P(HEMA-co-PEGDA) hydrogel coated PVDF Janus membrane with superior evaporation efficiency prepared via interfacial free radical polymerization

Interfacial Reinitiation of Free Radicals Enables the Regeneration of Broken Polymeric Hydrogel Actuators

A Janus membrane with silica nanoparticles interlayer for treating coal mine water via membrane distillation

A finely tuned-up and high-performance Monte Carlo simulation, which takes diffusion-controlled and chain-length-dependent bimolecular termination reactions into account, is developed to thoroughly simulate and compare free radical (FRP) and atom transfer radical polymerization (ATRP) of styrene. It is found out that the termination rate constant falls and eventually plateaus upon the increase of the chain length of radicals. In addition, average termination rate constant greatly decreases during ATRP; nonetheless, it remains almost unchanged and smaller in FRP. Moreover, there is an accumulation of CuBr2 in the reactor as the ATRP proceeds, while the concentration of CuBr decreases and finally plateaus. Polymer chains are entirely initiated at the beginning of the ATRP, whereas initiation of chains continues throughout the free radical polymerization up to the end of the reaction. Also, the dead polymers are much lower in concentration (only 20%) in ATRP as compared to FRP (about 50%). In addition, a shift (toward higher molecular weight) in the location of the peaks of molecular weight distributions can easily be seen for the ATRP system, whilst the chain length distribution of free-radically generated polymers remains the same throughout the free radical polymerization. The molecular weight distributions narrow as the atom transfer radical polymerization progresses. Finally, the simulation results correspond closely to the experimental data.

Batch-modified Janus membranes via in-membrane-module interfacial polymerization for robust membrane stripping of ammonia from coking wastewater.

In this paper, we report a microcapsule embedded PNIPAN in P (TPC-EDA) shell and it can be regarded as an interpenetrating polymer network (IPN) structure, which can accelerate the penetration of oily substances at a certain temperature, and the microcapsules are highly monodisperse and dimensionally reproducible. The proposed microcapsules were fabricated in a three-step process. The first step was the optimization of the conditions for preparing oil in water emulsions by microfluidic device. In the second step, monodisperse polyethylene terephthaloyl-ethylenediamine (P(TPC-EDA)) microcapsules were prepared by interfacial polymerization. In the third step, the final microcapsules with poly(N-isopropylacrylamide) (PNIPAM)-based interpenetrating polymer network (IPN) structure in P(TPC-EDA) shells were finished by free radical polymerization. We conducted careful data analysis on the size of the emulsion prepared by microfluidic technology and used a very intuitive functional relationship to show the production characteristics of microfluidics, which is rarely seen in other literatures. The results show that when the IPN-structured system swelled for 6 h, the adsorption capacity of kerosene was the largest, which was promising for water-oil separation or extraction and separation of hydrophobic drugs. Because we used microfluidic technology, the products obtained have good monodispersity and are expected to be produced in large quantities in industry.

To address the issue of metal corrosion caused by microcracks in the coating on the steel structures of offshore drilling platforms, this study employs interfacial polymerization to prepare microcapsules with self-healing functionality for coatings. The microcapsules are fabricated through free radical polymerization between methyl methacrylate (MMA) and ammonium persulfate (APS), along with crosslinking reactions involving divinylbenzene (DVB). The particle size distribution and surface morphology of the microcapsules were optimized by adjusting process parameters using optical microscopy and scanning electron microscopy. Fourier-transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) were used to characterize the chemical structure and thermal stability of the microcapsules. The results show that when polyvinyl alcohol is used as the emulsifier, the oil-water ratio was 7.5:200, the amount of emulsifier was 1 wt%, the emulsification speed was 2500 r/min, the amount of initiator was 2 g, the core-to-wall ratio was 4:1, and the ambient temperature was 60 °C showed good sphericity, the microcapsules prepared under the optimized parameters exhibit good sphericity, a smooth surface, and an average particle size of 35.17 μm. They have a good core material encapsulation effect and thermal stability, which impart excellent self-healing properties to the epoxy coating. Such microcapsules have promising applications in mitigating the problem of metal corrosion of coatings due to microcracks and improving the service life and reliability of equipment.

