Copolymers In Water Research Articles

Effects of Ionic Liquids on the Cylindrical Self-Assemblies Formed by Poly(ethylene oxide)-Poly(propylene oxide)-Poly(ethylene oxide) Block Copolymers in Water.

Aiming at the fundamental understanding of solvent effects in amphiphilic polymer systems, we considered poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers in water mixed with an ionic liquid-ethylammonium nitrate (EAN), 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6), or 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4)-and we investigated the hexagonal lyotropic liquid crystal structures by means of small-angle X-ray scattering (SAXS). At 50% polymer, the hexagonal structure (cylinders of self-assembled block copolymer) was maintained across the solvent mixing ratio. The effects of the ionic liquids were reflected in the characteristic length scales of the hexagonal structure and were interpreted in terms of the location of the ionic liquid in the self-assembled block copolymer domains. The protic ionic liquid EAN was evenly distributed within the aqueous domains and showed no affinity for the interface, whereas BMIMPF6 preferred to swell PEO and was located at the interface so as to reduce contact with water. BMIMBF4 was also interfacially active, but to a lesser extent.

Chlorophyllin-Containing Copolymers and Their Responsive Properties.

Copper-chlorophyllin is a water-soluble derivative of chlorophylls and shows low cytotoxicity and antimutagenic properties in cultured cells. It has multiple applications, including its use as a photosensitizer in photothermal therapy because of its green light-activated photothermal performance. In this work, it was copolymerized with a poly(ethylene glycol) methacrylic monomer to yield random copolymers by free radical polymerization, which showed dual temperature- and pH-dependent phase transitions in aqueous solutions. The cloud points of the copolymer solutions were raised by lowering the pH of the aqueous solutions due to the protonation of the carboxylic groups on the chlorophyllin moieties, which decreased the overall hydrophilicity of the polymers. At low pH values, complete protonation of the carboxylic acid groups of the chlorophyllin moieties led to an irreversible aggregation of the copolymers in water. The incorporation of chlorophyllin in the copolymer improved its stability over its single molecular form.

Microphase separation of double-hydrophilic poly(carboxybetaine acrylate)-poly(2-methoxyethyl acrylate) block copolymers in water

Microphase separation of double-hydrophilic poly(carboxybetaine acrylate)-poly(2-methoxyethyl acrylate) block copolymers in water

Cononsolvency-Induced Microphase Separation of Double Hydrophilic Poly(2-ethyl-2-oxazoline)–Polycarboxybetaine Diblock Copolymers in Water–Ethanol Mixtures

Cononsolvency-Induced Microphase Separation of Double Hydrophilic Poly(2-ethyl-2-oxazoline)–Polycarboxybetaine Diblock Copolymers in Water–Ethanol Mixtures

CO2-switchable thermoresponsiveness of poly(N,N-(diethylamino)ethyl acrylamide)-based homo- and copolymers in water

The properties of thermo-sensitive polymers can be easily and reversibly switched using addition/removal of carbon dioxide (CO2) as an innovative and ecological trigger. N,N-(diethylamino)ethyl acrylamide (DEAEAM) was copolymerized with N-isopropylacrylamide (NIPAM) by Reversible Addition-Fragmentation chain Transfer (RAFT) polymerization to obtain copolymers with various compositions and architectures. The properties (solubility, aggregation behavior…) of these polymers in aqueous solution in the presence of CO2 was studied via scattering, microscopy and turbidimetry measurements. The copolymerization of DEAEAM monomer with NIPAM enables to produce either statistical or diblock copolymers and to tune the cloud point temperature of obtained copolymers either by changing the composition or the architecture (statistical, block) or by CO2 addition/removal. Whereas, for a given composition, statistical copolymer does not display thermoresponsive behavior, block copolymers present a thermoresponsiveness which depends on the protonation degree of tertiary amine functions. Additionally, CO2 can be used to reversibly modulate the properties of these materials in aqueous media.

