Total Monomer Concentration Research Articles

Design of pH-responsive nanoparticles of terpolymer of poly(methacrylic acid), polysorbate 80 and starch for delivery of doxorubicin

This work focused on the design of new pH-responsive nanoparticles for controlled delivery of anticancer drug doxorubicin (Dox). Nanoparticles of poly(methacrylic acid)-polysorbate 80-grafted starch (PMAA-PS 80-g-St) were synthesized by using a one-pot method that enabled simultaneous grafting of PMAA and PS 80 onto starch and nanoparticle formation in an aqueous medium. The particles were characterized by FTIR, 1H NMR, TEM, DLS, and potentiometric titration. Dox loading and in vitro release from the nanoparticles were investigated. The FTIR and 1H NMR confirmed the chemical composition of the graft terpolymer. The nanoparticles were relatively spherical with narrow size distribution and porous morphology. They exhibited pH-dependent swelling in a physiological pH range. The particle size and magnitude of phase transition were dependent on polymer composition and formulation parameters such as concentrations of surfactant and cross-linking agent and total monomer concentration. The nanoparticles with optimized compositions showed high loading capacity for Dox and sustained Dox release. The results suggest that the new pH-responsive terpolymer nanoparticles are useful in controlled drug delivery.

Aqueous‐Phase Copolymerization of N‐Vinylpyrrolidone and N‐Vinylformamide

AbstractAqueous‐phase batch free‐radical copolymerization of NVP and NVF is studied at 60 and 85 °C with varying initial monomer mixture compositions and monomer to water ratios. The rate of monomer conversion is found to increase with increasing NVP molar fraction and with decreasing total monomer concentration, in accordance with the expected behavior based on homopolymerization kinetics. The copolymer composition is equal to the initial comonomer composition, indicating monomer reactivity ratios to be unity. A terminal copolymerization model provides a good description of polymerization rate, copolymer composition, and polymer molar mass distributions using the same kinetic rate coefficients as used to previously describe the homopolymerization of the two monomers.

Stimuli-responsive membranes through peroxidation radiation-induced grafting of 2-hydroxyethyl methacrylate (2-HEMA) onto isotactic polypropylene film (IPP)

Stimuli-responsive membranes were prepared by peroxidation radiation-induced grafting of 2-hydroxyethyl methacrylate (2-HEMA) onto IPP. The radioactive isotope 60Co was used as the source of gamma radiation. A plausible mechanism of grafting has been proposed. Using this method, the degree of grafting and morphology could be controlled through the variation of reaction parameters such as total dose, inhibitor concentration, monomer concentration, reaction time, reaction temperature and solvents. Maximum percentage of grafting (210 %) was obtained at total radiation dose of 20 kGy. The graft copolymerization reaction was carried out for 3 h with 20 v/v% of the monomer (2-HEMA) in methanol at 85 °C using 0.06 wt% of FeCl3 as inhibitor. The chemical structures of grafted membranes were characterized by Fourier transform infrared spectroscopy (FTIR) which indicates that HEMA has been grafted onto IPP. The atomic force microscopy (AFM), scanning electron microscopy (SEM) techniques were used to assess the morphological characterization of the membranes, revealing the roughness of the surface. These membranes were investigated for their swelling behavior. pH-sensitivity and the dyeability of the grafted and ungrafted membranes have also been studied.

Synthesis and Deswelling Behavior of Intelligent Thermosensitive Poly(N, N-Diethylacrylamide-Co-Itaconic Acid) Hydrogels

Poly(N,N-diethylacrylamide) (PDEA) hydrogels possess a lower critical solution temperature (LCST) at around 31oC. When the external temperature is raised above the LCST, the hydrogels experience abrupt and drastic shrinkage. This unique property makes them very useful for biomedical applications such as on-off switches for modulated drug delivery and tissue engineering. In this study, itaconic acid (IA) was co-polymerized with N, N-diethylacrylamide (DEA) monomer to improve the LCST to the physiologic temperature about 37oC. These copolymer hydrogels were prepared by changing the initial DEA/IA molar ratio and total monomer concentration. The interior morphologies of hydrogels were characterized by scanning electron microscopy (SEM). In comparison with the PDEA hydrogel, the equilibrium swelling ratio (ESR) and LCST of the hydrogels increase with the increase of IA content in the feed. The deswelling dynamics behaviors of the different composition ratios of the P(DEA-co-IA) hydrogels on the different temperatures was investigated in detail.

