Amphiphilic Random Copolymers Research Articles

Precision Self-Assembly of Amphiphilic Random Copolymers into Uniform and Self-Sorting Nanocompartments in Water

Self-assembly of amphiphilic molecules in water is a cornerstone to build compartmentalized materials toward unique functions, whereas it is yet challenging to create uniform, discrete, and size-controlled nanocompartments. This paper is to report that precision random copolymers, amphiphilic with hydrophilic poly(ethylene glycol) (PEG) and hydrophobic dodecyl pendants, induce precision self-assembly and self-recognition in water to form uniform, tunable, and self-sorting nanoparticles with inner-core hydrophobic compartments covered by PEG chains; the copolymers have been obtained via living or free radical copolymerization. The nanoparticles allow the on-target and predictable control of size, molecular weight, and aggregation number by tuning the primary structure of the copolymers; even mixtures of the copolymers with different composition underwent self-sorting to provide size-controlled discrete compartments.

Amphiphilic poly(ether sulfone) membranes for oil/water separation: Effect of sequence structure of the modifier

Oil‐contaminated wastewater threatens our environment and health thus novel membrane materials with low or nonfouling properties are an immediate need for oily wastewater treatment in a cost‐effective and environmentally friendly manner. In this study, three types of amphiphilic random, gradient, and block copolymers with similar molecular weights and chemical compositions, based on poly(ethylene glycol) methyl ether methacrylate (PEGMA) and 3,3,4,4,5,5,6,6,7,7,8,8,8‐tridecafluorooctyl acrylate (TFOA), were synthesized by the reversible addition‐fragmentation chain transfer (RAFT) method. The amphiphilic Poly(ether sulfone) membranes were then fabricated by blending with these copolymers via a facile coupled process of nonsolvent induced phase separation and surface segregation. Accompanying the phase inversion process of polymer matrix, the hydrophilic and hydrophobic segments in the amphiphilic modifiers would migrate and immobilize onto the membrane surfaces. This surface segregation process leaded to a chemical heterogeneous membrane surface comprising both hydrophilic PEGMA and low surface energy PTFOA brushes, which was confirmed by X‐ray photoelectron spectroscopy (XPS) and surface wettability analyses. Oil‐in‐water emulsion filtration test of the membranes displayed a lower permeate flux decline and a higher flux recovery (as high as 99.8%), establishing their considerably elevated antifouling properties. Additionally, cyclic oil/water separation and long‐term underwater immersion tests demonstrated that the as‐prepared membranes modified by these amphiphilic additives possessed excellent antifouling stabilities. © 2016 American Institute of Chemical Engineers AIChE J, 63: 739–750, 2017

A Solvent-Based Strategy for Tuning the Internal Structure of Metallo-Folded Single-Chain Nanoparticles.

Controlling the spatial distribution of catalytic sites in metallo-folded single-chain nanoparticles (SCNPs) is a first step toward the rational design of improved catalytic soft nano-objects. Here an unexplored pathway is reported for tuning the internal structure of metallo-folded SCNPs. Unlike the conventional SCNP synthesis in good solvent (protocol I), the proposed new route (protocol II) is based on the use of amphiphilic random copolymers and transfer, after SCNP formation, from selective to good (nonselective) solvent conditions. The size and morphology of the SCNPs obtained by the two protocols, and the corresponding spatial distribution of the catalytic sites, have been determined by combining results from size exclusion chromatography with triple detection, small-angle X-ray scattering and molecular dynamics (MD) simulations. Remarkably, the use of these protocols allows the tuning of the internal structure of the metallo-folded SCNPs, as supported by MD simulations results. While the conventional protocol I yields a homogeneous distribution of the catalytic sites in the SCNP, these are arranged into clusters in the case of protocol II.

