Effect Of Monomer Concentration Research Articles

Optimization of an α‐(Amino acid)‐N‐carboxyanhydride polymerization using the high vacuum technique: Examining the effects of monomer concentration, polymerization kinetics, polymer molecular weight, and monomer purity

ABSTRACTl‐Ornithine‐based poly(peptides) have been widely utilized in the field of drug delivery, however few studies have been conducted examining the details of polymerization. In this article, the effects of monomer concentration, polymerization kinetics, polymer molecular weight and monomer purity were investigated using l‐carboxybenzyl (Cbz)‐ornithine as a model monomer. The mechanism of polymerization herein follows the normal amine mechanism to produce poly(peptides) having controlled molecular weights, known chain ends and a narrow polydispersity index (PDI). A preferred monomer concentration range was determined, which required minimal polymerization times and allowed for predictable and reproducible molecular weights with narrow PDIs. The impact of monomer purity on the polymerization was established and monomer purification conditions are reported, which produce high‐purity monomer after a single recrystallization. Additionally, the optimized polymerization conditions and monomer purification protocol were combined with a sequential monomer addition technique to produce high molecular weight poly(ornithine) with a narrow PDI and known chain ends. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1385–1391

Preparation of Composite Materials of Waste Clay and Polymethyl Methacrylate Using Mechanochemial Polymerization in an Organic Solvent

In order to use a waste clay effectively and to investigate mechanochemical polymerization as preparation method of the inorganic-organic composite materials, the mechanochemical polymerization of methyl methacrylate (MMA) was carried out by grinding the waste clay in n-heptane solvent. The waste clay was a halloysite with 16.2m2/g in specific surface area. The grinding operation was performed using a vibrating ball mill with a laboratory scale. The effect of monomer concentration in n-heptane solvent on the polymerization rate and the molecular mass of polymer were examined. As a result, the mechanochemical polymerization of MMA also proceeded by the grinding of the clay in n-heptane solvent. It was found that the polymerization rate increased with the increase of MMA concentration and that the conversion of MMA reached than 90%. Although the number average molecular mass of resulting polymer was in the order of 104 to 105, the molecular mass was decreased with the grinding time due to the scissions of polymer chains by the mechanical action. This polymerization mechanism was found to be radical reaction from the investigation of polymer tacticity. As for the composite of clay and PMMA obtained by the mechanochemical polymerization, a die molding was possible directly without kneading process.

Enhanced melt free radical grafting efficiency of polyethylene using a novel redox initiation method

In this work, for the first time, redox initiation was employed in the melt free radical grafting of glycidyl methacrylate (GMA) and maleic anhydride (MA) onto polyethylene (PE) by reactive extrusion. Since it is very challenging to obtain high grafting degrees of GMA and MA onto polymer backbones through conventional free radical initiation, especially in the extrusion process, the strategy of using a peroxide/reducing agent initiator was introduced. The redox initiation system was composed of dicumyl peroxide (DCP) and Tin(II) 2-ethylhexanoate (Sn(Oct)2). The grafting reaction was monitored by torque rheometry and graft products were analyzed by Fourier Transform Infrared Spectroscopy. Effects of monomer concentration and DCP/Sn(Oct)2 ratio on the degree of grafting were studied. The redox initiation proved to be very effective in improving the grafting degree of GMA and MA onto PE. It is reasoned that, in the presence of Sn(Oct)2, the free radicals produced were not subject to a cage effect, yielding high initiator efficiency.

Selective recognition and electrochemical detection of p-nitrophenol based on a macroporous imprinted polymer containing gold nanoparticles

We have combined the molecular imprinting and the layer-by-layer assembly techniques to obtain molecularly imprint polymers (MIPs) for the electrochemical determination of p-nitrophenol (p-NPh). Silica microspheres functionalized with thiol groups and gold nanoparticles (Au-NPs) were assembled on a gold electrode surface layer by layer. The electrode was then immersed into a solution of pyrrole and p-NPh (the template), and electropolymerization led to the creation of a polymer-modified surface. After the removal of the silica spheres and the template, electrochemical impedance spectroscopy and differential pulse voltammetry (DPV) were employed to characterize the surface. The results demonstrated the successful fabrication of macroporous MIPs embedded with Au-NPs on the gold electrode. The effects of monomer concentration and scan rate on the performance of the electrode were optimized. Excellent recognition capacity is found for p-NPh over chemically similar species. The DPV peak current is linearly related to concentration of p-NPh in the 0.1 μM to 1.4 mM range, with a 0.1 μM limit of detection (at S/N = 3).