Preparation and Swelling Dynamics Characterization of Poly(N, N-Diethylacrylamide-Co-Itaconic Acid) Intelligent Hydrogels

Poly(N,N-diethylacrylamide) (PDEA) hydrogel is known for their intelligent reversible swelling/deswelling behavior in response to temperature changes across a lower critical solution temperature (LCST) at around 31oC. In this study, itaconic acid (IA) was co-polymerized with N, N-diethylacrylamide (DEA) monomer to improve the swelling behavior and the total absorbing water. These copolymer hydrogels were prepared by changing the initial DEA/IA molar ratio and total monomer concentration. The chemical structure of hydrogels was characterized by fourier transform infrared (FTIR) spectroscopy. In comparison with the PDEA hydrogel, the equilibrium swelling ratio (ESR) of the hydrogels increase with the increase of IA content in the feed and the swelling dynamics behaviors of the different composition ratios of the P(DEA-co-IA) hydrogels on the different temperatures was investigated in detail.

Synthesis and characterization of graft copolymers of Sago starch and acrylic acid

AbstractSago starch has been graft copolymerized with acrylic acid (AAc) by mutual gamma radiation method. Reaction conditions such as total dose, monomer concentration and amount of methanol were optimized to obtain maximum grafting percentage. Maximum percentage of grafting, Pg (158.00%) was obtained at an optimum total dose of 62.64 kGy using 4.37 moles/L of AAc in 1 mL of methanol. Using optimum conditions, the effect of cross‐linker, glyoxal, on percent grafting was also studied and maximum grafting was obtained at [Glyoxal] = 54.70 moles/L. Characterization of the graft copolymer was carried out by FTIR, TGA, SEM, XRD analytical methods. The grafted Sago starch was found to have increased crystalline and improved thermal behavior. Swelling and solubility kinetics were measured for each of the samples and correlation between the effects of the reaction parameter on swelling‐solubility kinetics was evaluated. Maximum swelling (4192.3%) at 37°C in 8 h was observed for the sample with 59.9% graft level. Higher swelling percentage is indicative of the graft copolymer to have the properties of a hydro gels that can be utilized for use as drug delivery vehicle and purification of industrial effluents.

Poly(acrylic acid/acrylamide/sodium humate) superabsorbent hydrogels for metal ion/dye adsorption: Effect of sodium humate concentration

AbstractA series of novel superabsorbent hydrogels based on acrylic acid (AAc), acrylamide (AM), and sodium humate (SH) were prepared by free‐radical solution copolymerization for removal of dye and metal ion from waste water. Ammonium per sulfate was used as initiator and N,N′ methylene bisacrylamide as crosslinker. The hydrogels were characterized with the help of FTIR and SEM. In this study the concentration of SH was varied in the range of 0.50–4.76 wt % based on total monomer content and the resulting hydrogels were investigated for the effect of SH on swelling and diffusion kinetic parameters such as equilibrium swelling ratio, initial swelling rate, swelling rate constant, maximum swelling at equilibrium, and type of diffusion, etc. Hydrogel having 2.43 wt % SH content showed the maximum water absorbency of 724 g of water per gram of hydrogel. Swelling exponent found in the range 0.68–0.79 thus suggesting Non‐Fickian diffusion mechanism. The swelling behavior was also studied in different concentrations of salt solutions [sodium chloride (NaCl), magnesium chloride (MgCl2), and ferric chloride (FeCl3)]. The synthesized superabsorbent hydrogels were used for the adsorption of Cu2+ ions and methylene blue (MB) dye from their aqueous solutions. The influence of SH concentration on the Cu2+ ions and MB molecules binding capacity of hydrogels was tested. The chelation behavior was modeled using Langmuir isotherm. The maximum binding capacity for Cu2+ ion was 299 mg/L at 1000 mg/L, initial Cu2+ ion concentration and 269 mg/L at 320 mg/L, initial MB dye molecules concentration per gm of AAc/AM/SH containing 2.43 wt % SH content. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Uniform molecularly imprinted poly(methacrylic acid) nanospheres prepared by precipitation polymerization: the control of particle features suitable for sustained release of gatifloxacin

