Redox Initiator Research Articles

Low-temperature preparation of solid-solid phase change polymer for thermal management modules

The high initiating temperature of polymerization up to 80–100 °C during the preparation of solid–solid phase change polymer (SSPCP) leads to the limitation of the embedding procedure during the construction of the battery modules. Herein, we develop a low-temperature preparation strategy for SSPCPs by introducing a redox initiation system to reduce the decomposition activation energy, thus realizing the procedure for embedding the SSPCP into a battery module. In addition to the intrinsic ~100% anti-leakage performance and ultrahigh heat tolerance up to 250 °C, the SSPCP/expanded graphite composite demonstrates a suitable phase change temperature of 47.8 °C, high thermal conductivity of 2.33 W m−1 K−1, and latent heat of 99.6 J g−1 for battery thermal management, thus delivering a lower maximum temperature (47.4 °C vs. 45.2 °C) for the battery module than traditional composite phase change material during 15 charge–discharge cycles. No leakage traces are detected in the SSPCP module.

Macroporous zwitterionic composite cryogel based on chitosan oligosaccharide for antifungal application

Chitosan oligosaccharide (COS), a time-dependent antimicrobial carbohydrate, is found antifungal active with a short duration of action due to excessive solubility. We attempted to address this issue by employing a hydrogel as a COS carrier. In this research, macroporous zwitterionic composite cryogels composed of COS and poly(N-methacryl arginine) (PMarg) were fabricated, serving as long-term antifungal dressings. Firstly, Marg was synthesized and characterized by Fourier transform infrared spectroscopy (FT-IR), 1H and 13C nuclear magnetic resonance (NMR), and high-resolution mass spectrometry (HRMS). Then, the COS/PMarg cryogels were prepared by redox initiation cryopolymerization. The macroporous morphology of the cryogels was confirmed by scanning electron microscope (SEM) with pore size varying from 20.86 to 50.87 μm. FTIR indicated that hydrogen bonding formed between COS and PMarg, and the interaction elevated thermal stability of the cryogels as evidenced by thermal-gravimetric analysis (TGA). Swelling capacity, mechanical properties, and COS release behavior of the COS/PMarg cryogels were investigated. With the release of COS, the antifouling activity of the cryogel increased. Antimicrobial tests indicated the COS/PMarg cryogel could effectively inhibit the proliferation of Candida albicans. It demonstrated that the macroporous zwitterionic COS/PMarg composite cryogel might be a potential antifungal dressing with sequential “sterilization-release” capacity.

Synergistic effects in cross-linked blends of ion-conducting PEO-/PPO-based unsaturated polyesters

Ion-conductive unsaturated polyesters (UP) were synthesised from poly(ethylene oxide) (Xn = 9, 13, 22, 90) or poly(propylene oxide) (Xn = 7, 13, 20, 34, 68) and maleic anhydride. Subsequently, the polyesters were doped with LiClO4 and cross-linked with styrene using a redox initiator. For PEO-based polyesters, the minimum resistivity is found at an O/Li+ molar ratio of 50/1. In contrast, more lithium is required to reach the minimum when using PPO (O/Li+ = 10/1). Unlike the PEO-based polyesters, cross-linking of the PPO types gives rise to decreasing resistivities at increasing molecular weight. This correlates well with the transverse proton relaxation time determined by single-sided NMR, which is an indicator of the chain mobility. The cross-linking reaction of these UP with styrene exactly follows the predictions based on the copolymerisation parameters and is, therefore, not dependent on the ratio of styrene to UP double bonds as previously reported. Due to the opposing effects of the molecular weight on the ion conductivity of PEO- and PPO-based UP, 1:1 blends of short-chain PPO and long-chain PEO polyesters were cross-linked with styrene. The resulting networks showed a resistivity of 4 kΩ m (σ = 2.5∙10−4 S∙m−1), which is 5 times lower than the pure PEO and 3 times lower than the pure PPO materials.