The Nanostructured Self-Assembly and Thermoresponsiveness in Water of Amphiphilic Copolymers Carrying Oligoethylene Glycol and Polysiloxane Side Chains.

Amphiphilic copolymer self-assembly is a straightforward approach to obtain responsive micelles, nanoparticles, and vesicles that are particularly attractive for biomedicine, i.e., for the delivery of functional molecules. Here, amphiphilic copolymers of hydrophobic polysiloxane methacrylate and hydrophilic oligo (ethylene glycol) methyl ether methacrylate with different lengths of oxyethylenic side chains were synthesized via controlled RAFT radical polymerization and characterized both thermally and in solution. In particular, the thermoresponsive and self-assembling behavior of the water-soluble copolymers in water was investigated via complementary techniques such as light transmittance, dynamic light scattering (DLS), and small-angle X-ray scattering (SAXS) measurements. All the copolymers synthesized were thermoresponsive, displaying a cloud point temperature (Tcp) strongly dependent on macromolecular parameters such as the length of the oligo(ethylene glycol) side chains and the content of the SiMA counits, as well as the concentration of the copolymer in water, which is consistent with a lower critical solution temperature (LCST)-type behavior. SAXS analysis revealed that the copolymers formed nanostructures in water below Tcp, whose dimension and shape depended on the content of the hydrophobic components in the copolymer. The hydrodynamic diameter (Dh) determined by DLS increased with the amount of SiMA and the associated morphology at higher SiMA contents was found to be pearl-necklace-micelle-like, composed of connected hydrophobic cores. These novel amphiphilic copolymers were able to modulate thermoresponsiveness in water in a wide range of temperatures, including the physiological temperature, as well as the dimension and shape of their nanostructured assemblies, simply by varying their chemical composition and the length of the hydrophilic side chains.

Improvements of Solubility and Bioavailability of Lutein Through Grafting with Hydrophilic Polyacrylic Acid

In this study, polyacrylic acid grafted lutein (PAA-g-lutein) was prepared by hydrophilic modification of lutein with polyacrylic acid (PAA) through Steglish esterification method. The unreacted lutein was loaded in micelles formed by self-assembly of graft copolymers in water to form composite nanoparticles. The bioaccessibility and bioavailability of lutein nanoparticles were studied by in vitro and in vivo digestion experiments. Compared with free lutein, the saturated solubility and bioaccessibility of lutein nanoparticles were increased by 78 times and 3.6 times, respectively. The pharmacokinetics results in the mice model showed that the maximum concentration (Cmax) and area under concentration-time curve (AUC) of plasma of mice were increased by 3.05 and 6.07 times with lutein nanoparticles compared with free lutein. Meanwhile, the prepared lutein nanoparticles also promoted the accumulation of lutein in the liver, mesenteric adipose, and eyeballs. These results indicate that graft copolymerization of lutein with water-soluble polymers to form nanoparticles is an effective method to promote the bioavailability of lutein in vivo. Moreover, this method is simple and applicable, and can also be used for the modification of other bioactive molecules.

Co-micellization conduct and structural dynamics of block copolymers in water and salt solution environment for drug solubilization enhancement

Co-micellization conduct and structural dynamics of block copolymers in water and salt solution environment for drug solubilization enhancement

Synthesis and application of amphiphilic copolymer as demulsifier for super heavy oil emulsions

A series of amphiphilic copolymers (PIDs) were synthesized through free radical copolymerization of isobutyl acrylate (IBA) with N,N-dimethylacrylamide (DMAA). The structure, composition, and average molecular weights of these copolymers were characterized by 1H NMR spectra, infrared spectra, elemental analyse, and gel permeation chromatography. The solubility and aggregation behavior of these copolymers in different solvents were studied. In addition, thermo-responsive behavior of water-soluble copolymers in water was investigated by means of transmittance tests and DLS tests. The demulsification experiment showed that PID demulsifiers had excellent demulsification efficiency toward super heavy oil emulsions. The dehydration ratio reached 92.69 % at a concentration of 400 mg·L−1 for 210 min at 80 °C. Combined with the morphological changes of water droplets and active substances during demulsification, the characteristics of viscosity and interfacial activity proved that the higher content of lipophilic segments in PID copolymer could facilitate the diffusion of demulsifiers at the oil-water interface and accelerate the condensation of water droplets. Therefore, it is envisioned that this heavy oil demulsifiers with excellent demulsification performance and clean water phase will have promising prospects.