Herein we have combined the molecular imprinting technique and thermally-initiated precipitation polymerization to develop novel molecularly imprinted poly(methacrylic acid) nanospheres (PMAA MIPNs) for sustained release of gatifloxacin (GFLX). In the process, ethylene glycol dimethacrylate (EGDMA) and GFLX were used as the cross-linker and template, respectively. The effects of reaction medium and concentration of the monomers such as MAA, EGDMA and GFLX were systematically investigated. Uniform nanospheres with diameter equal to 136.0 ± 8.1 nm and particle dispersion index (PDI) equal to 1.01 were obtained when the total monomer concentration was 1 vol%, the EGDMA content was 70 mol% and the GFLX/MAA ratio was 1 : 15 (mol/mol). The drug loading profiles and in vitro release studies indicated that PMAA MIPNs are better drug delivery vessels and have an improved release profile than non-imprinted ones, which was attributed to the reinforced interaction between GFLX and PMMA side groups due to the specific GFLX molecular arrangement in the PMAA polymeric matrix. Based on these results, these novel PMAA MIPNs are a promising candidate for sustained release of GFLX.

Synthesis and characterization of EFFE-g-(VBTAC-co-HEMA) anion exchange membranes prepared by a 60Co radiation-induced graft copolymerization for redox-flow battery applications

Vinyl benzyl trimethyl ammonium chloride (VBTAC) was grafted onto poly(ethylene-co-tetrafluoroethylene) (ETFE) film by γ-ray using simultaneous irradiation graft copolymerization in the presence of 2-hydroxyl ethyl methacrylate (HEMA). The structure of the ETFE-g-(VBTAC-co-HEMA) anion membrane was confirmed by Fourier transform infrared spectroscopy and thermogravimetric analysis. The degree of grafting (DG) of the membrane increased with total irradiation dose and VBTAC monomer concentration. The highest DG of an ETFE-g-(VBTAC-co-HEMA) membrane was 92%, which was synthesized by the treating of an ETFE film with a 0.8 M solution of VBTAC monomer in the presence of 50 kGy irradiation. Different properties of the anion membrane, such as water uptake and ion exchange capacity, increased as DG increased. The permeability and vanadium redox-flow battery performance were measured for a membrane with a DG of 92%. The average voltage efficiency, coulombic efficiency, and energy efficiency were 0.79, 0.88, and 0.70, respectively, all of which remained stable as the number of cycles increased. Open image in new window

Synthesis of monodisperse crosslinked poly(styrene‐co‐divinylbenzene) microspheres by precipitation polymerization in acetic acid

AbstractPoly(styrene‐co‐divinylbenzene) microspheres with size ranging from 1.6 to 1.8 μm were prepared in acetic acid by precipitation polymerization. The particle size and particle size distribution were determined by laser diffraction particle size analyzer, and the morphology of the particles was observed with scanning electron microscope. Besides, effects of various polymerization parameters such as initiator and total monomer concentration, divinylbenzene (DVB) content, polymerization time and polymerization temperature on the morphology and particle size were investigated in this article. In addition, the yield of microspheres increased with the increasing total monomer concentration, initiator loading, DVB concentration and polymerization time. In addition, the optimum polymerization conditions for synthesis of monodisperse crosslinked poly(styrene‐co‐divinylbenzene) microspheres by precipitation polymerization in acetic acid were obtained. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Network parameters of poly(N‐isopropylacrylamide)/montmorillonite hydrogels: effects of accelerator and clay content

AbstractThe results of network parameters of poly(N‐isopropylacrylamide)/montmorillonite (PNIPAAm/MMT) hydrogels prepared with two different types and concentrations of accelerators (tetramethylethylenediamine, TEMED and quaternary TEMED containing decyl bromide, QTEMED) using three different clay contents (1.0, 3.0, and 5.0 wt% of total monomer concentration) at two different polymerization temperatures (10 and 32°C) were presented and discussed. It was observed that when the reaction temperature of PNIPAAm crosslinked with MMT was chosen as 10°C both volume swelling ratios (i.e., thermodynamic interaction) and shear moduli, G increased. In hydrogels, thermodynamic interaction is reflected by polymer–water interaction parameter (χ). The lower is the value of χ, the stronger is the interaction between polymer and water, and the lower is the interaction between hydrophobic groups or between polymer chains. In addition, increase in MMT content was slightly affected on these intermolecular interactions. Therefore, this effect that combines high‐shear modulus with lower value of χ in the same molecular structure was defined as clay content‐independent diffusion behavior. On the other hand, in the case of the hydrogels synthesized with the higher concentration of TEMED and MMT, the values of χ and G decreased. These facts were interpreted that increase in both accelerator concentration and clay content, for fixed NIPAAm concentration made the number of effective crosslinks between MMT layers smaller. Copyright © 2010 John Wiley & Sons, Ltd.

