Influence Of Monomer Concentration Research Articles

Facile Synthesis of Poly(methyl methacrylate) Silica Nanocomposite Monolith by In Situ Free Radical Polymerization of Methyl Methacrylate in the Presence of Functionalized Silica Nanoparticles.

Novel porous poly(methyl methacrylate) (PMMA) silica nanocomposites have been produced by utilization of polymerization-induced phase separation in a simple one-pot approach. A facile free radical polymerization of MMA in the presence of surface methacrylate-functionalized silica nanoparticles was carried out in ethanol-based solvents, successfully producing novel, morphologically designable porous nanocomposite monoliths. Differing from standard free radical polymerization in solution, a mixture of good and poor solvents (ethanol/N,N-dimethylformamide ratio) for the resulting polymer was used to trigger spinodal phase separation. The influence of monomer concentration, as well as solvent composition, on the morphology of the resulting porous polymers has been investigated. Porous monolith structures composed of connected particles and co-continuous morphologies were observed under a scanning electron microscope depending on the polymerization conditions. The resulting polymers were insoluble and showed swelling characteristics in some organic solvents that are capable of dissolving regular PMMA, indicating covalent bonds between the functionalized silica nanoparticles and the polymer chains. The presence of silica particles in the final polymer was proven via an ATR-IR analysis. The glass transition temperature of the present PMMA-silica nanocomposite was higher than that of the conventional PMMA. The porous polymer immersed in a mixed organic solvent showed coloration induced by the Christiansen effect.

Influence of monomer concentration on structures of fully condensed polyphenylsilsesquioxanes

Fully condensed polyphenylsilsesquioxanes have been prepared via the hydrolysis and condensation of the same phenyltrimethoxysilane (PTMS) monomer in different concentrations. The effect of monomer concentration on molecular structure of the final products has been thoroughly investigated. Cage structured polyphenylsilsesquioxane (OPS) and ladder-like structured polyphenylsilsesquioxane (L-PPSQ) can be selectively synthesized from the same starting materials at lower and higher initial monomer concentrations. Meanwhile, online infrared detector, React IR TM15 was used to monitor the real time variation of the concentration and characteristic absorption peaks of any intermediate products that may exist. Then, React IR TM15 coupled with 29Si nuclear magnetic resonance spectroscopy (NMR), gel permeation chromatography (GPC) and matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS) were used to monitor and identify the intermediate species during the reaction. Mechanism studies indicated that the condensation reaction of OPS and L-PPSQ both proceed through a T1 structure dimer, which was formed by the quick hydrolysis of the PTMS monomer. As confirmed by 29Si-NMR, GPC and MALDI-TOF-MS, the synthesis mechanisms of OPS and L-PPSQ during the hydrolysis-condensation reactions were delineated.

Amphoteric nano‐ and microgels with acrylamide backbone for potential application in oil recovery

AbstractAmphoteric nano‐ and microgels based on acrylamide (AAm), 3‐acrylamidopropyltrimethylammonium chloride (APTAC) and 2‐acrylamido‐2‐propanesulfonate sodium salt (AMPS) were prepared via inverse emulsion polymerization in the presence of crosslinking agent—N,N′‐methylenebisacrylamide (MBAA). Several polyampholyte nano‐ and microgel samples AAm‐APTAC‐AMPS with compositions (70:15:15, 80:10:10, and 90:5:5 mol%) were obtained and they were abbreviated as AAm70‐APTAC15‐AMPS15, AAm80‐APTAC10‐AMPS10 AAm90‐APTAC5‐AMPS5 (where the lower indexes indicate the molar concentration of monomers). The nano‐ and microgels were characterized by Fourier‐transform infrared spectroscopy, dynamic light scattering (DLS), transmission electron microscope (TEM), thermogravimetric analysis and interfacial tension measurements. The most attention was paid to the AAm80‐APTAC10‐AMPS10 microgel because its linear analog showed the best swelling capacity and the viscosifying effect for potential application in oil recovery. The influence of monomer concentration, surfactants, volume ratio of the water/organic phases, and the hydrophilic–lyophilic balance (HLB) on the average hydrodynamic size of the AAm80‐APTAC10‐AMPS10 nano‐ and microgels was studied. The size distribution of nano‐ and microgels derived from DLS data and TEM images was compared as a function of monomer concentration at constant surfactant concentration (6 wt%), HLB = 5.5 and mixture of water:oil = 60:40 vol%. Swelling of microgel particles in saline water due to the antipolyelectrolyte effect was observed. The applicability of amphoteric microgels AAm80‐APTAC10‐AMPS10 for oil recovery was tested on cores simulating the conditions of a model oil reservoir. The obtained results indicated that after the injection of around three pore volumes of the 2500 ppm microgel suspension into the sandstone core the permeability to brine decreased from 1.5 to 0.78 mD. For the first half of core sample the residual resistance factor was higher than the resistance factor, whereas for the second part of core sample these parameters were almost equal. Additional experiments with longer cores are needed to evaluate in‐depth propagation of microgels and permeability reduction in porous media.