Significantly reduced adsorption and activation of blood components in a membrane oxygenator system coated with crosslinkable zwitterionic copolymer

A crosslinkable zwitterionic copolymer PMBT was coated onto the surfaces of polypropylene hollow fiber membrane (PP-HFM) oxygenator and its connecting tubes. The PMBT copolymer coating on the oxygenator circuit formed a cell outer membrane mimetic surface with excellent stability. The hemocompatibility of the PMBT copolymer coated PP-HFM oxygenator circuit was evaluated by animal extracorporeal circulation. The concentrations of clotting components fibrinogen and platelet in the blood were almost unchanged during the circulation through the PMBT copolymer coated oxygenator circuits. By contrast, the concentrations of fibrinogen and platelet were significantly reduced to 52% and 56% respectively in the uncoated oxygenator group due to adsorption and thrombogenesis of the blood during 2h circulation. Moreover, concentration of activation marker beta-thromboglobulin for platelet in the blood was remarkably lower in the PMBT group than the uncoated control group (p<0.01). All the results strongly supported that the hemocompatibility of the PP-HFM oxygenator circuit could be improved significantly by coating a stable and densely assembled zwitterionic polymer film. This simple, stable and highly effective cell membrane mimetic coating strategy may be applicable in developing advanced oxygenator systems and other artificial organs. Statement of SignificanceAlthough a number of studies have reported the fabrication of zwitterionic phosphorylcholine coated oxygenators to resist the adsorption and activation of blood components and eliminate heparin-induced thrombocytopenia, none of them have fabricated stable and densely assembled film, especially with crosslinkable amphiphilic random copolymer described in our manuscript. The novel features of our work include:•The first study of fabricating crosslinked and densely assembled zwitterionic copolymer coating on surfaces of a commercial oxygenator system.•The first study on hemocompatibility of both the PMBT coated and the bare commercial PP-HFM oxygenator circuits by animal extracorporeal circulation.•Much better hemocompatibility was measured on the PMBT coated oxygenator circuit compared with the bare and other polymer coated oxygenator systems.

Self-assembly of well-defined fatty acid based amphiphilic thermoresponsive random copolymers

Side-chain stearic acid containing thermoresponsive and crystalline random copolymers are synthesized via RAFT technique, which self-assembled to spherical micellar structures in aqueous solution depending on stearate content in the copolymer.

カテコール基含有ランダム・ブロック共重合体の合成とその応用展開

This review shows synthesis and application of catechol-containing random and block copolymers. We successfully synthesized amphiphilic random copolymers containing catechol moieties as side chains by free radical copolymerization of dopamine methacrylic amide and hydrophobic monomers including styrene. The synthesized amphiphilic copolymers firmly adhered onto inorganic materials and change surface properties from hydrophilic to hydrophobic. The polymer-immobilized inorganic nanoparticles can be dispersed in hydrophobic organic solvents and form porous hierarchic films after casting under humid conditions followed by calcination. Block copolymers containing catechol moieties have also been synthesized reversible addition-fragmentation transfer（RAFT）polymerization of 3,4-dihydroxy styrene and styrene followed by deprotection of methoxy groups. Metal ions can be reduced by using the synthesized block copolymers as templates and reductants, metal nanoparticles consequently formed by simple addition of metal ions into solution or film of catechol-containing block copolymers.

種々の疎水基を有する両親媒性ランダム共重合体の水溶液中での会合・ミセル化挙動

さまざまな疎水基をポリアクリル酸に高分子反応で導入した6種類の両親媒性ランダム共重合体の0.05 M NaCl水溶液に対して，沈降平衡，動的光散乱，および蛍光寿命測定を行い，ランダム共重合体の会合・ミセル化挙動に及ぼす疎水基の疎水性の強さおよび疎水基含量依存性を調べた．会合し始める疎水基含量は，疎水基の疎水性の強さの順に低かった．ドデシル基とヘキシル基を疎水基にもつ両親媒性ランダム共重合体では，疎水基含量の増加に伴い，会合数は1から一旦10以上に増加したのち再び1に戻り，粒子当たりの疎水性ミクロドメインの数は0から1以上に増加してのちに1に漸近した．以上の結果より，これらの両親媒性ランダム共重合体は，中間の疎水基含量では複数の疎水性ミクロドメインをもつランダムな分岐構造の会合体を形成し，疎水基含量が十分高くなると単核花形のユニマーミセルを形成するようになると結論した．

One-step formation of multiple Pickering emulsions stabilized by self-assembled poly(dodecyl acrylate-co-acrylic acid) nanoparticles.