Dynamic Characterization and Drug Release of Thermosensitive Poly(N, N-Diethylacrylamide-Co-Itaconic Acid) Copolymer Hydrogels

In this study, poly(N,N-diethylacrylamide-co-itaconic acid) (P(DEA-co-IA)) copolymer hydrogels were synthesized by changing the initial DEA/IA molar ratio, N,N-methylenebisacrylamide and total monomer concentration. The thermo-sensitive and mechanical performances were optimized by altering the above parameters. In comparison with the PDEA hydrogel, the equilibrium swelling ratio (ESR) and lower critical solution temperature (LCST) of the hydrogels changed with the alternation of the above parameters. The swelling and deswelling kinetics was also studied in dital. The release behaviors of the model drug, aminophylline, are found dependent on hydrogel composition and environmental temperature, which suggests that these materials have potential application as intelligent drug carriers.

Orthogonal Test Design for Optimization of Dispersive Type Cement Slurry Fluid Loss Control Additive Used in Petroleum Drilling

The fluid loss control additive plays a key role in reducing reservoir damage and improving the cementing quality of an oil well. Aiming at good fluid loss control ability and excellent dispersibility, a new dispersive type fluid loss control additive was synthesized through orthogonal experiment with 2-acrylamido-2- methyl propane sulfonic acid, acrylamide, N, N-dimethylacrylamide and maleic anhydride. The orthogonal experiment result shows that the influence on the properties of FLCA decreases in the order: PH value > monomer concentration > monomer mole ratio > initiator concentration > temperature. The result indicates that the optimal conditions for FLCA were 4/2.5/2.5/1 of mole ratio of AMPS/AM /NNDMA/MA, 32.5% total monomer concentration in deionized water, 1.0% (by weight of monomer) ammonium persulfate/sodium bisulfite, 4 of PH value, 40°Cof temperature. The synthesized copolymer was identified by FTIR analysis. The results show the dispersive type fluid loss control additive has excellent dispersibility, fluid loss control ability, thermal resistant and salt tolerant ability. As the temperature increases, the thickening time of the slurry containing the synthesized additive reduces. The copolymer is expected to be a good fluid loss control additive.

방사선을 이용한 스티렌-TMSPM 공중합체가 그래프트된 ETFE 필름의 제조

본 연구는 스티렌과 (trimethoxysilyl)propyl methacrylate(TMSPM)을 함유하여 그래프트된 ETFE 필름을 방사선 동시 조사방법으로 제조하는 것에 관한 연구이다. 스티렌/TMSPM을 혼합한 물질을 여러 종류의 용매를 사용하여 일정한 비율로 희석 후 조사선량, 조사선량률 및 희석된 용액의 농도 등의 조건을 달리하여 그래프트율에 미치는 영향을 관찰하였다. 그 결과 스티렌/TMSPM 단량체 혼합물에 아세톤 용매를 사용한 경우에 다른 용매를 사용한 것보다 높은 그래프트율을 보여주고 있음을 알 수 있었다. IR 스펙트럼 분석을 통하여 스티렌과 TMSPM이 동시에 ETFE 필름에 그래프트됨을 확인할 수 있었으며 SEM-EDX를 통하여 PTMSPM이 함유하고 있는 실리콘 분포도를 분석한 결과, PTMSPM 그래프트 고분자가 ETFE 필름 내부까지 균일하게 그래프트가 이루어졌음을 관찰할 수 있었다.