ШИРИНА ЗАБОРОНЕНОЇ ЗОНИ ТА ПОКАЗНИК ЗАЛОМЛЕННЯ ПОЛІАНІЛІНУ

e-mail: yuliia.stetsiv@lnu.edu.ua Polyaniline (PAn) films, doped with citric acid, were synthesized on a polyethylene substrate by chemical oxidative polymerization using ammonium peroxydisulfate as an oxidant. The influence of monomer concentration on the optical properties of PAn films was investigated. Optical band gap, absorption coefficient, extinction coefficient, refractive index were calculated as a function of wavelength. Different methods for determining the energy of the energy gap (Tauc method and absorption spectrum fitting) were considered. It was found that the optical band gap for all thin PAn films is due to the direct allowed optical transitions. It was found that the band gap of PAn films decreases with increasing thickness of deposited PAn films. It is established that the optical energies of the band gap of PAn films of different thickness, estimated by the results of optical absorption measurements using Tauc methods and absorption spectrum fitting, are practically commensurate and are in the range of 3.13–2.36 eV for film thicknesses equal to 18.7–137.4 nm, respectively. Based on the correlations between the optical energy of the band gap and the refractive index of semiconductors using Moss, Ravindra, Ravindra-Gupta, Reddy-Ahammed, Gerve-Vandamme, Kumar-Singh, Annani and Duffy-Reddy ratios, the value of the refractive index of PAn films was calculated and these results were compared with the values obtained from the experimental results. From the obtained results it is seen that the refractive index of PAn films increases with increasing polyaniline film thickness on a polyethylene substrate. The values obtained from the Ravindra and Ravindra-Gupta relations are the closest to the experimental ones. Therefore, the synthesized PE/PAn films can be an available material for the production of optoelectronic devices, for example, for organic field transistors and LEDs.

Influence of monomer concentration on the morphology, contact angle, water uptake, and antibacterial activity of grafted cellulose obtained from peel durian

The objective of the current study is to evaluate and determine the effect of monomer concentration of ClAETA on the grafting copolymerization of oxidized cellulose which isolated from peel durian. Four concentrations of ClAETA were used in this study, e.g., 40, 50, 60, and 70%. Several analyses were performed to determine the material characteristic, e.g., degree of grafting, FT-IR, surface morphology, contact angle, degree of swelling, and antibacterial activity. The result showed, monomer concetration plays a significant role to the physical and surface morphology of DAC-ClAETA. The degree of grafting of ClAETA was found in the range of 15-31%, and at the concentration of 50% the grafted oxidized cellulose has 30.4% of degree of grafting. SEM images showed the pore volume has linear correlation to the monomer concetration, it increased the surface roughness. Also, the contact angle confirmed the hydrophilicity and degree of swelling of grafted oxidized cellulose was increase that linear to ClAETA concentration. DAC-g- ClAETA was found antibacterial active against S. aureus, S. epidermis, and C. albicans than DAC.

