Water-soluble Diblock Copolymers Research Articles

Tertiary Amine Methacrylate based Polymers as Corrosion Inhibitors in Double Distilled Water. Part I

In the current study, the inhibitive performances of tertiary amine methacrylate based water soluble diblock copolymers on the corrosion behavior of AISI 304 stainless steel were investigated in double distilled water (DDW, at pH 7.6) using potentiodynamic polarisation, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), atomic force microscopy (AFM) and inductively coupled plasma optical emmision spectrometry (ICP OES) methods. Related diblock copolymers were poly[2-(dimethylamino)ethylmethacrylate] (PDMA), poly[2-(diethylamino)ethylmethacrylate] (PDEA), poly[2-(diisopropylamino)ethylmethacrylate] (PDPA) homopolymers and poly[2-(dimethylamino)ethylmethacrylate]-b-poly[methylmethacrylate] (PDMA-b-PMMA), poly[2-(diethylamino)ethylmethacrylate]-b-poly[methylmethacrylate] (PDEA-b-PDMA) and poly[2-(diisopropylamino)ethylmethacrylate]-b-poly[2-(dimethylamino)ethylmethacrylate] (PDPA-b-PDMA). Diblock copolymers having different molecular weight and different comonomer ratios. Polarisation curves indicated that all the studied polymers were acting as a mixed type inhibitors. All electrochemical measurements showed that inhibition efficiencies increased with an increase in the inhibitor concentration. It was determined that the increase of inhibitor efficiency by concentration resulted from the adsorption of polymers to metal surface, and the adsorption fitted to Langmuir adsorption equation. Adsorption equilibrium constant (Kads) and free energy of adsorption(ΔGads), which were thermodynamic parameters of adsorption were calculated by benefiting from the drawn adsorption isotherms. The variation in inhibitive efficiency mainly depended on the type and the nature of the substituents present in the inhibitor molecule and also depended on the molecular weight of the inhibitors. The best inhibition in DDW showed VB207 diblock copolymer. Surface images obtained with SEM, EDX and AFM methods, determined by verifying these results that inhibitors decreased the dissolution of metal, and prevented the corrosion.

One‐pot synthesis of amphiphilic diblock copolymers of poly(styrene) and poly(2‐methyl‐2‐oxazoline) by the direct combination of reverse iodine transfer polymerization (RITP) and cationic ring‐opening polymerization (CROP) processes

A iodo-terminated polystyrene (PS-I) synthesized by reverse iodine transfer polymerization (RITP) was directly used as macroinitiator in the cationic ring-opening polymerization of 2-methyl-2-oxazoline to afford a water-soluble diblock copolymer. This is the first example of combination of RITP and CROP in macromolecular engineering.

Synthesis and characterization of well-defined optically active methacrylic diblock copolymers

A new, simple, and cost-effective approach toward the development of well-defined optically active diblock copolymers based on methacrylate monomers is described for the first time. Starting from the low-cost optically active (S)-(−)-2-methyl-1-butanol, a new optically active methacrylic monomer, namely, (S)-(+)-2-methyl-1-butyl methacrylate [(S)-(+)-MBuMA], was synthesized. Reversible addition fragmentation chain transfer polymerization was then used for preparing well-defined poly[(S)-(+)-MBuMA] homopolymers and water-soluble diblock copolymers based on [(S)-(+)-MBuMA] and the hydrophilic and ionizable monomer 2-(dimethyl amino)ethyl methacrylate (DMAEMA). The respective homopolymers and diblock copolymers were characterized in terms of their molecular weights, polydispersity indices, and compositions by size exclusion chromatography and 1H NMR spectroscopy. Polarimetry measurements were used to determine the specific optical rotations of these systems. The structural and compositional characteristics of micellar nanostructures possessing an optically active core generated by p((S)-(+)-MBuMA)-b-p(DMAEMA) chains characterized by predetermined molecular characteristics may be easily tuned to match biological constructs. Consequently, the aggregation behavior of the p[(S)-(+)-MBuMA]-b-p[DMAEMA] diblock copolymers was investigated in aqueous media by means of dynamic light scattering and atomic force microscopy, which revealed the formation of micelles in neutral and acidified aqueous solutions. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Nanopatterned Protein Films Directed by Ionic Complexation with Water-Soluble Diblock Copolymers.

