PMAA Block Research Articles

Coacervation in Slow Motion: Kinetics of Complex Micelle Formation Induced by the Hydrolysis of an Antibiotic Prodrug.

Colistin methanesulfonate (CMS) is the less-toxic prodrug of highly nephrotoxic colistin. To develop and understand highly necessary new antibiotic formulations, the hydrolysis of CMS to colistin must be better understood. Herein, with the addition of poly(ethylene oxide)-b-poly(methacrylic acid) (PEO-b-PMAA) to CMS, we show that we can follow the hydrolysis kinetics, employing small-angle X-ray scattering (SAXS) through complex coacervation. During this hydrolysis, hydroxy methanesulfonate (HMS) groups from CMS are cleaved, while the newly formed cationic amino groups complex with the anionic charge from the PMAA block. As the hydrolysis of HMS groups is slow, we can follow the complex coacervation process by the gradual formation of complex micelles containing activated antibiotics. Combining mass spectrometry (MS) with SAXS, we quantify the hydrolysis as a function of pH. Upon modeling the kinetic pathways, we found that complexation only happens after complete hydrolysis into colistin and that the process is accelerated under acidic conditions. At pH = 5.0, effective charge switching was identified as the slowest step in the CMS conversion, constituting the rate-limiting step in colistin formation.

Microwave-assisted synthesis of polyoxometalate-Dy2O3 monolayer nanosheets and nanotubes.

Two-dimensional (2D) materials have shown unique chemical and physical properties; however, their synthesis is highly dependent on the layered structure of building blocks. Herein, we developed monolayer Dy2O3-phosphomolybdic acid (PMA) nanosheets and nanotubes based on microwave synthesis. Microwave-assisted synthesis with high-energy input gives a faster and dynamically driven growth of nanomaterials, resulting in high-purity nanostructures with a narrow size distribution. The reaction times of the nanosheets and nanotubes under microwave synthesis are significantly reduced compared with oven-synthesis. Dy2O3-PMA nanosheets and nanotubes exhibit enhanced activity and stability in photoconductance, with higher sensitivities (0.308 μA cm-2 for nanosheets and 0.271 μA cm-2 for nanotubes) compared to the individual PMA (0.12 μA cm-2) and Dy2O3 (0.025 μA cm-2) building blocks. This work demonstrates the promising application potential of microwave-synthesized 2D heterostructures in superconductors and photoelectronic devices.

PH-responsive intermediary layer cross-linked micelles from zwitterionic triblock copolymers and investigation of their drug-release behaviors.

ABC-type triblock copolymers, namely poly[(ethylene glycol)methyl ether]-block-poly(tert-butyl methacrylate)-block-poly[2-N-(diisopropylamino)ethyl methacrylate] (MPEG-b-PBuMA-b-PDPA), were first synthesized and then the middle blocks were successfully converted into poly(methacrylic acid) to obtain MPEG-b-PMAA-b-PDPA zwitterionic triblock copolymers. These block copolymers were soluble in water and formed micellar aggregates with complex cores via hydrogen bonding interactions between MPEG and PMAA blocks below pH 4.0. When the pH was between 5.0 and 7.0, due to charge compensation between partially protonated PDPA and partially ionized PMAA blocks, micelles with polyion complex cores were observed. If the solution pH was above 8.0, deprotonation of tertiary amine groups provided a hydrophobic character to the PDPA block, which resulted in the formation of PDPA-core micelles while MPEG/anionic PMAA hybrid blocks formed hydrated coronas. Intermediary layer cross-linked (ILCL) micelles from PDPA-core micelles were also prepared by cross-linking the inner PMAA shell. The hydrophobic drug dipyridamole (DIP) was used to investigate the release profile of ILCL micelles. DIP can be loaded to the PDPA cores of the micelles in basic aqueous media. An increase in the degree of cross-linking causes slower release for the model drug. It was concluded that the more complex matrix formation in the intermediary layer of the micelles via cross-linking retards the drug release from the core.

