A systematic study of a polymer-assisted carboxylate-based MOF synthesis: multiple roles of core cross-linked PMAA-b-PMMA nanoparticles

Carboxylate-based metal organic frameworks (MOFs) coordinated by multiple-functional carboxylic acid linkers and various metals represent a large family of MOFs. Carboxylic acid functionalized polymers, such as poly(acrylic acid), polystyrene-b-(acrylic acid) and poly(methacrylic acid)-co-(ethylene glycol di-methacrylate), have been used in the synthesis of carboxylate-based MOFs in order to modulate, or provide a template for, the growth of MOF crystals. Although this strategy has been used to prepare MOFs, the role of the carboxylic acid functionalized (co)polymers in the synthesis of MOFs is still not very clear. In this article, we report the synthesis of UiO-66 (a MOF designed at the University of Oslo) in the presence of core cross-linked poly(methacrylic acid)-b-poly(methyl methacrylate) (PMAA-b-PMMA) nanoparticles (NPs), with two different modulators (acetic acid (HAc) and hydrochloric acid (HCl)) and in the absence of any modulator. Additionally, a series of reactions were carried out where the classical terephthalic acid (TA) linker was replaced with PMAA-b-PMMA NPs. These experiments elucidated the role of NPs in the polymer-assisted synthesis as well as how the PMAA-b-PMMA NPs become incorporated into the final UiO-polymer hybrid investigated material. In this polymer-assisted UiO-MOF synthesis, the PMAA-b-PMMA NPs act as a stabilizer, a template and a (co)modulator to form the final UiO-polymer hybrid NPs with different colloidal aspects, sizes and crystallinit

Fluorinated nanotubes : synthesis and self-assembly of cyclic peptide–poly(vinylidene fluoride) conjugates

The synthesis of cyclic peptide–poly(vinylidene fluoride) (CP–PVDF) conjugates comprising (D-alt-L)-cyclopeptides as building blocks and their self-assembly into tube-like structures is described. By growing two PVDF polymeric chains from opposite sides of a preassembled cyclic-peptide macro-chain transfer agent, a PVDF–CP–PVDF conjugate was prepared. This “grafting-from” strategy, allowed the synthesis of the conjugate with high purity and using facile purification steps. The controlled self-assembly of the conjugate from DMF or DMSO solutions was carried out by addition of THF. This triggered the aggregation process that led to formation of tube-like structures. The mean length and width of the PVDF–CP–PVDF tubes were measured using atomic force microscopy (AFM) and transmission electron microscopy (TEM). Surprisingly, the self-assembly of the CP–PVDF conjugates in DMF/THF allowed the preparation of long (up to 25 μm) tube-like structures. The formation of such long tubular peptide–polymer aggregates, based on the stacking of cyclopeptides, is unprecedented and is believed to rely on synergetic effects between the stacking of the cyclic peptide and the interactions of the fluoropolymer–peptide conjugates

Semi-crystalline diblock copolymer nano-objects prepared via RAFT alcoholic dispersion polymerization of stearyl methacrylate

The RAFT dispersion polymerization of stearyl methacrylate (SMA) is conducted in ethanol at 70 °C using a poly(2-(dimethylamino)ethyl methacrylate) [PDMA] chain transfer agent. The growing PSMA block becomes insoluble in ethanol, which leads to polymerization-induced self-assembly (PISA) and hence produces a range of copolymer morphologies depending on the precise PDMAy–PSMAx formulation. More specifically, pure phases corresponding to either spherical nanoparticles, worm-like nanoparticles or vesicles can be prepared as judged by transmission electron microscopy. However, the worm phase space is relatively narrow, so construction of a detailed phase diagram is required for reproducible syntheses of this morphology. Inter-digitation of the stearyl (C18) side-groups leads to a semi-crystalline PSMA core block and the effect of systematically varying the mean degree of polymerization of both the PDMA and PSMA blocks on the Tm and Tc is investigated using differential scanning calorimetry. Finally, it is demonstrated that these cationic nanoparticles can be employed as colloidal templates for the in situ deposition of silica from aqueous solution

Block copolymer-based magnetic mixed matrix membranes-effect of magnetic field on protein permeation and membrane fouling

