Tripropylene Glycol Diacrylate Research Articles

Coumarin based glyoxylate photoinitiators for free radical and cationic Photopolymerizations with UV-Visible LED irradiation

High-performance photoinitiators (PIs) play a crucial role in ultraviolet–visible (UV–Vis) photopolymerization. In this study, three coumarin-3-oxoacetic acid methyl esters (COAEs) which demonstrate significant UV–Vis absorption within the 300–500 nm range were synthesized and studied. Real-time fourier transform infrared (RT-FTIR) and photo-differential scanning calorimetry (photo-DSC) experiments demonstrated that these PIs can function as Type I and Type II PIs for initiating free radical polymerization (FRP) of acrylate monomers. Additionally, they can serve as photosensitizers for iodonium salts and sulfonium salts, enabling cationic photopolymerization (CP) of epoxy and oxetane monomers. Remarkably, even at low concentrations of 0.01 wt%, they can effectively initiate the deep curing of Tri-(propylene glycol) diacrylate (TPGDA) to a depth of approximately 9 cm after 5 min of irradiation with a 415 nm or 450 nm LED light source. Furthermore, the COAEs exhibit satisfactory photobleaching properties, making them suitable for colorless applications in photopolymerization. The photochemical and photophysical properties of the COAEs were thoroughly investigated using absorption spectroscopy, electron spin resonance, cyclic voltammetry experiments, and photoinduced decarboxylation experiments to elucidate the photoinitiation mechanism. Cytotoxicity experiments revealed that COAE-N exhibited good cytocompatibility. Therefore, the exceptional polymerization properties of COAEs offer promising prospects for FRP and CP applications. Additionally, their efficient photobleaching characteristics make them highly suitable for deep photopolymerization applications. Moreover, the low cytotoxicity of COAEs suggests significant potential for biomedical applications such as dental restoration.

Photobleachable coumarin-thioester derivatives with low cytotoxicity as visible-light photoinitiators for free radical and cationic photopolymerization

The development of photoinitiators is suffering from deep color, low solubility, and biotoxicity caused by the introduction of large-conjugated structures, also the complex synthetic procedures constrain the application of photoinitiators. To overcome this issue, nine kinds of coumarin thioester photoinitiators (CTEs) have been delicately designed and synthesized through a simple, metal-free two-step reaction. CTEs with excellent light absorption properties in the visible light range can be used not only as a type I photoinitiator but also as a type II photoinitiator, and sensitizer in the cationic photoinitiating system. CTEs effectively initiate the photopolymerization of tripropylene glycol diacrylate (TPGDA) under the irradiation of 405 nm LED, and the double bond conversions are similar to or better than those of commercial photoinitiators. Also, the cationic photopolymerization of bisphenol A diglycidyl ether (BADGE) is successfully initiated by CTEs/IOD systems. Notably, the epoxy group conversion initiated by 6O-CTE/IOD reaches 72.1 %, surpassing that of the commercial photoinitiating system. The photoinitiating mechanism of CTEs is proposed and supported by theoretical calculations. Furthermore, the bond cleavage abilities of CS bonds endow CTEs with photobleaching properties. The colorless cured film initiated by 6O-CTE was obtained under only 15 s irradiation, indicating their application prospects of CTEs in colorless photopolymerization. More importantly, the cytotoxicity of CTEs is much lower than that of commercial photoinitiator TPO. This work provides new insight into the design of biocompatible photoinitiators with a photobleaching property for LED photopolymerization.

3D-printable hydrophobic silicone inks for antiadhesion tough objects via molecular engineering

3D printable hydrophobic ink is highly desirable to simply print hydrophobic objects for various applications, such as oil/water separation. However, printable hydrophobic monomers/inks are limited which seriously restricts the fabrication and application of 3D printing hydrophobic objects. Herein, simulating the crown, trunk, and roots of trees from the molecular levels, coatings/objects were designed and prepared using a 6-functional hyperbranching polyurethane acrylate (PUA) monomer as the “trunk”, mono-acrylate terminated polydimethylsiloxane (Vi-PDMS) as the “leaf”, and tripropylene glycol diacrylate (TPGDA) as the “root”. The printed objects with excellent mechanical properties and stable hydrophobicity with CAs and SAs in the range of 80°–110° and 10°–30°, respectively, and could be used in a variety of environments (e.g., acid-based solution, seawater) for a month. Cylindrical, ladder, and mushroom-shaped micro-nano structures could be prepared to improve the hydrophobicity of the printed objects to achieve CAs up to ∼170°. The antiadhesion tough teeth and microchannels could be prepared facilely with the hydrophobic inks. This work demonstrates a simple and rapid method to manufacture various complex and sophisticated hydrophobic coatings/objects and a broader strategy for 3D printing technology.