Self-healing polymeric materials based on microencapsulated healing agents: From design to preparation

Polystyrene-b-poly(2-vinyl phenacyl pyridinium) salts as photoinitiators for free radical and cationic polymerizations and their photoinduced molecular associations

Study of kinetics and properties of polystyrene/silica nanocomposites prepared via in situ free radical and reversible addition-fragmentation chain transfer polymerizations

To examine the effect of mobil composition of matter 41 (MCM-41) nanoparticles on the kinetics of free radical and 2-(dodecylthiocarbonothioylthio)-2-methylpropionic acid (DDMAT)-mediated reversible addition fragmentation chain transfer (RAFT) polymerization, the polymerization reaction using various amounts of as-synthesized MCM-41 were performed. To study the reaction kinetics, conversion, molecular weight and polydispersity index (PDI) were obtained during the polymerization. Also, differential scanning calorimetry (DSC) was used to determine the glass transition temperature (T g) values of samples. According to the results, in free radical polymerization, conversion was increased by adding nanoparticles but the reverse trend was observed in RAFT polymerization. The same results were obtained for molecular weight values. In free radical polymerization, increasing the MCM-41 content led to higher PDI value, while in RAFT polymerization it did not appreciably affect the PDI value. In RAFT polymerization, no induction time was observed which indicates that DDMAT is an appropriate RAFT agent for styrene polymerization. Also in free radical polymerization, the addition of MCM-41 particles reduced T g values in comparison to neat PS. On the other hand, there was an increase in T g value up to 5 wt% of MCM-41 loading and a drastic reduction was observed in 7 wt% MCM-41 loading in the RAFT polymerization. Finally, the T g values of nanocomposites produced by RAFT method were higher than those in the nanocomposites synthesized using the free radical method.

In recent years, various kinds of phase change material (PCM) as energy storage materials have been widely studied. Important features of PCM are high enthalpy change near temperature of use, high density, non-toxicity, low cost, and abundance. PCMs can be divided into organic and inorganic materials, and which are encapsulated as microor nano-size particular shapes with organic, inorganic, polymeric, and hybrid materials, in order to avoid leakage of PCM and enhance thermal responsibility. Therefore, encapsulation of PCM seems indispensable in applications of fibers, interior or exterior of buildings, heat exchangers, electronic materials, and optical materials. For this, several encapsulation techniques have been developed; for example, free-radical polymerization, interfacial polymerization, in-situ polymerization, coacervation, and so on. In free-radical polymerization, thermal initiators are generally used to initiate the vinyl or acryl monomers, and the representatives can be potassium persulfate (KPS) and 2,2'azobisisobutyronitrile (AIBN) for the preparation of PCM/ polymer capsules. However, the encapsulation efficiency in these systems varies significantly with polymerization conditions or ingredients. In addition, it is not easy to get high encapsulation efficiency in the encapsulation of PCM with less than 100 nm scale. This work aims to prepare PCM/polymer core/shell nanocapsules with having high encapsulation efficiency by using interfacial redox initiation system. With regard to initiation system, cumene hydroperoxide (CHP, oil-soluble oxidant) and tetraethylenepentamine (TEPA, water-soluble reductant) were used to encapsulate n-octadecane (as PCM) in the presence of styrene and methyl methacrylate monomers, respectively.

A high‐performance Monte Carlo simulation, which takes diffusion‐controlled and chain‐length‐dependent termination into account, is developed to thoroughly simulate the kinetics of free radical and atom transfer radical polymerization (ATRP) of styrene. The average termination rate constant greatly decreases during ATRP; nonetheless, it is almost independent of conversion and smaller in free radical polymerization (FRP). Polymer chains are entirely initiated at the beginning of the ATRP, whereas initiation of chains continues over the course of the FRP. The dead polymers are much lower in the concentration in ATRP too. In addition, unlike FRP, the rate of initiation decreases quickly at the beginning of the ATRP and amounts to zero. Besides, molecular weight linearly increases with conversion in the ATRP. Moreover, molecular weight distribution shifts toward higher molecular weight in the ATRP system, whereas that of free‐radically generated polymers remains intact throughout the reaction. Finally, the simulation results correspond closely to the experimental data. © 2011 Wiley Periodicals, Inc. Adv Polym Techn 30: 257–268, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.20221

