) as a potential vaccine target. We deciphered here the protective response generated by vaccination with plasmid DNA encoding the MA-PLC formulated with a tetra functional block copolymer 704, in CF (ΔF508) mice. Protection was tested against aerosolized smooth and rough (hypervirulent) variants of M. abscessus. ResultsMA-PLC DNA vaccination (days 0, 21, 42) elicited a strong antibody response. A significant protective effect was obtained against aerosolized M. abscessus (S variant) in ΔF508 mice, but not in wild-type FVB littermates; similar results were observed when: (i) challenging mice with the “hypervirulent” R variant, and; (ii) immunizing mice with purified MA-PLC protein. High IgG titers against MA-PLC protein were measured in CF patients with M. abscessus infection; interestingly, significant titers were also detected in CF patients positive for Pseudomonas aeruginosa versus P. aeruginosa-negative controls. ConclusionsMA-PLC DNA- and PLC protein-vaccinated mice cleared more rapidly M. abscessus than β-galactosidase DNA- or PBS- vaccinated mice in the context of CF. PLCs could constitute interesting vaccine targets against common PLC-producing CF pathogens like P. aeruginosa.

High-Resolution Metal Nanopatterning by Means of Switchable Block Copolymer Templates.

In this review, recent developments in the fabrication of hexagonal and parallel ordered arrays of metallic nanodomains on a substrate are described. We focus on the nanopatterning approach by means of switchable block copolymer thin films. This approach is highly advantageous, because it can lead to extremely regular patterns with metal subunits of only a few nanometers in diameter and center-to-center distances of tens of nanometers. Hence, the resulting 1D or 2D periodic arrays of metal nanodots and nanowires on silicon substrates can be fabricated with extremely high unit densities and on very large areas. The templated deposition of presynthesized metal nanoparticles on functional block copolymers is described in detail. Current challenges are discussed and an outlook for further developments is given.

Synthesis and characterization of polystyrene-block-poly(vinylbenzoic acid): a promising compound for manipulating photoresponsive properties at the nanoscale

Using reversible addition-fragmentation chain transfer (RAFT) polymerization, the effect of PSt macroRAFT and 4VBA ratio on the synthesis of a carboxylic acid functional block copolymer (PSt-b-P4VBA) was studied. PSt macroRAFT polymer was initially prepared followed by the insertion of 4-vinylbenzoic acid (4VBA) monomer. The chemical structure of the diblock copolymer was confirmed by NMR and FTIR. The effect of PSt macroRAFT and 4VBA ratio on copolymerization yield and on molecular weight distribution was assessed by gel permeation chromatography. The rate of polymerization did not change as the 4VBA/PSt macroRAFT ratio increased, indicating an ideal amount of 4VBA insertion. An optimal ratio of [PSt macroRAFT]:[AIBN]:[4VBA] was 1.2:1:180. DSC and XRD confirmed the amorphous structure of homo and copolymer. Thermal stability was higher for PSt-b-P4VBA forming activated porous carbon char by dehydration, carbonization and oxidation. SEM and STEM observations showed a morphological evolution between PSt macroRAFT and the correspondent copolymer.

Histamine-functionalized copolymer micelles as a drug delivery system in 2D and 3D models of breast cancer.

Histamine functionalized block copolymers based on poly(allyl glycidyl ether)-b-poly(ethylene oxide) (PAGE-b-PEO) were prepared with different ratios of histamine and octyl or benzyl groups using UV-initiated thiol-ene click chemistry. At neutral pH, the histamine units are uncharged and hydrophobic, while in acidic environments, such as in the endosome, lysosomes, or extracellular sites of tumours, the histamine groups are positively charged and hydrophilic. pH responsible polymer drug delivery systems is a promising route to site specific delivery of drugs and offers the potential to avoid side effects of systemic treatment. Our detailed in vitro experiments of the efficacy of drug delivery and the intracellular localization characteristics of this library of NPs in 2D and 3D cultures of breast cancer revealed that the 50% histamine-modified polymer loaded with DOX exhibited rapid accumulation in the nucleus of free DOX within 2 h. Confocal studies showed enhanced mitochondrial localization and lysosomal escape when compared to controls. From these combined studies, it was shown that by accurately tuning the structure of the initial block copolymers, the resulting self-assembled NPs can be designed to exploit histamine as an endosomal escape trigger and the octyl/benzyl units give rise to a hydrophobic core resulting in highly efficacious drug delivery systems (DDS) with control over intracellular localization. Optimization and rational control of the intracellular localization of both DDS and the parent drug can give nanomedicines a substantial increase in efficacy and should be explored in future studies.