In this study, a one-step generation of stable multiple Pickering emulsions using pH-responsive polymeric nanoparticles as the only emulsifier was reported. The polymeric nanoparticles were self-assembled from an amphiphilic random copolymer poly(dodecyl acrylate-co-acrylic acid) (PDAA), and the effect of the copolymer content on the size and morphology of PDAA nanoparticles was determined by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The emulsification study of PDAA nanoparticles revealed that multiple Pickering emulsions could be generated through a one-step phase inversion process by using PDAA nanoparticles as the stabilizer. Moreover, the emulsification performance of PDAA nanoparticles at different pH values demonstrated that multiple emulsions with long-time stability could only be stabilized by PDAA nanoparticles at pH 5.5, indicating that the surface wettability of PDAA nanoparticles plays a crucial role in determining the type and stability of the prepared Pickering emulsions. Additionally, the polarity of oil does not affect the emulsification performance of PDAA nanoparticles, and a wide range of oils could be used as the oil phase to prepare multiple emulsions. These results demonstrated that multiple Pickering emulsions could be generated via the one-step emulsification process using self-assembled polymeric nanoparticles as the stabilizer, and the prepared multiple emulsions have promising potential to be applied in the cosmetic, medical, and food industries.

Amphiphilic Random Copolymers Consisting of Styrene, EGMA, and HEMA for Anti-Biofouling Coatings

Amphiphilic random copolymers consisting of hydrophobic styrene and hydrophilic 2-hydroxyethyl methacrylate (HEMA)/(ethylene glycol) methacrylate (EGMA) were designed and synthesized for anti-biofouling coating materials in buffered aqueous solutions. Random copolymers such as PS-PEGMA, PS-PHEMA, and PS-PEGMA-PHEMA were synthesized, with different monomer ratios, by radical polymerization. The structures and molecular weights of the synthesized polymers were determined by 1H-NMR and gel permeation chromatography, respectively. Protein adsorption experiments on the polymer surfaces were carried out using fluorescein isothiocyanate conjugate-labeled bovine serum albumin. Experimental results suggest that the surfaces of the amphiphilic random copolymers have a good anti-biofouling effect.

Core-Corona Micelles Formed by Self-Assembly of Random Copolymer and Homopolymer Mixtures: Dissipative Particle Dynamics Simulations

Dissipative particle dynamics simulation was applied to investigate the cooperative aggregation of amphiphilic random copolymer and homopolymer mixtures in selective solvents. The amphiphilic random copolymers were set to contain more hydrophilic segments. The effects of the contents of homopolymers, the chain length of amphiphilic random copolymers, the interaction parameters, as well as the simulation time, on the cooperative aggregation were systematically studied with dissipative particle dynamics simulation method. The results showed that core-corona micelles could be formed with the addition of homopolymers, where the homopolymers accumulate at the core and the amphiphilic random copolymers as the corona. This work demonstrated that the morphology and the size of the micelles could be tuned by the controlled addition of homopolymers in the process of self-assembly.

Single-chain crosslinked star polymers via intramolecular crosslinking of self-folding amphiphilic copolymers in water

