Atom Transfer Radical Polymerization In Miniemulsion Research Articles

BaTiO3 catalyzed ultrasonic driven piezoelectric induced miniemulsion atom transfer radical polymerization (Piezo-miniATRP)

Compared with other stimulus such as light and heat, ultrasonic possesses much deeper penetration into tissues and organs and has lower scattering in heterogeneous systems as a noninvasive stimulus, and has already been used as the external stimulus to initiate reversible-deactivation radical polymerization (RDRP). However, the development of efficient ultrasonic drive RDRP in aqueous dispersed media remains a challenge. Here in this work, ultrasonic driven piezoelectric induced miniemulsion atom transfer radical polymerization (Piezo-miniATRP) was performed, with tetragonal BaTiO3 (BTO) nanoparticles as the piezoelectric catalyst. The Piezo-miniATRP exhibited features of controllable and livingness, such as linear increase of molar mass and narrow molar mass distributions (Mw/Mn < 1.30). The effect of different polymerization parameters on the polymerization reaction was investigated, including the amounts of surfactant, CuBr2 and BTO dosages. Excellent temporal control of the polymerization and the chain fidelity of polymers were illustrated by “ON and OFF” experiment and chain extension, separately. This novel BTO catalyzed Piezo-miniATRP process could also be extended to other aqueous dispersion RDRP systems.

Carbon Quantum Dot-Catalyzed, Highly Efficient Miniemulsion Atom Transfer Radical Polymerization Induced by Visible Light.

Owing to the benefits of using natural or artificial light sources as a stimulus, photoinduced reversible-deactivation radical polymerization (photoRDRP) techniques have been recognized to be a powerful "green" platform for the preparation of well-defined polymers. However, the development of highly efficient visible light-induced photoRDRP processes in aqueous dispersed media remains a challenge due to light scattering and refraction by monomer droplets or colloidal particles. In this work, an efficient green photocatalyst, carbon quantum dots (CQDs), was introduced to visible light-mediated miniemulsion atom transfer radical polymerization (ATRP), leading to highly efficient polymerizations with reaction rates (>80% monomer conversion within 1 h) much higher than in previous studies. This heterogeneous photocatalytic system is presumed to involve three catalytic cycles in (i) the aqueous phase, (ii) the oil-water interface, and (iii) the monomer droplets. The effect of different polymerization parameters on the polymerization reaction was investigated, including the amounts of surfactant and CQDs, CuBr2 dosage, and solid content. Excellent temporal control of the polymerization was illustrated by "ON/OFF" polymerizations, and natural sunlight was also used as an energy source. This novel CQDs-catalyzed miniemulsion photoATRP process may be easily extended to other aqueous dispersion RDRP systems. As an extension of our previous work (J. Am. Chem. Soc. 2022, 144 (22), 9817-9826) we also developed a "one-pot" method for the rapid preparation of heterogeneous hydrogels.

High‐efficient surface tailoring via reverse atom transfer radical polymerization and reversible addition‐fragmentation chain‐transfer polymerization in an aqueous system initiated by a monocenter redox pair

AbstractThe commonly used multi‐center initiation methods always lead to the formation of quantities of homopolymer in the surface tailoring based on reverse atom transfer radical polymerization (ATRP) and reversible addition‐fragmentation chain‐transfer (RAFT) polymerization. In this study, a monocenter redox pair constructed of silica bearing tert‐butyl hydroperoxide groups and ascorbic acid (SiO2‐TBHP/AsAc) was applied to substitute the commonly used initiation method of R‐supported RAFT grafting polymerization. All the propagating radicals were restricted on the surface of solid particles during the whole procedure theoretically, resulting in a higher grafting efficiency of 95.1% combined with the “controllable” feature at 10 h. This redox pair was also used to initiate the reverse ATRP in miniemulsion successfully with a grafting efficiency of 86.3% at 10 h. The grafting efficiency obtained under this monocenter initiation method was significantly higher than that of the frequently reported surface modification by reverse ATRP and RAFT polymerization. In addition, the high‐efficient surface tailoring was traced and confirmed by nuclear magnetic resonance, Fourier transform infrared, X‐ray photoelectron spectroscopy, thermogravimetric analysis, transmission electron microscopy, and other analysis tests. The advantage of this monocenter redox pair will open a new avenue for the potential “high‐efficient” surface tailoring of various materials.