Kinetics of the Aqueous-Phase Copolymerization of MAA and PEGMA Macromonomer: Influence of Monomer Concentration and Side Chain Length of PEGMA

An in situ nuclear magnetic resonance spectroscopy (NMR) technique is used to monitor the aqueous-phase copolymerization kinetics of methacrylic acid (MAA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) macromonomers. In particular, the study analyses the effect of the number of ethylene glycol (EG) groups along the lateral chains of PEGMA and is carried out under fully ionized conditions of MAA at different initial monomer ratios and initial overall monomer concentrations (5–20 wt % in aqueous solution). The composition drift with conversion indicates that PEGMA macromonomer is more reactive than MAA. Individual monomer consumption rates show that the rates of consumption of both monomers are not first order with respect to overall concentration of the monomer. The reactivity ratios estimated from the copolymerization kinetics reveal, that for the short PEGMA, the reactivity ratios rMAA and rPEGMA increase with the solids content (SC). A totally different trend is obtained for the longer PEGMA, whose reactivity ratio (rPEGMA23) decreases with solids content, whereas the reactivity ratio of MAA remains roughly constant.

Facile chemical bath deposition method for interconnected nanofibrous polythiophene thin films and their use for highly efficient room temperature NO2 sensor application

Interconnected nanofibrous polythiophene (INPTh) film was deposited on the glass substrate through a simple chemical bath deposition method. The influence of monomer concentration on INPTh film properties as well as on NO2 sensing properties of the film was studied. The morphological and structural studies were carried out using FTIR spectroscopy, FE-SEM microscope, and AFM analysis. The FTIR spectra confirmed the formation of PTH structure. The interconnected nanofibrous surface morphology was observed in FE-SEM images. The roughness of the film and thickness (225nm–442nm) was found to increase with monomer concentration up to 0.5M, after that, both decreased at 0.6M monomer concentration. The highest selectivity of PTh thin film towards NO2 was observed than the other gases like H2S, SO2, NH3, CO and LPG. The influence of film morphology and thickness on gas sensing properties was observed, which was varied with monomer concentration. The film deposited at 0.5M monomer concentration showed the highest NO2 gas response of 47.58% at room temperature. Present results revealed that monomer concentration was also one of the deposition parameters for tuning the morphological as well as gas sensing properties of the chemical bath deposited PTh film.

Ultrathin Polyamide Membranes Fabricated from Free-Standing Interfacial Polymerization: Synthesis, Modifications, and Post-treatment

The thin film composite (TFC) membrane synthesized via interfacial polymerization is the workhorse of the prevalent membrane technologies such as nanofiltration (NF), reverse osmosis (RO), forward osmosis (FO), and pressure retarded osmosis (PRO) membranes. The polyamide selective layer usually possesses a high selectivity and permeability, making it the heart of this membrane technology. To further improve and understand its formation, with entirely excluding the effect of substrate, an ultrathin membrane which consists of only the polyamide selective layer has been fabricated via free-standing interfacial polymerization between M-phenylenediamine (MPD) and trimesoyl chloride (TMC) in this study. The influences of monomer concentration on polyamide layer formation is first examined. Different from previous studies which indicated that the variation of MPD concentration might affect the polyamide layer formation even when in excess, the MPD concentration when in excess does not affect membrane properties ...

Optimization of acrylic acid grafting onto polypropylene using response surface methodology and its biodegradability

Simultaneous radiation grafting was optimized to graft acrylic acid monomer on the polypropylene (PP) films to make them hydrophilic and enhance their biodegradability. Experiments were designed based on full factorial central composite design (response surface methodology) and influence of monomer concentration, radiation dose, inhibitor concentration, solvent concentration on degree of grafting was investigated. The extent of grafting was found to increase with increasing monomer concentration, inhibitor concentration and radiation dose. The targeted 35% grafting could be achieved at optimum condition viz. monomer concentration 12.09wt%, radiation dose 12.40 kGy, inhibitor concentration 0.07M and solvent concentration 0.12M. The grafted PP films at different degrees of grafting were tested for tensile properties and characterized by swelling studies, fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Successful grafting of acrylic acid onto polypropylene films was indicated by FTIR and confirmed quantitatively by determination of carboxylic groups on the film surface. Tensile strength of grafted PP films decreased with increase in degree of grafting. The crystallinity of the grafted PP films was lower than that of PP film as indicated by DSC studies. Grafting of acrylic acid increased the roughness on the surface of PP films indicated by SEM studies. The maximum biodegradability of the 34.55% grafted film was 5.5%.

