Reversible Addition-fragmentation Chain Transfer Emulsion Research Articles

Synergistic Effects of the Superhydrophilic and Superhydrophobic Components on the Antifreezing Performances of Latex Particles and Anti-Icing Properties of Latex Films.

The development of new materials for antifreezing and anti-icing applications is a big challenge in industry and academic area. Inspired by the antifreeze proteins, latex particles with superhydrophilic zwitterionic shells and superhydrophobic cores are synthesized by reversible addition-fragmentation chain transfer emulsion polymerization, and the applications of the latex particles in antifreezing and anti-icing applications are investigated. In antifreezing study, the critical aggregate temperature (CAT) of the latex particles decreases, and the separation of the melting and freezing temperature of ice increases with the particle concentration. Enzyme molecules can be cryopreserved in the particle solution, andtheir bioactivities are well maintained. Latex particles are casted into latex films with dynamic surfaces. Anti-icing performances, including antifrosting properties, freezing delay time, and ice adhesion strengths, are studied; and the water-treated latex films present stronger anti-icing properties than other films, due to the synergistic effects of the superhydrophilic and superhydrophobic components. In addition, latex particles with zwitterionic shells and poly(n-butyl methacrylate) cores, and latex particles with small molecular surfactant on the surfaces are synthesized. The antifreezing performances of the latex particles and anti-icing properties of the latex films are compared.

Light-Triggered Reversible Swelling of Polymeric Spheres via Surfactant-Free RAFT Emulsion Polymerization-Induced Self-Assembly.

Responsive photonic crystals (RPCs) assembled by monodisperse colloidal particles have attracted enormous interest recently due to their tremendous applications in smart devices. Their structural colors can be determined by particle sizes. However, the lack of a reliable way to tune the sizes in situ limits their development. Herein, we present an efficient route to solve this problem through the fabrication of spherical polymeric particles with light-triggered reversible swelling behavior via surfactant-free reversible addition-fragmentation chain transfer (RAFT) emulsion polymerization-induced self-assembly (PISA). Amphiphilic macro-RAFT agents containing azobenzene groups were synthesized and subsequently employed to mediate the polymerization of methyl methacrylate. Uniform submicron spheres were obtained by modulating solid contents and other parameters. Benefiting from the photoisomerization of azobenzene moieties, the particle sizes expanded and contracted upon alternative ultraviolet/visible-light irradiation accordingly. This strategy will be a supplement to the emulsion PISA and especially give aid to the progress of the RPC materials.

Facile Synthesis of Soap-Free Latexes of Methacrylic Copolymers via Sulfur-Free Reversible Addition–Fragmentation Chain Transfer Emulsion Polymerization

Facile Synthesis of Soap-Free Latexes of Methacrylic Copolymers via Sulfur-Free Reversible Addition–Fragmentation Chain Transfer Emulsion Polymerization

Multiblock Copolymer Synthesis via Reversible Addition–Fragmentation Chain Transfer Emulsion Polymerization: Effects of Chain Mobility within Particles on Control over Molecular Weight Distribution

Synthesis of multiblock copolymers using seeded reversible addition–fragmentation chain transfer (RAFT) emulsion polymerization has been explored with a view to elucidate how certain experimental c...

Emulsifier‐free reversible addition–fragmentation chain transfer emulsion polymerization of alkyl acrylates mediated by symmetrical trithiocarbonates based on poly(acrylic acid)

AbstractEmulsifier‐free batch emulsion polymerization of n‐butyl acrylate and its semi‐batch copolymerization with 2,2,3,3,4,4,5,5‐octafluoropentyl acrylate and 2,2,3,4,4,4‐hexafluorobutyl acrylate both mediated by poly(acrylic acid) containing the trithiocarbonate group in the chain was employed to produce amphiphilic triblock copolymers. The polymerization‐induced self‐assembly of these copolymers in aqueous media gave rise to spherical core–shell particles. Irrespective of the experimental conditions, the polymeric product was characterized by a bimodal molecular weight distribution. The apparent violation of the reversible addition–fragmentation chain transfer polymerization mechanism may be attributed to restricted accessibility of the trithiocarbonate group in the self‐assembled block copolymers for propagating radicals that enter into the particle. Mean‐field theoretical arguments were employed to explain the exclusively spherical morphology of the particles observed in the experiment. © 2019 Society of Chemical Industry