Application of Bacterial Cellulose in the Textile and Shoe Industry: Development of Biocomposites

Several studies report the potential of bacterial cellulose (BC) in the fashion and leather industries. This work aimed at the development of BC-based composites containing emulsified acrylated epoxidized soybean oil (AESO) that are polymerized with the redox initiator system hydrogen peroxide (H2O2) and L-ascorbic acid and ferrous sulfate as a catalyst. BC was fermented under static culture. The polymerization of the emulsified organic droplets was tested before and after their incorporation into BC by exhaustion. The composites were then finished with an antimicrobial agent (benzalkonium chloride) and dyed. The obtained composites were characterized in terms of wettability, water vapor permeability (WVP), mechanical, thermal and antimicrobial properties. When AESO emulsion was polymerized prior to the exhaustion process, the obtained composites showed higher WVP, tensile strength and thermal stability. Meanwhile, post-exhaustion polymerized AESO conferred the composite higher hydrophobicity and elongation. The composites finished with the antimicrobial agent showed activity against S. aureus. Finally, intense colors were obtained more uniformly when they were incorporated simultaneously with the emulsified AESO with all the dyes tested.

Polyacrylamide Grafted Gum Acacia (GA-g-PAM) Graft Copolymer as Efficient Polymeric Scaffold

Abstract: Background: Natural polysaccharides are mostly not stable in their original form but their biodegradable properties can be beneficial for use as polymeric scaffolds for tissue engineering. Microwave irradiation assisted grafting synthesis being an easy and quick method enhances stability of these natural polysaccharides. Materials and Methods: Initially the optimization of the redox initiator ammonium per sulfate (APS) along with the monomer concentration acrylamide (AM) was done by % grafting efficiency (%GE) for getting the optimized grade of graft copolymer (GA-g-PAM). The microwave time was kept constant with the concentration of the polymer Gum acacia (GA). Different analytical techniques were used for the characterization of optimized grade G6 like Fourier transform infrared spectroscopy (FTIR), Differential scanning calorimetry (DSC), X-ray diffraction(XRD) and Nuclear magnetic resonance (NMR) which confirmed successful grafting reactions and scanning electron microscopy (SEM) was utilized to analyze the interior architecture as well the cell proliferation on to the polymer surface. The optimized grade G6 was inserted under the skin hypodermis for tissue proliferation. Results: The % grafting efficiency (%GE) of optimized grade of Polyacrylamide grafted Gum acacia (GA) graft copolymer (GA-g-PAM) was 94.54%. Histolology studies of local tissue of the test mice revealed that the polymer material after insertion onto the mice skin enhanced the cell proliferation as there were evidences of more collagen as well as fibroblast growth in test animal local tissue than in comparison to control mice. Conclusion: Thus, results indicate that polyacrylamide grafted gum acacia graft copolymer (GA-g-PAM) is sufficiently biocompatible and suitable as versatile material for tissue engineering purpose. Key words: Graft copolymer, Microwave assisted synthesis, Tissue engineered scaffold, Gum acacia, Acrylamide.

Nanofibers from chitosan/polyacrylonitrile/sepiolite nanocomposites

ABSTRACT Chitosan-graft-polyacrylonitrile (Ch-g-PAN), polyacrylonitrile/sepiolite (PAN-Sep) nanocomposites, and Ch-g-PAN/sepiolite (Ch-g-PAN-Sep) nanocomposites were produced via free radical polymerization using persulfate-metabisulfite redox initiators. The nanocomposites of sepiolite-modified PAN containing as much as 1%, 3% and 5% of acrylonitrile levels in sepiolite were successfully produced in situ. Chitosan and sepiolite increased thermal resistance and sorption of water is more advantageous and has more coverage. These copolymers and nanocomposites were electrospun to produce Ch-PAN derivative-based nanofibers. Nanofibers were successfully produced by the electrospinning method from the copolymers and nanocomposites containing sepiolite moiety.

