Faster Polymerization Rate Research Articles

Trace organic–inorganic hybrid lead halide perovskite nanocrystals as photocatalysts for PET-RAFT polymerization with high efficiency

Lead halide perovskite has emerged as a new class of materials in photocatalysis due to its promising photocatalytic performance. Here, we introduce organic–inorganic hybrid lead halide perovskite (OIHP) nanocrystals as photocatalysts (PCs) for efficient photoinduced electron/energy transfer–reversible addition–fragmentation chain transfer (PET-RAFT) polymerization. PET-RAFT polymerization is successfully conducted with 0.025 wt% PC loading under blue light (6 mW/cm2, 460 nm), yielding upwards of 90 % monomer conversion and polymer products with narrow dispersity (≤1.20) within 2 h, demonstrating a fast polymerization rate. Moreover, the oxygen resistance of the polymerization process has been demonstrated. Due to the advantages of low PC usage, fast polymerization rate and oxygen tolerance, OIHP mediated PET-RAFT polymerization is expected to be used for large-scale production and industrial applications.

Oxygen-tolerant and recyclable graphitic carbon nitride (g-C3N4) catalyzed photo-induced electron/energy transfer reversible addition-fragmentation chain transfer polymerization (PET-RAFT) without any additives

The existing photo-induced electron/energy transfer reversible addition-fragmentation chain transfer polymerization (PET-RAFT) systems using g-C3N4 as catalyst are complicated and often require modification of g-C3N4 or additives as co-catalyst. Herein, we propose an economical g-C3N4 catalyzed PET-RAFT polymerization without any additives. The good catalytic ability of g-C3N4 is attributed to the fact that the thermal exfoliation by secondary calcination increases the specific surface area and thus exposes more photocatalytic active sites. The g-C3N4 catalyzed PET-RAFT polymerizations of methyl methacrylate were successfully carried out under blue LEDs. The faster polymerization rates without prior deoxygenation showed good oxygen-tolerant. The g-C3N4 can be easily recovered after polymerization and cycled at least seven times with little loss of catalytic performance.

Self-adhesive frost-resistant conductive hydrogel electrolytes based on TA@WSCA-Zn autocatalytic system for flexible and foldable solid-state capacitors

In this study, we have successfully prepared a freeze-resistant conductive hydrogel with a fast polymerization rate and excellent mechanical and adhesive properties. In this paper, hydrogels capable of rapid polymerization in a short time were prepared based on the TA@WSCA-Zn (WSCA, water-soluble cellulose acetate; TA@WSCA, tannic acid-coated WSCA suspension; TA@WSCA-Zn, a certain amount of zinc chloride (ZnCl2) was added to TA@WSCA suspension;) autocatalytic system at room temperature or low temperature. TA@WSCA-Zn forms a stable reversible quinone-catechol redox reaction to activate the decomposition of ammonium persulfate (APS, initiator) to produce SO4−· radicals, which triggers the ultra-fast polymerization of amphoteric ([2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl), SBMA) and acrylic monomers (AA). To improve the frost resistance and electrical conductivity of the hydrogels, we also introduced amphoteric ions, which can provide migration channels for Zn2+ and greatly increase the migration rate. The TA@WSCA-7.5/PSA hydrogel (PSA, hydrogel prepared by polymerization of acrylic acid and SBMA as monomers;) can achieve tensile strength and toughness of 1.33 MPa and 4.89 MJ m−3. It can provide excellent electrical conductivity and interfacial adhesion over a temperature range of 25 to −60 °C. In addition, the supercapacitor assembled from the TA@WSCA-7.5/PSA hydrogel electrolyte still has good capacitance characteristics after folding and 10,000 charge/discharge cycles, with a capacitance retention of 93.33 % and an excellent cycle life. This autocatalytic system provides a new strategy and approach for the preparation of freeze-resistant conductive hydrogel electrolytes.

Photo‐RAFT Polymerization for Hydrogel Synthesis through Barriers and Development of Light‐Regulated Healable Hydrogels under NIR Irradiation

AbstractWe report an aqueous and near‐infrared (NIR) light mediated photoinduced reversible addition–fragmentation chain transfer (photo‐RAFT) polymerization system catalyzed by tetrasulfonated zinc phthalocyanine (ZnPcS4−) in the presence of peroxides. Taking advantage of its fast polymerization rates and high oxygen tolerance, this system is successfully applied for the preparation of hydrogels. Exploiting the enhanced penetration of NIR light, photoinduced gelation is effectively performed through non‐transparent biological barriers. Notably, the RAFT agents embedded in these hydrogel networks can be reactivated on‐demand, enabling the hydrogel healing under NIR light irradiation. In contrast to the minimal healing capability (<15 %) of hydrogels prepared by free radical polymerization (FRP), RAFT‐mediated networks display more than 80 % recovery of tensile strength. Although healable polymer networks under UV and blue lights have already been established, this work is the first photochemistry system using NIR light, facilitating photoinduced healing of hydrogels through thick non‐transparent barriers.

