Polymerization Rate Research Articles

Photoinitiation abilities of indeno- and indoloquinoxaline derivatives and mechanical properties of dental fillings based on multifunctional acrylic monomers and glass ionomer

Photopolymerization is a rapidly expanding technology with a wide variety of applications, from imaging to biomedical uses. Here, we present enhanced photosensitization of polymerization by photoredox pairs based on indene- and indoloquinoxaline dyes and thiophenoxyacetic acid for dental applications. The photoinitiating ability of the two-component systems was tested using several multifunctional monomers of various structures typical for dental fillings. The new photoinitiating systems show excellent efficiency in initiating free radical polymerization which occurs by photoinduced intermolecular electron transfer (PET) mechanism. Modification of the dye structure by extending the chain of conjugated π bonds, the arrangement of aromatic rings and the type of heteroatom, allowed to change the spectroscopic properties of the tested compounds and use them as absorbers of light emitted by dental lamps. The improved mechanical properties of the cured polymers, i.e., lowering the temperature during photopolymerization and an increase in polymer hardness were observed for the proposed photoinitiating systems compared to the camphorquinone – photoinitiator traditionally used in dentistry. This indicates that the dye – thiophenoxyacetic acid systems may be useful as photoinitiators in dental applications. The undoubted advantage of these photoinitiating systems is the elimination of the toxic aromatic amines traditionally used as co-initiators from the dental composition. It was possible thanks to the use of thiophenoxyacetic acid. Its application does not reduce the polymerization rate and does not extend the photocuring time.

Blue‐light‐induced atom transfer radical polymerization enabled by iron/copper dual catalysis

AbstractPhotoinduced initiators for continuous activator regeneration atom transfer radical polymerization (PICAR ATRP) using sodium pyruvate and blue light (λmax = 456 nm) is reported. Water‐soluble oligo(ethylene oxide) methyl ether methacrylate (OEOMA500) was polymerized under biologically relevant conditions. Polymerizations were conducted with 1000 ppm (with respect to the monomer) concentrations of CuBr2, tris(2‐pyridylmethyl)amine, and 1000 ppm or less FeCl3 as a cocatalyst in water. Well‐defined polymers with up to 90% monomer conversion, high molecular weights (Mn > 190,000), and low dispersity (1.14 < Ð < 1.19) were synthesized in less than 60 min. The polymerization rate and dispersity were tuned by varying the concentration of sodium pyruvate (SP), iron, and supporting halide, as well as light intensity. The Cu/Fe dual catalysis provided oxygen tolerance enabling rapid, well‐controlled, aqueous PICAR ATRP of OEOMA500 without deoxygenation.

Excitation Dependence in Photoiniferter Polymerization.

We report on a fundamental feature of photoiniferter polymerizations mediated with trithiocarbonates and xanthates. The polymerizations were found to be highly dependent on the activated electronic excitation of the iniferter. Enhanced rates of polymerization and greater control over molecular weights were observed for trithiocarbonate- and xanthate-mediated photoiniferter polymerizations when the n → π* transition of the iniferter was targeted compared to the polymerizations activating the π → π* transition. The disparities in rates of polymerization were attributed to the increased rate of C-S photolysis which was confirmed using model trapping studies. This study provides valuable insight into the role of electronic excitations in photoiniferter polymerization and provides guidance when selecting irradiation conditions for applications where light sensitivity is important.

Cost-Effective Control of Molecular Weight in Ultrasound-Assisted Emulsion Polymerization of Styrene.

This paper focuses on the determination of economically most feasible conditions to obtain polystyrene with various target molecular weights through ultrasound-assisted emulsion polymerization. Briefly, batch polymerizations of styrene have been performed by ultrasound-assisted emulsion polymerization process using different reaction feed compositions. Polymerization rates were calculated using the monomer conversions at various reaction times. Also, molecular weights of the synthesized polymers, as well as the Mark-Houwink constants, were determined by intrinsic viscosity and gel permeation chromatography measurements. It was found that the polydispersity index of the polymers is ranging from 1.2 to 1.5, and the viscosity average molecular weights are in between 100000-1500000 g/mol depending on the reaction conditions. Finally, model equations were also developed for response variables, and the most economical ways of reaching various target molecular weights were interpreted by response surface methodology based multi objective optimization.

