Radical Polymerization In Presence Research Articles

Synthesis of block copolymers by radical polymerization in presence of Si-based chain transfer agent

A new versatile method of block-copolymer synthesis is based on classic radical polymerization with a multifunctional Si-organic chain transfer agent.

Enhanced interfacial stability with a novel boron-centered crosslinked hybrid polymer gel electrolytes for lithium metal batteries

Low coulombic efficiency and serious safety issues due to uncontrollable lithium dendrite growth has severely impeded the practical application of lithium-ion batteries (LIBs) with lithium metal as the anode. In this work, we design and fabricate a novel single ion conducting crosslinked polymer gel electrolytes containing negatively charged delocalized state borate structures and rich EO units via one-step photoinitiated in-situ radical polymerization in presence of PVDF-HFP as reinforcing materials. Herein, we synthesize a novel lithium bis(macid acid) borate to give anion covalently bonded to the polymer main chain and vinyl monomers containing rich EO units are chosen to build polymer framework to ensure fast ion transport. As expected, the tailored boron-centered single-ion-conducting polymer gel electrolytes exhibit high ionic conductivity up to 1.03×10−3 S cm−1 at 32 °C, excellent oxidation potential up to 5.05 V vs Li+/Li at 1 mV/s, and a near-single ion conducting behavior (lithium ion transference number of 0.65). The Lithium (Li) metal symmetric cells assembled with the novel boron-centered single-ion-conducting polymer gel electrolytes show long-term stable cycling over >700 h at room temperature without short circuit, which implies the excellent stability of blend membranes during lithium metal deposition and stripping processes. Moreover, the Li/LiFePO4 cells assembled with the boron-centered single-ion-conducting polymer gel electrolytes exhibit excellent rate performance and cycling performance. The initial discharge capacity is 161.3 mAh g−1 at 0.1 C and a capacity of 127.7 mAh g−1 maintains with nearly 100% coulombic efficiency after 100 cycles. Moreover, the Li/LiFePO4 cells deliver stable coulombic efficiency close to 100% at 0.5 C after 300 cycles.

Poly[4-pyridinyl-4´-(2-methacryloyloxyethoxy)styryl ketone-co-2-hydroxypropyl methacrylate]: Synthesis, Characterization, Thermal and Electrical properties, and Photocrosslinking behavior

Synthesis of a chalcone bearing pyridine ring, 4-pyridinyl-4´-(2-hydroxyethoxy)styryl ketone, was carried out from the reaction of 4-acetyl pyridine and 4-(2-hydroxyetoxy)benzaldehyde in an aqueous solution of NaOH. 4-Pyridinyl-4´-(2-methacryloyloxyethoxy)styryl ketone which is the methacrylate monomer bearing chalcone structure in side chain, was obtained from acylation of 4-pyridinyl-4´-(2-hydroxyethoxy)styryl ketone with methacryloyl chloride in the cold. The copolymer of 4-pyridinyl-4´-(2-methacryloyloxyethoxy)styryl ketone and 2-hydroxypropyl methacrylate was prepared by free radical polymerization in presence of AIBN at 70 oC. FTIR, 1H-NMR and 13C-APT spectroscopic techniques were used for structural characterization of the Chalcone, the monomer and the copolymer. Thermal characterization of the copolymer was carried out using DSC and TGA techniques. DSC curve shows that this copolymer has a glass transition temperature of 78 oC. The TGA curve shows that decomposition given volatile product started at 230 °C and a residue of 21% left at 500 °C. Dielectric constant (ε´) of the copolymer decreased rapidly from 8.8 to 4.2 with increasing frequency in the range of 100-1000 Hz, and after this frequency ε´ quantity remained constant at a value such as 4.2. ε´ Value of the copolymer increased only from 4.2 to 4.9 with increasing from 290 K to 385 K. The AC conductivity of the copolymer increases from 5.01x10-10 S/cm to 126.0x10-10 S/cm as the frequency increase from 100 Hz to 5000 Hz. The AC conductivity increases slightly with increasing temperature, 2.52x10-9 S/cm at 300 K, and 2.89x10-9 S/cm at 385 K. After a solution of the copolymer was irradiated using UV light at 365 nm at room temperature, the absorption band at 356 nm disappeared and a new band was seen at 284 nm.

Biodegradable-stimuli sensitive xanthan gum based hydrogel: Evaluation of antibacterial activity and controlled agro-chemical release

Biodegradable hydrogel based on xanthan gum graft co-polymerized with polyacrylic acid was fabricated by free radical polymerization in presence of microwave radiations and its potential utility as bactericidal agent along with controlled agro-chemical release device was explored. The biodegradability was tested using soil burial method and it has been observed that the synthesized semi-interpenetrating (semi-IPN) was degraded upto 78.3% by weight with 1.11% rate of degradation per day within 70days. FT-IR and SEM micrographs further confirmed the biodegradable nature of the test sample. The Phaseolus vulgaris plants were grown in the soil containing the degraded sample and depicted healthy growth characteristic indicated the absence of any harmful end products from degraded sample. The semi-IPN was also found to bactericidal in nature against bacterial strains such as Bacillus subtilis and Salmonella enteritis probably due to ion-exchange effect. Also, the synthesized sample was used for the controlled release of urea and its release dynamics were studied. The macromolecular relaxation of the matrix was found to be comparable to diffusion rate of urea indicated by the non-Fickian (n=0.76) diffusion mechanism. Initial diffusion coefficient (Di=3.50×10−5m2h−1) was found to be greater than late diffusion coefficient (DL=2.31×10−6m2h−1) and indicated the prolonged release of urea. So, synthesized semi-IPN could be labeled as biodegradable, non-toxic, stimuli sensitive, antibacterial along with controlled release device for agro-chemicals.