The use of ionic interactions to direct both protein templating and block copolymer self-assembly into nanopatterned films with only aqueous processing conditions is demonstrated using block copolymers containing both thermally responsive and pH responsive blocks. Controlled reversible addition-fragmentation chain-transfer (RAFT) polymerization is employed to synthesize poly(N-isopropylacrylamide-b-2-(dimethylamino)ethyl acrylate) (PNIPAM-b-PDMAEA) diblock copolymers. The pH-dependent ionic complexation between the fluorescent protein, mCherry, and the ionic PDMAEA block is established using dynamic light scattering (DLS) and UV-Vis spectroscopy. DLS shows that the size of the resulting coacervate micelles depends strongly on pH, while UV-Vis spectroscopy shows a correlation between the protein's absorption maximum and the ionic microenvironment. Zeta potential measurements clearly indicate the ionic nature of the complex-forming interactions. Spin casting was used to prepare nanostructured films from the protein-block copolymer coacervates. After film formation, the lower critical solution temperature (LCST) of the PNIPAM blocks allows the nanomaterial to be effectively immobilized in aqueous environments at physiological temperatures, enabling potential use as a controlled protein release material or polymer matrix for protein immobilization. At pH 9.2 and 7.8, the release rates are at least 10 times faster than that at pH 6.4 due to weaker interaction between protein and PNIPAM-b-PDMAEA (PND) diblock copolymer. Due to the ionic environment in which protein is confined, the majority of the protein (80%) remains active, independent of pH, even after having been dehydrated in vacuum and confined in the films.

Click Coupling Fullerene onto Thermoresponsive Water-Soluble Diblock Copolymer and Homopolymer Chains at Defined Positions

We report on the synthesis of well-defined thermoresponsive water-soluble diblock copolymer and homopolymers functionalized with controlled numbers of C60 moieties at predetermined positions via the combination of atom transfer radical polymerization (ATRP) and click chemistry. Azide-containing polymer precursors including monoazide-terminated and α,α-diazide-terminated poly(N-isopropylacrylamide), N3- PNIPAM and (N3)2-PNIPAM, as well as poly(ethylene glycol)-b-PNIPAM with one azide moiety at the diblock junction, PEG(-N3)-b-PNIPAM, were synthesized via ATRP using specific azide-functionalized small molecule and polymeric initiators. On the other hand, the reaction of 4-prop-2-ynyloxybenzaldehyde with pristine C60 in the presence of glycine afforded alkynyl-modified C60, alkynyl-C60. Subsequently, the click reaction of N3-PNIPAM, (N3)2-PNIPAM, and PEG(-N3)-b-PNIPAM led to the facile preparation of thermoresponsive diblock copolymer and homopolymers functionalized with controlled numbers of C60 at designed positions, including C60-PNIPAM, (C60)2-PNIPAM, and PEG(-C60)-b-PNIPAM. All the intermediate and final products were characterized by 1H NMR, Fourier transform infrared spectroscopy (FT-IR), UV−vis spectroscopy, thermogravimetric analysis (TGA), and gel permeation chromatograph (GPC) equipped with UV/RI dual detectors. C60-containing hybrid nanoparticles were then fabricated via supramolecular self-assembly of C60-PNIPAM, (C60)2-PNIPAM, and PEG(-C60)-b-PNIPAM in aqueous solution, which were characterized by dynamic and static laser light scattering (LLS) and transmission electron microscopy (TEM). These novel fullerenated polymers retain the thermoresponsiveness of PNIPAM-based precursors, and self-assembled hybrid nanoparticles exhibit thermo-induced collapse/aggregation behavior due to the lower critical solution temperature (LCST) phase transition of PNIPAM chains.