Molecular Insights on Morphology, Composition, and Stability of Mixed Micelles Formed by Ionic Surfactant and Nonionic Block Copolymer in Water Using Coarse-Grained Molecular Dynamics Simulations.

The nanoscale association domains are the ultimate determinants of the macroscopic properties of complex fluids involving amphiphilic polymers and surfactants, and hence, it is foremost important to understand the role of polymer/surfactant concentration on these domains. We have used coarse-grained molecular dynamics simulations to investigate the effect of polymer/surfactant concentration on the morphology of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO, i.e., pluronics or poloxamers) block copolymer, and ionic surfactants sodium dodecyl sulfate (SDS), mixed micelles in aqueous solution. The proclivity of the surfactant to form the mixed micelles is also probed using umbrella sampling simulations. In this study, we observed that the core of the pluronic + SDS formed mixed micelles consists of PPO, the alkyl tail of SDS, and some water molecules, whereas the PEO, water, and sulfate headgroups of SDS form a shell, consistent with experimental observations. The micelles are spherical at high-pluronic/low-SDS compositions, ellipsoidal at high-SDS/low-pluronic compositions, and wormlike-cylindrical at high-pluronic/high-SDS compositions. The transitions in micelle morphology are governed by the solvent accessible surface area of mixed aggregates, electrostatic repulsion between SDS-headgroups, and dehydration of PEO and PPO segments. The free energy barrier for SDS escape is much higher in mixed micelles than in pure SDS micelles, indicating a stronger tendency for SDS to form pluronic-SDS mixed micelles.

Lactate and glucose responsive boronic acid-substituted amphiphilic block copolymer nanoparticles of high aspect ratio

The establishment of conditions for formation of higher order morphologies (e.g. rods and worms) is important, as such nanoparticles are more efficient than spheres in drug delivery. Glucose-binding of core–shell nanoparticles comprising of boronic acid (BA) moieties occurs under basic conditions at above the pKa of the BA (pH 8.7). The resulting increased solubility of the core-forming BA-containing block is utilised in the delivery of therapeutics to diabetics. In contrast, the binding of the key anaerobic metabolite lactate to the BA moiety of amphiphilic block copolymers is unreported, despite occurring at lower physiological neutral pH 7.4. Herein, for the first time, high aspect ratio nanoparticles are observed for (unprotected) BA-substituted amphiphilic block copolymers in water, achieved by incorporating a non-stimuli responsive hydrophobic (tert-butylacrylamide) block. Amphiphilic diblock (Mn = 24,100 and 27,700 gmol−1) and triblock copolymers (Mn = 21,500 and 25,200 gmol−1) with relatively narrow molecular weight distributions (ᴆ = 1.31–1.48) were prepared by reversible addition-fragmentation chain transfer (RAFT) solution polymerizations. Aggregates formed upon dialysis with lactate at pH 7.4 were generally similar to those formed upon self-assembly with glucose at pH 8.7. Spherical nanoparticles for poly(N,N-dimethylacrylamide, DMA)28-b-(3-(acrylamidophenyl)boronic acid, 3-BAPhA)84-TTC (trithiocarbonate) decreased in size from Dh = 259 nm to mostly 100–150 nm upon ionization of BA-moieties with lactate, base, and glucose. Poly(DMA)96-b-(3-BAPhA)62 gave ∼ 500 nm long worms and lamellae under basic conditions, which transitioned to irregular spheres and rods upon addition of glucose. Self-assembly for triblock copolymers with BA-binding gave worms and fused spherical micelle rod-like structures.