Photo-assisted ultrasonic curing for ultrafast and deep prototyping based on coumarin derivatives

Although photocuring is currently the most commonly used method in 3D additive manufacturing, it still faces significant challenges in rapid prototyping of thick materials due to the limited penetration of light. Ultrasonic technology has the advantages of high penetration depth and unparalleled cavitation, offering opportunities for enabling additive manufacturing of thick materials. In this study, a coumarin-based two-component system composed of Coum-Ph-OC12H25 and N-phenylglycine as initiator and hydrogen supplier, respectively, was developed to achieve ultrasonic curing of tripropylene glycol diacrylate (TPGDA). The ideal curing efficiency of this two-component system was optimized to 90 %, and ultrasonic curing of thick materials was achieved with a penetration depth of up to 15 cm. Moreover, electron spin resonance (ESR) spectroscopic measurements demonstrated the free-radical reaction mechanism. It is believed that this research has the potential to expand the 3D additive manufacturing technology and pave the way for future developments in this field.

Enhancing the sound and thermal insulation properties of polypropylene foam by preparing high melt strength polypropylene.

High-performance polypropylene (PP) foam is a vital polymer product in industrial areas. However, the poor melt strength of ordinary PP homopolymer limits its foaming molding. In this work, high melt strength polypropylene (HMSPP) was prepared by using styrene (St) and tripropylene glycol diacrylate (TPGDA) as comonomers, and then PP foams were prepared by mold foaming method. The results showed that adding St in the grafting process of TPGDA will obviously improve the melt strength of the PP matrix, and its melt strength (28184Pa.s) is 7.4 times higher than that of pure PP. HMSPP foam has more regular and uniform cells and higher cell density, which significantly improves the sound and thermal insulation properties of PP foam. Compared with pure PP foam, the average sound transmission loss (52.9dB) of HMSPP foam with a low foaming ratio increased by 64%, and the thermal conductivity (0.0867W/mK) decreased by 46%. Therefore, the obtained HMSPP foam can be used in sound insulation or thermal insulation area. This work provides an available route for the high-performance utilization of PP foam. This article is protected by copyright. All rights reserved.

Study on The Emulsion Stability of Tripropylene Glycol Diacrylate in Water

Study on The Emulsion Stability of Tripropylene Glycol Diacrylate in Water

A surrogate modelling strategy to improve the surface morphology quality of inkjet printing applications

Current trends in manufacturing electronics feature digital inkjet printing as a key technology to enable the production of customised and microscale functional devices. However, electrical device performance depends on the accuracy and uniformity of the printed-track morphology, which presents significant quality challenges in current applications. Several studies to predict the morphology of printed features have been developed using computationally expensive physics-based simulations, but little attention has been paid to reduced order models suitable for fast production conditions. Here we propose a surrogate modelling framework to improve the inkjet-printed track morphology created by the sequential deposition of microdroplets on non-porous substrates. Assuming physical properties of a UV-curable dielectric ink made from tripropylene glycol diacrylate (TPGDA), a set of response surface equations built from a validated lattice Boltzmann simulation predict the track morphology as a function of drop spacing and contact angle hysteresis with an error percentage less than 10 %. Furthermore, the surrogate model is able to capture transient effects observed in experiments and builds track morphology in seconds, enabling efficient optimisation of printing and wetting parameters. The simplicity of the proposed technique makes it a promising tool for model driven inkjet printing process optimization, including real time process control and paves the way for better quality devices in the printed electronics industry.