Synthesis, characterization and self-assembly behavior in water as fluorescent sensors of cationic water-soluble conjugated polyfluorene-b-poly(N-isopropylacrylamide) diblock copolymers

A series of well-defined novel water-soluble diblock copolymers containing conjugated amino-terminal polyfluorene (PF) block and coil-like poly(N-isopropylacrylamide) (PNIPAM) have been successfully synthesized through atom transfer radical polymerization (ATRP) initiated by a 2-bromoisobutyrate end-capped PF macroinitiator using CuCl/HMTETA (1,1,4,7,10,10-hexamethyltriethylenetetramine) as the catalyst. The first-order kinetic plots indicate the presence of a constant number of active species during the polymerization. The molecular weight and molecular weight distribution can be well controlled, implying synthesis of well-defined block structures of the copolymers. The chemical structures of block copolymers have been characterized by 1H NMR, UV–vis, and photoluminescence (PL) spectra. PF aggregates are formed in water with the increase of temperature for the conjugated-ionic diblock copolymer synthesized, as confirmed by dynamic light scattering (DLS). The formation of excimers within the PF aggregates results in improved Förster resonance energy transfer (FRET) efficiencies.

Micelles and ‘reverse micelles’ with a novel water-soluble diblock copolymer

A series of poly[2-(diisopropylamino)ethyl methacrylate]-block-poly[2-(N-morpholino)ethyl methacrylate], [PDPA-b-PMEMA], have been synthesized by using group transfer polymerization. These novel PDPA-b-PMEMA diblock copolymers dissolved molecularly in aqueous solution at low pH (<6.0) due to the protonation of all tertiary amine residues of both blocks and formed PDPA-core micelles at pH 7.5 by PMEMA block forming the micelle coronas. On the other hand, it was also observed that these diblock copolymers formed near-monodisperse ‘reverse micelles’, PMEMA-core micelles, in n-alkanes with or without requiring cosolvent depending on comonomer ratios. Dynamic light scattering studies indicated monodisperse or near-monodisperse micelles in both cases. The intensity-average radii of the PDPA-core and the PMEMA-core micelles were between 10nm and 17nm (polydispersity index, μ2/Γ2<0.08) and between 10nm and 13nm in n-hexane (μ2/Γ2<0.09), respectively.

Double‐Faced Micelles from Water‐Soluble Polymers

Asymmetric disk-shaped Janus micelles form spontaneously and reversibly when simple water-soluble diblock copolymers in aqueous solutions are mixed. The combination of associative and segregative phase separation within one nanostructure results in a disk-shaped micelle with a complex coacervate core and an asymmetric water-swollen corona which is microphase-separated into two distinct domains or faces.

Heck and Suzuki coupling reactions in water using poly(2-oxazoline)s functionalized with palladium carbene complexes as soluble, amphiphilic polymer supports

This paper describes the application of a novel class of amphiphilic, water-soluble diblock copolymers based on 2-oxazoline derivatives with pendant N-heterocyclic carbene/palladium catalysts in the hydrophobic block for Heck and Suzuki coupling in neat water. Heck coupling reaction of iodobenzene with styrene proceeded rapidly after optimization of various reaction parameters such as the base, the reaction temperature and the catalyst amount. High activities with turn over frequencies ( TOF) of up to 2700 h −1 were observed at 110 °C. Furthermore, the Suzuki coupling reaction of phenylboronic acid was studied in detail with different haloarenes (iodobenzene and various bromoarenes). The observed catalytic activity is even higher and TOF numbers of up to 5200 h −1 were achieved at 80 °C. Therefore, the presented micellar catalytic system reveals turn over frequencies which are the highest ever reported for such transformations in neat water without the addition of an organic cosolvent.