Morphology Control of Multicompartment Micelles in Water through Hierarchical Self-Assembly of Amphiphilic Terpolymers

Multicompartment micelles (MCMs) allow the simultaneous storage of multiple cargoes such as dyes, catalysts, or drugs, and have therefore gained attention in catalysis, nanotechnology, and nanomedicine. In the present work, we describe design rules to control the morphology of MCMs in water including spheres, cylinders, sheets, and vesicles. For that, we synthesized a series of poly(ethylene oxide) (PEO)-b-polystyrene (PS)-b-poly(methyl acrylate) (PMA) triblock terpolymers and systematically varied the length of the PS and PMA block. Using a stepwise hierarchical assembly process, we first form patchy precursor micelles in organic solvent with PS core and mixed PEO/PMA corona. In the second step, these micelles act as subunits, which assemble (or cluster) in water into MCMs, where PEO forms the stabilizing corona, PS the compartment, and PMA the inner core. We find that the shape of the final MCM can be predicted by ascribing a Janus balance to precursor micelles as the molar ratio of PEO to PMA, which provides a synthetic handle to target specific MCM morphologies.

Application of poly(amidoamine) dendrimer as transfer agent to synthesize poly(amidoamine)-b-poly(methyl acrylate) amphiphilc block copolymers: Self-assembly in aqueous media and drug delivery

Herein, second generation cystamine-cored poly(amidoamine) (PAMAM) dendrimer has been synthesized and used as transfer agent in atom transfer radical polymerization (ATRP) of poly(methyl acrylate) (PMA). Transfer reaction to dendrimer has been resulted in synthesis of PAMAM-b-PMA block copolymers with different degree of polymerization of PMA block. Synthesized block copolymers have been self-assembled in aqueous media to prepare cubic/hexagonal and spherical supramolecular structures with nanoscale particle size. Finally, the behavior of drug release from supramolecular structures as nanocarriers of the anticancer drug, doxorubicin (DOX), has been investigated under different conditions. Results showed that in block copolymers with shorter length of hydrophobic block, drug loading capacity was increased due to predominant interactions between dendrimer and drug molecules. Higher hydrophobic block length led to higher cumulative release of drug due to presence of hydrophobic interactions between PMA block and DOX molecules. Moreover, nanocarriers showed significant drug release in acidic media whereas no remarkable release was observed at pH = 7.4.

Temperature-induced self-assembly of amphiphilic triblock terpolymers to low cytotoxic spherical and cubic structures as curcumin carriers

In this study, self-assembly of amphiphilic thermo- and UV-sensitive block terpolymers, namely poly (methyl acrylate-b-[(7-(allyloxy)-2H-chromen-2-one)-co-(2-hydroxyethyl methacrylate(]-b-N-vinylpyrrolidone) P (MA-b-[AC-co-HEMA]-b-NVP) in water at different temperatures is studied. The synthesis of terpolymers, in three various block length for hydrophobic PMA block, is carried out by atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain-transfer (RAFT)/macromolecular design by interchange of xanthate (MADIX) polymerization. Three different critical micelle temperatures (CMT) of terpolymers are calculated via UV-VIS-NIR absorptions at 600 nm. Results of self-assembly behavior of terpolymers under CMT showed spherical micelle aggregation whereas cubic-like particles with larger particle size were self-assembled at the temperatures above CMT because of second aggregation phenomena. Additionally, UV light irradiation is used to photo-crosslinking of particles owing to presence of photo-responsive coumarin derivative of AC in the middle block. The self-assembled structures are loaded with curcumin (Cur) before and after photo-crosslinking and Cur-release behavior is investigated at different temperatures of 37 and 25 °C. Drug-release behavior of samples illustrated that cumulative Cur-release above the CMT of terpolymers is higher than under CMT due to squeezing of PVP coronas and expelling of drug molecules to outside. Moreover, cumulative release of photo-crosslinked self-assembled structures was lower than before crosslinking. The cytotoxicity of terpolymers and Cur-loaded micelles was examined through culturing on the MG-63 cells which showed high cell viability after 48 h.

Preparation of giant vesicles containing quaternary ammonium salt of 2-(dimethylamino)ethyl methacrylate through photo nitroxide-mediated controlled/living radical polymerization-induced self-assembly

Giant vesicles containing 2-(dimethylamino)ethyl methacrylate (DMAEMA) and its quaternary ammonium salt in the hydrophobic cores or hydrophilic shells composed of poly(methacrylic acid)-block-poly(methyl methacrylate-random-methacrylic acid), PMAA-b-P(MMA-r-MAA), were prepared using the photo nitroxide-mediated controlled/living radical polymerization (photo NMP). The photo NMP of DMAEMA and its quaternary ammonium salt with trifluoroacetic acid was confirmed to have the living nature based on the gel permeation chromatography analysis. The photo NMP was performed for the block copolymerization of methyl methacrylate (MMA), methacrylic acid (MAA), and DMAEMA or its quaternary salt using PMAA end-capped with 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl in an aqueous methanol solution. The photo NMP-induced self-assembly of the amphiphilic diblock copolymer produced spherical vesicles. The vesicles with DMAEMA in the hydrophobic phases of the P(MMA-r-MAA) block were unstable and had many holes in the surface, while those with the quaternized DMAEMA were stable and had much smaller size. An increase in the quaternized DMAEMA in the hydrophobic block transformed the vesicles into unstable and larger spherical vesicles, and finally into stratiform sheet. On the other hand, the incorporation of the quaternized DMAEMA into the hydrophilic shells of the PMAA block reduced the size of the spherical vesicles and retained the vesicle structure against an increase in the hydrophilicity of the hydrophobic P(MMA-r-MAA) block.

