Polymerization In Aqueous Media Research Articles

BaTiO3 Catalyzed Ultrasonic-Driven Piezoelectric-Induced Reversible Addition-Fragmentation Chain-Transfer Polymerization in Aqueous Media.

Compared with normal 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. Reversible addition-fragmentation chain-transfer polymerization (RAFT) in aqueous media is performed in a commercial ultrasonic wash bath with 40kHz frequency ultrasonic, in the presence of piezoelectric tetragonal BaTiO3 (BTO) nanoparticles. Owing to the electron transfer from BTO under the ultrasonic action, the water can be decomposed to produce hydroxyl radical (HO•) and initiate the RAFT polymerization (piezo-RAFT). The piezo-RAFT polymerization exhibits features of controllable and livingness, such as linear increase of molar mass and narrow molar mass distributions (Mw/Mn < 1.20). Excellent temporal control of the polymerization and the chain fidelity of polymers are illustrated by "ON and OFF" experiment and chain extension, separately. Moreover, this ultrasonic-driven piezoelectric-induced RAFT polymerization in aqueous media can be directly used for the preparation of piezoelectric hydrogel which have potential application for stress sensor.

Amphiphilic Heterograft Copolymers Bearing Biocompatible/Biodegradable Grafts.

The amphiphilic heterograft copolymers bearing biocompatible/biodegradable grafts [poly(2-methyl-2-oxazoline-co-2-pentyl-2-oxazoline)-g-poly(d-l-lactic acid)/poly(2-ethyl-2-oxazoline)] were synthesized successfully by the combination of cationic ring-opening polymerization and click chemistry via the ⟨"grafting to"⟩ approach. The challenge of this synthesis was to graft together hydrophobic and hydrophilic chains on a hydrophilic platform based on PMeOx. The efficiency of grafting depends on the chemical nature of the grafts and of the length of the macromolecular chains. The self-assembly of these polymers in aqueous media was investigated by DLS, cryo-TEM, and SANS. The results demonstrated that different morphologies were obtained from nanospheres and vesicles to filaments depending on the hydrophilic weight ratio in the heterograft copolymer varying from 0.38 until 0.84. As poly(2-ethyl-2-oxazoline) is known to be thermoresponsive, the influence of temperature rise on the nanoassembly stability was studied in water and in a physiological medium. SANS and DLS measurements during a temperature ramp allowed to show that nanoassemblies start to self-assemble in "raspberry like" primary structures at 50 °C, and these structures grow and get denser as the temperature is increased further. These amphiphilic heterograft copolymers may include hydrophobic drugs and should find important applications for biomedical applications which require stealth properties.

Doped activated carbons obtained from nitrogen and sulfur-containing polymers as metal-free catalysts for application in nitroarenes hydrogenation

Activated carbons doped with nitrogen and/or sulfur have been obtained by pyrolysis followed of steam activation of a sulfur containing polymer (polythiophene) and two nitrogen-containing polymers (polyaniline and polypyrrole). These polymers were synthesized by oxidative chemical polymerization in aqueous media of their corresponding monomers.The influence of the steam activation on the textural properties and surface chemistry of the carbons has been evaluated and their catalytic activity has been determined in the hydrogenation reaction of 1-chloro-4-nitrobenzene. The degree of conversion in the reaction depends on the development of adequate porosity in the activated carbon (which is determined by the activation conditions) together with the presence of heteroatoms that act as active catalytic sites, with S showing considerably greater effectiveness than N. A compromise between an acceptable level of doping with sulfur and an adequate porosity is necessary, which has been achieved in a carbon obtained from polythiophene pyrolyzed at 900 °C and steam activated at 800 °C for 4 h, with a specific surface area of 742 m2/g and S content of 1.71 at%.

Colloidally Stable Polypyrrole Nanoparticles Synthesized by Surfactant-Free Coupling Polymerization.

Surfactant-free polypyrrole (PPy) nanoparticles, which were colloidally stable in aqueous medium, were successfully synthesized by coupling polymerization of pyrrole using Fe(NO3)3 solids in the absence of any colloidal stabilizer. The pyrrole monomers were gradually supplied from the vapor phase, and the coupling reaction of the monomers could proceed to generate PPy in a water medium. The resulting PPy nanoparticles were extensively characterized in terms of diameter, bulk chemical composition, surface chemistry, and colloidal stability by dynamic light scattering, electron microscopy, elemental microanalysis, Fourier transform infrared spectroscopy, Raman spectroscopy, electrophoresis, and X-ray photoelectron spectroscopy. The characterization results indicated that the PPy nanoparticles can be colloidally stable based on the electrostatic stabilization mechanism due to cationic charges generated on the PPy molecules by doping during the polymerization. General chemical oxidative polymerization in aqueous medium using the Fe(NO3)3 oxidant without a colloidal stabilizer as a control experiment resulted in generation of atypical PPy aggregates with over a micrometer size, indicating that the polymerization at low ionic strength is essential for colloidal particle formation. Finally, it was demonstrated that the PPy nanoparticles worked as a surfactant-free black-colored particulate emulsifier by adsorption at the oil-water interface to stabilize Pickering-type oil-in-water emulsions.