Compounded Interplay of Kinetic and Thermodynamic Control over Comonomer Sequences by Lewis Pair Polymerization.

The design of facile synthetic routes to well-defined block copolymers (BCPs) from direct polymerization of one-pot comonomer mixtures, rather than traditional sequential additions, is both fundamentally and technologically important. Such synthetic methodologies often leverage relative monomer reactivity toward propagating species exclusively and therefore are rather limited in monomer scope and control over copolymer structure. The recently developed compounded sequence control (CSC) by Lewis pair polymerization (LPP) utilizes synergistically both thermodynamic (Keq) and kinetic (kp) differentiation to precisely control BCP sequences and suppress tapering and misincorporation errors. Here, we present an in-depth study of CSC by LPP, focusing on the complex interplay of the fundamental Keq and kp parameters, which enable the unique ability of CSC-LPP to precisely control comonomer sequences across a variety of polar vinyl monomer classes. Individual Lewis acid equilibrium and polymerization rate parameters of a range of commercially relevant monomers were experimentally quantified, computationally validated, and rationalized. These values allowed for the judicious design of copolymerizations which probed multiple hypotheses regarding the constructive vs conflicting nature of the relationship between Keq and kp biases, which arise during CSC-LPP of comonomer mixtures. These relationships were thoroughly explored and directly correlated with resultant copolymer microstructures. Several examples of higher-order BCPs are presented, further demonstrating the potential for materials innovation offered by this methodology.

Preparation and characterization of cross-linked poly (vinyl alcohol-co-methyl methacrylate) colloidal nanoparticles from hydrolysis of poly (vinyl acetate-co-methyl methacrylate) as a promising cancer drug delivery system

Amphiphilic cross-linked poly (vinyl alcohol-methyl methacrylate) (PVA-PMMA) copolymer nanoparticles (NPs) were prepared using a two-step process. Unlike other polymers, which are typically produced via direct polymerization, PVA is produced from the hydrolysis of polyvinyl acetate (PVAc). Therefore, in the first part of the project, copolymeric PVAc-PMMA NPs were prepared by using the radical emulsion polymerization method in different concentrations of BDOD (0–10% mol.) and water: methanol compositions. Conversion degree, morphology, particle size, and polymerization rate of non-agglomerated samples were evaluated. The optimal sample that synthesized in water: methanol % (90:10) as polymerization medium and 2.5% mol. crosslinker was hydrolyzed by 0.6 M NaOH solution. To confirm the hydrolysis reaction, FE-SEM, FT-IR, DLS, 1H NMR, and TGA tests were performed. The optimal sample was loaded by methotrexate (MTX), and drug release investigated at different times by UV-vis spectrophotometry. The sustained and pH-responsive profile of drug release in vitro was observed, and 47.24% of the drug was released at pH = 7.4 and 65.39% at pH = 5.8 after 96 h. Also, the MTT assay and dual-fluorescent acridine orange/propidium iodide assay showed that drug-loaded nanocarriers exhibited anticancer activity as applied to MCF-7 cells.

Colorfully Patterned Epoxy Resin Films with a Cholesteric Structure Prepared through a Photopolymerization Approach

Structurally colored epoxy resin films were prepared using a liquid crystalline (LC) epoxy monomer of E11M and a chiral additive of CA-iso through a photopolymerization approach. With the addition of the co-photoinitiator isopropyl thioxanthone and comonomer 3′,4′-epoxycyclohexylmethyl 3,4-epoxycyclohexylcarboxylate, the polymerization rate was increased. Since the epoxy resin films can be obtained within several seconds, they are feasible for large-area preparation on the coating line. The reflective wavelength was tunable by changing the concentration of CA-iso in the LC mixture. Diffuse-reflectance circular dichroism spectra indicated a right-handed helical supramolecular structure. Field-emission scanning electron microscopy images indicated a multilayer structure. Since the LC mixtures were thermochromic, colorfully patterned epoxy resin films were prepared by controlling the polymerization temperature. Moreover, LC gratings were also prepared, which were expected to be applied for anticounterfeiting.