Water-soluble polyphosphonate-based bottlebrush copolymers via aqueous ring-opening metathesis polymerization.

Ring-opening metathesis polymerization (ROMP) is a versatile method for synthesizing complex macromolecules from various functional monomers. In this work, we report the synthesis of water-soluble and degradable bottlebrush polymers, based on polyphosphoesters (PPEs) via ROMP. First, PPE-macromonomers were synthesized via organocatalytic anionic ring-opening polymerization of 2-ethyl-2-oxo-1,3,2-dioxaphospholane using N-(hydroxyethyl)-cis-5-norbornene-exo-2,3-dicarboximide as the initiator and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as the catalyst. The resulting norbornene-based macromonomers had degrees of polymerization (DPn) ranging from 25 to 243 and narrow molar mass dispersity (Đ ≤ 1.10). Subsequently, these macromonomers were used in ROMP with the Grubbs 3rd-generation bispyridyl complex (Ru-G3) to produce a library of well-defined bottlebrush polymers. The ROMP was carried out either in dioxane or in aqueous conditions, resulting in well-defined and water-soluble bottlebrush PPEs. Furthermore, a two-step protocol was employed to synthesize double hydrophilic diblock bottlebrush copolymers via ROMP in water at neutral pH-values. This general protocol enabled the direct combination of PPEs with ROMP to synthesize well-defined bottlebrush polymers and block copolymers in water. Degradation of the PPE side chains was proven resulting in low molar mass degradation products only. The biocompatible and biodegradable nature of PPEs makes this pathway promising for designing novel biomedical drug carriers or viscosity modifiers, as well as many other potential applications.

Phase Behavior of Double Zwitterionic Block Copolymers in Water: Morphology Transition through Concentration Dependent Selectivity of Water Partitioning

AbstractPhase behavior of double zwitterionic diblock copolymers composed of a poly(carboxybetaine methacrylate) (PCB2) and a poly(sulfobetaine methacrylate) (PSB4) (PCB2n‐b‐PSB4m) has been mapped out in aqueous solutions. Phase diagrams are constructed with polymer concentration, ϕ, ranging from 0.08 to 0.80 and PSB4 volume fraction in the PCB2n‐b‐PSB4ms, fPSB4, ranging from 0.23 to 0.93 at 25 °C. PCB2n‐b‐PSB4m aqueous solutions show symmetric phase diagram above ϕ = 0.55, indicating that water is nearly neutral with respect to PCB2 and PSB4. The morphology transforms from columnar with PCB2 cylinders to lamellar to columnar with PSB4 cylinders with decreasing ϕ, and the phase boundaries exhibit a negative slope below ϕ = 0.45. The morphology transition is rationalized in terms of interfacial curvature modulation through the volume expansion of the PCB2 phase due to the selective water partitioning. The lyotropic mesophase of double hydrophilic block copolymers is a unique molecular compartment for hydrophilic molecules with low interfacial tension.

Influence of the Nature of Aliphatic Hydrophobic Physical Crosslinks on Water Crystallization in Copolymer Hydrogels.

The local environment within a hydrogel influences the properties of water, including the propensity for ice crystallization. Water-swollen amphiphilic copolymers produce tunable nanoscale environments, which are defined by hydrophobic associations, for the water molecules. Here, the antifreeze properties for equilibrium-swollen amphiphilic copolymers with a common hydrophilic component, hydroxyethyl acrylate (HEA), but associated through crystalline (octadecyl acrylate, ODA) or rubbery (ethylhexyl acrylate, EHA) hydrophobic segments, are examined. Differences in the efficacy of the associations can be clearly enunciated from compositional solubility limits for the copolymers in water (<2.6 mol % ODA vs ≤14 mol % EHA), and these differences can be attributed to the strength of the association. The equilibrium-swollen HEA-ODA copolymers are viscoelastic solids, while the swollen HEA-EHA copolymers are viscoelastic liquids. Cooling these swollen copolymers to nearly 200 K induces some crystallization of the water, where the fraction of water frozen depends on the details of the nanostructure. Decreasing the mean free path of water by increasing the ODA composition from 10 to 25 mol % leads to fractionally more unfrozen water (66-87%). The swollen HEA-EHA copolymers only marginally inhibit ice (<13%) except with 45 mol % EHA, where nearly 60% of the water remains amorphous on cooling to 200 K. In general, the addition of the EHA leads to less effective ice inhibition than analogous covalently crosslinked HEA hydrogels (19.9 ± 1.8%). These results illustrate that fluidity of confining surfaces can provide pathways for critical nuclei to form and crystal growth to proceed.