Photo-RAFT Polymerization for Hydrogel Synthesis through Barriers and Development of Light-Regulated Healable Hydrogels under NIR Irradiation.

We report an aqueous and near-infrared (NIR) light mediated photoinduced reversible addition-fragmentation chain transfer (photo-RAFT) polymerization system catalyzed by tetrasulfonated zinc phthalocyanine (ZnPcS4-) in the presence of peroxides. Taking advantage of its fast polymerization rates and high oxygen tolerance, this system is successfully applied for the preparation of hydrogels. Exploiting the enhanced penetration of NIR light, photoinduced gelation is effectively performed through non-transparent biological barriers. Notably, the RAFT agents embedded in these hydrogel networks can be reactivated on-demand, enabling the hydrogel healing under NIR light irradiation. In contrast to the minimal healing capability (< 15%) of hydrogels prepared by free radical polymerization (FRP), RAFT-mediated networks display more than 80% recovery of tensile strength. Although healable polymer networks under UV and blue lights have already been established, this work is the first photochemistry system using NIR light, facilitating photoinduced healing of hydrogels through thick non-transparent barriers.

In-depth mechanistic and kinetic investigation of sonochemically mediated atom transfer radical polymerization using modeling approach

Mechano/sonochemically mediated reversible deactivation radical polymerization has attracted great attention because of the novel electron transfer regulation process and high-efficient process intensification on mass transfer. Herein, a multi-scale modeling strategy combining quantum chemical calculation and kinetic modeling was developed for sonochemically induced electron transfer controlled atom transfer radical polymerization (SET-ATRP) to study the complicated SET process and its effects on polymerization. At the molecular scale, density functional theory (DFT) calculations were used to acquire the electron characteristic and structure–reactivity of the reactants, intermediates and products during SET process, which provides guideline to figure out the underlying mechanism. Results showed that DMSO•• generated under ultrasonication could react with free Me6TREN to induce electron transfer for the reduction of CuIIBr/L+ to produce CuI/L+, which is the key step for a successful polymerization. The corresponding elementary reaction rate coefficients were calculated by thermodynamic formulae combining transition state theory and Marcus theory. At the micro-scale, kinetic modeling based on method of moment was established to account for the role of SET process in regulating polymerization. Good agreements between the simulation results and experimental data confirmed the reliability of the as-developed multi-scale modeling strategy. More Me6TREN and CuIIBr/L+ resulted in more electron transfer and faster polymerization rate. This work provides an in-depth mechanism insights and kinetic understanding for SET-ATRP, which has a promising potential to promote its progress of application.

Visible light‐catalyzed living cationic homopolymerization and copolymerization of isobutyl vinyl ether: Characteristics and mechanism

AbstractOn the basis of synthesizing a highly efficient chain‐transfer agent ethyl (1‐isobutoxyethyl) carbonotrithioate(CTA), living cationic polymerization of isobutyl vinyl ether (IBVE) was successfully initiated by visible light catalysis. The random copolymerization of isobutyl vinyl ether and propyl vinyl ether (PVE), cyclohexyl vinyl ether (CyVE), and 2‐chloroethyl vinyl ether (CEVE) was achieved on the basis of investigating the reactivity ratios of vinyl ether monomers. The influence of photocatalyst (PC) concentration and wavelength on the copolymerizations was investigated. It was found that high PC concentration results in a fast polymerization rate. The wavelength of the blue LED was most suitable for this reaction system. This photocatalytic reaction provides a new way for molecular design of cationic polymerization.

The influence of particle size distribution on the curing behavior of ceramic-filled resins for vat photopolymerization

Optimizing the process of vat photopolymerization for ceramics necessitates the thorough understanding of the complex interactions between light and ceramic particles. However, it is not yet fully described how the size distribution of ceramic particles affects the curing behavior of ceramic-filled resins. Thus, this contribution provides insight into the influence of the particle size distribution (PSD) on the rheological behavior and the polymerization kinetics of photo-curable ceramic-filled resins. Four grades of alpha-aluminum oxide with different PSDs in an acrylate-based photo-curable resin were investigated. The PSD was measured using a laser diffraction particle size analyzer based on the Mie theory. The quantum of attenuated light was measured with an Ultraviolet/Visible (UV/Vis) spectrophotometer equipped with a modified integrating sphere accessory. UV/Vis measurements revealed that samples with a smaller mean particle size result in larger attenuation in the UV region of the spectrum (i.e., ∼190 nm–420 nm). Moreover, photo-rheology measurements revealed that larger particles generally result in faster polymerization rates without a noticeable change in the degree of conversion. In addition, rheological and sedimentation tests revealed that ceramic-filled resins with a larger mean particle size exhibit lower viscosity and lower sedimentation stability. The findings of this work contribute to the optimization of the process of ceramic powder selection. This results in an increase in the sedimentation stability of ceramic-filled resins, and a customization of their curing behavior.