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.

Effect of Collagen-Reactive Functional Monomer on Etch-and-Rinse Adhesives

In this study, we evaluated a novel functional monomer (4-formylphenyl acrylate [FA]) that can specifically and covalently bind to the dentin collagen matrix as a potential alternative hydrophobic diluent-like monomer for improving the durability of dentin bonding. Experimental adhesives with different FA contents (0%, 10%, 20%, and 30%) were evaluated as partial substituents for the hydrophilic monomer 2-hydroxyethyl methacrylate, with the commercial adhesive One-Step (Bisco, Inc.) employed as the positive control. Their degree of conversion, viscosity, hydrophobicity, mechanical properties, and water absorption/solubility were measured as the comprehensive characterization. In situ zymographic assays were performed to determine the extent to which FA inhibits the endogenous hydrolytic activity of dentin. Finally, the bonding performances of the novel adhesives were evaluated with microtensile strength tests and scanning electron microscopy. The results showed that the incorporation of FA significantly improved the mobility of experimental adhesives attributable to the dilution property of FA. In contrast to the possible compromised rate of polymerization by hydroxyethyl methacrylate, FA exhibited typical characteristics of favorable copolymerization with polymerizable monomers in adhesives and improved the degree of conversion of experimental adhesives. The rigidity and hydrophobic properties of the phenyl framework of the FA molecule conferred superior mechanical properties and hydrolysis resistance to the novel experimental adhesives. An inhibitory effect on gelatinolytic activities within the hybrid layer was also observed in the in situ zymographic assays, even at a low FA concentration (10%). In conjunction with the significantly improved infiltration found via scanning electron microscopy, the experimental adhesives containing FA possessed significantly better-maintained microtensile strength, even after aging. Thus, the incorporation of this novel monomer endowed the experimental adhesives with multiple enhanced functionalities. These remarkable advantages highlight the suitability of the monomer for further applications in clinical practice.

How we can improve ARGET ATRP in an aqueous system: Honey as an unusual solution for polymerization of (meth)acrylates

Aqueous solutions of various types of honey as a source of reducing sugars – glucose and fructose, were used to accelerate or control activators regeneration by electron transfer atom transfer radical polymerization (ARGET ATRP) in a homogeneous or heterogeneous environment. The aqueous or alcoholic-aqueous solution was applied for the polymerization of hydrophilic methacrylates i.e. 2-(dimethylamino)ethyl methacrylate (DMAEMA), glycidyl methacrylate (GMA), 2-hydroxyethyl methacrylate (HEMA), while the polymerization of a hydrophobic monomer – n-butyl acrylate (nBA) was conducted in miniemulsion under ion-pair and interfacial catalysis. The polymerization of DMAEMA in a honey solution accelerated the polymerization rate up to 30-fold with a significant improvement in the control over the structure of the product, namely, the polymers were characterized by narrow molecular weight distribution (Mw/Mn = 1.33), and initiation efficiency up to 98 %. Controlled polymerization of nBA was conducted in a honey-contained miniemulsion. Honey-based miniemulsion was successfully checked for the synthesis of both linear and branched polymers. The use of chemical reducing agents found in commercially available food products for polymerization is an economic concept that eliminates the need for high purity laboratory reagents, moreover, food products are widely available and therefore much cheaper. The proposed concept has great potential for industrial applications.

Polymerization and shrinkage kinetics and fracture toughness of bulk-fill resin-composites.