Interrelationship between feeding profiles and chains composition-morphology-mechanical properties for forced composition copolymers synthesized by redox initiation

Interrelationship between feeding profiles and chains composition-morphology-mechanical properties for forced composition copolymers synthesized by redox initiation

Graft copolymerization of Diallylamine onto starch for water treatment use characterization, removal of Cu (II) cations and antibacterial activity

Cyclopolymerization of diallylamine (DAA) onto starch backbone was studied. The graft copolymerization (St-g-DAA) occurred using redox initiators (potassium persulfate/sodium bisulfite). The graft parameters have been studied to obtain the maximum percentage graft. The percentage of graft reached 56%. The copolymer’s structure was characterized by 13CNMR spectrometer. The thermal property of the synthesized copolymer was investigated to adjust the copolymer to water treatment, which involved the removal of Cu (II) ions from aqueous solution. The removal of cations was confirmed by X-Ray diffraction (XRD) and Emission scanning electron micrograph (ESEM). Also, the (St-g-DAA) showed better antibacterial activity than native starch.

Synthesis and Inhibitive Mechanism of a Novel Clay Hydration Inhibitor for Water-based Drilling Fluids

In order to solve wellbore instability problem, a novel clay hydration inhibitor PDWC for water-based drilling fluids was synthesized by copolymerization of tris hydroxyethyl diallyl ammonium bromide (THDAB), sodium allyl sulfonate (AS) and methyl methacrylate (MMA) initiated by redox initiation in an aqueous solution. PDWC was characterized by Fourier transform infrared spectroscopy (FT-IR), Gel Permeation Chromatography (GPC) and Thermo-gravimetry-Differential Scanning Calorimetry (TGA-DSC), respectively. Evaluation of experiments indicated that PDWC showed superior clay hydration inhibition ability compared to some polymer and inorganic inhibitors. Characterization methods included particle size analysis, FT-IR, X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) were utilized to study the inhibition mechanism of PDWC, it was observed that PDWC can be adsorbed on the surface of sodium montmorillonite (Na-MMT) by its hydroxyl functional group, which changed the micro-structure of Na-MMT and made the clay particles increased obviously. However, results of XRD demonstrated that it was difficult for PDWC to enter the inner layer crystal of Na-MMT.

Research of a novel double cross-linking fracturing fluid

A kind of JDL-1 thickener for betaine hydrophobic association polymer was prepared by aqueous solution polymerization of mixed micelles, AM, AA, AMPS and DM16 were used as raw materials, which was synthesized by redox initiator system. Friction tester and high-temperature rheometer were used to evaluate the resistance reduction and temperature and shear resistance of the thickener. The results show that the viscosity average molecular weight of the polymer prepared with AM, AA, AMPS and DM16 mass ratio of 70∶20∶5∶5 was higher than 12 million, and the dissolution time of the polymer was less than 3 min. When the surfactant is used for physical cross-linking, the apparent viscosity of the cross-linked fracturing fluid is larger than that of 60 mPa·s at 90 °C, 170 s-1 sheared 1 h; when metal cross-linking agent is used for coordination cross-linking, the apparent viscosity is larger than that of 80 mPa·s at 120 °C, 170 s-1 sheared 1 h. The drag reduction rate was 73%, the anti-swelling rate was higher than70%, and the damage rate was less than10%. The field trial was successful and confirmed the multifunctional effect of betaine-type hydrophobic associating polymer.