Hairy nanoparticles by atom transfer radical polymerization in miniemulsion

Polymer nanoparticles with various architectures and functionalities are promising materials in numerous fields. Miniemulsion polymerization is one of the suitable pathways to prepare polymer nanoparticles since each droplet could act as a “nanoreactor”. A “smart” atom transfer radical polymerization (ATRP) catalytic system comprising Cu-TPMA/DS− (TPMA = tris(2-pyridylmethyl)amine, DS−= dodecyl sulfate anion) ion pair catalyst was efficiently applied in miniemulsion ATRP at low catalyst concentrations. Herein, hairy nanoparticles consisting of hydrophobic poly(n-butyl methacrylate) (P(BMA/EGDMA), EGDMA = ethylene glycol dimethacrylate) network “core” and hydrophilic oligo(ethylene oxide) methyl ether methacrylate (OEOMA) chains as “hair” were prepared by miniemulsion ATRP and a successive chain extension by aqueous ATRP from the particle surface. The addition of an inimer, 2-(α-bromoisobutyryloxy)ethyl methacrylate (HEMA-iBBr) to the P(BMA/EGDMA) network introduced more ATRP initiation sites for ATRP of OEOMA, enabling adjustment of the particle size from >400 nm to <150 nm. The miniemulsion system remained stable after the one pot synthesis of P(BMA/EGDMA)-g-POEOMA and P(BMA/EGDMA/HEMA-iBBr)-g-POEOMA, and the resulting polymer nanoparticles were re-dispersed in water for further modification. A zwitterionic monomer, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA), was grafted from P(BMA/EGDMA/HEMA-iBBr)-g-POEOMA. The resulting hairy nanoparticles provide an avenue for the design and preparation of novel nanostructured materials.

Multi-reactive surfactant and miniemulsion Atom Transfer Radical Polymerization: An elegant controlled one-step way to obtain dextran-covered nanocapsules

A convenient one-step method is developed to prepare potentially biocompatible nanocapsules (NCs) with a biocompatible oily core (Miglyol 810, M810), a poly(methyl methacrylate) (PMMA) shell and a dextran coverage. For that, a multi-reactive dextran derivative containing both hydrophobic phenoxy and ATRP initiator groups is used as inisurf (macroinitiator and stabilizer) in an Activator Generated by Electron Transfer-Atom Transfer Radical Polymerization (AGET-ATRP) miniemulsion process. Such dextran inisurfs are shown to efficiently stabilize the direct miniemulsion of MMA with M810 as co-stabilizer, and to confine the polymerization at the oil/water interface via their multiple initiator sites. Grafted copolymers are produced from the inisurf, whose grafts constitute the inner polymeric shell of NCs and are linked to the dextran coverage. The confinement of such polymerization at interface is found to reduce initiator group efficiency, but also to improve both polymerization kinetics and control in comparison with one molecular model initiator. Increasing M810 content promotes the oily core/PMMA shell phase separation during polymerization and the formation of slightly larger NCs, without affecting polymerization kinetics.

Synthesis of Biodegradable Hydroxy-Functionalized Poly(oligo(ethylene Oxide) Monomethyl Ether Methacrylate) (HO-POEOMA) Polymer by Inverse Miniemulsion ATRP

The biodegradable hydroxy-functionalized poly(oligo(ethylene oxide) monomethyl ether methacrylate) (HO-POEOMA) polymer is synthesized by inverse miniemulsion atom transfer radical polymerization (ATRP). The chain structure and component of such polymer is characterized by spectroscopic studies (1HNMR, IR and GPC).

Effect of Nanoclay on Styrene and Butyl Acrylate AGET ATRP in Miniemulsion: Study of Nucleation Type, Kinetics, and Polymerization Control

ABSTRACTPoly(styrene‐co‐butyl acrylate)/clay nanocomposites were synthesized in miniemulsion via activators generated by electron transfer (AGET) for atom transfer radical polymerization (ATRP). Optimum amounts of catalyst and reducing agent were chosen by considering a linear increase in ln([M0]/[M]) versus time, narrow molecular distribution, and low polydispersity index (PDI). Critical micelle concentration and cross‐sectional surface area per surfactant head group were determined by surface tension analysis. Calculations show that droplet nucleation is the dominant mechanism of nucleation in a miniemulsion system, and there is no micelle in the system. Gel permeation chromatography was used to characterize molecular weight, PDI, and molecular weight distribution. After determination of appropriate conditions, poly(styrene‐co‐butyl acrylate)/clay nanocomposite latexes were synthesized. Low PDI, narrow molecular weights, and first‐order kinetics of the nanocomposites justify that polymerization is well controlled. Kinetics of polymerization decreases by clay loading. The apparent propagation rate constant (kapp) of polymerization in the case of poly(styrene‐co‐butyl acrylate) is 4.079 × 10−6, which becomes 0.558 × 10−6 in the case of poly(styrene‐co‐butyl acrylate)/clay nanocomposite with 2% nanoclay. A decrease in the polymerization rate is related to the hindrance effect of nanoclay layers on monomer diffusion toward the loci of growing macroradicals.