CO₂-Philic Thin Film Composite Membranes: Synthesis and Characterization of PAN-r-PEGMA Copolymer.

In this work, we report the successful fabrication of CO2-philic polymer composite membranes using a polyacrylonitrile-r-poly(ethylene glycol) methyl ether methacrylate (PAN-r-PEGMA) copolymer. The series of PAN-r-PEGMA copolymers with various amounts of PEG content was synthesized by free radical polymerization in presence of AIBN initiator and the obtained copolymers were used for the fabrication of composite membranes. The synthesized copolymers show high molecular weights in the range of 44–56 kDa. We were able to fabricate thin film composite (TFC) membranes by dip coating procedure using PAN-r-PEGMA copolymers and the porous PAN support membrane. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were applied to analyze the surface morphology of the composite membranes. The microscopy analysis reveals the formation of the defect free skin selective layer of PAN-r-PEGMA copolymer over the porous PAN support membrane. Selective layer thickness of the composite membranes was in the range of 1.32–1.42 μm. The resulting composite membrane has CO2 a permeance of 1.37 × 10−1 m3/m2·h·bar and an ideal CO2/N2, selectivity of 65. The TFC membranes showed increasing ideal gas pair selectivities in the order CO2/N2 > CO2/CH4 > CO2/H2. In addition, the fabricated composite membranes were tested for long-term single gas permeation measurement and these membranes have remarkable stability, proving that they are good candidates for CO2 separation.

Surface modification and immobilization in poly(acrylic acid) of Ag/ZnO for photocatalytic degradation of endocrine‐disrupting compounds

ABSTRACTSilver‐modified ZnO particles (Ag/ZnO) are effective catalysts for the photodegradation of water pollutants such as bisphenol‐A. However, until now, their use in continuous processes was back‐drawn because of difficulties associated with their recovery. To overcome this problem, the present work aimed at immobilizing Ag/ZnO in cross‐linked poly(acrylic acid) ‐PAA‐. Ag/ZnO was first silanized using (3‐glycidyloxypropyl)trimethoxysilane and thoroughly dispersed in a water‐acrylic acid solution. The suspension was then submitted to radical polymerization in presence of a cross‐linker (N,N′‐Methylenebisacrylamide). The resulting composites were characterized in terms of chemical structure, morphology, crystallinity, thermal properties, and photostability. Their analyses showed that the silanized particles were chemically anchored to PAA and homogeneously distributed in the matrix. UV‐assisted photocatalysis of bisphenol‐A aqueous solutions showed that immobilized Ag/ZnO can achieve photodegradation performances comparable to pure Ag/ZnO and allows its use in successive cycles and, consequently, in continuous processes. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43528.

Swelling and Diffusion Properties of Poly(acrylamide-co-maleic acid) Hydrogels: A Study with Different Crosslinking Agents

Crosslinked hydrogels comprising acrylamide (AAm) and maleic acid (MA) were synthesized by free radical polymerization in presence of a crosslinker using ammonium persulfate (APS) and N,N,N1,N1-tetramethylethylenediamine (TMEDA) as initiator and activator, respectively. The crosslinked hydrogel formation was confirmed by IR analysis. The swelling/de-swelling characteristics were studied in detail for crosslinked poly(acrylamide-co-maleic acid) [poly(AAM-co-MA)] hydrogels containing different amounts of maleic acid. Four different crosslinkers such as 1,2-ethyleneglycol dimethacrylate (EGDMA), 1,4-butanediol diacrylate (BDDA), 1,6-hexanediol diacrylate (HDDA), and diallyl phthalate (DP) were utilized to study their influence on the swelling behavior of the hydrogels. The effect of reaction parameters such as the concentration of crosslinker and initiator on swelling capacity of the crosslinked poly(AAm-co-MA) hydrogels was also investigated. Further, the influence of various salts, simulated biological fluids, and pH solutions on the swelling pattern of hydrogels was studied extensively. Phase separation morphology of crosslinked hydrogels was also studied by differential scanning calorimetry. The morphology of crosslinked hydrogels were revealed using scanning electron microscopy (SEM).

Synthesis and characterisation of urethane-methacrylates I

The paper describes the synthesis of urethane methacrylate resins by reaction of tolylene diisocyanate (TDI), butanol-1 (B) and 2-hydroxyethylmethacrylate (HEMA) by a two step procedure. Characterisation was done using FT-IR, FT-NMR, Mass Spectroscopy. The effect of temperature on the UV-curing behaviour was investigated by differential photocalorimetry. An activation energy of 8.4 kJ/mole was found in the temperature range of 50–100°C. Free radical polymerisation in presence of benzoyl peroxide was also investigated. The polymers were stable upto 200°C in N2 atmosphere. A two step decomposition was observed in the temperature range of 200–500°C.

Chain transfer reactions for styrene free radical polymerization in presence of mixed ethylbenzene and EPDM rubber

AbstractInvestigations were made on the radical polymerization of styrene in presence of ethylene propylene diene terpolymers and ethylbenzene. The results obtained allowed to calculate the transfer constants of polystyryl radical to terpolymer and ethylbenzene in a mixed system. Meanwhile the same results showed a lower radical reactivity of the elastomer in presence of the aromatic transfer agent.