Synthesis and long‐term stability of acrylic acid and N, N‐methylene‐bis‐acrylamide radiation grafted polypropylene fibers

AbstractNew carboxyl ion‐exchange fibers prepared by acrylic acid (AA) and N, N‐methylene‐bis‐acrylamide (MBAA) monomer grafting to polypropylene (PP) fibers based on the method of γ‐rays pre‐irradiation in air followed by a Mohr's salt redox initiation of grafting reaction were studied. Grafting degree, homopolymer quantity, monomer conversion and grafting efficiency were determined. FTIR spectroscopy was used to establish the nature of the grafted fibers. The thermal stability of the materials was investigated based on DSC analysis in N2/O2 mixture. The long‐term stability during 6–8 years of storage was examined by the measurement of the tensile strength and the elongation at break of the fibers, and the chemical oxygen demand in water extracts as well as in the oxygen uptake experiments. The influence of some factors on the useful life of the grafted fibers was studied: a MBAA cross‐linking, exposure to day light, the Fe (III) residue presence, a grafting reaction temperature. It was found that small amounts of the adsorbed Fe (III) ions increase the deterioration rate of the grafted fibers, while small amounts of MBAA delay this negative process.

SYNTHESIS OF GRAFT COPOLYMER FROM ETHYL METHACRYLATE ONTO DELIGNIFIED GREWIA OPTIVA FIBER

Ethyl methacrylate was grafted onto delignified Grewia optiva fiber using ascorbic acid/H2O2 as redox initiators in an aqueous medium. The reaction variables including concentration of ascorbic acid, H2O2, monomer and amount of backbone as well as time and temperature have been varied for establishing grafting. The influence of these reaction conditions on the grafting yield has been discussed. The overall activation energy of grafting has been calculated. The FT-IR spectroscopy, Thermal Gravimetric Analysis (TGA) and Scanning Electron Microscopic (SEM) techniques have been used for the characterization of graft copolymer.

Tough and self‐healing hydrophobic association hydrogels with cationic surfactant

AbstractHydrophobic association (HA) hydrogels with outstanding mechanical, rheological and recovery properties were successfully synthesized by micellar copolymerization of acrylamide with lauryl methacrylate. The synthesis occurred at room temperature and the synthesis condition was moderate by using the redox initiator system of Ammonium persulfate ‐ sodium bisulfite as initiators. Cationic surfactant (dodecyl trimethyl ammonium bromide) was utilized to form micelles with hydrophobe, served as physical cross‐linking points in the 3D networks of hydrogels. The HA hydrogels showed a high tensile strength of 181 kPa, superior stretchability of 2300% and excellent toughness of 2.16 MJ m−3. Moreover, they owned extraordinary self‐recovery under different conditions. It is hopeful that the hydrogels with superior mechanical strength and self‐healing properties would be applied to the fields of biomedicine and engineering. Meanwhile, based on above materials, HA hydrogels could also be synthesized with the combination of hydrophobic association and other synergistic effects, such as latex particles, electrostatic effect and nanoparticles.

Low-cost synthesis of high-performance polycarboxylic ether by Co2+-, Ni2+- and Zn2+-catalyzed H2O2-NaHSO3 initiation system

As a new type of high-performance water-reducing agent, polycarboxylate ether (PCE) has excellent properties such as small dosage and high water reduction rate. However, it is still necessary to develop a synthetic process to improve the performance of PCE at a low cost. In this paper, Co2+-, Ni2+- or Zn2+-catalyzed H2O2-NaHSO3 redox initiation system is designed as a new cost-effective composite initiator system to synthesize PCE(Co2+), PCE(Ni2+) and PCE(Zn2+). The synthesized PCEs were characterized by FTIR, GPC, Zeta potential, XRD, TG, SEM and HPLC. Compared with PCE0 synthesized by H2O2-NaHSO3 system without metal ion catalyst, FTIR and GPC data show that the molecular weights of PCE(Co2+), PCE(Ni2+) and PCE(Zn2+) were slightly reduced without any functional group type changed. When the double bond retention rate of isopentenol polyoxyethylene ether (TPEG) is 94.34%, the conversion rate of TPEG catalyzed by Co2+, Ni2+ or Zn2+ is up to 93.82%, which is much higher than 77.34% of PCE0. Compared with PCE0, PCE(Co2+), PCE(Ni2+) and PCE(Zn2+) have better dispersion and retention abilities, a 51-mm larger fluidity and a bigger early hydration rate of cement slurries. Interestingly, the water reduction rates of PCE(Co2+), PCE(Ni2+) and PCE(Zn2+) are 13.7%-25.3% higher than that of PCE0.