Active Ligand for Low PPM Miniemulsion Atom Transfer Radical Polymerization

Modification of bis(2-pyridylmethyl)octadecylamine (BPMODA), a ligand commonly used in ATRP in aqueous dispersed media, was accomplished through the incorporation of electron-donating substituents,...

Synthesis and characterization of exfoliated poly(styrene‐co‐methyl methacrylate) nanocomposite via miniemulsion atom transfer radical polymerization: an activators generated by electron transfer approach

AbstractExfoliated poly(styrene‐co‐methyl methacrylate) nanocomposites were synthesized using activators generated by electron transfer for atom transfer radical polymerization (AGET ATRP). Miniemulsion polymerization was used for its abundant advantages to encapsulate inorganic materials and eliminate organic solvents from products for environmentally friendly purposes. Cetyltrimethylammonium bromide (CTAB) as a cationic surfactant, which is an effective surfactant at higher temperatures, was used to stabilize the miniemulsion system. Successful miniemulsion AGET ATRP was carried out by using 4,4'‐dinonyl‐2,2'‐bipyridine (dNbPy) as a hydrophobic ligand. Formation of monodispersed droplets and particles with sizes in the range of 200nm was examined by dynamic light scattering (DLS). Conversion and molecular weight study were also carried out using gravimetry and gel permeation chromatography, respectively. By adding clay content, a decrease in the conversion and molecular weight of the nanocomposites are observed. However, an increase in the PDI values of nanocomposites was observed by the addition of nanoclay content. Thermogravimetric analysis results demonstrate that thermal stability of all the nanocomposites in comparison with the neat copolymer increases. Differential scanning calorimetry results show that Tg decreases by increasing clay content. Monodisperse distribution of spherical shape particles with sizes in the range of ∼ 200 nm was demonstrated by using scanning electron microscopy images of nanocomposite containing 1 wt% of nanoclay, which is more compiled with DLS results. Transmission electron microscopy results shows well‐dispersed exfoliated clay layers in the polymer matrix of PSMNM 1, which is coincidence with X‐ray diffraction data. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

Synthesis of clay‐dispersed poly(styrene‐co‐methyl methacrylate) nanocomposite via miniemulsion atom transfer radical polymerization: A reverse approach

AbstractPoly(styrene‐co‐methyl methacrylate) nanocomposites were synthesized using reverse atom transfer radical polymerization (RATRP) in miniemulsion. Cetyltrimethylammonium bromide (CTAB) as a cationic surfactant applicable at higher temperatures was used for miniemulsion stabilization. Successful RATRP was carried out by using 4,4′‐dinonyl‐2,2′‐bipyridine (dNbPy) as ligand. Monodispersed droplets and particles with sizes in the range of 200 nm were revealed by dynamic light scattering (DLS). Conversion and molecular weight study was carried out using gravimetry and size exclusion chromatography (SEC) respectively. By adding clay content, a decrease in the conversion and molecular weight and an increase in the PDI value of the nanocomposites are observed. Thermal stability of the nanocomposites in comparison with the neat copolymer is revealed by thermogravimetric analysis (TGA). Increased Tg values by adding clay content was also obtained using differential scanning calorimetry (DSC). Scanning electron microscopy (SEM) images of the nanoconposite with 1 wt % of nanoclay loading, display monodispersed spherical particles with sizes in the range of ∼ 200 nm. SEM findings are more compiled with dynamic light scattering (DLS) results. Well‐dispersed exfoliated clay layers in the polymer matrix of the nanocomposite with 1 wt % nanoclay loading is confirmed by transmission electron microscopy (TEM) images and X‐ray diffraction (XRD) data. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Cellular uptake of functional nanogels prepared by inverse miniemulsion ATRP with encapsulated proteins, carbohydrates, and gold nanoparticles.