Synthesis of novel modified acrylamide copolymers for montmorillonite flocculants in water-based drilling fluid

A study was conducted to treat the water-based drilling fluid through coagulation-flocculation. Innovative modified acrylamide copolymers were utilized as montmorillonite flocculants to improve drilling performance and reduce environmental contamination. A series of acrylamide copolymers was prepared by in situ free radical polymerization in aqueous medium using ammonium persulfate as a radical initiator. The chemical structure of the prepared copolymers was confirmed by FT-IR (Fourier-Transform Infrared Spectroscopy) and the polydispersity indices of the copolymers determined using gel permeation chromatography. Thermal gravimetric analysis showed that the copolymers have a very high temperature tolerance, i.e. they are stable up to 390 °C. In this paper, acrylamide copolymers were used as coagulant with cationic, anionic groups or both of them simultaneously. Consequently, in order to clarify the relationship between inhibitive properties, sedimentation volume measurement, SEM (scanning electron microscope), XRD (X-ray diffraction) and contact angle were adopted. Some factors including molecular weight and molecular chain affecting the interaction between copolymers and clay particles were analyzed. Anionic sample with the highest molecular weight can reduce the interlayer spacing of the hydrated clay to the minimum. Amphoteric sample exhibits the best performance as a coagulant in comparison with other copolymers.

Synthesis and Characterization of a Thermoresponsive Copolymer with an LCST-UCST-like Behavior and Exhibiting Crystallization.

In this work, the diblock copolymer methoxy-poly(ethylene glycol)-block-poly(ε-caprolactone) (MPEG-b-PCL) was synthesized with a block composition that allows this polymer in aqueous media to possess both an upper critical solution temperature (UCST) and a lower critical solution temperature (LCST) over a limited temperature interval. The value of the UCST, associated with crystallization of the PCL-block, depended on heating (H) or cooling (C) of the sample and was found to be CPUCSTH = 32 °C and CPUCSTC = 23 °C, respectively. The LCST was not affected by the heating or cooling scans; assumed a value of 52 °C (CPLCSTH = CPLCSTC). At intermediate temperatures (e.g., 45 °C), dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), and cryogenic transmission electron microscopy (cryo-TEM) showed that the solution consisted of a large population of spherical core-shell particles and some self-assembled rodlike objects. At low temperatures (below 32 °C), differential scanning calorimetry (DSC) and wide-angle X-ray scattering (WAXS) in combination with SAXS disclosed the formation of crystals with a cylindrical core-shell structure. Cryo-TEM supported a thread-like appearance of the self-assembled polymer chains. At temperatures above 52 °C, incipient phase separation took place and large aggregation complexes of amorphous morphology were formed. This work provides insight into the intricate interplay between UCST and LCST and the type of structures formed at these conditions in aqueous solutions of MPEG-b-PCL diblock copolymers.

Soft Self-Assembled Mechanoelectrical Transducer Films from Conductive Microgel Waterborne Dispersions.

The present study aims in the developing of new soft transducers based on sophisticated stimuli-responsive microgels that exhibit spontaneous self-assembly forming cohesive films with conductive and mechanoelectrical properties. For that, oligo(ethylene glycol)-based stimuli-responsive microgels have been synthesized using bio-inspired catechol cross-linkers by one-step batch precipitation polymerization in aqueous media. Then, 3,4-ethylene dioxyyhiophene (EDOT) has been directly polymerized onto stimuli-responsive microgels using catechol groups as the unique dopant. PEDOT location is dependent on the cross-linking density of microgel particles and EDOT amount used. Moreover, the spontaneous cohesive film formation ability of the waterborne dispersion after evaporation at soft application temperature is demonstrated. The films obtained present conductivity and enhanced mechanoelectrical properties triggered by simple finger compression. Both properties are function of the cross-linking density of the microgel seed particles and PEDOT amount incorporated. In addition, to obtain maximum electrical potential generated and the possibility to amplify it, several films in series were demonstrated to be efficient. The present material can be a potential candidate for biomedical, cosmetic, and bioelectronic applications.