Molecular Tailoring of Poly(styrene-b-methyl methacrylate) Block Copolymer Toward Perpendicularly Oriented Nanodomains with Sub-10 nm Features.

We demonstrate a novel approach for fabricating vertically orientated, sub-10 nm, block copolymer (BCP) nanodomains on a substrate via molecular tailoring of poly(styrene-b-methyl methacrylate) (PS-b-PMMA) BCP, one of the most widely used BCPs for nanopatterning. The idea is to incorporate a short middle block of self-attracting poly(methacrylic acid) (PMAA) between the PS and PMMA blocks, where the PMAA middle block promotes phase separation between PS and PMMA, while maintaining the domain orientation perpendicular to the substrate. The designed PS-b-PMAA-b-PMMA triblock copolymers, which were synthesized via well-controlled anionic polymerization, exhibited order-disorder transition temperatures higher than that of pristine PS-b-PMMA BCPs, indicating the promotion of phase separation by the middle PMAA block. For PS-b-PMAA-b-PMMA BCPs with total molecular weights of 21 and 18 kg/mol, the domain spacing corresponds to 19.3 and 16.7 nm, respectively, allowing us to fabricate sub-10 nm nanodomain structures. More importantly, it was demonstrated that the PMAA middle block, which has a higher surface energy than PS and PMMA, does not significantly alter lateral concentration fluctuations, which are responsible for phase-separation in the lateral direction. This enabled the vertical orientation of microdomains with sub-10 nm feature size on a PS-r-PMMA neutral surface without an additional neutral top layer. We anticipate that this approach provides an important platform for next-generation lithography and nanopatterning applications that require sub-10 nm features over large areas with simple process and reduced cost.

Synthesis of sharply thermo and PH responsive PMA-b-PNIPAM-b-PEG-b-PNIPAM-b-PMA by RAFT radical polymerization and its schizophrenic micellization in aqueous solutions

Sharply thermo- and pH-responsive pentablock terpolymer with a core-shell-corona structure was prepared by RAFT polymerization of N-isopropylacrylamide and methacrylic acid monomers using PEG-based benzoate-type of RAFT agent. The PEG-based RAFT agent could be easily synthesized by dihydroxyl-capped PEG with 4-cyano-4-(thiobenzoyl) sulfanylpentanoic acids, using esterification reaction. This pentablock terpolymer was characterized by 1H NMR, FT-IR, and GPC. The PDI was obtained by GPC, indicating that the molecular weight distribution was narrow and the polymerization was well controlled. The thermo- and pH-responsive micellization of the pentablock terpolymer in aqueous solution was investigated using fluorescence spectroscopy technique, UV–vis transmittance, and TEM. The LCST of pentablock terpolymer increased (over 50 °C) compared to the NIPAM homopolymer (~32 °C), due to the incorporation of the hydrophilic PEG and PMA blocks in pentablock terpolymer (PNIPAM block as the core, PEG the block and the hydrophilic PMA block as the shell and the corona). Also, pH-dependent phase transition behavior shows at a pH value of about ~5.8, according to pKa of MAA. Thus, in acidic solution at room temperature, the pentablock terpolymer self-assembled to form core–shell–corona micelles, with the hydrophobic PMA block as the core, the PNIPAM block and the hydrophilic PEG block as the shell and the corona, respectively.