Sugar-Core Synthesized Multibranched Polylactic Acid and Its Diacrylate Blends as a UV LED-Curable Coating with Enhanced Toughness and Performance

Exploring the application of biodegradable/bioplastic coating material for eco-friendly and sustainable packaging is one of the global challenges being tackled. In this context, we propose (i) the synthesis of multibranched polylactic acid (PLA) using table sugar mainly composed of sucrose as a core initiator, and (ii) a model formula for sugar-based PLA (suPLA) and its diacrylate blends as a UV LED-curable coating. The synthesis of suPLA through ring-opening polymerization (ROP) was optimized by sugar: l-lactide (L-LA) molar ratio, temperature, and reaction time. suPLA, with a Mw of ∼1000 g/mol, was obtained with a maximum yield of around 80%. To establish a model UV LED-curable bioplastic-based coating, the suPLA with different content was formulated in tripropylene glycol diacrylate (TPGDA) as a diluent monomer. The influence of curing time (0–60 s) on double bond conversion for turning the liquid coating to a solid film of the suPLA/TPGDA blending system was assessed. Aiming to validate the influence of the curing degree, changes in the chemical function, thermal stability, glass transition temperature, crystallization temperature, and enthalpy were also characterized. By increasing the suPLA content, the tensile tests on the UV LED-cured suPLA-TPGDA films showed significant improvement in terms of toughness. The coating surface morphologies and optical properties (i.e., gloss value, color difference, yellowness, and whiteness indexes) were also determined. It is worth noting that the sugar molecule and multibranched structure play an important role in moisture absorption. The biodegradation test demonstrated that the UV LED-cured suPLA-TPGDA film exhibited biodegradation phenomena, as analyzed from CO2 production, physical appearance, changes of mass, chemical functions, and thermal stability. The current study showed that the suPLA and its diacrylate blends are promising biobased, printable, and UV LED-curable coating prototypes to create a tough film for a sustainable packaging approach in the future.

UV curing behavior of a liquid polyborosilazane and stereolithography to SiBCN ceramic components

The ultraviolet (UV) curing behavior and kinetics both in air and in nitrogen atmosphere of a liquid polyborosilazane were investigated by differential scanning photo calorimeter (DPC) measurement and real-time FTIR techniques. The results showed that the bifunctional acrylic reactive diluent tripropylene glycol diacrylate (TPGDA) content, photo-initiator concentration, and temperature had their optimal values to get the maximum ultimate reaction rate and conversion percentage. It's noteworthy that the addition of TPGDA will greatly enhance polymerization rate and conversion percentage within a very short time-frame. While the rate in air is higher than in nitrogen atmosphere, probably owing to the effect of oxidation curing, which is coordinated with the calculation results of activation energy.Based on the above experiment, we also report on the direct fabrication of SiBCN ceramic components from preceramic polyborosilazanes by stereolithography and subsequent pyrolysis at 900 ○C for 4 h. The TGA curve shows the ceramic yield is 51.1% after pyrolysis at 1200 ○C. A linear shrinkage of 27%, associated with the polymer-to-ceramic conversion, was observable and the density of pyrolyzed SiBCN is about 2 g cm−3 with slight residual porosity. The indentation hardness is 9.83 GPa and the modulus is 77.1 GPa after heat-treatment at 1400 ○C for 3 h.

Coumarin Ketoxime Ester with Electron-Donating Substituents as Photoinitiators and Photosensitizers for Photopolymerization upon UV-Vis LED Irradiation.

High-performance photoinitiators (PIs) are essential for ultraviolet-visible (UV-Vis) light emitting diode (LED) photopolymerization. In this study, a series of coumarin ketoxime esters (COXEs) with electron-donating substituents (tert-butyl, methoxy, dimethylamino and methylthio) were synthesized to study the structure/reactivity/efficiency relationships for substituents for the photoinitiation performance of PIs. The introduction of heteroatom electron-donating substituents leads to a redshift in the COXE absorption of more than 60 nm, which matches the UV-Vis LED emission spectra. The PIs also show acceptable thermal stability via differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The results from real-time Fourier transform infrared (RT-FTIR) measurements indicate that COXEs show an excellent photoinitiation efficiency for free radical polymerization under UV-Vis LED irradiation (365-450 nm); in particular, the conversion efficiency for tri-(propylene glycol) diacrylate (TPGDA) polymerization initiated by COXE-O and COXE-S (4.8 × 10-5 mol·g-1) in 3 s can reach more than 85% under UV-LED irradiation (365, 385 nm). Moreover, the photosensitization of COXEs in the iodonium hexafluorophosphate (Iod-PF6) and hexaarylbiimidazole/N-phenylglycine (BCIM/NPG) systems was investigated via RT-FTIR. As a coinitiator, COXEs show excellent performance in dry film photoresist (DFR) photolithography. This excellent performance of COXEs demonstrates great potential for UV-curing and photoresist applications, providing a new idea for the design of PIs.