Photochemical and Thermal Isomerizations of Azobenzene-Containing Amphiphilic Diblock Copolymers in Aqueous Micellar Aggregates and in Film

Homopolymers of azobenzene methacrylates (azo) and their diblock copolymers with 2-(dimethylamino)ethyl metharylate (DMAEMA) were synthesized via atom transfer radical polymerization (ATRP). Polymers of cyano- and butoxy-substituted azobenzenes exhibited liquid crystalline textures. Water-soluble diblock copolymers could be obtained with a long DMAEMA block and a short azo block. These diblock copolymers self-assembled into polymeric micelles with core−shell structure in aqueous solutions. The rates of trans−cis photoisomerization were almost the same for the DMAEMA copolymers of 6-[4-phenylazo]phenoxy]hexyl methacrylate (PPHM), p(DMAEMA172-b-PPHM9), and 6-[4-(4-cyanophenylazo)phenoxy]hexyl methacrylate (CPHM), p(DMAEMA172-b-CPHM7), whereas slightly slower rates were observed for the copolymer of 6-[4-(4-butoxyphenylazo)phenoxy]hexyl methacrylate (BPHM), p(DMAEMA172-b-BPHM7), most likely due to steric hindrance presented by the bulky butoxy group. The rates in aqueous micellar solutions were only marginally faster than those in films for all the three diblock copolymers. In contrast, marked rate differences for the thermal cis−trans isomerization of p(DMAEMA172-b-CPHM7) were observed in film and in solution due to the donor−acceptor effect of CPHM. The observation of a sizable rate difference in different environment for p(DMAEMA172-b-CPHM7) suggests that a rotational mechanism might be operative for these water-soluble amphiphilic diblock copolymers.

Poly(2-oxazoline)s Functionalized with Palladium Carbene Complexes: Soluble, Amphiphilic Polymer Supports for C−C Coupling Reactions in Water

This paper describes the synthesis and characterization of a new class of amphiphilic, water-soluble diblock copolymers based on 2-oxazoline derivatives with pendent N-heterocyclic carbene/palladium catalysts in the hydrophobic block. The synthetic strategy involves a four-step synthesis of three functionalized monomers, each composed of a bis(imidazoline-2-ylidene)palladium(II) diiodide derivative that is covalently linked to a 2-oxazoline monomer via a flexible alkyl spacer (alkyl = butyl, hexyl, octyl). The structure of the monomers was analyzed by 1H and 13C NMR spectroscopy, MALDI-TOF, and elemental analysis. Three diblock copolymers P1−P3 with the monomers being part of the hydrophobic block were prepared by living cationic ring-opening polymerization. The structure and composition of the polymers was characterized by 1H and 13C NMR spectroscopy as well as GPC measurements and indicated rather low PDI of 1.3 and about 65% incorporation of the N-heterocyclic carbene/palladium-functionalized monomer i...

Heat-Induced Association and Dissociation Behavior of Amphiphilic Diblock Copolymers Synthesized via Reversible Addition−Fragmentation Chain Transfer Radical Polymerization

A water-soluble diblock copolymer was prepared from sodium 2-(acrylamido)-2-methylpropanesulfonate (NaAMPS) and N-isopropylacrylamide (NIPAM) via reversible addition−fragmentation chain transfer (RAFT) controlled radical polymerization. The RAFT “living” radical polymerization process of NIPAM using an NaAMPS-based macrochain transfer agent was confirmed by the fact that the number-average molecular weight increased linearly with monomer consumption while the molecular weight distribution remained to be narrow for the polymerization. The NIPAM block exhibited a lower critical solution temperature (LCST) in water. Both the NaAMPS and NIPAM blocks are soluble in water at room temperature. At temperatures above the LCST, the NIPAM blocks associated into a polymer aggregate. The polymer aggregate was assumed to be an elongated micelle or a multiple aggregate due to intermicellar association of the spherical core−corona micelles based on characterization data obtained from 1H NMR, turbidity, light scattering, ...

Scattering Measurements for High Throughput Materials Science Research

AbstractSummary: We present a high throughput X‐ray scattering study (SAXS/WAXS) of the formation and stability of the vesicle phase of a water soluble diblock copolymer. The vesicle shape and shell thickness were investigated as a function of block copolymer concentration and temperature. We were able to establish a growth in the SAXS peak as concentration increased, indicating a greater polymer concentration of vesicles. The effect of temperature was also investigated.Library sample of a discrete concentration gradient of EO(6)BO(11) in water.magnified imageLibrary sample of a discrete concentration gradient of EO(6)BO(11) in water.