Interfacially Polymerized Composite Hollow Fiber Membrane for CO<sub>2</sub> Separation

PEAm-TMC/PDMS/PVC composite hollow fiber membrane for CO2 separation was developed through interfacial polymerization (IP) on the PDMS pre-coated inner surface of PVC hollow fiber. Polyetheramine (PEAm) and Trimesoyl chloride (TMC) were selected as aqueous monomer and organic monomer, respectively. SEM observation result shows that the thickness of PEAm-TMC IP layer is about 215 nm. The effects of monomer concentrations and acid acceptor concentration on the membrane performance were investigated. The results shows that the CO2 permeance decareses and CO2/N2 selectivity increases with the increasing concentrations of PEAm, TMC and Na2CO3. At 0.12 MPa, the composite hollow fiber membrane possesses a very high CO2 permeance of 964 GPU and CO2/N2 selectivity of 40.6.

Catalytic Reduction of N-Nitrosodimethylamine by Palladium/ Iron Bimetallic Composite Catalytic Fiber

The polypropylene (PP) fibers were chosen as substrate materials. Functional fibers containing iron were prepared by UV irradiation-coordination method, and then Pd/Fe bimetallic composite catalytic fibers were prepared by replacement reaction and used for the removement of N-nitrosodimethylamine (NDMA). The effect of monomer concentration, the pH of the reaction system and reaction temperature on NDMA catalytic degradation was investigated. The results indicate that the degradation rate of NDMA can reach 69.97% when the AA monomer concentration is 20%, which is the best catalytic reduction effect of composite catalytic fiber on NDMA. The pH of solution and reaction temperature can not greatly influence the catalytic reduction of NDMA.

Low-voltage-modulated laser based on dye-doped polymer stabilized cholesteric liquid crystal

An electrically-modulated laser was fabricated based on cholesteric liquid crystal photonic band gap. To lower the modulation voltage, the nematic liquid crystals with high dielectric constant was selected, and thus, the emission energy can be modulated with a voltage of less than 10 V. Polymer stabilization was carried out to obtain a stable and switchable helical liquid crystal system. It is noteworthy that visible light initiation system was adopted to prevent the deformation of photonic band gap. The monomer concentration effects on lasing performances were studied and discussed. The results indicate that the laser emission threshold is decreased and the response time is shortened with the increasing of monomer, while the hysteresis may be enhanced. This study provides some new insights into the fabrication, materials improvements and performances of dye-doped liquid crystal laser, and such electrically modulated laser will be a prospective candidate in the laser displays, micro-light-source or the other optical systems.

Hydrogen phosphates: Self initiated organocatalysts for the controlled ring-opening polymerization of cyclic esters

A series of arylhydrogenphosphates and aryldihydrogenphosphates was synthesized and characterized using spectroscopic methods and single crystal X-ray diffraction. These compounds were assessed as catalysts towards the ring-opening polymerization and proved to be potent organocatalysts for the ring-opening polymerization of cyclic esters. The bulk polymerizations were performed in the absence of external initiator. The polymerization proceeds in a controlled fashion which leads to well defined polyesters with narrow molecular weight distributions. In the post polymerization experiments, kinetics, mechanism and monomer concentration effects were investigated. The kinetic results have confirmed the pseudo-living character of the polymerizations and mechanistic studies suggest that the polymerization operates through a cationic mechanism.