THE EFFECT OF THE ACRYLATE MONOMER ON THE CHARACTERISTICS OF PHOTOPOLYMERIZABLE SUSPENSIONS FOR THE PRODUCTION OF CERAMICS FROM STABILIZED ZrO2

The influence of the structure and properties of acrylate monomers on the rheology and polymerization of suspensions containing partially stabilized zirconium dioxide, a dispersant and a photoinitiator as a ceramic filler is investigated. It has been shown that the use of the DISPERBYK 2013 additive makes it possible to obtain suspensions containing 1,6-hexanediol diacrylate, dipropylene glycol diacrylate and tripropylene glycol diacrylate with a viscosity value below 5 Pa?s at high (up to 41 vol. %) filling with TZ-3YS-E powder. The possibility of using the obtained suspensions for three-dimensional printing of high-density ceramic products with complex geometry has been established.

Molecular Dynamics Study on Behavior of Resist Molecules in UV-Nanoimprint Lithography Filling Process.

In this study, we performed molecular dynamics (MD) simulations of the filling process of few-nanometer-wide trenches with various resist materials in ultraviolet nanoimprint lithography (UV-NIL) to identify the main molecular features necessary for a successful filling process. The 2- and 3-nm wide trenches were successfully filled with the resist materials that had (experimentally determined) viscosities less than 10 mPa·s. The resist composed of a three-armed bulky and highly viscous molecule could not fill the trenches. The radius of gyration of this molecule was smaller than half of the distance in which the first peak of its radial distribution function occurred. The available shapes of 1,6-hexanediol diacrylate (HDDA) and tri(propylene glycol) diacrylate (TPGDA), which are linear photopolymers, were compared to reveal that TPGDA is more flexible and adopts more conformations than HDDA. The terminal functional groups of TPGDA can be close due to its flexibility, which would increase the probability of intramolecular crosslinking of the molecule. This simulation result could explain the difference in hardness between the UV-cured HDDA and TPGDA based materials observed by experiments. The findings revealed by our MD simulations provide useful information for selecting and designing resists for fine patterning by UV-NIL.

Four-Level Structural Hierarchy: Microfluidically Supported Synthesis of Polymer Particle Architectures Incorporating Fluorescence-Labeled Components and Metal Nanoparticles.

Hierarchical assemblies of functional polymer particles are promising due to their surface as well as physicochemical properties. However, hierarchical composites are complex and challenging to form due to the many steps necessary for integrating different components into one system. Highly structured four-level composite particles were formed in a four-step process. First of all, gold (Au) nanoparticles, poly(methyl methacrylate) (PMMA) nanoparticles, and poly(tripropylene glycol diacrylate) (poly-TPGDA) microparticles were individually synthesized. By applying microfluidic techniques, polymer nano- and microparticles were formed with tunable size and surface properties. Afterwards, the negatively charged gold nanoparticles and PMMA particles functionalized with a positively charged surface were mixed to form Au/PMMA assemblies. The Au/PMMA composites were mixed and incubated with poly-TPGDA microparticles to form ternary Au/PMMA/poly-TPGDA assemblies. For the formation of composite-containing microparticles, Au/PMMA/poly-TPGDA composites were dispersed in an aqueous acrylamide-methylenebisacrylamide solution. Monomer droplets were formed in a co-flow microfluidic device and photopolymerized by UV light. In this way, hierarchically structured four-level composites consisting of four different size ranges─0.025/0.8/30/1000 μm─were obtained. By functionalizing polymer nano- and microparticles with different fluorescent dyes, it was possible to visualize the same composite particle under two different excitation modes (λex = 395-440 and λex = 510-560 nm). The Au/PMMA/poly-TPGDA composite-embedded polyacrylamide microparticles can be potentially used as a model for the creation of composite particles for sensing, catalysis, multilabeling, and biomedical applications.