Single-chain crosslinked star polymers with multiple hydrophilic short arms and a hydrophobic core were created as novel microgel star polymers of single polymer chains. The synthetic process involves the intramolecular crosslinking of self-folding amphiphilic random copolymers in water. For this process, amphiphilic random copolymers bearing hydrophilic poly(ethylene glycol) (PEG) and hydrophobic olefin pendants were synthesized by ruthenium-catalyzed living radical copolymerization of PEG methyl ether methacrylate, dodecyl methacrylate and hydroxyl-functionalized methacrylates, and the in situ or postesterification of the hydroxyl pendants of the resulting copolymers with methacryloyl chloride. The olefin-bearing copolymers with 20–40 mol% hydrophobic units efficiently self-folded because of hydrophobic interactions in water. These folded structures were then crosslinked intramolecularly using a free radical initiator or a ruthenium catalyst to selectively yield single-chain crosslinked star polymers, whereas a counterpart containing 50 mol% hydrophobic units induced bimolecular aggregation in water to give double-chain crosslinked star polymers. The primary structure of the star polymers can be precisely controlled with random copolymer precursors. Owing to the PEG arm units, the star polymers further showed thermosensitive solubility in water. Single-chain crosslinked star polymers with hydrophilic and thermoresponsive poly(ethylene glycol) short arms and a hydrophobic core were created as novel microgel star polymers of single polymer chains via the intramolecular crosslinking of self-folding amphiphilic random copolymers in water. For this, well-controlled amphiphilic random copolymers bearing hydrophobic olefin pendants were synthesized as self-folding precursors by ruthenium-catalyzed living radical polymerization and the subsequent introduction of olefin units. The copolymers with 20–40 mol% hydrophobic units efficiently gave single-chain crosslinked star polymers in water.

Zwitterionic copolymer self-assembly for fouling resistant, high flux membranes with size-based small molecule selectivity

Membranes that exhibit size-based rejection between small molecules (<1500g/mol) independent of solute charge would be valuable for many separations, but commercial membranes show poor and unpredictable selectivity at this size range. This arises from high pore size polydispersity and charged membrane surfaces that lead to separations affected by solute charge. Furthermore, these membranes are susceptible to fouling. Self-assembly is a promising technique for making polymeric membranes with fouling resistance, high permeability and selectivity along with opportunity for easy fabrication and scalability. We report the first examples of a new class of membrane materials that derive their permeability, size-based selectivity and fouling resistance from the self-assembly of zwitterion-containing amphiphilic random copolymers. Zwitterionic groups strongly resist biomacromolecular fouling due to their high affinity with water, and self-assemble into channel-type clusters of 0.6–2nm in size. We show that these copolymers self-assemble into bicontinuous nanodomains. Thin film composite membranes formed by coating these copolymers onto porous supports exhibit permeances as high as 8.4Lm−2h−1bar−1, over three times that of a commercial membrane with similar MWCO. They show size-based selectivity, with a cut-off around 1nm. This closely matches the size of zwitterionic domains measured by transmission electron microscopy, indicating permeation occurs through these self-assembled “nanochannels.” These membranes show excellent fouling resistance during filtration of protein solutions and oil emulsions, completely resisting irreversible fouling and retaining over 96% of their permeance during filtration. These membranes have potential uses in biomolecule separations, purification of pharmaceuticals, and wastewater treatment.

Random Copolymer as Polymeric Surfactant in Seed Emulsion Polymerization

AbstractAn amphiphilic random copolymer was synthesized and applied as a surfactant in seed emulsion polymerization. The composition and structure of the copolymer were confirmed by Fourier transforms infrared spectroscopy (FTIR), 1H nuclear magnetic resonance spectroscopy (1H NMR), gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The effect of the copolymer content on the properties of latexes and their sizing properties was discussed. The average size, size distribution and stability of latexes were measured by quasi-elastic light scattering. The results suggest that the copolymer was a random copolymer, and displayed surface-active properties in water. The copolymer content affected strongly the properties of latex and its sizing performance. Monodisperse and nano-sized latex particles were obtained in the presence of 10.5 % copolymer. The thermal characteristics of latex films could be regulated by controlling the content of the copolymer. Adding an appropriate amount of the copolymer could reduce the surface tension of the latexes and promote their adsorption on the paper surface. Latex-treated paper showed a better water resistance and higher surface strength.

Shape Transformation of Light-Responsive Pyrene-Containing Micelles and Their Influence on Cytoviability.