Hybrid Hydrogels for pH Indicator

Hybrid hydrogels were prepared by copolymerization of 2-hydroxyethyl methacrylate and diallyldimethylammonium chloride mixed with alginate, bromothymol blue, and fume silica. The polymerization reaction occurred by free radical polymerization using potassium persulfate and N,N,N/, N/−tetramethyethylenediamine as a redox initiator and N,N/−methylenebisacrylamide as a crosslinker. The results showed that the hydrogels responded to pH and exhibited color change. The bromothymol blue ionization was the main reason for the color change of the hydrogels. Also, the alginate and fume silica incorporated in the hydrogels moved the color from light shade to dark shade. The alginate, fume silica, and diallyldimethylammonium chloride affected the swelling property of the hydrogels. The alginate and fume silica increased water absorption. However, the diallyldimethylammonium chloride decreased the swelling property. The hydrogel can be used as a sensor to detect acids or bases, such as urine, causing irritation in the elderly or bed-bound patients.

Concentration Polarization Enabled Reactive Coating of Nanofiltration Membranes with Zwitterionic Hydrogel.

In this study, the bottleneck challenge of membrane fouling is addressed via establishing a scalable concentration polarization (CP) enabled and surface-selective hydrogel coating using zwitterionic cross-linkable macromolecules as building blocks. First, a novel methacrylate-based copolymer with sulfobetain and methacrylate side groups was prepared in a simple three-step synthesis. Polymer gelation initiated by a redox initiator system (ammonium persulfate and tetramethylethylenediamine) for radical cross-linking was studied in bulk in order to identify minimum (“critical”) concentrations to obtain a hydrogel. In situ reactive coating of a polyamide nanofiltration membrane was achieved via filtration of a mixture of the reactive compounds, utilizing CP to meet critical gelation conditions solely within the boundary layer. Because the feasibility was studied and demonstrated in dead-end filtration mode, the variable extent of CP was estimated in the frame of the film model, with an iterative calculation using experimental data as input. This allowed to discuss the influence of parameters such as solution composition or filtration rate on the actual polymer concentration and resulting hydrogel formation at the membrane surface. The zwitterionic hydrogel-coated membranes exhibited lower surface charge and higher flux during protein filtration, both compared to pristine membranes. Salt rejection was found to remain unchanged. Results further reveal that the hydrogel coating thickness and consequently the reduction in membrane permeance due to the coating can be tuned by variation of filtration time and polymer feed concentration, illustrating the novel modification method’s promising potential for scale-up to real applications.

Process Characterization of Polyvinyl Acetate Emulsions Applying Inline Photon Density Wave Spectroscopy at High Solid Contents.

The high solids semicontinuous emulsion polymerization of polyvinyl acetate using poly (vinyl alcohol-co-vinyl acetate) as protective colloid is investigated by optical spectroscopy. The suitability of Photon Density Wave (PDW) spectroscopy as inline Process Analytical Technology (PAT) for emulsion polymerization processes at high solid contents (>40% (w/w)) is studied and evaluated. Inline data on absorption and scattering in the dispersion is obtained in real-time. The radical polymerization of vinyl acetate to polyvinyl acetate using ascorbic acid and sodium persulfate as redox initiator system and poly (vinyl alcohol-co-vinyl acetate) as protective colloid is investigated. Starved–feed radical emulsion polymerization yielded particle sizes in the nanometer size regime. PDW spectroscopy is used to monitor the progress of polymerization by studying the absorption and scattering properties during the synthesis of dispersions with increasing monomer amount and correspondingly decreasing feed rate of protective colloid. Results are compared to particle sizes determined with offline dynamic light scattering (DLS) and static light scattering (SLS) during the synthesis.