Preparation and Properties of Ecological Colored Cellulose Material

Ecological colored cellulose material was prepared via UV initiated photografting of acrylic acid/cationic dye system in this study. The colored cellulose material was characterized using scanning electron microscopy (SEM) and fourier transform infrared spectroscopy (FTIR). The effects of monomer concentration, photoinitiator amount, dye amount, pH value, grafting time, heating temperature and grafting method on the coloration of cellulose material were discussed. The results showed that the optimum process was as follows: the monomer concentration of 50wt%, photoinitiator amount of 3o.w.m.%, grafting time of 4min, and heating temperature of 70.

Research on Polymerization of PMN-PZT Piezoelectric Ceramic by Gelcasting Using NMAM System

The industrialization of gelcasting technique has been prevented because acryamide is a neurotoxin monomer. In this paper, a low-toxicity gel system based on the polymerization of low-toxicity N-hydroxymothl acrylamide was used for the gelcasting PMN-PZT piezoelectric ceramic. The effects of monomer concentration, the dosage of initiator and catalyst, pH value on polymerization were studied. The results showed that the condition suitable for gelcasting PMN-PZT piezoelectric ceramics could be obtained while monomer concentration was 10wt%～15wt%, the dosages of initiator and catalyst were respectively 0.4 vol%～0.5vol% and 0.4vol%, pH value of slurry was about 10. The highest bending strength of PMN-PZT green body prepared at the aboved conditions can reach 19.5Mpa

R-ATRP of Acrylamide under the Action of Copper Complex System in Aqueous Two-Phase

Polyacrylamide (PAM) was synthesized by combining reverse atom transfer radical polymerization (R-ATRP) with aqueous two-phase polymerization. In aqueous two-phase system, polyethylene glycol 20000 (PEG20000) is used as dispersing agent, potassium persulfate (KPS) and Cu(en)2+ are used as initiator and control agent, respectively. In this paper the effect of monomer concentration, the amount of Cu(en)2+, reaction temperature, the ratio of Cu(Ⅱ), and ethylenediamine (en) were investigated. The experimental result shows the optimum conditions are as follows: m(AM)∶m(PEG)=1∶1, the monomer concentration is 10%, n(AM)∶n(CuCl2•2H2O)∶n(en)∶n(KPS)=3000∶10∶20∶1, polymerization time is 6 h, and polymerization temperature is 45°C. Under these conditions, the monomer conversion is 91.5%，the linear correlation coefficient is 0.9911.

Preparation of Chitin-g-poly(4-vinylpyridine) Beads

Chitin was modified via grafting with poly(4-vinylpyridine) (P4VP) to form chitin-g-P4VP. The reaction was carried out under homogeneous conditions using potassium persulphate (K2S2O8) (KPS) as a redox initiator. The effect of monomer concentration on the extent of grafting (%G) was studied by the gravimetric method. Grafting percentages up to 226% were obtained. The capability of chitin to form physical gels was exploited to form beads of modified chitin. Grafted chitins were coagulated from the non-solvent ethanol in the form of beads. Chitin-g-P4VP was characterized by FTIR, TGA, XRD and SEM analyses. The swelling behavior of the beads was studied in distilled water, in acid and phosphate buffers. XRD analysis showed that the P4VP grafted product had lower crystallinity when compared to chitin. Thermal analysis carried out by TGA analyses revealed that the grafted products were less stable against thermal treatment than chitin. The gel beads were tested for their cholesterol and Fe3+ adsorption capacities. The beads derived from chitin-g-P4VP were found to have higher adsorption capacities than chitin beads due to a microporous bead surface and chemical modification.

Selective adsorption of Hg(II) by γ-radiation synthesized silica-graft-vinyl imidazole adsorbent

Silica-based adsorbent was prepared by γ-radiation induced grafting of vinyl imidazole (VIM) onto the silanized silica, which was silanized by chlorotrimethylsilane (TMCS). The effects of monomer concentration and absorbed dose on the grafting yield were investigated to optimize the reaction conditions. Thermodynamic analysis, FTIR analysis and XPS spectra manifested that VIM was successfully grafted onto the silica surface. The SS-g-VIM adsorbent had excellent selectivity for Hg(II) adsorption in mixture divalent cationic metal solution and a high adsorption capacity of Hg(II). The theoretical maximum adsorption capacity was calculated to be 355.9mgg−1 (1.774mmolg−1) in HgCl2/HNO3 solution at pH 5 at room temperature. The adsorption kinetics and adsorption isotherm were investigated. It was found that the Langmuir isotherm model fitted well with the adsorption process and the adsorption of Hg(II) onto SS-g-VIM adsorbent could be considered as a spontaneous, endothermic and chemical sorption process. The comprehensive results suggested that SS-g-VIM adsorbent has potential application for the removal of Hg(II) from wastewater.

