Tailor-made polyfluoroacrylate and its block copolymer by RAFT polymerization in miniemulsion; improved hydrophobicity in the core–shell block copolymer

Synthesis and Properties of Cationic Core-Shell Fluorinated Polyurethane Acrylate

Vinyl-capped cationic waterborne polyurethane (CWPU) was prepared using isophorone diisocyanate (IPDI), polycarbonate diol (PCDL), N-methyldiethanolamine (MDEA), and trimethylolpropane (TMP) as raw materials and hydroxyethyl methacrylate (HEMA) as a capping agent. Then, a crosslinked FPUA composite emulsion with polyurethane (PU) as the shell and fluorinated acrylate (PA) as the core was prepared by core-shell emulsion polymerization with CWPU as the seed emulsion, together with dodecafluoroheptyl methacrylate (DFMA), diacetone acrylamide (DAAM), and methyl methacrylate (MMA). The effects of the core-shell ratio of PA/PU on the surface properties, mechanical properties, and heat resistance of FPUA emulsions and films were investigated. The results showed that when w(PA) = 30~50%, the stability of FPUA emulsion was the highest, and the particles showed a core-shell structure with bright and dark intersections under TEM. When w(PA) = 30%, the tensile strength reached 23.35 ± 0.08 MPa. When w(PA) = 50%, the fluorine content on the surface of the coating film was 14.75% and the contact angle was as high as 98.5°, which showed good hydrophobicity; the surface flatness of the film was observed under AFM. It is found that the tensile strength of the film increases and then decreases with the increase in the core-shell ratio and the heat resistance of the FPUA film is gradually increased. The FPUA film has excellent properties such as good impact resistance, high flexibility, high adhesion, and corrosion resistance.

Stimuli-Responsive Block Copolymer Micelles Based on Mussel-Inspired Metal-Coordinated Supramolecular Networks

Amphiphilic diblock copolymers containing dopamine and zwitterions are synthesized via the RAFT polymerization method, which undergo temperature-mediated micellization in aqueous media. The presence of catechol moiety in dopamine is exploited to form pH-responsive cross-links with ferric ions (Fe³⁺ ) at different pH value. Herein, a comprehensive study of the effect of pH as well as temperature on the size and solution behavior of these cross-linked micelles is presented. These micelles cross-linked via metal-catechol coordination bonds can have several important biomedical applications such as degradable scaffolds for payload delivery.

Graphene Quantum Dots-Ornamented Waterborne Epoxy-Based Fluorescent Adhesive via Reversible Addition-Fragmentation Chain Transfer-Mediated Miniemulsion Polymerization: A Potential Material for Art Conservation

Epoxy-based adhesives have gotten significant attention in the conservation of antiquities and repair or reconstruction of artifacts due to their excellent adhesion strength. However, it has become hard to detect repaired work in artifacts due to the transparent nature of epoxy-based adhesives. Hence, the making of fluorescent adhesives has become an exciting topic for art conservators. Here, we have synthesized a new kind of waterborne epoxy-based fluorescent adhesive decorated with graphene quantum dots (GQDs) via reversible addition-fragmentation chain transfer (RAFT)-mediated surfactant-free miniemulsion polymerization. In this case, a new block copolymer (BCP), poly(1-vinyl-2-pyrrolidone)-block-poly(glycidyl methacrylate), has been synthesized via surfactant-free RAFT-mediated miniemulsion polymerization using a polymerization-induced self-assembly technique. The GQDs were prepared from citric acid by a hydrothermal process, and this was used for making a fluorescence-active BCP/GQD nanocomposite emulsion. The obtained BCP/GQD nanocomposite adhesive was transparent and showed blue fluorescence under ultraviolet-visible light, indicating the easy detection of its mark on the artifacts. The BCP and BCP/GQD emulsions were applied to adhere ceramic and glass substrates, and their adhesion strength was evaluated by lap shear tests. The BCP/GQDs showed better adhesion strength than the BCP only, indicating better adhesive performance. Additionally, the synthesis process was carried out in aqueous media, indicating the sustainability and environment-friendliness of the process. We believe that this kind of new waterborne epoxy-based fluorescent adhesive will provide a new contrivance among art conservators to repair or reconstruct artifacts.

Cellulose Acetate Nanofibrous Membranes for Antibacterial Applications

BACKGROUNDS

N-halamine antibacterial materials have been extensively explored over the past few decades due to their fast inactivation of a broad spectrum of bacterial and rechargeability. Electrospun nanofibers loaded with N-halamines have gained great attention because of their enhanced antibacterial capability induced by the larger specific surface area. The patents on electrospun nanofibers (US20080679694), (CN2015207182871) helped in the method for the preparation of nanofibers.