Amphiphilic polymer supports for the asymmetric hydrogenation of amino acid precursors in water.

This paper describes the synthesis and characterization of a new class of amphiphilic, water-soluble diblock copolymers based on 2oxazoline derivatives with pendent (2S,4S)-4-diphenylphosphino-2-(diphenylphosphinomethyl)pyrrolidine (PPM) units in the hydrophobic block. The synthetic strategy involves the preparation of a diblock copolymer precursor with ester functionalities in the side chain; which were converted into carboxylic acids in a polymer-analogous step and finally reacted with the PPM ligand. The structures of the copolymers were characterized by (1)H and (31)P NMR spectroscopy and GPC measurements. Subsequently, these polymers were successfully utilized as a polymeric support for the asymmetric hydrogenation of 1) (Z)-alpha-acetamido cinnamic acid and 2) methyl (Z)-alpha-acetamido cinnamate in water, showing 90 % substrate conversion at 25 degrees C within 20 minutes at atmospheric H(2) pressure (1 bar) for methyl (Z)-alpha-acetamido cinnamate.

Capillary electrophoresis of associative diblock copolymers

Water soluble diblock copolymers composed of a long poly(styrene sulfonate) chain (between 200 and 400 monomers) and a short poly(ethylene propylene) or poly( tert.-butylstyrene) hydrophobic end (20–50 monomers) are highly associative and form micelles in aqueous solution. The micelles are composed of a small hydrophobic core and a polyelectrolyte corona, the dimensions of which can be estimated by neutron and light scattering. These physical techniques are, however, not amenable to discriminate easily between the free copolymer and the copolymer micelle. Capillary electrophoresis was implemented in this work as a new and effective tool to investigate the behaviour of such associative copolymer systems. Since the rate of exchange between the micellised and free states is very slow in comparison with the time scale of the electrophoretic process, the electropherograms of the diblock copolymers obtained in plain aqueous borate buffers exhibit two peaks assigned to the two states mentioned above. The identification of the two peaks was first made on the basis of the retention orders of the two peaks equally obtained in similar conditions by size-exclusion chromatography. The copolymer micelles appeared to have a smaller electrophoretic mobility than the free copolymers. This peak assignment is also consistent with the observed ratio of the time-corrected peak areas and peak dispersions. The effects of the copolymer concentration, electric field, temperature and hydroorganic composition of the medium was also studied. Such systems do not exhibit a defined concentration threshold equivalent to a classical critical micelle concentration. Adding methanol to the electrolyte resulted in the progressive loss of baseline return between the two peaks, which might be attributed to a slight increase in the rate of exchange between the two states. Finally, adding a neutral surfactant to the electrolyte at a concentration in excess of its critical micelle concentration resulted in a decrease in the electrophoretic mobility of the peak attributed to the free copoplymer, while the electrophoretic mobility of the copolymer micelle remained unperturbed.

Direct synthesis of novel acidic and zwitterionic block copolymers via TEMPO-mediated living free-radical polymerization

A series of novel acidic and zwitterionic water-soluble diblock copolymers has been synthesized directly (i.e. without protecting group chemistry) via the TEMPO-mediated living free-radical polymerization of various hydrophilic styrenic monomers. In all syntheses TEMPO-capped poly(sodium 4-styrenesulfonate) was utilized as a well-defined macro-initiator. Chain extension of this macro-initiator with 2-vinylpyridine proved very inefficient. Using 4-vinylbenzyltrimethylammonium chloride as comonomer led to an insoluble zwitterionic complex, whereas water-soluble zwitterionic block copolymers were obtained with 4-(dimethylamino)methylstyrene. Micellar solutions were obtained with the less hydrophilic 4-vinylbenzyl alcohol comonomer. A series of strong acid–weak acid block copolymers with varying sodium 4-styrene-sulfonate contents (20–80mol%) were prepared via chain extension of the macro-initiator using sodium 4-styrenecarboxylate. These acidic block copolymers undergo reversible pH-induced aggregation in aqueous solution and 13C n.m.r. spectroscopy studies suggest that the carboxylic acid block forms the hydrophobic micellar core. Dynamic light scattering studies indicate intensity-average micelle diameters of 20–60nm.