Effects of monomer concentration on the structure and properties of polybenzidine micro rods

Polybenzidine was synthesized by interfacial polymerization under various monomer concentrations. Effects of monomer concentration on morphology, structure, and properties of polybenzidine were studied by techniques of Fourier Transform Infrared Spectroscopy, Ultraviolet Visible Absorption Spectroscopy, Scanning Electron Microscopy, Transmission Electron Microscopy, X-ray Diffraction, and Cyclic Voltammetry. The results showed that the synthesized polybenzidine with monomer concentration less than 0.15 mol/L were micro rod-like and the surface of the micro rods was smooth and uniform, However, the micro rod-like polybenzidine cannot be obtained under high monomer concentration because of the explosive polymerization. The results of structural analysis indicated that the monomer concentration should not be very high to obtain the polybenzidine with the optimal degree of conjugation and order arrangement of molecular chain. The polybenzidine synthesized in different monomer concentrations showed different electrochemical activities and the sample with the best electrochemical activity was obtained at monomer concentration of 0.02 mol/L.

Electrochemical polymerization of pyrrole over AZ31 Mg alloy for biomedical applications

Electrochemical polymerization of pyrrole (Py) from aqueous salicylate solution over AZ31 Mg alloy was carried out using cyclic voltammetry (CV). The effect of monomer concentration on the surface and electrochemical corrosion in simulated body fluid (SBF) were analysed. Attenuated total reflection-infrared (ATR-IR) spectra showed the characteristic ring stretching peaks for polypyrrole (PPy). Scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies exhibited typical cauliflower morphology with rough surface for PPy coated AZ31 Mg alloy. Open circuit potential measurement and potentiodynamic polarization studies revealed that the coating prepared using 0.25M of Py had positive shift of about 120mV in corrosion potential and lower corrosion current density (0.03mA/cm2) compared to other concentrations and uncoated AZ31 Mg alloy (0.25mA/cm2). Electrochemical impedance spectroscopic (EIS) studies of uncoated and PPy coated Mg alloy in SBF revealed three-time constants behaviour with about one order of increment in impedance value for 0.25M of Py.

ω-Pentandecalactone Polymerization and ω-Pentadecalactone/ε-Caprolactone Copolymerization Reactions Using Organic Catalysts

The catalytic behavior of several inexpensive and simple N-heterocyclic organic catalysts in ring-opening polymerization (ROP) of ω-pentadecalactone (PDL) and e-caprolactone (CL) has been studied. The polymerization reactions, carried out in bulk monomer and in toluene solution at 100 °C, identified 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) in combination with benzyl alcohol (BnOH) as initiator as the only active catalyst for the ring-opening polymerization of PDL and for the copolymerization of PDL and CL. The guanidine N-methyl-TBD (MTBD), 1,2,3-triisopropylguanidine, the amidine 1,8-diazabicycloundec-7-ene (DBU), and other N-heterocyclic organic catalysts such as dialkylaminopyridine (DMAP), imidazole, indoles, and N-heterocyclic carbenes (NHC’s) tested in this study proved to be inactive in the ROP of PDL even for the long reaction times. The polymerization mechanism, kinetic studies, temperature, and monomer concentration effects were investigated both in solution and in bulk monomer. The pseudolivin...