The amphiphilic pyrene-containing random copolymers with light-responsive pyrene ester bonds were synthesized by copolymerizing 1-pyrenemethyl acrylate (PA) and N,N-dimethylacrylamide (DMA). The P(DMA-co-PA) copolymers formed spherical micelles in water, which were transformed into nanorods as a result of cleavage of the pyrene ester bonds under UV irradiation. In vitro culture with A549 cells and Raw cells showed that compared to the nonphotodegradable ones, the photodegradable P(DMA-co-PA) micelles caused significantly higher cytotoxicity under the same UV irradiation. The intracellular reactive oxygen species (ROS) level had a positive correlation with the cytotoxicity regardless of the cell types. The nonphotodegradable pyrene-containing micelles produced a lower level of ROS under UV irradiation. However, the photodecomposable P(DMA-co-PA) micelles produced a significant higher level of ROS under the same trigger of UV irradiation, which caused the shape transformation of micelles to nanorods and higher cytotoxicity simultaneously.

Light-Triggered Disruption of PAG-Based Amphiphilic Random Copolymer Micelles.

The amphiphilic random copolymer of P(NVP-co-NHPSS) with photocleavable N-O sulfonate side groups has been prepared to investigate the light-triggered disruption of copolymer micelles. Methods of absorption and emission spectra, solution transmittance, dynamic light scattering (DLS), and transmission electron microscopy (TEM) were applied. It was found that P(NVP-co-NHPSS) could form polymeric nanoaggregates in aqueous solution. And the photocleavage of the N-O bond within copolymer micelles upon 365 nm UV light could be conveniently controlled by changing the irradiation intensity, leading to the disruption of copolymer micelles and the photocontrolled release of Nile red encapsulation. And by encapsulating NaLuF4:Gd/Yb/Tm UCNPs inside copolymer micelles, the response of the photocleavable N-O bond to the 980 nm laser was much weaker than the response to 365 nm light; however, the photocontrolled release of Nile red could still be effectively triggered by the NIR light of the 980 nm laser.

Enhanced permeability of Rhodamine B into bilayers comprised of amphiphilic random block copolymers by incorporation of ionic segments in the hydrophobic chains

The permeability of Rhodamine B (Rh) into bilayers comprised of amphiphilic block copolymers was explored using ionic segments incorporated in the hydrophobic chains. The amphiphilic block copolymer consisting of a hydrophilic poly(methacrylic acid) block and a hydrophobic poly(methyl methacrylate-random-methacrylic acid) block containing 0.2 mol% units of the 3-sulfopropyl methacrylate potassium salt (SpMA) produced giant vesicles by photopolymerization-induced self-assembly in an aqueous methanol solution. The spherical vesicles were transformed into films as the SpMA ratio increased. The SpMA units incorporated in the hydrophobic chains enhanced the Rh permeability into the bilayer, whereas the vesicles without SpMA units captured no Rh molecules. However, the Rh was released from the hydrophobic phases in the isolation process of the bilayers by repeated sedimentation-redispersion. The permeability enhancement was attributed to the pore formation in the bilayers by the capture and release of the Rh by the SpMA units in the hydrophobic phases.

Self-Assembly of Catecholic Moiety-Containing Cationic Random Acrylic Copolymers.

Amphiphilic polyelectrolytes (APEs), exhibiting particular self-association properties in aqueous media, can be used in different industrial applications, including drug delivery systems. Their typical core-shell structure (micelle) depends on the balance of interactions between hydrophobic and ionizable monomer units. In this work, the structure of amphiphilic cationic random copolymers, obtained by employing different molar ratios of two acrylic monomers, one bearing in the side chain a tertiary amine (N,N-diethylethylendiamine, DED) and the other one a hydrophobic catecholic group (hydroxytyrosol, HTy), was investigated by atomistic molecular dynamics (MD) simulation, (1)H NMR analysis, dynamic light scattering (DLS), and zeta potential measurements. The structures of p(AcDED-co-AcHTy) copolymers were compared with that of the cationic homopolymer (pAcDED). MD simulation showed a chain folding in water solution of all polymer materials consistent with the degree of hydrophobicity of the chain, that increases with the number of aromatic residues. This phenomenon was induced by the interaction between the charged amine groups with water and by the associated attraction between aromatic rings inside the molecule. In addition, the p(AcDED-co-AcHTy) 70/30 copolymer had a marked tendency to self-assemble as shown by the radial distribution function among catechol carbon atoms. Electrical conductivity measurements evidenced a micellar arragment for all of the synthesized copolymers, and specially for p(AcDED-co-AcHTy) 70/30, a flower micelle structure seem to be more likely. The stacking interactions among catecholic groups present in the side chain of the copolymers reduced the size and charge density specially for the p(AcDED-co-AcHTy) 70/30 copolymer. Finally, the good antimicrobial activity of all copolymers confirmed the right reached amphiphilic balance. Indeed, a considerable reduction of the minimum inhibitory concentration (from 100 μg/mL to 40 μg/mL for pAcDED and p(AcDED-co-AcHTy) 70/30, respectively) was obtained by introducing a hydrophobic group molar fraction of 0.3.