The microstructure of polyphosphoesters controls polymer hydrolysis kinetics from minutes to years

The stability and degradation rates of polymers in aqueous media are critical factors for their biomedical applications, as they must remain intact for a specific period of time before degrading or degrading on-demand to prevent potential accumulation and harmful effects. Polyphosphoesters (PPEs) are highly compatible with biological systems, and the ester bonds in the backbone allow for hydrolytic degradation. In this study, we have demonstrated that the degradation rate of various PPEs can be precisely controlled by minor modifications to the side-chain and the binding pattern around the phosphorous center in the polymer backbone. We synthesized a systematic library of water-soluble PPEs using ring-opening polymerization, resulting in polyphosphates and in-chain or side-chain polyphosphonates. Specifically, we investigated the degradation rates of side-chain polyphosphonates with different side-chain structures (methyl, ethyl, allyl, iso- or n-propyl) at pH = 8 and pH = 11. Our results indicate that the degradation mechanism is influenced by the type and size of the side-chain, as well as the pH. At pH = 11, hydrophilicity is a key factor, while at pH = 8, electron density on the phosphorus is crucial, leading to a random chain scission or a backbiting mechanism. We also observed that changing the binding pattern of the phosphorus or incorporating additional “breaking points” allowed us to tune the half-life times of the polymer from less than a day to several years. This study highlights the versatile stability of water-soluble PPEs, making them a promising option for various applications that require different hydrolysis rates, such as tissue regrowth.

Controlled Fabrication of Uniform Digital Nanorods from Precise Sequence-Defined Amphiphilic Polymers in Aqueous Media

Controlled Fabrication of Uniform Digital Nanorods from Precise Sequence-Defined Amphiphilic Polymers in Aqueous Media

Tailoring of Textural Properties of 3D Reduced Graphene Oxide Composite Monoliths by Using Highly Crosslinked Polymer Particles toward Improved CO2 Sorption.

The main constraint on developing a full potential for CO2 adsorption of 3D composite monoliths made of reduced graphene oxide (rGO) and polymer materials is the lack of control of their textural properties, along with the diffusional limitation to the CO2 adsorption due to the pronounced polymers' microporosity. In this work, the textural properties of the composites were altered by employing highly crosslinked polymer particles, synthesized by emulsion polymerization in aqueous media. For that aim, waterborne methyl methacrylate (MMA) particles were prepared, in which the crosslinking was induced by using different quantities of divinyl benzene (DVB). Afterward, these particles were combined with rGO platelets and subjected to the reduction-induced self-assembly process. The resulting 3D monolithic porous materials certainly presented improved textural properties, in which the porosity and BET surface area were increased up to 100% with respect to noncrosslinked composites. The crosslinked density of MMA polymer particles was a key parameter controlling the porous properties of the composites. Consequently, higher CO2 uptake than that of neat GO structures and composites made of noncrosslinked MMA polymer particles was attained. This work demonstrates that a proper control of the microstructure of the polymer particles and their facile introduction within rGO self-assembly 3D structures is a powerful tool to tailor the textural properties of the composites toward improved CO2 capture performance.

Bioinspired Polysaccharide-Derived Zwitterionic Brush-like Copolymer as an Injectable Biolubricant for Arthritis Treatment.

Developing highly efficient and biocompatible biolubricants for arthritis treatment is extraordinarily demanded. Herein, inspired by the efficient lubrication of synovial joints, a paradigm that combines natural polysaccharide (chitosan) with zwitterionic poly[2-(methacryloyloxy) ethyl phosphorylcholine] (PMPC), to design a series of brush-like Chitosan-g-PMPC copolymers with highly efficient biological lubrication and good biocompatibility is presented. The Chitosan-g-PMPC copolymers are prepared via facile one-step graft polymerization in aqueous medium without using any toxic catalysts and organic solvents. The as-prepared Chitosan-g-PMPC copolymers exhibit very low coefficient of friction (μ < 0.01) on Ti6 Al4 V alloy substrate in both pure water and biological fluids. The superior lubrication is attributed primarily to the hydrated feature of PMPC side chains, interface adsorption of copolymer as well as to the hydrodynamic effect. In vivo experiments confirm that Chitosan-g-PMPC can alleviate the swelling symptom of arthritis and protect the bone and cartilage from destruction. Due to their facile preparation, distinctive lubrication properties, and good biocompatibility, Chitosan-g-PMPC copolymers represent a new type of biomimetic lubricants derived from natural biopolymer for promising arthritis treatment and artificial joint lubrication.