Double UV polymerisation with variable temperature-controllable selective reflection of polymer-stabilised liquid crystal (PSLC) composites

ABSTRACTIn this study, a method of preparing wide-band reflection cholesteric liquid crystals (CLCs) films by UV-radical polymerisation in combination with UV-cationic polymerisation is proposed. Because the helical twisting power (HTP) of the chiral dopant decreases with increasing temperature and the polymerisation rate of UV-initiated free radical polymerisation is faster than UV-initiated cationic polymerisation, by adjusting the temperature, broadband reflective films with non-uniform pitch distribution are obtained. The fractured surface of the polymer network of the broadband reflective films is observed by scanning electron microscopy (SEM), which reveals the presence of non-uniform pitch distribution. In addition, the influences of monomer concentration, UV light intensity and UV curing time on the consequent non-uniform pitch distribution have been studied.

Modification of Low Density Polyethylene with 2-Hydroxyethyl Acrylate by a Swollen-Phase Grafting Method

ABSTRACTLow-density polyethylene (LDPE) was modified with 2-hydroxyethyl acrylate (HEA) by a swollen phase grafting method with azobisiso-butyronitrile (AIBN) as initiator and xylene as a swelling agent. Fourier transform infrared spectroscopy (FTIR) and 1H-nuclear magnetic resonance (1H-NMR) showed that the HEA was grafted onto the PE molecular chains and the copolymer (LDPE-g-PHEA) was formed. The rheological data illustrated that the content of long chain branches (LCB) in LDPE-g-PHEA was higher than in LDPE. Melt flow index (MFI) measurements indicated that the LDPE backbone was degraded slightly when the HEA content was small in the process of grafting. X-ray diffraction (XRD) and water contact angle measurements demo-nstrated that the grafting degree had an influence on the crystallinity and polarity of the graft polymer. A staining analysis indicated that the dyeing of the product was improved continuously with increasing of the grafting degree. Polyvinylpyrrolidone (PVP), NaCl, and ultrasound were shown to contribute to the staining, with ultrasound being the most productive. The probable grafting reaction mechanism is pro-posed. The results of the influence of monomer concentration on the grafting reaction revealed that the grafting ratio and gel content of the product increased with increasing of HEA amount.

Influence of Monomer Concentration on the Morphologies and Electrochemical Properties of PEDOT, PANI, and PPy Prepared from Aqueous Solution

Poly(3,4-ethylenedioxyhiophene) (PEDOT), polyaniline (PANI), and polypyrrole (PPy) were prepared on indium tin oxide (ITO) substrate via potentiostatic from aqueous solutions containing monomer and lithium perchlorate. The concentration of monomers was varied between 1 and 10 mM. The effects of monomer concentration on the polymers formation were investigated and compared by using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) measurements. FTIR and Raman spectra showed no changes in the peaks upon the increment of the concentration. Based on the SEM images, the increment in monomer concentration gives significant effect on morphologies and eventually affects the electrochemical properties. PEDOT electrodeposited from 10 mM solution showed excellent electrochemical properties with the highest specific capacitance value of 12.8 mF/cm2.

Zinc complexes supported by (benzimidazolyl)pyridine alcohol ligands as highly efficient initiators for ring-opening polymerization of ε-caprolactone

A series of air-stable zinc complexes (1–3) supported by (benzimidazolyl)pyridine alcohol ligands {tridentate [N,N,O]} has been synthesized and well characterized by FT-IR, 1H and 13C NMR, elemental analysis and single-crystal X-ray diffraction analysis. In combination with methyllithium, these zinc complexes were proved to be highly efficient initiators for the ring-opening polymerization (ROP) of ε-caprolactone (ε-CL). The ROP of ε-CL in the absence or presence of benzyl alcohol, as well as the influences of monomer concentration, reaction temperature and the substituent on the ligand, were investigated in detail.