Simulation of Asphaltene Aggregation and Related Properties Using an Equilibrium-Based Mathematical Model

Aggregation of asphaltenes was simulated using a mathematical model based on the following consecutive equilibrium: nA⇄K1An and mA+An⇄K2An+m, where A, An, An+m, K1, K2 represent asphaltenes, n aggregates, n + m aggregates, and equilibrium constants, respectively. A mass balance lead to a n + m polynomial in C (C0, n, m, K1, K2, M), where C is the concentration of free solute (monomer), M is the monomer molecular mass, and C0 is the total monomer concentration added to solution. Using numerical methods, this polynomial was solved in terms of C0, K1, and K2 for given values of n, m, and M. Selection of n = 3, m = 5, and M = 800 g L–1 was consistent with data in the literature, and determination of K1 and K2 was achieved by fitting to experimental data from ultrasound velocity, thermal diffusion [thermal lens and dual-beam photothermal reflection (DBPR)], and self-diffusion coefficient techniques. The good fittings found suggest that asphaltene aggregation is adequately described by the present model. A procedure based on the present model was employed to simulate the stepwise adsorption of asphaltenes at the toluene/glass interface. The above sequential equilibrium is discussed in terms of aggregation of the toluene-insoluble asphaltene fraction molecules (A1TM, first equilibrium), followed by incorporation into aggregates of toluene-soluble fraction molecules (A2TM, second equilibrium). This sequential scheme is proposed as a means to keep fraction A1 as nanoaggregates (first step), which, were it not by the presence of A2 (second step), would lead to phase separation. The formation of small aggregates at very low concentrations, predicted by the model, is consistent with the very low solubility of the A1 fraction. When the above mathematical model is combined with the Hansen solubility parameter (HSP) method, it is concluded that asphaltenes form stable colloid solutions in toluene and similar solvents where A1 is insoluble. In other words, for these colloidal solutions, interfacial tension would be zero.

Synthesis, characterization, and aqueous solution behavior of copolymers of acrylamide and sodium 10-acryloyloxydecanoate

A new water-soluble monomer of sodium 10-Acryloyloxydecanoate (NaAD), which possesses a hydrophobic group and an ionizable group, was synthesized from acryloyl chloride and 10-hydroxydecanoic acid, and the series of copolymers of NaAD with acrylamide (AM) were prepared by the free radical polymerization in aqueous solution using ammonium persulfate as the initiator. The feed ratio of NaAD:AM was varied from 5:95 to 70:30 mol%, with the total monomer concentration held constant at 0.5 M. The copolymer compositions were determined from elemental analysis. The molecular weights of the copolymers were determined by gel permeation chromatography ranged from 0.76 × 106 to 1.37 × 106 g/mol. All copolymers were soluble in deionized water and salt solutions at pH > 5. The dilute and semidilute solution behavior of the copolymers was studied as a function of composition, pH, and added electrolytes, and the results indicated that NaAD30 exhibited much higher viscosity values. At moderate pH values, the copolymers coils become slightly more expanded and intermolecular association interactions occur, which was indicated by fluorescence and apparent viscosity measurements. Upon the addition of NaCl and in low pH, viscosities tended to decrease because of the disruption of the intermolecular associations.

Preparation and characterization of lauryl methacrylate-based monolithic microbore column for reversed-phase liquid chromatography

Poly(lauryl methacrylate-co-ethylene dimethacrylate) monoliths were in situ synthesized within the confines of a silicosteel tubing of 1.02 mm i.d. and 1/16″ o.d. for microbore reversed-phase HPLC. In order to obtain practically useful monoliths with adequate column efficiency, low flow resistance, and good mechanical strength, some parameters such as total monomer concentration (% T), cross-linking degree (% C) and polymerization temperature were optimized. High-efficiency monoliths were successfully obtained by thermal polymerization of a monomer mixture (40% T, 10% C) with a binary porogenic solvent consisting of 1-propanol and 1,4-butandiol (7:4, v/v) at a high temperature of 90 °C. The morphology and porous structure of the resulting monoliths were assessed by scanning electron microscope (SEM) and inverse size exclusion chromatography (ISEC), while the column performance was evaluated through the separations of a series of alkylbenzenes in acetonitrile–water (50:50, v/v) eluent. At a normal flow rate of 50 μL/min (corresponding to 1.66 mm/s), the optimized monolithic columns typically exhibited theoretical plate numbers of 6000 plates/10 cm-long column for amylbenzene ( k > 40), and the pressure drop was always less than 1 MPa/10 cm. The monoliths, which were chemically anchored to the tube inner wall surface using a bifunctional silylation agent, exhibited adequate mechanical strength of up to 12–13 MPa, and were properly operated at 10 times higher flow rate than normal, reducing the separation time to one tenth. The lauryl methacrylate-based monolithic column was applied to a rapid and efficient separation of ten common proteins such as aprotinin, ribonuclease A, insulin, cytochrome c, trypsin, transferrin, conalbumin, myoglobin, β-amylase, and ovalbumin in the precipitation-redissolution mode. Using a linear CH 3CN gradient elution at a flow rate of 500 μL/min (10-times higher flow rate), 10 proteins were baseline separated within 2 min.