Morphological changes in giant vesicles comprised of amphiphilic block copolymers by incorporation of ionic segments into the hydrophilic block chain

AbstractThe morphological changes in giant spherical vesicles comprised of amphilhilic poly(methacrylic acid)-block-poly(methyl methacrylate-random-methacrylic acid), PMAA-b-P(MMA-r-MAA), by incorporation of the 3-sulfopropyl methacrylate potassium salt (SpMA) into the hydrophilic PMAA block chains were investigated. The vesicles were reduced in size as the SpMA ratio increased due to the variation in the critical packing shape by the expansion of the hydrophilic surface area by the incorporation of the more hydrophilic ionic segments. The increase in the SpMA ratio also delayed the transition from the spherical vesicles to a film-like bilayer. The giant vesicles containing the SpMA segments were disrupted into a nonspecific form by the electrostatic interaction with poly(allylamine hydrochloride) at a 2.5 M ratio of the unit for the allylamine hydrochloride (AH) to the SpMA. A large excess of the AH/SpMA above 5.0 caused no disruption, but partial fusion of the vesicles accompanied by a decrease in size.

Polymer brushes modified by photosensitive azobenzene containing polyamines

Abstract This paper describes a strategy for preparing photosensitive polymeric grafts on flat solid surfaces by loading diblock-copolymer or homopolymer brushes with cationic azobenzene-containing surfactants. In contrast to previous work, we utilize photosensitive surfactants that bear positively-charged polyamine head groups whose charge varies between 1+ and 3+. Poly(methylmethacrylate-b-methacrylic acid) (PMMA-b-PMAA) brushes were prepared by employing atom transfer radical polymerization, where the bottom poly(methyl methacrylate) block was grown first followed by the synthesis of t-butyl methacrylate block that after de-protection yielded poly(methacrylic acid). We used PMMA-b-PMAA brushes with constant grafting density and length of the PMMA block, and three different lengths of the PMAA block. The azobenzene-based surfactants attached only to the PMAA block. The degree of binding (i.e., the number of surfactant molecules per binding site on the brush backbone) of the surfactants to the brush depends strongly on the valence of the surfactant head-group; within the brushes the concentration of the surfactant carrying unit charge is larger than that of multivalent surfactants. We detect pronounced response of the brush topography on irradiation with UV interference pattern even at very low degree of binding (as small as 0.08) of multi-valence surfactant. Areas on the sample that receive the highest UV dose exhibit chain scission. By removing the ruptured chains from the substrate via good solvent, one uncovers a surface topographical relief grating, whose spatial arrangement follows the intensity distribution of the UV light on the sample during irradiation. Due to strong coupling of the multi-valence surfactants to the polymer brush, it was possible in some cases to completely remove the polyelectrolyte block from the PMMA layer. The application of multi-valence azobenzene surfactants for triggering brush photosensitive has important advantage over usage of surfactant with unit charge because relative to single-valence surfactants much lower concentrations of the multivalent surfactant are needed to achieve comparable response upon UV irradiation.

Fabrication of MPEG-b-PMAA capped YVO4:Eu nanoparticles with biocompatibility for cell imaging

A novel nanoparticle with multilayer core–shell architecture for cell imaging is designed and synthesized by coating a fluorescent YVO4:Eu core with a diblock copolymer, MPEG-b-PMAA. The synthesis of YVO4:Eu core, which further makes MPEG-b-PMAA-YVO4:Eu NPs adapt for cell imaging, is guided by the model determined upon the evaluation of pH and CEu%. The PMAA block attached tightly on the YVO4:Eu core forms the inner shell and the MPEG block forms the biocompatible outermost shell. Factors including reaction time, reaction temperature, CEu% and pH are optimized for the preparation of the YVO4:Eu NPs. A precise defined model is established according to analyzing the coefficients of pH and CEu% during the synthesis. The MPEG-b-PMAA-YVO4:Eu NPs, with an average diameter of 24nm, have a tetragonal structure and demonstrate luminescence in the red region, which lies in a biological window (optical imaging). Significant enhancement in luminescence intensity by MPEG-b-PMAA-YVO4:Eu NPs formation is observed. The capping copolymer MPEG-b-PMAA improves the dispersibility of hydrophobic YVO4:Eu NPs in water, making the NPs stable under different conditions. In addition, the biocompatibility MPEG layer reduces the cytotoxicity of the nanoparticles effectively. 95% cell viability can be achieved at the NPs concentration of 800mgL−1 after 24h of culture. Cellular uptake of the MPEG-b-PMAA-YVO4:Eu NPs is evaluated by cell imaging assay, indicating that the NPs can be taken up rapidly and largely by cancerous or non-cancerous cells through an endocytosis mechanism.