Photo-dimerization characteristics of coumarin pendants within amphiphilic random copolymer micelles

The photo-dimerization characteristics of coumarin pendants within amphiphilic random copolymer micelles in aqueous solution was comprehensively investigated using various selected wavelength light in the UV-Vis-NIR region. The time-dependent photo-dimerization degree (PD) changes in the photo-dimerization experiments showed saturating behaviors with intensity-independent of PDmax values at 28%, 44%, 92%, 85%, 36%, 35%, 32% and 31% for 254, 288, 320, 360, 400, 500, 650 and 900 nm irradiations, respectively. The irradiation experiments at 254 and 288 nm announced the occurring of an asymmetric equilibrium of photo-dimerization and photo-cleavage at the used conditions. Both the alternative irradiation cycles of 360 and 254 nm, 650 and 254 nm showed a partially, but evidently reversible photo-dimerization tendency.

Synthesis of spiropyran-containing random copolymer by atom transfer radical polymerization and its complexation with metal ions

An amphiphilic random copolymer containing a monomer 2-(dimethylamino) ethyl methacrylate (DMAEMA) and a light-responsive unit 1′-(2-acryloxyethyl)-3′,3′- dimethyl-6-nitrospiro-(2H-1-benzopyran-2,2′-indoline) (SPMA) was synthesized by atom transfer radical polymerization. The solvatochromic and light responsive behaviors of the resulting P(SPMA-co-DMAEMA) copolymer in solution were investigated by UV–vis absorption spectroscopy. The ‘negative’ solvatochromism upon the increasing solvents polarity was observed. A strong absorption band was recorded at 589 nm in THF, while the lower values were found at 542 and 520 nm in methanol and water, respectively. Moreover, the random copolymer exhibited a good cycling performance by the alternating illumination with ultraviolet (UV) and visible (Vis) lights. Finally, we studied the complexation of zwitterionic merocyanine (MC) with divalent metal ions, and an obvious shift of the location for the maximum absorption peak was found upon addition of Co2+ or Mn2+. A slight color change of the copolymer solution from blue to purple after complexation with Co2+ or Mn2+ was also observed and this phenomenon might provide a potential visual observation for the complexation of P(SPMA-co-DMAEMA) with different metal ions.

Fabrication of microvillus-like structure by photopolymerization-induced self-assembly of an amphiphilic random block copolymer

A microvillus-like structure observed in digestive systems and glands was fabricated by the photopolymerization-induced self-assembly using an amphiphilic random block copolymer consisting of hydrophilic poly(methacrylic acid), PMAA, and hydrophobic poly(methyl methacrylate-random-methacrylic acid), P(MMA-r-MAA). The random block copolymerization of methyl methacrylate and methacrylic acid using a PMAA end-capped with 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl for the photopolymerization-induced self-assembly produced spherical vesicles and micelles during the early stage of the polymerization. These spherical particles transformed into worm-like vesicles, accompanied by the precipitation of a film-like product as the hydrophobic block chain grew according to the polymerization progress. Further extension of the hydrophobic block length produced the microvillus-like structure on the surface of the precipitating film. The finger-like structure in the microvilli had an ca. 8.5-μm height. An inverted cone-like critical packing shape of the copolymer with the hydrophobic block longer than the hydrophilic block contributed to the formation of the microvillus-like structure.