Influence of monomer concentration during polymerization on performance and catalytic mechanism of resultant poly(3,4-ethylenedioxythiophene) counter electrodes for dye-sensitized solar cells

Poly(3,4-ethylenedioxythiophene) (PEDOT) films doped by perchlorate ions (ClO4−) have been prepared via electropolymerization with different EDOT monomer concentration and used as counter electrodes (CEs) in dye-sensitized solar cells (DSSCs). The effect of EDOT monomer concentration on the properties of obtained PEDOT CEs has been thoroughly investigated. The sponge like porous microstructure of the PEDOT films breaks gradually with the increase of EDOT concentration. Meanwhile, the conductivity of the PEDOT CEs decreases gradually due to the decreased ClO4− doping level. The catalytic mechanism is mainly comprised of the formation of weakly bonded iodine species on the undoped EDOT units, and formation and reduction of the intermediates. The undoped EDOT units in the PEDOT chain are the key catalytic reaction centers for I−/I3− redox reaction. The catalytic activity of the PEDOT CEs for I−/I3− redox reaction increases with the increase of EDOT concentration by virtue of the increased catalytic reaction centers in the PEDOT chain (i.e., increased undoped EDOT units due to the decreased ClO4− doping level). DSSC based on PEDOT CE polymerized with 0.05M of EDOT and 0.1M of LiClO4 shows good photovoltaic performance, with a power conversion efficiency of 7.42%. This result is comparable to the Pt CE based-solar cell (7.41%), suggesting that PEDOT CEs may substitute the expensive Pt CEs in the DSSCs.

Preparation of cellulose graft copolymer based on the combination of ionic liquids and microwave heating

Cellulose is a promising raw material that can be modified through a variety of chemical modifications to obtain many functional materials. Cellulose-g-acrylamide copolymer was prepared in a homogeneous medium by using N,Nʹ-methylenebisacrylamide as the crosslinker without any radical initiator using microwave radiation. The 1-butyl-3-methylimidazolium chloride ionic liquid, which is an environmentally friendly and effective reaction medium, was chosen to dissolve the cellulose and the homogeneous graft polymerisation of acrylamide onto the cellulose. Owing to the effects of microwave heating, the reaction time was significantly shortened: 1 minute microwave heating was adequate, compared to 30 minutes to 5 hours with a conventional heating method. The influences of monomer concentration, crosslinker dosage, microwave power and reaction time were investigated. The obtained cellulose graft copolymer was characterised by infrared spectrum, thermogravimetric analysis and scanning electron microscopy. A feasible reaction mechanism of grafting based on microwave heating was proposed.

New Low-Toxic PEG(200)DMA/AM Gel System for 3YSZ Gel-Casting

Gel-casting is promising in fabricating uniform and complex-shaped ceramic body, but it is confined in industrial application for the neurotoxic acrylamid (AM) gel system. Ether-contained oligomer poly(ethylene glycol)(200) dimethacrylate (PEG(200)DMA) with methacrylate end-group on either side of the long chain can act as cross-linking agent in free radical polymerization to form branchy gel network structure, which improves the green body strength. In this study, low-toxic PEG(200)DMA was chosen as the main binder and crosslinker and small dosage AM was applied to adjust the viscosity of the ceramic slurry to gel-cast 3YSZ (PEG(200)DMA: AM = 4:1, mass ratio). Influence of monomer concentration, dispersant concentration and solid loading on the rheological behavior of the slurry and the flexural strength of the green body were investigated using aqueous PEG(200)DMA/AM gel system to gel-cast 3YSZ. The results show that the flexural strength of green bodies notably increases with the increasing of monomer concentration and reaches high up to 14.4 MPa when gel-cast 3YSZ ceramics using PEG(200)DMA/AM gel system with appropriate amount of PAA-NH4, monomer and solid loading. This gel system obviously reduces the toxicity of the conventional AM system and, at the same time, ensures high flexural strength of green bodies.