Giant vesicles comprised of mixed amphiphilic poly(methacrylic acid)-block-poly(methyl methacrylate-random-methacrylic acid) diblock copolymers

The morphological changes in giant vesicles were investigated using mixed amphiphilic diblock copolymers consisting of poly(methacrylic acid)-block-poly(methyl methacrylate-random-methacrylic acid), PMAA-b-P(MMA-r-MAA). The mixed copolymers had the identical length of the hydrophobic P(MMA-r-MAA) block and different lengths of the hydrophilic PMAA block; long-length PMAA (PMAA-L) was about three times longer than short-length PMAA (PMAA-S). Large contorted vesicles formed by the copolymer containing PMAA-S were transformed into various elliptical and spherical vesicles, followed by worm-like vesicles as the ratio of the PMAA-L-containing copolymer increased. It was found that the vesicular morphology of the mixed copolymers was determined by the average length of the PMAA blocks contained in the mixed copolymers based on the comparison with the spherical vesicles formed only by the copolymer containing the middle length of the PMAA block.

Cross-linking effect of hydrophobic cores on morphology of giant vesicles formed by amphiphilic random block copolymers

The cross-linking effect of the hydrophobic cores on the morphology of giant vesicles was explored using amphiphilic poly(methacrylic acid)-block-poly(methyl methacrylate-random-methacrylic acid), PMAA-b-P(MMA-r-MAA), and ethylene glycol dimethacrylate (EGMA) as the cross-linking agent. Spherical vesicles without cross-linking were transformed into large contorted vesicles with a rough surface by the cross-linking of the P(MMA-r-MAA) blocks with EGMA. An increase in the EGMA ratio promoted a further transformation into huge spherical particles with a smooth surface, followed by smaller partly joined particles. A still higher EGMA ratio caused the joining of particles along with a further decrease in the particle size. The cross-linking of the hydrophobic blocks also dominated the crystallization of the hydrophilic PMAA blocks. The thermal analysis demonstrated that the glass transition temperature of the PMAA blocks increased with the EGMA ratio for the identical PMAA block length. The crystallinity of the hydrophobic cores enhanced that of the hydrophilic surface.

Self-Assembled Structures of PMAA–PMMA Block Copolymers: Synthesis, Characterization, and Self-Consistent Field Computations

Block copolymers composed of methacrylic acid (MAA) and methyl methacrylate (MMA) blocks are interesting candidates for replacing surfactants in emulsion polymerization methods. Here the synthesis and experimental characterization of well-defined PMAA–PMMA block copolymers made via RAFT polymerization are reported. It is shown that these block copolymers self-organize in water into micellar spherical or cylindrical structures or into highly size disperse structures (probably vesicles) in aqueous salt solutions upon increasing the pH. The physical properties of the polymer dispersions depend on the self-organization morphology which is determined by the diblock copolymer PMAA and PMMA block lengths. The relation between diblock copolymer block lengths and the self-organized structures is rationalized using self-consistent field theory (SCFT). Theoretically predicted self-assembled structures of MAAx–MMAy block copolymers are compared with the results obtained from experiments. Size and morphology of the self-assembled structures are in good agreement with SCFT.

Morphology control of giant vesicles by composition of mixed amphiphilic random block copolymers of poly(methacrylic acid)-block-poly(methyl methacrylate-random-methacrylic acid)

The morphology of giant vesicles comprised of mixed amphiphilic poly(methacrylic acid)-block-poly(methyl methacrylate-random-methacrylic acid), PMAA-b-P(MMA-r-MAA), was effectively controlled by its composition. The mixed copolymers with different lengths of the hydrophilic PMAA blocks varied the morphology depending on the composition at a constant length of the hydrophobic P(MMA-r-MAA) block. Large contorted vesicles formed by the copolymer containing a short PMAA block (PMAA-S) were changed into more severely contorted vesicles, accompanied by the formation of much smaller spherical vesicles as the composition of the copolymer with a middle PMAA block (PMAA-M) increased. Spherical vesicles produced by the PMAA-M copolymer were transformed into worm-like vesicles, followed by key-shaped vesicles with the increasing composition of the copolymer with a long PMAA block (PMAA-L). Worm-like vesicles with an uneven surface formed by the PMAA-L copolymer were changed into various spherical and elliptical vesicles due to the coexistence of the PMAA-S copolymer.