METHODS

In this study, a novel N-halamine precursor, 3-(3'-Chloro-propyl)-5,5-dimethylimidazolidine- 2,4-dione(CPDMH), was synthesized. Antimicrobial electrospun Cellulose Acetate (CA) nanofibers were fabricated through impregnating CPDMH as an antimicrobial agent into CA fibers by the bubble electrospinning. The surface morphologies of CA/CPDMH nanofibrous membranes were characterized by Scanning Electron Microscope (SEM).

RESULTS

The chlorinated fibrous membranes (CA/CPDMH-Cl) exhibited effective antimicrobial activity against 100% of S. aureus and E. coli O157:H7 within 1 min and 5 min, respectively. The CA/CPDMH-Cl nanofibrous membranes showed good storage stability under the dark and excellent durability towards UVA light exposure. Meanwhile, the release of active chlorine from the chlorinated nanofibrous membranes was stable and safe. Besides, the addition of CPDMH could improve the mechanical property, and chlorination did not obviously affect the strength and elongation of the nanofibrous membranes.

CONCLUSION

CPDMH could endow the electrospun CA nanofibers with powerful, durable and regenerable antimicrobial properties. It will provide a continuous and effective method for health-care relative industrial application.

Thermo-reversible self-healing in a fluorous crosslinked copolymer

Self-healing in a fluorous copolymer material enhances its safety index and extends its working lifetime.

Tailor-Made Fluorinated Copolymer/Clay Nanocomposite by Cationic RAFT Assisted Pickering Miniemulsion Polymerization

Fluorinated polymers in emulsion find enormous applications in hydrophobic surface coating. Currently, lots of efforts are being made to develop specialty polymer emulsions which are free from surfactants. This investigation reports the preparation of a fluorinated copolymer via Pickering miniemulsion polymerization. In this case, 2,2,3,3,3-pentafluoropropyl acrylate (PFPA), methyl methacrylate (MMA), and n-butyl acrylate (nBA) were copolymerized in miniemulsion using Laponite-RDS as the stabilizer. The copolymerization was carried out via reversible addition-fragmentation chain transfer (RAFT) process. Here, a cationic RAFT agent, S-1-dodecyl-S'-(methylbenzyltriethylammonium bromide) trithiocarbonate (DMTTC), was used to promote polymer-Laponite interaction by means of ionic attraction. The polymerization was much faster when Laponite content was 30 wt % or above with 1.2 wt % RAFT agent. The stability of the miniemulsion in terms of zeta potential was found to be dependent on the amount of both Laponite and RAFT agent. The miniemulsion had particle sizes in the range of 200-300 nm. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) analyses showed the formation of Laponite armored spherical copolymer particles. The fluorinated copolymer films had improved surface properties because of polymer-Laponite interaction.

Synthesis of well-defined α-fluorinated alkyl ester, ω-carboxyltelechelic polystyrenes and fabrication of their hydrophobic highly ordered porous films and microspheres

Porous films and microspheres of α-fluorinated alkyl ester, ω-carboxyl telechelic polystyrenes synthesized via combining aminolysis of RAFT-polystyrene with thiol–ene “click” reaction.

Hydrophobe-free miniemulsion polymerization: towards high solid content of fatty acid-based poly(urethane-urea) latexes

High solid content of aqueous fatty acid-based PU latexes.

Fluorinated amphiphilic block copolymers via RAFT polymerization and their application as surf-RAFT agent in miniemulsion polymerization

Preparation of an amphiphilic block copolymer (Am-BCP) based on poly(ethylene glycol) methyl ether methacrylate (PEGMA) and heptafluorobutyl acrylate (HFBA) via RAFT polymerization and application of this Am-BCP as surf-RAFT agent for polymerization of styrene.

Synthesis of Fluorinated Amphiphilic Block Copolymers Based on PEGMA, HEMA, and MMA via ATRP and CuAAC Click Chemistry

Synthesis of fluorinated amphiphilic block copolymers via atom transfer radical polymerization (ATRP) and Cu(I) catalyzed Huisgen 1,3-dipolar cycloaddition (CuAAC) was demonstrated. First, a PEGMA and MMA based block copolymer carrying multiple side-chain acetylene moieties on the hydrophobic segment for postfunctionalization was carried out. This involves the synthesis of a series of P(HEMA-co-MMA) random copolymers to be employed as macroinitiators in the controlled synthesis of P(HEMA-co-MMA)-block-PPEGMA block copolymers by using ATRP, followed by a modification step on the hydroxyl side groups of HEMA via Steglich esterification to afford propargyl side-functional polymer, alkyne-P(HEMA-co-MMA)-block-PPEGMA. Finally, click coupling between side-chain acetylene functionalities and 2,3,4,5,6-pentafluorobenzyl azide yielded fluorinated amphiphilic block copolymers. The obtained polymers were structurally characterized by1H-NMR,19F-NMR, FT-IR, and GPC. Their thermal characterizations were performed using DSC and TGA.