Electron beam-cured linseed oil - Diacrylate blends as a green alternative to overprint varnishes: Monitoring curing efficiency and surface coating properties

Electron beam (EB)-cured unsaturated vegetable oil and diacrylate was formulated as an alternative and green overprint varnish (OPV) for coatings in a finishing process. Linseed oil (LO) was applied with tripropylene glycol diacrylate (TPGDA) in different ratios to obtain EB-curable LO-based OPV (eLOPV). The eLOPV were irradiated by EB for curing using various absorbed doses of 10–100 kGy. Change of the functional groups, chemical structure and transition temperature of EB-cured eLOPV were characterized by FTIR, 13C-NMR and DSC. The curing efficacy was assessed by measuring conversion, gel fraction, swelling degree and by characterizing surface properties using solvent rub-test and cross-cut tape test methods. The EB-cured eLOPV exhibited great surface adhesion on substrates. The surface morphologies of the EB-cured eLOPV on papers and plywood sheets were observed by SEM. The results indicate that the eLOPV (LO-TPGDA blend 40: 60 w/w) was completely cured using EB at 30 kGy. Th optical properties were observed via yellowness and whiteness indexes according to ASTM E 313. Color difference and gloss value were measured using colorimeter and gloss meter, respectively. The eLOPV provide good surface qualities, i.e, good surface adhesion, low yellowness, homogeneous cured surface, high gloss value, and hydrophobic surface. Aiming at well-optimized formula and effective EB-curing process, the synthetic chemical can be reduced at least 50% w/w by using vegetable oil without photo-initiator. The utilization of LO and EB curing technology is a promising strategy for bio-/green-coatings approach.

Digital light processing of SiC ceramic from allylhydridopolycarbosilane with limited acrylate monomers

Digital light processing of ceramic precursor was used to prepare SiC rich ceramic parts in this study. In order to achieve appropriate light curing rate, the ceramic precursor allylhydropolycarbosilane (LHBPCS) was mixed with acrylate monomers tripropylene glycol diacrylate and trimethylolpropane triacrylate. The content of acrylate monomers was optimized to increase the ceramic yield and reduce the shrinkage during pyrolysis. According to the results of thermogravimetric analysis and photolithography experiment, 15 wt% acrylate monomers was appropriate. 330 mJ/cm2 UV irradiation dose was selected for every layer with a thickness of 25 μm, and green bodies with different shapes were successfully printed. During pyrolysis, these printed parts changed from transparent yellow to black accompanying uniform shrinkage. At 1000 °C, the shrinkage was 24.0–26.0%, and crack-free SiC rich ceramic parts with density of 2.11 g/cm3 and chemical formula of SiC1.31O0.26 were obtained.

A UV-LED excited photoinitiator with low toxicity and low migration for photocurable inks

With the improvement of public's environmental protection awareness, the market share of LED in the photocuring field is also expanding rapidly, so it is necessary to develop matching photoinitiators. Here, we prepared a molecule (ND-1) possessing both co-initiating and polymerizable groups, and it exhibits a good initiation effect on acrylate monomers under UV-LED irradiation. The double bond conversion rate reaches up to 80% especially for tripropylene glycol diacrylate (TPGDA). Due to excellent photocuring effect of ND-1, it can initiate monomer polymerization in the presence of color paste and was successfully applied to photocurable inks. In addition, ND-1 exhibits low migration and low toxicity, which is very important to promote the application of packaging with photocurable inks in the food, medical, personal care and tobacco fields. Finally, the photoinitiation mechanism of ND-1 was explored. The free radicals not only come from the cleavage of C─O bond, but also intermolecular hydrogen abstraction.

Controllable Fabrication of Molecularly Imprinted Microspheres with Nanoporous and Multilayered Structure for Dialysate Regeneration.

Adsorption of urea from dialysate is essential for wearable artificial kidneys (WRK). Molecularly imprinted microspheres with nanoporous and multilayered structures are prepared based on liquid–liquid phase separation (LLPS), which can selectively adsorb urea. In addition, we combine the microspheres with a designed polydimethylsiloxane (PDMS) chip to propose an efficient urea adsorption platform. In this work, we propose a formulation of LLPS including Tripropylene glycol diacrylate (TPGDA), ethanol, and acrylic acid (30% v/v), to prepare urea molecularly imprinted microspheres in a simple and highly controllable method. These microspheres have urea molecular imprinting sites on the surface and inside, allowing selective adsorption of urea and preservation of other essential constituents. Previous static studies on urea adsorption have not considered the combination between urea adsorbent and WRK. Therefore, we design the platform embedded with urea molecular imprinted microspheres, which can disturb the fluid motion and improve the efficiency of urea adsorption. These advantages enable the urea absorption platform to be highly promising for dialysate regeneration in WRK.