One-pot synthesis of poly(methacrylic acid)-b-poly(2,2,2-trifluoroethyl methacrylate) diblock copolymers via RAFT polymerization

In this work, the reversible addition-fragmentation chain transfer (RAFT) polymerization was utilized to synthesize the amphiphilic diblock copolymers of poly(methacrylic acid)-b-poly(2,2,2-trifluoroethyl methacrylate) (PMAA-b-PTFEMA) via one-pot two-step reaction protocol. The controlled radical polymerization of MAA monomer was first carried out in pure water by using 4-cyanopentanoic acid dithiobenzoate (CADB) as chain transfer agent. Subsequently, the as-synthesized PMAA homopolymers with dithiobenzoate end-groups were employed as macro-CTA and chain-extended in situ with the hydrophobic TFEMA monomer. The reactions were carried out in 1,4-dioxane/water medium. Both the polymerization of PMAA and PTFEMA blocks showed the well controllability on the molecular weighs and distributions. It was found that the amphiphilic diblock copolymers formed the stable spherical particles via the polymerization-induced self-assembly. Meanwhile, the effect of various parameters, such as the concentration ratio of TFEMA monomer over PMAA macro-CTA, the solvent condition (different ratio of 1,4-dixane/water), and the pH, on the RAFT polymerization of TFEMA monomer were investigated in detail. Their kinetic results suggested that the propagation of TFEMA monomer on the macro-CTA was performed at the particle/water interfaces. The concentration of chain transfer agents at the interfaces determined the polymerization rate. Finally, the stability of the fluorinated polymer dispersions was also evaluated in this work.

Chain Length Effect of the Multidentate Block Copolymer Strategy to Stabilize Ultrasmall Fe3O4Nanoparticles

A multidentate block copolymer (MDBC) strategy to stabilize ultrasmall superparamagnetic iron oxide nanoparticles (USNPs) as biocompatible T1-positive contrast agents for magnetic resonance imaging (MRI) is explored. The MDBC is designed with a poly(methacrylic acid) (PMAA) block having pendant carboxylates as multidentate anchoring groups and a hydrophilic polymethacrylate block having pendant oligo(ethylene oxide) chains (POEOMA). A series of multifunctional MDBCs with different chain lengths of POEOMA and PMAA blocks were synthesized by atom transfer radical polymerization and subsequent hydrolytic cleavage. The resultant aqueous MDBC/USNP colloids fabricated through a ligand-exchange process were characterized to investigate the effect of chain lengths of POEOMA-b-PMAA copolymers on size, morphology, and colloidal stability as well as relaxometric properties and in vitro MRI performance. The results suggest that the optimal design of chain lengths of both anchoring and hydrophilic blocks is required for enhanced colloidal stability under biologically relevant conditions as well as effective T1-weighted contrast enhancement.

Lamellar Microdomains of Block-Copolymer-Based Ionic Supramolecules Exhibiting a Hierarchical Self-Assembly

Based on a parent diblock copolymer of poly(styrene)-b-poly(methacrylic acid), PS-b-PMAA, linear-b-amphiphilic comb (L-b-AC) ionic supramolecules [Soft Matter 2013, 9, 1540-1555] are synthesized in which the poly(methacrylate) backbone of the ionic supramolecular AC-block is neutralized by alkyl (Cn; n = 8, 12, and 16) trimethylammonium counterions (i.e., side chains) at various ion (pair) fractions X [i.e., counterion/side-chain grafting density; X = number of alkyl counterions (i.e., side chains) per acidic group of the parent PMAA block] these L-b-AC ionic supramolecules exhibit a spherical-in-lamellar hierarchical self-assembly. For these systems, (1) the effective Flory-Huggins interaction parameter between L- and AC-blocks chi'(Cn/x) was extracted, and (2) analysis of the lamellar microdomains showed that when there is an increase in X, alkyl counterion (i.e., side chain) length l(sc), or both, there is an increase in both the average interfacial area per block junction Sigma and the thickness of the microlayer of the AC-block d(Ac).

The effect of hydrophilic and hydrophobic block length on the rheology of amphiphilic diblock Polystyrene-b-Poly(sodium methacrylate) copolymers prepared by ATRP

Following our previous investigation on the effect of molecular architecture on the rheology of Polystyrene-b-Poly(sodium methacrylate) copolymers (PS-b-PMAA), we consider here diblock PS-b-PMAA copolymers characterized by a different length of either the hydrophilic or the hydrophobic block. Various copolymers characterized by different PS or PMAA block length have been prepared by ATRP (kinetics is also discussed) and studied from the point of view of their rheological behaviour in water. To the best of our knowledge, this is the first systematic investigation concerning the effect of block length on the rheology of diblock polyelectrolytes. We found that the hydrophobic block length has small influence on the rheology. Surprisingly, the polymers with shortest PMAA blocks yield the strongest gels at high concentration. A simple model based on the classical theories of self-assembly and percolation of amphiphilic polymers has been here developed in order to explain the observed data.