A unique design paradigm to form core–shell particles based on interfacial radical polymerization is described. The interfacial initiation system is comprised of an enzymatic reaction between glucose and glucose oxidase (GOx) to generate hydrogen peroxide, which, in the presence of iron (Fe2+), generates hydroxyl radicals that initiate polymerization. Shell formation on prefabricated polymeric cores is achieved by localizing the initiation reaction to the interface of the core and a surrounding aqueous monomer formulation into which it is immersed. The interfacially confined initiation reaction is accomplished by incorporating one or more of the initiating species in the particle core and the remainder of the complementary initiating components in the surrounding media such that interactions and the resulting initiation reaction occur at the interface. This work is focused on engineering the reaction behavior and mass transport processes to promote interfacially confined polymerization, controlling the rate of shell formation, and manipulating the structure of the core–shell particle. Specifically, incorporating GOx in the precursor solution used to fabricate cores ranging from 100 to 200 μm, and the remainder of the complementary initiating components and monomer in the bulk solution prior to interfacial polymerization yielded shells whose average thickness was 20 μm after 4 min of immersion and at a bulk iron concentration of 12.5 mM. When the locations of glucose and GOx are interchanged, the average thickness of the shell was 15 or 100 μm for bulk iron concentrations of 45 and 12.5 mM, respectively. The initial locations of glucose and GOx also determine the degree of interpenetration of the core and the shell. Specifically, for a bulk iron concentration of 45 mM, the thickness of the interpenetrating layer averaged 12 μm when GOx was initially within the core, whereas no interpenetrating layer was observed when glucose was incorporated in the core. The polymeric shell formed by this technique is also demonstrated to be self-supporting following core degradation. This behavior is accomplished by fabricating the particle core hydrogel from monomers possessing degradable groups that can be irreversibly cleaved by light exposure following shell formation. When the coated particle was exposed to light, the shell remained intact while the core degraded as evidenced by a dramatic change in diffusion coefficient of fluorescent beads immobilized within the core.

ABSTRACTPoly(sodium styrenesulfonate)-functionalized graphene was prepared from graphene oxide, using atom transfer radical polymerization and free radical polymerization. In atom transfer radical polymerization route, the amine-functionalized GO was synthesized through hydroxyl group reaction of GO with 3-amino propyltriethoxysilane. Atom transfer radical polymerization initiator was grafted onto modified GO (GO-NH2) by reaction of 2-bromo-2-methylpropionyl bromide with amine groups, then styrene sulfonate monomers were polymerized on the surface of GO sheets by in situ atom transfer radical polymerization. In free radical polymerization route, the poly(sodium 4-styrenesulfonate) chains were grafted on GO sheets in presence of Azobis-Isobutyronitrile as an initiator and styrene sulfonate monomer in water medium. The resulting modified GO was characterized using range of techniques. Thermal gravimetric analysis, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy results indicated the successful graft of polymer chains on GO sheets. Thermogravimetric analysis showed that the amount of grafted polymer was 22.5 and 31 wt% in the free radical polymerization and atom transfer radical polymerization methods, respectively. The thickness of polymer grafted on GO sheets was 2.1 nm (free radical polymerization method) and 6 nm (atom transfer radical polymerization method) that was measured by atomic force microscopy analysis. X-ray diffractometer and transmission electron microscopy indicated that after grafting of poly(sodium 4-styrenesulfonate), the modified GO sheets still retained isolated and exfoliated, and also the dispersibility was enhanced.

In this study, microcapsules containing a cumene hydroperoxide (CHP) core were produced by interfacial polymerization and tested in a variety of free-radical frontal polymerization systems. It was observed that the microcapsules could be used successfully in number of systems, and comparisons were made with typical frontal polymerization systems. The effect of encapsulation of CHP on the pot life was tested in a variety of systems, and it was observed that systems containing microcapsules underwent a dramatic increase in pot life, from hours to weeks in certain systems and from a few days to several weeks in other systems. Polymer samples that were produced from 1,6-hexanediol diacrylate (HDDA) systems with and without microcapsules were tested for modulus and toughness. It was observed that the use of CHP microcapsules resulted in an increase in the modulus and toughness (up to 2×) of polymer samples.