Atom transfer radical polymerization (ATRP) was used to produce a versatile drug delivery system capable of encapsulating a range of molecules. Inverse miniemulsion ATRP permitted the synthesis of biocompatible and uniformly cross-linked poly(ethylene oxide)-based nanogels entrapping gold nanoparticles, bovine serum albumin, rhodamine B isothiocyanate-dextran, or fluoresceine isothiocyanate-dextran. These moieties were entrapped to validate several biological outcomes and to model delivery of range of molecules. Cellular uptake of nanogels was verified by transmission electron microscopy, gel electrophoresis, Western blotting, confocal microscopy, and flow cytometry. Fluorescent colocalization of nanogels with a fluorophore-conjugated antibody for clathrin indicated clathrin-mediated endocytosis. Furthermore, internalization of nanogels either with or without GRGDS cell attachment-mediating peptides was quantified using flow cytometry. After 45 min of incubation, the uptake of unmodified FITC-Dx-loaded nanogels was 62%, whereas cellular uptake increased to >95% with the same concentration of GRGDS-modified FITC-Dx nanogels. In addition, a spheroidal coculture of human umbilical vascular endothelial cells (HUVECs) and human mesenchymal stem cells (hMSCs) validated cell endocytosis. Application of ATRP enabled the synthesis of a functionalized drug delivery system with a uniform network that is capable of encapsulating and delivering inorganic, organic, and biological molecules.

Bicompartmentalized Polymer Particles by Tandem ROMP and ATRP in Miniemulsion

This study describes an original approach to prepare biphasic particles by simultaneous ring-opening metathesis polymerization (ROMP) of norbornene and atom-transfer radical polymerization (ATRP) of methyl methacrylate under miniemulsion conditions. A single water-soluble ruthenium macrocatalyst was used to initiate ROMP and mediate ATRP. All situations led to high conversions, and well-distributed particles containing two incompatible homopolymers grown under controlled conditions could indeed be prepared.

Biodegradable Nanogels Prepared by Atom Transfer Radical Polymerization as Potential Drug Delivery Carriers: Synthesis, Biodegradation, in Vitro Release, and Bioconjugation

Stable biodegradable nanogels cross-linked with disulfide linkages were prepared by inverse miniemulsion atom transfer radical polymerization (ATRP). These nanogels could be used for targeted drug delivery scaffolds for biomedical applications. The nanogels had a uniformly cross-linked network, which can improve control over the release of encapsulated agents, and the nanogels biodegraded into water-soluble polymers in the presence of a biocompatible glutathione tripeptide, which is commonly found in cells. The biodegradation of nanogels can trigger the release of encapsulated molecules including rhodamine 6G, a fluorescent dye, and Doxorubicin (Dox), an anticancer drug, as well as facilitate the removal of empty vehicles. Results obtained from optical fluorescence microscope images and live/dead cytotoxicity assays of HeLa cancer cells suggested that the released Dox molecules penetrated cell membranes and therefore could suppress the growth of cancer cells. Further, OH-functionalized nanogels were prepared to demonstrate facile applicability toward bioconjugation with biotin. The number of biotin molecules in each nanogel was determined to be 142,000, and the formation of bioconjugates of nanogels with avidin was confirmed using optical fluorescence microscopy.

Atom Transfer Radical Polymerization in Miniemulsion: Partitioning Effects of Copper(I) and Copper(II) on Polymerization Rate, Livingness, and Molecular Weight Distribution

The effects of partitioning of Cu(I) and Cu(II) species to the aqueous medium on the polymerization rate (Rp), molecular weight and molecular weight distribution in the miniemulsion atom transfer radical polymerization system of styrene/CuBr/4,4‘-dinonyl-2,2‘-bipyridyl at 90 °C were investigated. According to both simulation (invoking the partitioning data for n-butyl methacrylate (Macromolecules 2000, 33, 7310−7320)) and experiment showed that the Rp and polydipersity (Mw/Mn) were higher in miniemulsion than in the corresponding solution polymerization as a result of a decrease in deactivator concentration (Cu(II) species) in the organic phase. Simulations indicated quantitatively that the increase in Mw/Mn was caused by (i) a decrease of activation−deactivation cycles and (ii) an increase of bimolecular termination.

