Stable Nonspherical Fluorine-Containing Colloidal Dispersions: Synthesis and Film Formation

Functional design of PGMA-co-PDFHM/Ti3C2Tx MXene composite materials for anti-icing in simulated outdoor environment

To improve anti-icing traits of outdoor coatings, a synergy between photothermal and hydrophobic anti-icings was utilized to fabricate copolymer/Ti3C2Tx MXene composite coatings with good transparency and adhesion. MXene contributes to photothermal trait from local surface plasmon resonance effect. Copolymer enables hydrophobicity from perfluoroalkyls-induced low surface energy and high surface roughness. An increase in MXene dose results in an increased surface roughness. With 140.0 ± 2.2° of water contact angle and 70% of light transmittance, the optimal film bears 2 wt% of MXene. High MXene dose results in large temperature-increase of film under sunlight. After 15 min of sunlight exposure, the temperature of optimal film surface in icing simulation increases from - 18 ℃ to 7.2 ℃. After 48 h of acid immersion, the temperature-increase of optimal film surface based on 300 s of sunlight irradiation reaches 28.7 ± 1.2 ℃. After 48 h of ultraviolet irradiation, the temperature-increase of optimal film surface is 30.7 ± 0.8 ℃. This surface has a water contact angle of 132.7 ± 1.1° after 48 h of acid immersion. This study gives impetus to a preparation of various composite coatings for outdoor anti-icing/deicing.

Semi-batch synthesis of colloidal spheres with fluorinated cores and varying grafts of poly(ethylene glycol)

Fluorinated spheres with grafted poly(ethylene glycol) (PEG) have been synthesized using a semi-batch emulsion polymerization in which the initiator is fed slowly to the reaction. In this way, PEG-grafted colloidal spheres can be fabricated with varying PEG chain length, different cores and varying degrees of crosslinking. The resulting batches have been characterized using disc centrifuge photosedimentometry and small-angle X-ray scattering. The size distribution is shown to be a sensitive function of the molar ratio of the reactive PEG macromonomer to fluorinated monomer, and with some optimization latices of very low polydispersity can be obtained with this simple synthesis method. For short PEG grafts too high a molar ratio results in a build up of smaller size particles and a broadening of the size distribution, whereas for longer grafts the mean particle size increases with decreasing molar ratio.

Achieving low dielectric, surface free energy and UV shielding green nanocomposites via reinforcing bio-silica aerogel with polybenzoxazine

Silica aerogel (SA) derived from rice husk ash was functionalized using benzoxazine terminated silane (FSA) and was used as a nanoreinforcement for industrial valuable resin polybenzoxazine (PBZ) in order to achieve low dielectric, to improve the surface as hydrophobic and to enhance the UV shielding behavior of the resulting nanocomposites.

RAFT-Mediated Polymerization-Induced Self-Assembly of Poly(Acrylic Acid)-b-Poly(Hexafluorobutyl Acrylate): Effect of the pH on the Synthesis of Self-Stabilized Particles

This paper describes a very simple strategy towards self-stabilized poly(acrylic acid)-block-poly(hexafluorobutyl acrylate) (PAA-b-PHFBA) block copolymer particles via reversible addition-fragmentation chain transfer (RAFT)-mediated polymerization-induced self-assembly. Hexafluorobutyl acrylate (HFBA) monomer conversion and number-average molar mass of PAA-b-PHFBA increased gradually with the increase in the pH value of the aqueous phase. When pH < 10, the molecular weight distributions of PAA-b-PHFBA were narrow, however, when the pH was raised to 11.55, PAA-b-PHFBA block copolymers had a broader distribution (Đ_M = 1.82) with a serious trailing toward the low molecular weight. Furthermore, the morphology and size of PAA-b-PHFBA latex particles were measured by transmission electron microscopy and dynamic light scattering. The results indicated that the PAA-b-PHFBA latex particles had a clear spherical core-shell structure and the latex particles’ size increased with the increase of pH value.

Instantaneous Directional Growth of Block Copolymer Nanowires During Heterogeneous Radical Polymerization (HRP)

Polymeric nanowires that consist of ultrahigh molecular weight block copolymers were instantaneously prepared via one-step surfactant-free heterogeneous radical polymerization (HRP). Under heterogeneous reaction and initiator-starvation conditions, the sequential copolymerization of hydrophilic and hydrophobic monomers facilitates the formation of amphiphilic ultrahigh molecular weight block copolymers, which instantaneously assemble to polymeric nanowires. As polymerization progresses, initially formed nanoparticles exhibit the directional growth due to localized repulsive forces of hydrophilic blocks and confinement of the hydrophobic blocks that adopt favorable high aspect ratio nanowire morphologies. Using one-step synthetic approach that requires only four ingredients (water as a solvent, two polymerizable monomers (one hydrophilic and one hydrophobic), and water-soluble initiator), block copolymer nanowires ∼70 nm in diameter and hundreds of microns in length are instantaneously grown. For example, when 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA) and styrene (St) were copolymerized, high aspect ratio nanowires consist of ultrahigh (>10(6) g/mol) molecular weight pDMAEMA-b-St block copolymers and the presence of temperature responsive pDMAEMA blocks facilitates nanowire diameter changes as a function of temperature. These morphologies may serve as structural components of the higher order biological constructs at micro and larger length scales, ranging from single strand nanowires to engineered biomolecular networks capable of responding to diverse and transient environmental signals, and capable of dimensional changes triggered by external stimuli.