New insights into humic acid-boosted conversion of bisphenol A by laccase-activated co-polyreaction: Kinetics, products, and phytotoxicity

How humic acid (HA) modifies bisphenol A (BPA) conversion in exoenzyme-activated polyreaction is poorly understood. Herein, the influencing mechanism of HA on laccase-induced BPA self-polymerization was investigated, and the phytotoxicity of the produced BPA self/co-polymers was assessed for the first time. HA prominently boosted BPA elimination, and the rate constants of BPA conversion augmented from 0.61 to 1.43 h−1 as HA level raised from 0 to 50 mg·L−1. It is because the generated BPA-HA co-polymers promptly lowered the yields of long-chain BPA self-oligomers, consequently maintaining laccase activity through opening enzymatic substrate-binding pockets. Notably, a few BPA monomers were re-released from the loosely bound self-polymers and co-polymers, and the releasing amounts respectively were 13.9 − 22.4% and 0.3 − 0.5% at pH 2 − 11. Formation of self/co-polymers was greatly conducive to avoiding BPA biotoxicity. Compared with BPA self-polymers, the phytotoxicity of BPA co-polymers to germinated radish (Raphanus sativus L.) seeds was lower due to these covalently bound products were more complex and stable. It follows that laccase-mediated co-polymerization played a significant role in BPA conversion, contaminant detoxification, and carbon sequestration. These findings are not only beneficial to clarifying exoenzyme-activated the generation mechanism of BPA co-polymers in water, but to reusing these supramolecular aggregates in crop growth.

Core–Satellite Micelles by a Linear A1B1A2B2 Tetrablock Copolymer

Block copolymers in water or compatible solvents show micelles with various shapes, such as worm-like, vesicles, and spheres. In this study, we prepared core–satellite micelles by employing a polystyrene-block-polyisoprene-block-polystyrene-block-polyisoprene (S1I1S2I2) linear tetrablock copolymer. When a PS-compatible solvent, for example, dimethylacetamide or diethylphthalate, is used, the PI chains form the inside core, while the PS chains become a shell as long as the volume fraction of mid PI1 chains (fPI1) is large enough (0.2) to form a loop configuration, resulting in merging into spherical cores consisting of the PI2 chains. However, at smaller fPI1 (0.08), the short mid PI1 chains cannot merge into the PI2 core and therefore exist separately as small spherical micelles, which are referred to as the “satellite” micelles. Thus, the micelles consist of large central core spheres and smaller outside satellite spherical micelles.

Micellar aggregation and thermogelation of amphiphilic random copolymers in water hierarchically dependent on chain length

Micellar aggregates and thermoresponsive gelation of amphiphilic random copolymers in water were examined in detail, focused on effects of the degree of polymerization (DP) on the behavior. For this purpose, we designed random copolymers carrying hydrophilic poly(ethylene glycol) and hydrophobic dodecyl groups, where the DP was varied from 63 to 358. The content of the hydrophobic monomer was set to 60 mol% to facilitate thermogelation. All the copolymers formed multichain aggregates in water, while the size distribution depended on DP. Since copolymers with larger DP had less composition distribution, the copolymers with 145 or more of DP formed size-controlled aggregates in water. Their concentrated solutions, above the overlap concentration of the aggregates, gelled entirely upon heating, followed by syneresis. In contrast, the short copolymer with 63 of DP formed aggregates with multimodal size distribution, and the concentrated solution underwent macroscopic phase separation upon heating, followed by gelation of the polymer-rich lower layer. As confirmed by small-angle neutron scattering, the copolymer suitable for thermogelation originally formed aggregates consisting of multiple micelle subunits in the aqueous dilute solution, and the thermogelation of the concentrated solution was driven by the physical packing of the micelle subunits upon heating. Thus, we revealed that the DP hierarchically affected not only the self-assembly of the copolymers into size-controlled micellar aggregates in water but also the thermogelation of the concentrated solutions via intermicellar association.