Equilibrium Swelling Study of Cationic Acrylamide-Based Hydrogels: Effect of Synthesis Parameters, and Phase Transition in Polyelectrolyte Solutions

Cationic copolymer gels of acrylamide and [(methacrylamido) Propyl] trimethyl ammonium chloride (MAPTAC) were synthesized by free radical aqueous solution polymerization. The Taguchi method, a robust experimental design, was employed for the optimization of the synthesis based on the equilibrium swelling capacity of the hydrogels. Based on Taguchi method a standard L16 orthogonal array with five factors at four levels was designed and experiments were done in accordance with it. The effects of network composition such as cross-linker density, ionizable monomer and total monomer concentration together with the initiator concentration on the equilibrium swelling capacity of hydrogels in distilled water were studied. From the analysis of variance (ANOVA) of the test results, the most effective factor controlling equilibrium swelling capacity was obtained and maximum water absorbency of the optimized hydrogel was found to be 3570 g/g. The presence of counterions in the external solution suppressed swelling of optimized hydrogel and this effect was pronounced with bivalent counterions. By using the thermodynamic model, the experimental data were analyzed and the cross-linking efficiency for the polymerization reaction was calculated to be about 40%.

Kinetic Analysis of β-Galactosidase and β-Glucuronidase Tetramerization Coupled with Protein Translation

Both β-galactosidase (GAL) and β-glucuronidase (GUS) are tetrameric enzymes used widely as reporter proteins. However, little is known about the folding and assembly of these enzymes. Although the refolding kinetics of GAL from a denatured enzyme have been reported, it is not known how the kinetics differ when coupled with a protein translation reaction. Elucidating the assembly kinetics of GAL and GUS when coupled with protein translation will illustrate the differences between these two reporter proteins and also the assembly process under conditions more relevant to those in vivo. In this study, we used an in vitro translation/transcription system to synthesize GAL and GUS, measured the time development of the activity and oligomerization state of these enzymes, and determined the rate constants of the monomer to tetramer assembly process. We found that at similar concentrations, GAL assembles into tetramers faster than GUS. The rate constant of monomer to dimer assembly of GAL was 50-fold faster when coupled with protein translation than that of refolding from the denatured state. Furthermore, GAL synthesis was found to lack the rate-limiting step in the assembly process, whereas GUS has two rate-limiting steps: monomer to dimer assembly and dimer to tetramer assembly. The consequence of these differences when used as reporter proteins is discussed.

Radiation-induced graft polymerization of amphiphilic monomers with different polymerization characteristics onto hydrophobic polysilane

The structures of poly(methyl-n-propylsilane) (PMPrS) amphiphilically modified through γ-ray-induced graft polymerization were investigated with 1H NMR measurement. By the use of methyl methacrylate (MMA) or diethyl fumarate (DEF) as monomers for the graft polymerization, grafting yield rose with increasing total absorption dose and monomer concentrations, but decreased with increasing dose rate. This result means that grafting yield of modified PMPrS can be controlled by changing irradiation conditions. However, the number of PMMA or PDEF graft chains per PMPrS chain was estimated to be less than 1.0 by analysis of 1H NMR spectra, and this value was lower than that we had expected. To improve graft density, maleic anhydride (MAH), which is known as a non-homopolymerizable monomer in radical polymerization, was used as a monomer for grafting. As a result, high density grafting (one MAH unit for 4.2 silicon atoms) was attained. It demonstrates that the structure of γ-ray-modified polysilane strongly depends on the polymerization characteristics of grafted monomers.