Influence of Initiator Concentration on the Polymerization Course of Methacrylate Bone Cement.

Background: The amount of oxidant (initiator) and reductant (co-initiator) and their ratio have a significant effect on the properties of polymethacrylate bone cement, such as maximum temperature (Tmax), setting time (tset) and compressive strength (σ). The increase in the initiating system concentration causes an increase in the number of generated radicals and a faster polymerization rate, which shortens the setting time. The influence of the redox-initiating composition on the course of polymerization (rate of polymerization and degree of double bond conversion) and the mechanical properties of bone cement will be analyzed. Methods: Bone cements were synthesized by mixing a powder phase composed of two commercially available methacrylate copolymers (Evonic) and a liquid phase containing 2-hydroxyethyl methacrylate (HEMA), methyl methacrylate (MMA), and triethylene glycol dimethacrylate (D3). As an initiating system, the benzoyl peroxide (BPO) as an oxidant (initiator) in combination with a reducing agent (co-initiator), N,N-dimethylaniline (DMA), was used. Samples were prepared with various amounts of peroxide BPO (0.05%, 0.1%, 0.2%, 0.3%, 0.5% and 0.7% by weight) with a constant amount of reducing agent DMA (0.5 wt.%), and various amounts of DMA (0.25%, 0.35% and 0.5% by weight) with a constant amount of BPO (0.3 wt.%). The polymerization kinetics were studied by differential scanning calorimetry (DSC). Doughing time and compressive strength tests were carried out according to the requirements of the ISO 5833:2002 standard. Results: The increase in polymerization rate was due to the increase in the amount of BPO. In addition, the curing time was shortened, as well as the time needed to achieve the maximum polymerization rate. The final conversion of the double bonds in the studied compositions was in the range 74-100%, and the highest value of this parameter was obtained by the system with 0.3 wt.% of BPO. The doughing times for each BPO concentration were in the range of 90-140 s. The best mechanical properties were obtained for the cement following the initiating system concentrations: 0.3 wt.% of BPO and 0.5 wt.% of DMA. Nevertheless, all tested cements met the requirements of the ISO 5833:2002 standard. Conclusions: Based on the conducted polymerization kinetic studies, the best reaction conditions are provided by an initiating system containing 0.3 wt.% of BPO oxidant (initiator) and 0.5 wt.% of DMA reductant (co-initiator). A decrease in the DMA amount caused a decrease in the polymerization rate and the amount of heat released during the reaction. The change in BPO and DMA concentrations in the composition had little effect on the doughing time of the studied bone cement. The cements showed similar doughing times, ranging from 90-225 s, which is comparable to the bone cement available on the market.

The Emergence of Reversible–Deactivation Radical Polymerization in 3D Printing

AbstractThe majority of materials 3D printed using vat photopolymerization techniques are prepared by uncontrolled polymerization methods and cannot be easily modified to introduce additional functionality; these materials can be considered as effectively “dead” materials. Fortunately, a suite of photocontrolled reversible–deactivation radical polymerization (photoRDRP) techniques is recently implemented in 3D printing. In addition to their fast polymerization rate and oxygen tolerance, the high livingness imparted by photoRDRP methods is beginning to disrupt the field of 3D printing by providing access to materials with advanced properties, including on‐demand editing of surface and bulk properties, self‐healing, and control over nanostructuration and mechanical properties. This mini‐review analyzes the development of photoRDRP techniques in the field of photoinduced 3D printing with an emphasis on the advanced and highly tailorable materials possible through these techniques.