Synthesis of Controlled Structure Water-Soluble Diblock Copolymers via Oxyanionic Polymerization

Synthesis of Controlled Structure Water-Soluble Diblock Copolymers via Oxyanionic Polymerization

Synthesis and Aqueous Solution Properties of Amphiphilic Diblock Copolymers Based on Methyl Triethylene Glycol Vinyl Ether and Benzyl Vinyl Ether

Water-soluble diblock copolymers of methyl triethylene glycol vinyl ether and benzyl vinyl ether were synthesized by living cationic polymerization, giving molecular weights in the range 13 400−17 300 and narrow molecular weight distributions (Mw/Mn = 1.18−1.28). The MTEGVE block length was fixed at 56 monomer units and the BzVE block length varied from 6 to 56 units. Aqueous solutions were studied by using dynamic light scattering and turbidimetry to determine the effect of block ratio on micellization and precipitation. Dynamic light scattering at room temperature in water revealed two intensity-average populations for all the copolymers, assigned as well-defined micelles and large aggregates. The hydrodynamic radii of the micelles ranged from 10.2 to 26.2 nm. Turbidimetry showed a cloud point of 83.5 °C for the MTEGVE homopolymer. The cloud points of the block copolymers decreased with increasing BzVE content and leveled off at higher BzVE contents. Selective removal of the benzyl group was achieved by catalytic hydrogenolysis, as a route to block copolymers with poly(vinyl alcohol) sequences. The maximum extent of deprotection was only 88%. Incomplete deprotection was attributed to the adsorption of the MTEGVE block onto the carbon support, thus blocking the catalyst sites.

Synthesis and characterization of amphiphilic diblock copolymers of methyl tri(ethylene glycol) vinyl ether and isobutyl vinyl ether

Water-soluble diblock copolymers of methyl tri(ethylene glycol) vinyl ether (hydrophilic block) and isobutyl vinyl ether (hydrophobic block) of different molecular weights and composition were synthesized by living cationic polymerization. The molecular weight and comonomer composition of these copolymers were determined by GPC and 1H NMR spectroscopy, respectively. Aqueous solutions of the copolymers were characterized in terms of their micellar behavior using dynamic light scattering, aqueous GPC, and dye solubilization. All the copolymers formed aggregates with the exception of a diblock copolymer with only two hydrophobic monomer units. The micellar hydrodynamic size scaled with the 0.61 power of the number of hydrophobic units, in good agreement with a theoretical exponent of 0.73. An increase in the length of the hydrophobic block at constant hydrophilic block length or an increase in the overall polymer size at constant block length ratio both resulted in lower critical micelle concentrations (cmcs). The cloud points of 1% w/w aqueous solutions of the polymers were determined by turbidimetry. An increase in the length of the hydrophobic block at constant hydrophilic block length caused a decrease in the cloud points of the copolymers. However, an increase in the overall polymer size at constant block length ratio led to an increase in the cloud point. © 1996 John Wiley & Sons, Inc.

Synthesis and Solution Properties of Water-Soluble Hydrophilic−Hydrophobic Block Copolymers

A series of water-soluble diblock copolymers containing 2-(dimethylamino)ethyl methacrylate and various alkyl methacrylates has been synthesized using group transfer polymerization. These hydrophilic−hydrophobic copolymers have been characterized with respect to chemical composition and molecular weight by NMR spectroscopy, elemental microanalyses, and gel permeation chromatography. Block copolymers containing methyl methacrylate as the hydrophobic component were water-soluble provided that the hydrophilic monomer content was greater than 60 mol % of the overall block copolymer. Quaternization of the DMAEMA block with methyl iodide was near-quantitative and considerably enhanced the water-solubility of the copolymers. NMR studies, surface tension measurements, and photon correlation spectroscopy all indicated that the PDMAEMA-b-MMA block copolymers form micelles in deionized water. However, in acidic solution (pH 2), copolymer micellization occurred only in the presence of added electrolyte. The block cop...