PH and Salt Responsive Hydrogel based on Guar Gum as a Renewable Material for Delivery of Curcumin: A Natural Anti-Cancer Drug

The manuscript represents synthesis of pH and salt responsive hydrogel based on guar gum as a renewable substrate for drug delivery of natural anticancer drug i.e. curcumin. Initially acrylic acid grafted guar gum (GG-g-PAA) hydrogel was obtained in the presence of ammonium persulphate as a redox initiator. Structural stability of grafted copolymer was improved using N, N-methylenebisacrylamide as a crosslinker with simultaneous loading of curcumin as a natural anticancer drug. Delivery rate of curcumin from GG-g-PAA was studied by UV spectrophotometer. The neat and drug loaded hydrogels were characterized using FTIR, NMR, TGA, and SEM techniques for their structural, morphological, and thermal behaviours. Swelling of the hydrogels and water diffusion properties were studied in salt and aqueous solutions of different pH. Finally, the fabricated hydrogel matrices were tested for curcumin release studies to understand the release kinetic. The results indicated that the prepared renewable source based hydrogel can be used in drug delivery of curcumin as a natural medicine. As curcumin and guar gum are products of agricultural food crops viz. turmeric and guar, the current research can be a good contribution towards preparation of an eco-friendly drug delivery system based on agriculture products.

Ghatti gum-base graft copolymer: a plausible platform for pH-controlled delivery of antidiabetic drugs.

In the present study, we aimed to develop a novel pH-sensitive polymeric delivery system (GG-g-PMMA) for antidiabetic therapy via grafting ghatti gum (GG) with methyl methacrylate (MMA) chains. The free radical polymerization technique was adopted to graft ghatti gum with methyl methacrylate, using ceric ammonium nitrate (CAN) as a redox initiator. The impact on grafting parameters such as grafting percentage (G%) and grafting efficiency (GE), of monomer and initiator concentrations was evaluated. The batch with higher grafting efficiency and percentage grafting was selected and characterized by elemental analysis (C, H and N), DSC, FT-IR spectroscopy, XRD, 1H-NMR and SEM morphology study. In addition, the efficacy of GG-g-PMMA-based pellets loaded with the hypoglycemic agent, metformin hydrochloride, to sustain drug release was investigated. In vitro release studies demonstrated a pH-dependent sustained release of the drug from GG-g-PMMA pellets. In addition, acute oral toxicity studies and histopathological analysis suggested the safety and biocompatibility of the grafted gum. Most importantly, in vivo efficacy studies underscored the efficient hypoglycemic potential of the prepared formulation, which was comparable to that of a sustained release marketed formulation. These results suggest that the developed pH-sensitive polymeric delivery system (GG-g-PMMA) might represent a promising delivery vehicle for facilitated antidiabetic therapy.

Synthesis of cationic graft modified chitosan and its antibacterial finish on rabbit wool fabric

As a natural polymer antibacterial agent, chitosan itself has excellent characteristics, but its application is limited due to its poor solubility. Based on this, using ammonium persulfate ((NH4)2S2O8) and sodium bisulfite (NaHSO3) as redox initiators, a cationic antibacterial monomer was grafted onto chitosan to prepare a new type of modified chitosan. The target product was successfully analyzed by infrared spectrum analysis and XPS energy spectrum analysis. Using polycarboxylic acid as a cross-linking agent and modified chitosan as an antibacterial agent, the rabbit wool fabric was finished, and the finished fabric was tested for antibacterial properties and washing resistance. The effect of graft-modified chitosan with different reaction conditions on the antibacterial finishing fabric, such as the ratio of monomer to chitosan substance, reaction temperature, and the amount of initiator added, was studied. The results showed that the finished rabbit wool fabrics had good antibacterial effects on E. coli, and their antibacterial rates reached 100%, and after 20 washings, the antibacterial rate still reached 100%, with long-lasting antibacterial properties. Considering the cost, the ratio of the amount of the chitosan to the monomer was finally selected as 4: 1 to prepare the modified chitosan.