In this study, we report the impact of the magnetic field on protein permeability through magnetic-responsive, block copolymer, nanocomposite membranes with hydrophilic and hydrophobic characters. The hydrophilic nanocomposite membranes were composed of spherical polymeric nanoparticles (NPs) synthesized through polymerization-induced self-assembly (PISA) with iron oxide NPs coated with quaternized poly(2-dimethylamino)ethyl methacrylate. The hydrophobic nanocomposite membranes were prepared via nonsolvent-induced phase separation (NIPS) containing poly (methacrylic acid) and meso-2, 3-dimercaptosuccinic acid-coated superparamagnetic nanoparticles (SPNPs). The permeation experiments were carried out using bovine serum albumin (BSA) as the model solute, in the absence of the magnetic field and under permanent and cyclic magnetic field conditions OFF/ON (strategy 1) and ON/OFF (strategy 2). It was observed that the magnetic field led to a lower reduction in the permeate fluxes of magnetic-responsive membranes during BSA permeation, regardless of the magnetic field strategy used, than that obtained in the absence of the magnetic field. Nevertheless, a comparative analysis of the effect caused by the two cyclic magnetic field strategies showed that strategy 2 allowed for a lower reduction of the original permeate fluxes during BSA permeation and higher protein sieving coefficients. Overall, these novel magneto-responsive block copolymer nanocomposite membranes proved to be competent in mitigating biofouling phenomena in bioseparation processes

Synthesis and characterization of poly(amino acid methacrylate)-stabilized diblock copolymer nano-objects

Amino acids constitute one of Nature's most important building blocks. Their remarkably diverse properties (hydrophobic/hydrophilic character, charge density, chirality, reversible cross-linking etc.) dictate the structure and function of proteins. The synthesis of artificial peptides and proteins comprising main chain amino acids is of particular importance for nanomedicine. However, synthetic polymers bearing amino acid side-chains are more readily prepared and may offer desirable properties for various biomedical applications. Herein we describe an efficient route for the synthesis of poly(amino acid methacrylate)stabilized diblock copolymer nano-objects. First, either cysteine or glutathione is reacted with a commercially available methacrylate-acrylate adduct to produce the corresponding amino acid-based methacrylic monomer (CysMA or GSHMA). Well-defined water-soluble macromolecular chain transfer agents (PCysMA or PGSHMA macro-CTAs) are then prepared via RAFT polymerization, which are then chain-extended via aqueous RAFT dispersion polymerization of 2-hydroxypropyl methacrylate. In situ polymerization-induced self-assembly (PISA) occurs to produce sterically-stabilized diblock copolymer nano-objects. Although only spherical nanoparticles could be obtained when PGSHMA was used as the sole macro-CTA, either spheres, worms or vesicles can be prepared using either PCysMA macro-CTA alone or binary mixtures of poly(glycerol monomethacrylate) (PGMA) with either PCysMA or PGSHMA macro-CTAs. The worms formed soft free-standing thermo-responsive gels that undergo degelation on cooling as a result of a worm-to-sphere transition. Aqueous electrophoresis studies indicate that all three copolymer morphologies exhibit cationic character below pH 3.5 and anionic character above pH 3.5. This pH sensitivity corresponds to the known behavior of the poly(amino acid methacrylate) steric stabilizer chains

Nano-structured Membranes: A journey from colloidal particles to isoporous films,

International audienc

Nano-structured membrane from layer-by-layer assembly of cationic and anionic di-block copolymer particles

National audienc

Preparation of fluorinated polymeric particles using RAFT alcoholic dispersion polymerization

National audienc

Magneto-Responsive Nano Structured Membranes from Block Copolymer Particle

Mixed matrix membranes having combined properties of both polymeric and inorganic materials become an integral part in separation technology. Mixed matrix membrane preparation incorporates positively charged inorganic nanoparticles (INPs) with negatively charged polymeric nanoparticles (PNPs) and in the reverse way negatively charged inorganic nanoparticles (INPs) with positively charged polymeric nanoparticles (PNPs) by use of spin coating technique. The PNPs made of poly ((methacrylic acid)-b-(methyl methacrylate)) and poly (2 dimethylaminoethyl methacrylate)-b-(methyl methacrylate)) diblock copolymers were synthesized by use of RAFT dispersion polymerization in ethanol at 70°C. In the same way cationic quaternized poly (2-(dimethylamino) ethyl methacrylate)b- poly (benzyl methacrylate) and anionic poly (potassium 3-sulfopropyl methacrylate)-b- poly (benzyl methacrylate) were synthesizes by use of RAFT emulsion polymerization in water at 70°C. The inorganic counterpart, iron oxide nanoparticles coated with [3-(2Aminoethylamino)propyl] trimethoxysilane (TPED) and Dimercaptosuccinic acid (DMSA) were synthesized and incorporated into the membrane acting as a bridge between the oppositely charged polymeric particles (due to the presence of opposite electrostatic charges). Filtration tests were carried out by using the feed of different pH at various pressures