Controlled LCST Behavior and Structure Formation of Alternating Amphiphilic Copolymers in Water

Controlled LCST Behavior and Structure Formation of Alternating Amphiphilic Copolymers in Water

Self-Assembled Catalytic Nanoreactors from Molecular Brushes by Utilizing Postpolymerization Modification for Catalyst Attachment

Polymer-based catalytic nanoreactors, with the characteristics of easy preparation, good dispersion, and facile modulation of molecular structures, have been widely applied for various organic transformations. Usually, polymeric nanoreactors are fabricated via the self-assembly of amphiphilic copolymers in water, while the disassembly and instability of the relevant nanoreactors often compromise their potential applicability. Molecular brushes (MBs), as a kind of polymer with high-density grafted side chains on the linear polymer main chain, can be rapidly self-assembled into highly ordered nanostructures even at low concentrations. This study reports the fabrication of catalytic nanoreactors from molecular brushes of poly[norbornene–poly(bromoethyl methacrylate-co-methyl methacrylate)]-co-poly[norbornene polyethylene glycol monomethyl ether] (P[NB-(BEMA-co-MMA)]-co-P[NB-PEG]). The amphiphilic molecular brush was synthesized by combining reversible addition–fragmentation chain transfer (RAFT) polymerization and ring-opening metathesis polymerization (ROMP) techniques. Homogeneous catalysts, such as triethylenediamine and 4-(dimethylamino)pyridine analogues, were introduced by nucleophilic substitution with alkyl bromide on the side chain of molecular brushes. Furthermore, micellar catalytic nanoreactors were fabricated via self-assembly in deionized water. The resulted nanoreactors display high catalytic activities toward the Knoevenagel condensation reaction and acylation reaction of alcohol in water, respectively. This contribution describes a general method for constructing highly efficient molecular brush-based catalytic nanoreactors utilizing postpolymerization modification (PPM) for aqueous catalysis.

Synthesis, Hydrophilicity and Micellization of Coil-Brush Polystyrene-b-(polyglycidol-g-polyglycidol) Copolymer-Comparison with Linear Polystyrene-b-polyglycidol.

In this paper, an original method of synthesis of Coil-Brush amphiphilic polystyrene-b-(polyglycidol-g-polyglycidol) (PS-b-(PGL-g-PGL)) block copolymers was developed. The hypothesis that their hydrophilicity and micellization can be controlled by polyglycidol blocks architecture was verified. The research enabled comparison of behavior in water of PS-b-PGL copolymers and block–brush copolymers PS-b-(PGL-g-PGL) with similar composition. The Coil-Brush copolymers were composed of PS-b-PGL linear core with average DPn of polystyrene 29 and 13 of polyglycidol blocks. The DPn of polyglycidol side blocks of coil–b–brush copolymers were 2, 7, and 11, respectively. The copolymers were characterized by 1H and 13C NMR, GPC, and FTIR methods. The hydrophilicity of films from the linear and Coil-Brush copolymers was determined by water contact angle measurements in static conditions. The behavior of Coil-Brush copolymers in water and their critical micellization concentration (CMC) were determined by UV-VIS using 1,6-diphenylhexa-1,3,5-trien (DPH) as marker and by DLS. The CMC values for brush copolymers were much higher than for linear species with similar PGL content. The results of the copolymer film wettability and the copolymer self-assembly studies were related to fraction of hydrophilic polyglycidol. The CMC for both types of polymers increased exponentially with increasing content of polyglycidol.