An investigation of polyphosphinoboranes as flame-retardant materials

Phosphorus-containing polymers are of considerable interest as flame-retardants additives. We report investigations into the flame-retardant properties of a series of polyphosphinoboranes [RR’PBH 2 ] n prepared by iron-catalyzed dehydrocoupling protocols. When cotton towel was impregnated with the polyphosphinoboranes and exposed to a flame, the presence of polyphosphinoborane was found to result in self-extinguishing of the flame leaving behind a charred material. In contrast, under analogous conditions, untreated cotton and cotton treated with polystyrene burnt and was completely consumed. Analysis of the char revealed the formation of phosphoric and boric acids, species commonly invoked for the action of related flame-retardant species. The use of P-disubstituted polyphosphinoboranes was found to slightly slow burning; however, the presence of halogenated groups in the side chain had little effect suggesting that it is the main chain that imparts any flame-retardant effect. Exposure of cotton treated with poly(phenylphosphinoborane) to water was not found to have any effect on flame-retardancy demonstrating the non-leachability of these polymers in aqueous media. • Polyphosphinoboranes were shown to function as flame retardant materials for cotton. • The polymers were prepared by catalytic dehydrocoupling and, in some cases, poly-polymerisation modification. • The polymers display self-extinguishing behaviour. • On impregnation into cotton, the polymers were non-leachable in water.

Core–shell to Janus morphologies from co-assembly of polyaniline and hydrophobic polymers in aqueous media

Core–shell to Janus morphologies from co-assembly of polyaniline and hydrophobic polymers in aqueous media

Solution properties of amphiphilic amino- and oligoethylene glycol-containing methacrylic copolymers

The behavior of methacrylic copolymers with oligoethylene glycol and amine groups in aqueous solutions has been studied. The eff ect of the composition of copolymers of alkoxyoligo(ethylene glycol) methacrylates and N-[3-(dimethylamino) propyl] methacrylamide on their solubility in aqueous media, aggregation properties and surface activity at the water-oil phase boundary was demonstrated. The presence of thermo- and pH-responsive properties, characterized by lower critical solution temperature, has been shown. Polymers exhibit high interfacial activity at the water-toluene interface, which increases with an increase in the proportion of methacrylic ether units in the copolymer. For polymers in aqueous media the value of the critical micelle concentration was found in the region of 10-3 g/L.

Ionic supramolecular polymerization of water-soluble porphyrins: balancing ionic attraction and steric repulsion to govern stacking.

We have synthesized novel water-soluble anionic porphyrin monomers that undergo pH-regulated ionic supramolecular polymerization in aqueous media. By tuning the total charge of the monomer, we selectively produced two different supramolecular polymers: J- and H-stacked. The main driving force toward the J-aggregated supramolecular polymers was the ionic interactions between the sulfonate and protonated pyrrole groups, ultimately affording neutral supramolecular polymers. In these J-aggregated supramolecular polymers, amide groups were aligned regularly along polymer wedges, which further assembled in an edge-to-edge manner to afford nanosheets. In contrast, the H-aggregated supramolecular polymers remained anionic, with their amide NH moieties acting as anion receptors along the polymer chains, thereby minimizing repulsion. For both polymers, varying the steric bulk of the peripheral ethylene glycol (EG) units controlled the rates of self-assembly as well as the degrees of polymerization. This steric effect was further tunable, depending on the solvation state of the EG chains. Accordingly, this new family of supramolecular polymers was created by taking advantage of unique driving forces that depended on both the pH and solvent.

Aqueous broadband photopolymerization on microreactor arrays: from high throughput polymerization to fabricating artificial cells

Microreactor arrays combining ZnO and polyaniline are fabricated onto the bottom of multi-well plates to catalyze broadband sunlight-driven open-to-air polymerization in aqueous media.

Thermoelectric Properties of ex-situ PTH/PEDOT Composites

A thermoelectric material can convert temperature difference into electrical potential difference. Today, intensive researches are being carried out in order to use flexible, non-toxic and inexpensive conductive polymers instead of hard, hard-to-shape, expensive and toxic semiconductor metals used as thermoelectric materials. Among the conductive polymers investigated for this purpose, poly(3,4-ethylenedioxythiophene) (PEDOT) is the most promising. However, its thermoelectric properties alone are not sufficient. Thermoelectric properties can be increased by incorporating nanoparticles in inorganic, organic or polymeric structures into conductive polymers. In this study firstly, PTh was synthesized with and without magnetic field by oxidative polymerization in aqueous media in the presence of poly(sulfonic acid diphenyl aniline). Secondly, PEDOT was synthesized with and without magnetic field in aqueous media by oxidative polymerization. Then, ex-situ PTH/PEDOT composites were obtained with different ratios of PTh/PEDOT. Particle sizes of polymers were measured and their FTIR and UV-vis. spectra were taken. Seebeck coefficient and electrical conductivity were measured from thin films of polymers. Power factor values were calculated. It was found that the Seebeck coefficients of PTh and ex-situ PTH/PEDOT composites increased with magnetic field. The highest Seebeck coefficient and power factor of PEDOTs were obtained from PEDOT synthesized without magnetic field as 1683.3 µV/K and 98.2 µW/mK2, respectively. The highest Seebeck coefficient and power factor of ex-situ PTh/PEDOT composites were obtained from (PTh/PEDOT3)m synthesized with magnetic field as 400 µV/K and 0.1 µW/mK2, respectively.