The influence of monomer concentration on the optical properties of electrochemically synthesized polypyrrole thin films

Polypyrrole (PPy) thin films were deposited on stainless steel and ITO coated glass substrate at a constant deposition potential of 0.8 V versus saturated calomel electrode (SCE) by using the electrochemical polymerization method. The PPy thin films were deposited at room temperature at various monomer concentrations ranging from 0.1 M to 0.3 M pyrrole. The structural and optical properties of the polypyrrole thin films were investigated using an X-ray diffractometer (XRD), FTIR spectroscopy, scanning electron microscopy (SEM), and ultraviolet—visible (UV—vis) spectroscopy. The XRD results show that polypyrrole thin films have a semi crystalline structure. Higher monomer concentration results in a slight increase of crystallinity. The polypyrrole thin films deposited at higher monomer concentration exhibit high visible absorbance. The refractive indexes of the polypyrrole thin films are found to be in the range of 1 to 1.3 and vary with monomer concentration as well as wavelength. The extinction coefficient decreases slightly with monomer concentration. The electrochemically synthesized polypyrrole thin film shows optical band gap energy of 2.14 eV.

Cross-linked bovine serum albumin composite membranes prepared by interfacial polymerization with stimuli-response properties

The novel cross-linked bovine serum albumin (BSA) composite membranes were prepared by interfacial polymerization method upon porous polycarbonate track-etched (PCTE) substrates. There was chemical cross-linking reaction between the amine groups of BSA and acyl chloride groups of trimesoyl chloride (TMC) in the water/oil interfacial zone. The composite membranes were characterized by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The influence of monomer concentration, interfacial polymerization reaction time and temperature on the properties of cross-linked BSA composite membranes was investigated in detail. The repulsive and attractive electrostatic interactions among BSA molecules in the thin films could be controlled by adjusting pH value and ionic concentration in feed solutions, so that the cross-linked BSA composite membranes possessed stimuli-responsive properties.

The synthesis, deprotection and properties of poly(γ-benzyl-l-glutamate)

Diethylamine, di-n-hexylamine, dicyclohexylamine and triethylamine have been used as initiators for the ring-opening polymerization of γ-benzyl-l-glutamate N-carboxyanhydride (BLG NCA) to synthesize poly(γ-benzyl-l-glutamate) (PBLG). The relationship between the molecular weight of PBLG and the molar ratio of monomer and initiator was studied. With dicyclohexylamine as initiator, the influence of monomer concentration, and reaction temperature and time on the polymerization of BLG NCA was examined. Three reagents were used for the deprotection of benzyl groups in PBLG, including hydrobromic acid/acetic acid (33 wt.%), NaOH aqueous solution and trimethylsilyl iodide (TMSI). Through examining the molecular weight of PLGA obtained using different deprotection methods, it was revealed that TMSI could minimize chain cleavage in the process of deprotection and retain the degree of polymerization. The biocompatibilities of PBLG obtained using different initiators were evaluated by a live/dead assay against L929 fibroblast cells. The in vitro cytotoxicities of PLGA obtained using different deprotecting agents were evaluated by a methyl thiazolyl tetrazolium assay. The results revealed that both PBLG and PLGA exhibited good biocompatibilities.

The facile preparation for temperature sensitive silica/PNIPAAm composite microspheres

The temperature sensitive SiO2/PNIPAAm composite microspheres were designed and successfully synthesized. The influences of monomer concentration, reaction time, reaction temperature and initiator amount on water contact angel of the prepared microspheres were investigated. The structure, morphology, and surface composition were characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS). The temperature sensitive properties in aqueous solution were studied by water contact angle measurement instrument and dynamic light scatter (DLS). The results show that the low critical solution temperature (LCST) of SiO2/PNIPAAm composites is around 304K and the particle is monodisperse microsphere.