To determine degree of conversion (DC), maximum polymerization rate (RPmax), polymerization shrinkage (PS), maximum shrinkage rate (PS Rmax) and fracture toughness (KIC) of different types of bulk-fill (BF) composites plus the effect of viscosity reduction techniques. BF specimens were created in 2 mm deep molds: SonicFill 3 (SF3), Viscalor (VC), One Bulk Fill (OBF) and Beautifil Bulk (BBR). SF3 was applied via sonic insertion using a SonicFill handpiece (Kerr Corp. USA). Viscalor was pre-heated in a Caps Warmer in T3 mode (at 68 °C) for 30 s (T3-30 s) and 3 min (T3-3 min), respectively. Specimens were irradiated at zero distance from the upper surface with an Elipar S10 LED unit (3 M ESPE, USA) of mean irradiance 1200 mW/cm2 for 40 s. Real-time polymerization kinetics and DC at 5 min and 24 h post-irradiation (DC5 min and DC24 h) were measured using ATR-FTIR (n = 3). PS was measured up to 1 h on 1 mm thick discs via the bonded-disk technique (n = 3) and PS Rmax obtained by numerical differentiation (n = 3). For fracture toughness, single-edge-notched specimens (32 × 6 ×3 mm) of each BF composite were prepared and measured by three-point bending after 7 d water storage (n = 5). Data were analysed using One-way ANOVA, independent T-tests and Tukey post-hoc tests (p < 0.05). SF3 showed the significantly highest DC5 min, DC24 h and RPmax (p < 0.05), followed by OBF (p < 0.05). Regardless of pre-heating, VC showed comparable conversion kinetics to BBR (p > 0.05). There was no significant difference in PS of these BF composites, except OBF had the highest PS (p > 0.05). However, PS Rmax significantly varied among materials (p = 0.047) and SF3 had the highest PS Rmax. Regarding fracture toughness, BBR had the lowest KIC (p < 0.05), whereas other composites showed similar KIC (p > 0.05). Strong correlations of filler content (wt%)-PS/KIC were found. Different pre-heating times had no significant influences on DC %, RPmax, PS, PS Rmax and KIC of VC (p > 0.05). Different types of bulk-fill composites showed comparable shrinkage. A highly filled BF giomer composite (BBR) had the lowest fracture toughness, whereas others had similar KIC. Pre-heating had no adverse effects on Viscalor properties. Sonication and pre-heating are beneficial techniques to enhance composite flowability without either increasing shrinkage or reducing fracture toughness.

Synthesis and characterization of well-defined star-shaped poly(L-lactides)

The main goal of research is to study ring-opening polymerization of L-lactide in the presence of multifunctional alcohols in order to determine the optimal conditions for synthesis of star-shaped molecules of a predetermined well-defined structure, which is necessary for fine adjustment of material properties for various biomedical applications. The degree of polymerization of 3-, 4- and 6-arm star-shaped poly(L-lactides) varied from 10 to 100 monomer units per arm. It was found that under the same conditions polymerization rate and rate of initiation of co-initiator's hydroxyl groups can vary significantly depending on the structure and concentration of the selected alcohol. To prove the absence of cyclic, linear and comet-like structures in synthesized star-shaped PLLA, a variety of instrumental methods were used including GPC with triple detection, 1H NMR and MALDI. Study of properties and supramolecular structure of poly(L-lactides) using DSC and WAXS demonstrated that branching limits segmental mobility of the PLLA chains, especially for short arms, and hinders crystallization of star-shaped poly(L-lactides).