Simple Approach to Macrocyclic Carbonates with Fast Polymerization Rates and Their Polymer-to-Monomer Regeneration

Designing polymeric materials for closed-loop material streams is the key to achieving a circular society. Here, a library of macrocyclic carbonates (MCs) was designed by a facile and direct one-pot, two-step synthesis approach without the use of a solvent at a 10 g scale. We demonstrate that anionic polymerization with tert-butoxide enables the ultrafast ring-opening polymerization (ROP) of MCs with high conversion (>97%) within seconds (3–10 s) at ambient temperature. The polymerization rate depends on the odd or even number of methylene groups between the carbonate linkages in the MCs, and not the overall ring size, yielding an “odd–even” effect. This polymerization rate is related to the difference in molecular conformation of the MCs, as determined by X-ray crystallography. The polymers (polypenta-, hexa-, heptamethylene carbonate) were subsequently regenerated back to their original MCs at a high selectivity (95–99 mol %) and good yields (70–85%), hence taking a step toward closing the loop on these long alkyl chain polycarbonates.

Effects of dispersion techniques on the emulsion polymerization of methyl methacrylate

Poly(methyl methacrylate) (PMMA) latices for organic coating systems were prepared via emulsion polymerization using various emulsifying techniques. The dispersion modes have an important effect on the particle size and particle size distribution (PSD) of polymeric latices during the emulsion polymerization process. The different dispersion modes, such as magnetic stirring, ultrasound, and the combination of magnetic stirring and ultrasound, were examined to prepare particle size small and narrow PSD polymer latex. PMMA latex of size less than 20 nm in diameter and narrow PSD was successfully produced using the probe ultrasound method. By modifying the amplitude, temperature, and duration of the ultrasound probe and surfactant/water ratio, the optimal ultrasound conditions for the microemulsion polymerization were determined. This research provides new insights into the relationship between the dispersion modes and the colloidal properties of latex, which may offer more effective and simpler routes to prepare latices with fast polymerization rate and high conversion.

Mechanistic Investigation on Copper-Arylacetylide Polymerization and Sensing Applications.

Exploration of new polymerization reactions is very intriguing in fundamental and practical research, which will advance reaction theories and produce various functional materials. Herein, we report a new polymerization method based on the reaction of CuI and arylacetylide, which generates linear polymers with high molecular weight and low polydispersity index of molecular weight. The Cu-arylacetylide polymerization exhibits different characteristics with traditional polymerizations such as mild reaction temperature, air atmosphere reaction, high molecular weight, fast polymerization rate, and imprecise molar ratio between monomers. The bond formation path and activation energy of each step was investigated by density functional theory calculations to understand the reaction mechanism. The poly(Cu-arylacetylide)s exhibit strong fluorescence emission and inherent semiconductive properties, which have been used to fabricate an electronic device for streptavidin sensing.

Mechanistic Investigation on Copper–Arylacetylide Polymerization and Sensing Applications

AbstractExploration of new polymerization reactions is very intriguing in fundamental and practical research, which will advance reaction theories and produce various functional materials. Herein, we report a new polymerization method based on the reaction of CuI and arylacetylide, which generates linear polymers with high molecular weight and low polydispersity index of molecular weight. The Cu–arylacetylide polymerization exhibits different characteristics with traditional polymerizations such as mild reaction temperature, air atmosphere reaction, high molecular weight, fast polymerization rate, and imprecise molar ratio between monomers. The bond formation path and activation energy of each step was investigated by density functional theory calculations to understand the reaction mechanism. The poly(Cu‐arylacetylide)s exhibit strong fluorescence emission and inherent semiconductive properties, which have been used to fabricate an electronic device for streptavidin sensing.

Preparation of Iron Filler‐Based Photocomposites and Application in 3D Printing

AbstractThe introduction of metallic fillers to polymers via the photopolymerization approach can endow the composite materials with some unique properties, but the relevant research is still scarce due to the issue of light penetration and inner filter effect. Herein, for the first time the fabrication of photocomposites based on fine iron powder (i.e., a typical kind of metallic filler) is reported in this work. The free radical polymerization of two different acrylate monomers, poly(ethylene glycol) diacrylate and trimethylolpropane triacrylate, is performed in the presence of iron filler under mild conditions (i.e., light emitting diode (LED)@405 nm irradiation at room temperature under air). And the real‐time Fourier transform infrared spectroscopy reveals remarkable photopolymerization kinetics of acrylates with high final conversions and fast polymerization rates despite the increasing contents of iron filler in the composites. Interestingly, the 3D printing technique is applied to the iron filler‐based composites to produce tridimensional patterns with excellent spatial resolution. This work not only paves the way for the investigation of photocomposites based on metallic fillers through photochemical methods, but also broadens the potential application prospects.