Synthesis of functional block copolymers and terpolymers containing polyglycidyl methacrylate blocks

ABSTRACTHere, the synthesis of triblock terpolymers using tert‐butyl acrylate, glycidyl methacrylate, and methyl methacrylate was studied in detail using atom transfer radical polymerization. Those polymers are promising candidates for irreversible linked microstructured layers on surfaces. The experiments showed that the polymerization has to be started with the acrylate and can be extended with the methacrylates. The first two steps can be done in a one pot procedure employing the method of halogen exchange. With optimized reaction conditions in the last step, the obtained terpolymers show narrow molecular weight distributions and the polymerization process is well controlled. Conducting the synthesis in the opposite direction mostly a nonuniform product was obtained as the GPC analysis showed. Further characterization was done with 1H NMR spectroscopy, thermogravimetric analysis, and differential scanning calorimetry, the latter showing different glass points for the single blocks in the terpolymers if they are not too short. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 675–684

Well-Defined Block Copolymers with Triphenylamine and Isocyanate Moieties Synthesized via Living Anionic Polymerization for Polymer-Based Resistive Memory Applications: Effect of Morphological Structures on Nonvolatile Memory Performances

The anionic block copolymerization of 4,4′-vinylphenyl-N,N-bis(4-tert-butylphenyl)benzenamine (A) with n-hexyl isocyanate (B) was performed using potassium naphthalenide (K-Naph) in THF at −78 and −98 °C in the presence of sodium tetraphenylborate (NaBPh4) to afford the well-defined block copolymers for investigating the effect of morphological structures on electrical memory performances. The well-defined functional block copolymers (PBAB) with different block ratios had predictable molecular weights (Mn = 17 700–79 100 g/mol) and narrow molecular weight distributions (Mw/Mn = 1.14–1.19). It was observed from transmission electron microscopy (TEM) that the block copolymers showed different morphological structures depending on block ratios. Although all memory devices fabricated from the resulting block copolymers with different block compositions equally exhibited nonvolatile resistive switching characteristics, which are governed by the trap-controlled space-charge-limited current (SCLC) conduction mec...

Synthesis and Microphase Separation of PS‐b‐P(MA‐alt‐St) Block Copolymers and Their Ionomers for the Design of Polymer Crystallization Nucleation Agents

Several well‐controlled polystyrene‐block‐poly(styrene‐alt‐maleic anhydride) (PS‐b‐P(St‐alt‐MA)) functionalized block copolymers (BCs) and their sodium salt ionomers with different block ratios and molecular weights are synthesized through two‐step reversible addition–­fragmentation chain transfer (RAFT) polymerization. The atomic force microscopy (AFM) images and differential scanning calorimetry (DSC) results reveal that the prepared BCs and their ionomers microphase separate into various nanostructures depending on the block ratios. By taking advantage of the formation of amphiphilic nanostructures via the microphase, the block ionomers serve as nucleation agents to improve the crystallization rate of poly(ethylene terephthalate) (PET). The crystallization behavior of PET upon the addition of block ionomers is investigated isothermally and non‐isothermally by DSC. The results show that the block ionomers can effectively accelerate the crystallization rate of PET, which strongly depends on the molecular weights and block ratios image

Facile anionic synthesis of well-defined block copolymers with pendent triphenylamine and ethynylpyridine for nonvolatile memory device applications with high performances

The sequential block copolymerization of 4,4′-vinylphenyl-N,N-bis(4-tert-butylphenyl)benzenamine (A) with 2-(2-(4-vinylphenyl)ethynyl)pyridine (B) was simply carried out using only potassium naphthalenide (K-Naph) as an initiator without any additives in tetrahydrofuran (THF) at −78 °C. The well-defined functional block copolymers containing A block as an electron donor and B block as a weak electron acceptor had predictable molecular weights (Mn = 8,800–14,500 g/mol) and narrow molecular weight distributions (Mw/Mn = 1.09–1.10). The bicontinuous microphase-separated film morphology of the precisely synthesized poly(B-b-A-b-B) (PBAB) with 0.71 of fpoly(A), formed by thermal annealing at 230 °C for 9 h, was expected to be a potential active layer for nonvolatile memory device applications. Indium tin oxide (ITO)/PBAB/aluminum (Al) memory devices with an 8 × 8 cross-bar array structure exhibited nonvolatile resistive switching characteristics. The memory devices showed reliable memory performance in terms of ON/OFF ratios of ∼104, endurance cycles and retention time, and statistical data with regard to cumulative probability of the switching currents and threshold voltage distribution. Filamentary conduction mechanism was proposed to explain the switching of PBAB-based memory devices. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2625-2632