Temperature Dependence of the Kinetic Parameters of the Titanium–Magnesium Catalyzed Propylene Polymerization

This paper provides a study of the liquid-phase polypropylene polymerization on a heterogeneous titanium-magnesium Ziegler-Natta-type catalyst. A kinetic model was developed that included the activation of potential active centers, chain growth, transferring the chains to hydrogen and monomer, and the deactivation of active centers. The model was created to predict the polymerization rate, polymer yield, and average molecular weights of polymer chains where the polymerization temperature changes from 40 to 90 °C. In developing polycentric kinetic models, there is a difficulty associated with evaluating the kinetic constants of the rates of elementary reactions/stages in polymerization. Each heterogeneous titanium-magnesium catalyst (TMC), including a co-catalyst, as well as an internal and an external electron donor, has its own set of kinetic parameters. Therefore, its kinetic parameters must be defined for each new catalyst. The presented algorithm for identifying the kinetic constants of rates starts with a kinetic model that considers one type of active centers. At the second stage, a deconvolutional analysis is used for the molecular weight distribution (MWD) of the gel permeation chromatography (GPC) data of the polypropylene samples and the most probable distribution of Flory chain lengths is found for each type of active centers. At the third stage, the single-center model is transformed into a polycentric kinetic model. For the catalyst system, five types of active centers were identified, together with a mass fraction and a number-average molecular weight for each active center type of the catalyst, which is consistent with the published results for similar Ti-based Ziegler-Natta catalysts.

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 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.

Microwave Irradiation-Assisted Reversible Addition-Fragmentation Chain Transfer Polymerization-Induced Self-Assembly of pH-Responsive Diblock Copolymer Nanoparticles.

Herein, we present a versatile platform for the synthesis of pH-responsive poly([N-(2-hydroxypropyl)]methacrylamide)-b-poly[2-(diisopropylamino)ethyl methacrylate] diblock copolymer (PHPMA-b-PDPA) nanoparticles (NPs) obtained via microwave-assisted reversible addition-fragmentation chain transfer polymerization-induced self-assembly (MWI-PISA). The N-(2-hydroxypropyl) methacrylamide (HPMA) monomer was first polymerized to obtain a macrochain transfer agent with polymerization degrees (DPs) of 23 and 51. Subsequently, using mCTA and 2-(diisopropylamino)ethyl methacrylate (DPA) as monomers, we successfully conducted MWI-PISA emulsion polymerization in aqueous solution with a solid content of 10 wt %. The NPs were obtained with high monomer conversion and polymerization rates. The resulting diblock copolymer NPs were analyzed by dynamic light scattering (DLS) and cryogenic-transmission electron microscopy (cryo-TEM). cryo-TEM studies reveal the presence of only NPs with spherical morphology such as micelles and polymer vesicles known as polymersomes. Under the selected conditions, we were able to fine-tune the morphology from micelles to polymersomes, which may attract considerable attention in the drug-delivery field. The capability for drug encapsulation using the obtained in situ pH-responsive NPs, the polymersomes based on PHPMA23-b-PDPA100, and the micelles based on PHPMA51-b-PDPA100 was demonstrated using the hydrophobic agent and fluorescent dye as Nile red (NR). In addition, the NP disassembly in slightly acidic environments enables fast NR release.

Kinetics of Polymer Network Formation by Nitroxide-Mediated Radical Copolymerization of Styrene/Divinylbenzene in Supercritical Carbon Dioxide

The kinetics of nitroxide-mediated dispersion copolymerization with crosslinking of styrene (STY) and divinylbenzene (DVB) in supercritical carbon dioxide (scCO2) is addressed experimentally. 2,2,6,6-Tetramethylpiperidinyl-1-oxy (TEMPO) and dibenzoyl peroxide (BPO) were used as nitroxide controller and initiator, respectively. A high-pressure cell with lateral sapphire windows at 120 °C and 207 bar was used to carry out the polymerizations. The nitroxide-mediated homopolymerization (NMP) of STY, as well as the conventional radical copolymerization (FRC) of STY/DVB, at the same conditions were also carried out as reference and for comparison purposes. The effect of nitroxide content on polymerization rate, evolution of molecular weight averages, gel fraction, and swelling index was studied.