Enhanced dewatering of oil sands tailings by a novel water-soluble cationic polymer

This work investigates how poly(vinylbenzyl trimethylammonium chloride)–poly(VBTMAC)–flocculates oil sands mature fine tailings (MFT). This water-soluble cationic polymer contains pendant benzene rings that make it partially hydrophobic. The positive charges on the poly(VBTMAC) backbone neutralize the negatively-charged MFT clays while the hydrophobic benzene rings help expel the water trapped in the aggregates. Vinylbenzyl trimethylammonium chloride can be polymerized to produce long chains (comparable to anionic polyacrylamide) with fast polymerization rates. Focused beam reflectance measurement (FBRM) experiments showed that larger aggregates were formed using higher molecular weight poly(VBTMAC), which is evidence of the bridging mechanism. The flocculation performance of poly(VBTMAC) was tested against commercially available anionic polyacrylamides for undiluted MFT by measuring the extent of dewatering in filtration tests and the rheological properties of the sediments. Our results showed that poly(VBTMAC) is a better flocculant in terms of ease of production, fast dewatering rate, and formation of sediments with high shear strength, but required substantially higher dosages to perform better than commercially available anionic polyacrylamides.

66‐4: Reactive Monomers Optimized for Fast Response Liquid Crystals with High Reliability

The demand for fast response liquid crystals (LC) with high reliability for high performance liquid crystal displays (LCD) is increasingly urgent. In this work, the relationships between the conditions of the UV process and the reliability of fast response LC were investigated. By the application of novel reactive monomers (RM) with faster polymerization rate and longer reaction wavelength, a kind of fast response LC with high voltage holding ratio (VHR) and low ion concentration has been obtained. This work provides new insights for the improved reliability of fast response LC without electro‐optical performance loss.

Monocomponent Photoinitiators based on Benzophenone-Carbazole Structure for LED Photoinitiating Systems and Application on 3D Printing.

In this article, different substituents (benzoyl, acetyl, styryl) are introduced onto the carbazole scaffold to obtain 8 novel carbazole derivatives. Interestingly, a benzoyl substituent, connected to a carbazole group, could form a benzophenone moiety, which composes a monocomponent Type II benzophenone-carbazole photoinitiator (PI). The synergetic effect of the benzophenone moiety and the amine in the carbazole moiety is expected to produce high performance photoinitiating systems (PISs) for the free radical photopolymerization (FRP). For different substituents, clear effects on the light absorption properties are demonstrated using UV-Visible absorption spectroscopy. Benzophenone-carbazole PIs can initiate the FRP of acrylates alone (monocomponent Type II photoinitiator behavior). In addition, fast polymerization rates and high function conversions of acrylate are observed when an amine and/or an iodonium salt are added in systems. Benzophenone-carbazole PIs have good efficiencies in cationic photopolymerization (CP) upon LED @ 365 nm irradiation in the presence of iodonium salt. In contrast, other PIs without synergetic effect demonstrate unsatisfied photopolymerization profiles in the same conditions. The best PIS identified for the free radical photopolymerization were used in three-dimensional (3D) printing. Steady state photolysis and fluorescence quenching experiments were carried out to investigate the reactivity and the photochemistry and photophysical properties of PIs. The free radicals, generated from the studied PISs, are detected by the electron spin resonance - spin trapping technique. The proposed chemical mechanisms are provided and the structure/reactivity/efficiency relationships are also discussed. All the results showed that the benzophenone-carbazole PIs have a good application potential, and this work provides a rational design route for PI molecules. Remarkably, BPC2-BPC4, C6, C8 were never synthetized before; therefore, 5 of the 8 compounds are completely new.

Merging New Organoborane Chemistry with Living Radical Polymerization

In this issue of Cell Reports Physical Science, Pan and co-workers synthesize alkylcatecholboranes that can be oxidized by oxygen to drive the release of carbon-centered radicals for initiating reversible addition-fragmentation chain transfer (RAFT) polymerization. These organoboranes can slowly decompose to radicals that enable RAFT polymerization with exceptional control yielding ultra-high molecular weight (UHMW) polymers.

Rapid Polymerization of Aromatic Vinyl Monomers to Porous Organic Polymers via Acid Catalysis at Mild Condition.

Porous organic polymers (POPs) have enormous applications in various fields and thus have received a lot of research attention in recent decades. Numerous synthetic methods have been developed, but mild synthesis conditions and fast polymerization rate are highly desired. Herein, high porous POPs with high surface areas from aromatic vinyl monomers by using acid catalysis method is reported. The polymerization is ultrafast and could be accomplished even in 5 min at room temperature. Furthermore, the surface area can be tuned by using various acid catalysts and controlling the reaction time. Due to the high surface area, these POPs show promising adsorption of carbon dioxide and hydrogen, respectively. Furthermore, the large π-system of the building block and high surface area of the POPs also make them show potential applications in photocatalytic hydrogen evolution as well as promising catalyst support for metal nanoparticles.