One-Step Synthesis of Amphiphilic Ultrahigh Molecular Weight Block Copolymers by Surfactant-Free Heterogeneous Radical Polymerization

Ultrahigh molecular weight (>10⁶ g/mol) amphiphilic block copolymers were synthesized using one-step surfactant-free heterogeneous radical polymerization (SFHRP). The polymerization initially involves formation of water-soluble homopolymer blocks, followed by copolymerization of a hydrophobic monomer, resulting in ultrahigh molecular weight block copolymers. Facilitating heterogeneous reaction conditions and continuous supply of an initiator controls the process. Using this synthetic approach, we synthesized amphiphilic block copolymers of poly(2-(N,N-dimethylamino)ethyl methacrylate)-block-poly(n-butyl acrylate) (pDMAEMA-b-pnBA), pDMAEMA-block-p(tert-butyl acrylate) (pDMAEMA-b-tBA), and pDMAEMA-block-polystyrene (pDMAEMA-b-pSt) with molecular weights of 1.98 × 10⁶, 1.18 × 10⁶, and 0.91 × 10⁶ g/mol, respectively. These ultrahigh molecular weight block copolymers can self-assemble in nonpolar solvents to form thermochromic inverse polymeric micelles as well as other shapes and exhibit many potential applications.

Hydrolysis of p-nitrophenyl esters promoted by semifluorinated quaternary ammonium polymer latexes and films

Semifluorinated polymer latexes were prepared by emulsion polymerization of 2.5-25% of a fluoroalkyl methacrylate, 25% chloromethylstyrene, 1% styrylmethyl(trimethyl)ammonium chloride, and the remainder 2-ethylhexyl methacrylate under surfactant-free conditions. The chloromethylstyrene units were converted to quaternary ammonium ions with trimethylamine. In aqueous dispersions at particle concentrations of less than 1 mg mL(-1) the quaternary ammonium ion latexes promoted hydrolyses of p-nitrophenyl hexanoate (PNPH) in pH 9.4 borate buffer and of diethyl p-nitrophenyl phosphate (Paraoxon) in 0.1 M NaOH at 30 °C with half-lives of less than 10 min. Thin 0.7-2 μm films of the latexes on glass promoted fast hydrolysis of Paraoxon but not of PNPH under the same conditions. Even after annealing the quaternary ammonium ion polymer films at temperatures well above their glass transition temperatures, AFM images of the film surfaces had textures of particles. Contact angle measurements of the annealed films against water and against hexadecane showed that the surfaces were not highly fluorinated.

Repairing polymers using oscillating magnetic field

Repair of physically separated thermoplastic polymers containing γ-Fe2 O3 nanoparticles without sacrificing their mechanical properties is achieved by applying an oscillating magnetic field. As γ-Fe2 O3 nanoparticles oscillate at the frequency of the magnetic field, localized amorphous flow occur, and a permanent repair of physically separated polymeric films is achieved.

Acorn-shape polymeric nano-colloids: synthesis and self-assembled films

These studies show for the first time that the synthesis of two distinct phase-separated copolymers within one colloidal particle, i.e., poly(methyl methacrylate) (PMMA)/n-butylacrylate (nBA) and poly(nBA)/pentafluorostyrene (p-PFS) phases, results in unique acorn-shaped morphologies and are capable of coalescence. Spectroscopic and morphological analysis combined with contact angle measurements as well as thermodynamic modeling reveal that in an effort to create stable heterogeneous two-phase particle morphologies it is essential to provide desirable interfacial energetic conditions during polymerization and to utilise monomers that have a similar glass transition temperature (T(g) ). Such colloidal particles are stable and are able to self-assemble during coalescence, depending upon the surface energy of a substrate. When a particle monolayer coalesces on a high surface tension substrate, the p-PFS phase expresses itself near the film-air interface, whereas for low surface energy substrates, the p-PFS phase dominates the film-substrate interfacial regions.

Phospholipid-assisted synthesis of stable F-containing colloidal particles and their film formation

This letter illustrates for the first time the preparation of p-methyl methacrylate/n-butyl acrylate/heptadecafluorodecyl methacrylate (p-MMA/nBA/FMA) colloidal dispersions containing up to 15% w/w FMA, which is accomplished by the utilization of biologically active phospholipids (PLs) and ionic surfactants. The use of monomer-starved conditions during emulsion polymerization and the utilization of 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC), sodium dodecyl sulfate (SDS), and phosphoric acid bis(tridecafluoro-octyl) ester ammonium salt (FSP) as surfactants, which function as transfer and dispersing agents, facilitate a suitable environment for the polymerization of p-MMA/nBA/FMA colloidal dispersions that exhibit nonspherical particle morphologies. Such nonspherical particles upon coalescence form phase-separated films with unique surface properties.

Cocklebur-shaped colloidal dispersions

Unique cocklebur-shaped colloidal dispersions were prepared using a combination of a nanoextruder applied to the aqueous solution containing methyl methacrylate (MMA) and n-butyl acrylate (n-BA) with azo-bis-isobutyronitrile (AIBN) or potassium persulfate (KPS) initiators and stabilized by a mixture of sodium dioctyl sulfosuccinate (SDOSS) and 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DCPC) phospholipid. Upon extrusion and heating to 75 degrees C, methyl methacrylate/n-butyl acrylate (MMA/nBA) colloidal particles containing tubules pointing outward were obtained as a result of DCPC phospholipids present at the particle surfaces. The same cocklebur-shaped particles were obtained when classical polymerization was used without a nanoextruder under similar compositional and thermal conditions, giving a particle size of 159 nm. However, when Ca(2+) ions are present during polymerization, cocklebur morphologies are disrupted. Because DCPC tubules undergo a transition at 38 degrees C, such cocklebur morphologies may offer numerous opportunities for devices with stimuli-responsive characteristics.