Evaluation of allyl sulfides bearing methacrylate groups as addition-fragmentation chain transfer agents for low shrinkage dental composites

Polymerization shrinkage and the consequential shrinkage stress in methacrylate-based dental composites are crucial drawbacks for restorative dentistry. An effective way for the reduction of shrinkage stress is the incorporation of addition fragmentation chain transfer agents (AFCT agents). In this contribution, four novel polymerizable allyl sulfides were synthesized and evaluated in dental composites. Photo-DSC and DMTA measurements were performed to evaluate their influence on the polymerization rate and on the network homogeneity. Good to excellent shrinkage force values and mechanical properties were obtained for all AFCT based composites. Especially, the incorporation of AFCT agents containing multiple urethane and methacrylate moieties improved the mechanical properties. Hence, the incorporation of polymerizable and urethane-based allyl sulfides in dental composite is a promising strategy to obtain low shrinkage materials exhibiting high flexural strength and modulus.

Manipulating the distribution of surface charge of PEDOT toward zwitterion-like antifouling properties

Poly(3,4-ethylenedioxythiophene) (PEDOT) has been regarded as one of the most attractive conductive materials for making bioelectronics. Surface modification is one of the most important methods to enhance the performance of PEDOT-based bioelectronics. To investigate the surface charge effect on the behavior of protein binding on PEDOT, we develop a new positively charged functionalized EDOT monomer, EDOT-N+, to copolymerize with another negatively charged carboxylic acid-modified EDOT monomer, EDOT-COOH. The poly(EDOT-N+-co-EDOT-COOH) film is prepared by the electropolymerization method. By mixing the two monomers with different feed ratios, we can tune the distribution of surface charges. The actual composition of the copolymer is determined by toluidine blue O staining. Based on the result of TBO staining, a copolymer with a 1:1 ratio of EDOT-N+ to EDOT-COOH is obtained when the monomer solution of composition at [EDOT-N+]: [EDOT-COOH] = 8 : 2, which is due to a slower polymerization rate of EDOT-N+ compared to EDOT-COOH. To further testify the antifouling property of poly(EDOT-N+-co-EDOT-COOH), nonspecific protein binding of bovine serum albumin and lysozyme were measured in situ by using a quartz crystal microbalance. The results also show that at [EDOT-N+]: [EDOT-COOH] = 8 : 2, poly(EDOT-N+-co-EDOT-COOH) presented good antifouling property. Therefore, we propose a zwitterion-like antifouling property from the poly(EDOT-N+-co-EDOT-COOH) with an equal density of both positive and negative functional groups.

Working performance and microscopic mechanistic analyses of municipal solid waste incineration (MSWI) fly ash-based self-foaming filling materials

To solve the problems of MSWI fly ash with no place stacking and the lack of filling materials in goaf, a scheme using MSWI fly ash for goaf filling is proposed. Using MSWI fly ash and slag as the main raw materials, geopolymer foaming materials with different proportions were prepared after alkali excitation to meet the differential filling requirements of goafs with different depths. The effects of curing temperature, activator dosage and MSWI fly ash content on the indexes of filling materials were investigated. The results showed that when the curing temperature was increased from 20 °C to 40 °C, the 28 d compressive strength of the material increased by approximately 31.9 %. The increase in curing temperature significantly improved the degree of polymerization and heavy metal curing rate of the material, resulting in more polymerization products in the system and promoting the conversion of calcium silicate hydrate (CSH) to calcium aluminosilicate hydrate (C-ASH) with a higher degree of polymerization. The pore structure of the material was mainly affected by the amount of activator used and the MSWI fly ash content. The higher the MSWI fly ash content was, the less round the pores and the more complex the spatial distribution. Scanning electron microscopy (SEM) showed that increasing the curing temperature and activator dosage made the raw material particles more compact and improved the integrity of the polymeric materials. Finally, three proportions involving an activator dosage of 20 % and a fly ash content of 40 %, an activator dosage of 15 % and a fly ash content of 40 % and an activator dosage of 10 % and a fly ash content of 60 % were selected for goaf filling at 20 °C, 30 °C and 40 °C, respectively.