Preparation of Nanoparticles of Well-Controlled Water-Soluble Homopolymers and Block Copolymers Using an Inverse Miniemulsion ATRP

Stable colloidal nanoparticles of well-controlled water-soluble poly(oligo(ethylene glycol) monomethyl ether methacrylate) (P(OEOMA)) homo- and copolymers were successfully synthesized by inverse miniemulsion atom transfer radical polymerization using activators generated by electron transfer (AGET ATRP) at ambient temperature (30 °C). Oil-soluble sorbitan monooleate (Span 80) surfactant, ascorbic acid as a reducing agent, oxidatively stable CuBr2/tris[(2-pyridyl)methyl]amine (TPMA) catalyst complex, and [initiator] 0 /[CuBr 2 / TPMA] 0 = 1/0.5 were selected for the controlled AGET ATRP inverse miniemulsion. The effect of reaction parameters on control over AGET ATRP and colloidal stability were explored. It was found that the use of water-soluble poly(ethylene oxide)-based bromoisobutyrate macroinitiators (PEO-Br) with long chain EO units, up to 90% ascorbic acid of Cu(II) complex, and appropriate amount of water resulted in the formation of stable colloidal particles with less than 200 nm diameter and well-controlled P(OEOMA) with M w /M n < 1.3. The addition of a long chain poly(ethylene glycol) monomethyl ether (PEOH) as a costabilizer improved colloidal stability without interfering the polymerization. A water-soluble CuBr 2 /bipyridine catalyst complex was also suitable for AGET ATRP of OEOMA in inverse miniemulsion. Finally, colloidal particles of well-controlled block copolymers of OEOMA with different sizes of OEO side chains (degree of polymerization of EO = 5 and 9) were produced with relatively low M w /M n = 1.3 at 85% conversion.

Inverse Miniemulsion ATRP: A New Method for Synthesis and Functionalization of Well-Defined Water-Soluble/Cross-Linked Polymeric Particles

A new methodology for the synthesis and functionalization of nanometer-sized colloidal particles consisting of well-defined, water-soluble, functional polymers with narrow molecular weight distribution (M(w)/M(n) < 1.3) was developed, utilizing atom transfer radical polymerization (ATRP) of water-soluble monomers in an inverse miniemulsion. The optional introduction of a disulfide-functionalized cross-linker allowed for the synthesis of cross-linked (bio)degradable nanogels. Dynamic light scattering (DLS) and atomic force microscopy (AFM) measurements indicated that these particles possessed excellent colloidal stability. ATRP in inverse miniemulsion led to materials with several desirable features. The colloidal particles preserved a high degree of halogen chain-end functionality, which enabled further functionalization. Cross-linked nanogels with a uniformly cross-linked network were prepared. They were degraded to individual polymeric chains with relatively narrow molecular weight distribution (M(w)/M(n) < 1.5) in a reducing environment. Higher colloidal stability, higher swelling ratios, and better controlled degradability indicated that the nanogels prepared by ATRP were superior to their corresponding counterparts prepared by conventional free radical polymerization (RP) in inverse miniemulsion.

Preparation of Homopolymers and Block Copolymers in Miniemulsion by ATRP Using Activators Generated by Electron Transfer (AGET)

A new initiating/catalytic system for atom transfer radical polymerization (ATRP) is reported. This system starts with alkyl halides as initiators and transition metal complexes in their oxidatively stable state (e.g., Cu(II)Br2/ligand) as catalysts. The activators are generated by electron transfer (AGET) without involvement of initiating organic radicals. AGET ATRP has a significant advantage over simultaneous reverse and normal initiation (SR&NI) ATRP, because it provides a simple route for synthesizing pure polymers with complex architectures such as star copolymers, block copolymers, etc. Furthermore, AGET ATRP can be also successfully carried out in miniemulsion. Homopolymers and pure block copolymers were successfully synthesized via ATRP in miniemulsion using AGET ATRP. The final products were analyzed via two-dimensional chromatography, which combines high performance liquid chromatography (HPLC) and gel permeation chromatography (GPC). The resulting chromatograms showed that pure linear block copolymers and star block copolymers were prepared without the presence of any homopolymers.

Preparation of block copolymer particles by two-step atom transfer radical polymerization in aqueous media and its unique morphology

Submicron-sized poly( i-butyl methacrylate)- block-polystyrene particles were successfully prepared by two-step atom transfer radical polymerization (ATRP) in aqueous media: ATRP in miniemulsion (miniemulsion–ATRP) followed by ATRP in seeded emulsion polymerization (seeded-ATRP). When P iBMA particles, which were prepared by the miniemulsion–ATRP process with polyoxyethylene sorbitan monooleate (Tween 80, nonionic emulsifier) of 6–10 wt % based on iBMA, were used as seed in the seeded-ATRP of styrene, the block copolymer particles having narrow molecular weight distribution and pre-determined molecular weight were prepared at high conversion. Some block copolymer particles had an ‘onion-like’ multilayered structure. In this way, controlled/living free radical polymerization can be employed to obtain unique particle morphologies that may not be easily accessible using conventional free radical polymerization.