Synthesis of 5-(3,6-di(thiophene-2-yl)-9H-carbazole-9-yl)pentane-1-amine and Electrochemical Impedance Spectroscopy

In this article, 5-(3,6-di(thiophene-2-yl)-9H-carbazole-9-yl) pentane-1-amine, (ThCzPA) comonomer was newly synthesized and characterized by Fourier transform infrared reflectance-attenuated total reflection spectroscopy (FTIR-ATR) and 1H-NMR spectroscopy. ThCzPA was electrochemically deposited onto carbon fiber micro electrode (CFME). Poly(ThCzPA)/CFME is characterized by Cyclic voltammetry (CV) and Electrochemical impedance spectroscopy (EIS). Capacitive behaviors of modified CFMEs were defined via Nyquist, Bode-magnitude and Bode-phase plots. The equivalent circuit model of R(Q(R(QR)(Q(RW))) was used for polymer-electrolyte system. The effect of monomer concentration (0.5, 1.0 and 1.5 mM) on the formation of alternating copolymer is reported in 0.1 M sodium perchlorate (NaClO4)/acetonitrile (ACN) solution. The highest low frequency capacitance (CLF = 5.07 µF cm−2 for R(Q(R(QR)(Q(RW))) was obtained in the initial monomer concentration of 1.5 mM.

Synthesis and Characterization of Linear Low Density Polyethylene Grafted Glycerol Monolauric Acid Monoitaconic Acid Diester

A reactive type dripping agent, glycerol monolauric acid monoitaconic acid diester (GLID) was synthesized in our laboratory. Grafting-copolymerization of linear low density polyethylene (LLDPE) with GLID was carried out by using β-ray irradiation in air in a twin-screw extruder. FT-IR was used to characterize the formation of grafting copolymer and evaluate their degree of grafting. The effects of monomer concentration, reaction temperature and screw run speed on degree of grafting were studied systematically. Crystallization rates of grafted LLDPE were faster than that of plain LLDPE at a given crystallization temperature. The tensile properties and light transmission of blown films were determined. Comparing with neat LLDPE film, no obvious changes could be found for the tensile strength, elongation at break and right angle tearing strength of LLDPE-g-GLID film. Acceleration dripping property of film samples was investigated. The dripping duration of LLDPE-g-GLID film and commercial antifog dripping film at 60° C were 69 days and 17 days, respectively.

Preparation of porous honeycomb monolith from UV‐curable monomer/dioxane solution via unidirectional freezing and UV irradiation

AbstractA well‐ordered micrometer‐scale honeycomb monolith porous polymeric material with aligned channels was successfully prepared from UV‐curable urethane diacrylate monomer and 1,4‐dioxane solutions by conducting unidirectional freezing, photopolymerization, and sublimation of the frozen solvent. UV light was irradiated into the frozen solution, and the monomer was photopolymerized and solidified in a template of 1,4‐dioxane crystals. The effects of monomer concentration, freezing rate, and viscosity of the solution on the porous structure were investigated. High monomer concentration increases the solution viscosity, decreases the diffusivity of solute, and consequently, increases the degree of the supercooling. Thus, the pore size was decreased, and the channel wall feature was changed from smooth to dendrite as the solution viscosity increased. Pre‐UV irradiation was also conducted before the unidirectional freezing process so as to control the solution viscosity and change the porous structure. Experiments elucidated that the solution viscosity is one of the key factors of determining the cell structure in the unidirectional freezing technique. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Synthesis of Super-High Molecular Weight Polyacrylamides and their Flocculation Properties

The super-high molecular weight polyacrylamide flocculants were synthesized using potassium persulfate/sodium hydrogen sulfite as initiators via free radical solution polymerization. The effects of monomer concentration and initiator dosage on the molecular weight, insoluble fraction and dissolution rate of PAM were investigated. The flocculation properties of PAMs prepared was examined by flocculating kaolin suspensions. The results show that the PAM products synthesized at the monomer concentration 30% and the initiator dosage 0.5‰ can meet the requirements. The molecular weight of this kind of PAM can reach 5.84×106, insoluble fraction can decrease to 0, and the dissolution can be completed in 10 minutes. Using this kind of PAM as flocculants (1.45mg PAM/100g kaolin suspension), the clear water transmittance can be up to 99% at pH 3.5~4.0.