Nano-Engineered Multiblock Copolymer Nanoparticles via Reversible Addition–Fragmentation Chain Transfer Emulsion Polymerization

Block copolymers composed of polymer segments of sufficiently high molecular weight such that microphase separation and self-assembly into complex nanostructured materials can occur provide a pathway to a myriad of nano-engineered materials with applications ranging from nanomedicine to materials science and microelectronics. In the present work, we have developed a methodology based on reversible addition–fragmentation chain transfer polymerization that allows the synthesis of multiblock copolymers based on sequential aqueous emulsion polymerization using the three most common industrially employed monomer families in emulsion polymerization systems: methacrylates, acrylates, and styrene. By exploiting the segregation effect (compartmentalization) resulting from polymerization within polymeric nanoparticles, a high molecular weight multiblock copolymer (up to 140,000 g·mol–1) is obtained in a relative short time period of 3 h for each cycle of polymerization. The concept of nano-engineering of polymer na...

Toughening of an epoxy thermoset with poly[styrene-alt-(maleic acid)]-block-polystyrene-block-poly(n-butyl acrylate) reactive core–shell particles

Reactive core–shell particles for epoxy toughening were synthesized via reversible addition–fragmentation chain transfer emulsion polymerization mediated by an amphiphilic macro-RAFT agent followed by core-crosslinking to increase stability.

Influence of Dioctyl Maleate Concentration on Performance Behavior of Water Based Pressure-sensitive Adhesives via Reversible Addition–Fragmentation Chain Transfer Emulsion Polymerization

Reversible addition–fragmentation chain transfer (RAFT)-mediated polymerization was successfully applied for the synthesis of pressure-sensitive adhesives (PSAs) of predetermined molar mass and of low polydispersity index (PDI). The performances of the adhesives were investigated by testing tack, peel, and shear resistance on seven different substrates (coated paper, uncoated paper, polyethylene terephthalate (PET), biaxially oriented polyethylene terephthalate (BOPP), aluminum strip, low linear density polyethylene (LLDPE), and low density polyethylene (LDPE). The influence of monomer composition on the adhesive performance was evaluated by varying the molar ratio of butyl acrylate (BA)/dioctyl maleate (DOM) while keeping the molar ratio of acrylic acid (AA) and 2-hydroxy ethyl acrylate (2-HEA) constant. As the DOM content increased, shear, peel strength, and loop tack were found to increase. It was noted that the adhesive properties of PSAs can be tailored by incorporating small amounts of hydrophobic DOM into the PSAs, which significantly increases the peel and shear strength of the resulting PSAs. Carboxyl terminated bifunctional trithiocarbonate RAFT agent possess the strong potential to polymerize hydrophobic DOM in aqueous phase and exhibit better living character with PDI less than 1.5.

Particle Size Limits of RAFT Living Emulsion Polymerization, with Xanthate-Based Transfer Agent

With a xanthate-based low activity RAFT (reversible addition–fragmentation chain transfer) agent, the living emulsion polymerization system follows zero-one kinetics and particles are smaller than their characteristic cross over diameter. The size and kinetic limitations in RAFT emulsion were investigated by using the concept of crossover size, based on a mechanistic approach. The main reason for these limitations is attributed to the low transfer constant, which tends to render desorption of a radical from particles difficult, the incoming z-mer has a higher probability to propagate relative to the addition process in RAFT equilibrium. In contrast, the living mini-emulsion polymerization follows either zero-one or pseudo-bulk kinetics, depending on the initial droplet size and reaction conditions.

Synthesis of Polystyrene-b-poly(n-butyl acrylate)-b-Polystyrene Triblock Copolymers as Binder for Pigment Dyeing

Well-controlled polystyrene-b-poly (n-butyl acrylate)-b-polystyrene (PSt-b-PnBA-b-PSt) triblock copolymers were prepared by RAFT (reversible addition-fragmentation chain transfer) emulsion polymerization process. The mechanical properties of the triblock copolymers were investigated in comparison to the P(nBA-co-St) statistical copolymers. When the PSt content is 20%, the ultimate tensile strength of triblock copolymer is nearly six times the strength of statistical copolymer, while their modulus are all around 3.0×103 Pa. The triblock copolymer films feel smooth and non-tacky as the PSt content is higher than 20%. It indicates that PSt-b-PnBA-b-PSt triblock copolymers can be used as binders in pigment dyeing, providing the dyed fabrics with soft non-tacky handle and good fastness properties.