Unveiling Polymerization Mechanism in pH-regulated Supramolecular Fibers in Aqueous Media.

An amine functionalized C3‐symmetric benzotrithiophene (BTT) monomer has been designed and synthetized in order to form pH responsive one‐dimensional supramolecular polymers in aqueous media. While most of the reported studies looked at the effect of pH on the size of the aggregates, herein, a detailed mechanistic study is reported, carried out upon modifying the pH to trigger the formation of positively charged ammonium groups. A dramatic and reversible change in the polymerization mechanism and size of the supramolecular fibers is observed and ascribed to the combination of Coulombic repulsive forces and higher monomer solubility. Furthermore, the induced frustrated growth of the fibers is further employed to finely control the one‐dimensional supramolecular polymerisation and copolymerization processes.

Insights in the Thermal Volume Transition of Poly(2‐oxazoline) Hydrogels

AbstractPolymers with a lower or an upper critical solution temperature (LCST or UCST) can precipitate in a very narrow temperature range. Cross‐linking of such polymers and adding them to suited solvent results in smart gels that are capable of greatly changing their dimensions with changing temperature. This transition occurs very often in a broad temperature range, which limits the applicability of smart materials. To shed some light into the design of thermo‐responsive hydrogels with a narrow phase transition, poly(2‐ethyl‐2‐oxazoline) (PEtOx), poly(2‐isopropyl‐2‐oxazoline), and statistical copolymers of 2‐butyl‐2‐oxazoline and 2‐ethyl‐2‐oxazoline, respectively, are synthesized and the concentration‐dependent cloud point temperatures (Tcp) of the free polymers in aqueous media are determined in relation to the thermo‐responsive swelling behavior of the respective hydrogels. A narrow thermal transition of the hydrogels can only be achieved when the Tcp of the free polymers in water is independent on the concentration. Aqueous salt solutions can render even PEtOx into a concentration independent LCST polymer. However, this salt effect does not work for hydrogels.

Synthesis of gum tragacanth-grafted pentapolymer hydrogels for As(III) exclusion: Roles of microwaves, RSM optimization, and DFT studies

Microwave assisted homogeneous heating, selectivity in radical formation, and the faster polymerization facilitate the synthesis, structures, properties, and the higher branching associated stability of multifunctional multipolymers. Thus, the optimum gum tragacanth (GMTR)-grafted pentapolymer hydrogel/ HG2 was synthesized from three monomers, i.e., cis-butenedioic acid (cBDA), N-hydroxymethylacryalamide (NHMAm), and 2-(methacryloyloxy)ethanol (MAOE), and in situ generated 2-(3-((hydroxymethyl)amino)-3-oxopropoxy)ethyl-2-methylbutanoate (CM1) and 2-hydroxyethyl 3-(N-(hydroxymethyl)-2-methylbutanamido)-2-methylpropanoate (CM2) comonomers through microwave assisted facile polymerization in aqueous medium. Here, twenty-one GMTR-grafted-[cBDA-co-CM1-co-NHMAm-co-CM2-co-MAOE/ HG1] hydrogels were prepared by using variable amounts of synthesis parameters, of which the optimum HG2 was chosen for the scale-up repetitive As(III)-exclusion. RSM was used to measure the optimum power-temperature-time of microwave irradiation. The structures of HG1, HG2, and As(III)-adsorbed HG2/ As(III)-HG2, in situ anchored comonomers, GMTR-grafting, reusability, thermostability, and surface phenomena were comprehended by XPS, NMR, UV–vis, FTIR, TG, XRD, DLS, and SEM analyses; pHPZC; network parameters; and thermodynamic variables. The geometries, electronic structures, and variable coordinations of As(III) with HG2 were investigated through DFT studies of HG2 and As(OH)3-HG2. The highest exclusion efficiency of 25 mg HG2 within 5–100 mg L−1 As(III) and at 298 K was 192.91 mg g−1, which was significantly higher than that of HG1.