Allergic contact dermatitis caused by dipropylene glycol diacrylate in the Omnipod® insulin pump.

Cases of allergic contact dermatitis (ACD) caused by isobornyl acrylate (IBOA) in the Omnipod® insulin pump have previously been reported. To present three cases of patients with ACD caused by a new allergen in the pump, and results from chemical analyses. Omnipod pumps from different batches were analysed by gas chromatography-mass spectrometry. Aimed testing, with the department's medical device (MD) series and substances identified in the pump including dipropylene glycol diacrylate (DPGDA) at 0·01% and 0·1% in petrolatum (pet.), was performed. Patch testing also included extracts from the device, the adhesive patch as is, and allergens from baseline series. All patients tested positive to 0·1% DPGDA in pet., and two patients additionally to a 0·01% concentration. DPGDA was found in extracts of the Omnipod pumps brought by the patients. An Omnipod pump from an earlier batch contained tripropylene glycol diacrylate, IBOA, N,N-dimethylacrylamide, di(ethylene glycol)ethyl ether acrylate (DEGEA) but no DPGDA. One of the patients reacted positively to all of these allergens except DEGEA, which was not tested. When suspecting ACD to MDs, DPGDA at 0·1% in pet. should be tested. The contents of Omnipod have changed over time. Patch testing with updated test series and relevance assessment of positive reactions is a delicate task. Children, with lifelong use of MDs, risk contracting many allergies with potential cross-allergies. A question should be raised as to whether these low molecular weight acrylates should be used at all in devices constantly worn on the skin.

An anti-shrinkage model of an ultraviolet-curing coating filled with hollow polyurethane acrylate microspheres

The application of ultraviolet (UV)-curing coatings in precision devices is restricted because of their high shrinkage performance. In this study, hollow polyurethane acrylate (PUA) microspheres are filled into a mixed tripropylene glycol diacrylate (TPGDA) coating with different volume fractions to regulate shrinkage ratios of the coating, where hollow PUA microspheres with different diameters and thicknesses are synthesized using the microfluidics technology. The thickness-dependent mechanical properties of PUA thin films (the same thickness with the shell of each microsphere) are obtained by combining in-situ tensile and nanoindentation experiments with finite element (FE) method. The empirical formula between geometrical parameters (diameter, shell thickness, volume fraction) of hollow PUA microspheres and shrinkage ratios of the TPGDA coating filled with these PUA microspheres are derived using the present representative volume element (RVE) method. Checking against the results of UV-curing shrinkage experiments shows the current empirical formula has high accuracy. This study provides a physical insight into modulating their shrinkage ratios of different UV-curing materials.

Highly conductive polymer electrolytes based on PAN-PEI nanofiber membranes with in situ gelated liquid electrolytes for lithium-ion batteries

The development of solid state electrolytes is considered as an effective approach to build safer lithium-ion batteries by replacing the conventional liquid electrolytes. However, the solid state electrolytes face continuous challenges to improve their ionic conductivities and mechanical properties. Herein, we report the synthesis of novel polymer electrolytes based on cross-linked polyacrylonitrile-polyethylenimine (PAN-PEI) nanofiber membranes infiltrated with in-situ gelated electrolytes using tripropylene glycol diacrylate as crosslinking agent in the organic carbonate-based liquid electrolytes. The PAN-PEI nanofiber membranes with different mass ratios of PAN/PEI prepared by electrospinning method are constructed with entangled nanofibers of an average diameter of ~600 nm. The optimized PAN-PEI based electrolyte has a high ionic conductivity up to 3.39 mS cm−1 at room-temperature and decent tensile strength of 9.36 MPa. Linear sweep voltammetry shows that the polymer electrolyte also has a wide electrochemical window of 5.4 V (vs. Li/Li+). This polymer electrolyte exhibits excellent cycling stability even in the high energy density of LiNi0.8Co0.1Mn0.1O2/Graphite, delivering an initial discharge capacity of 175 mAh g−1 at 0.5 C with a capacity retention of 91.4% after 200 cycles.