Increase In Graft Yield Research Articles

Synthesis and characterization of temperature-sensitive microspheres based on acrylamide grafted hydroxypropyl cellulose and chitosan for the controlled release of amoxicillin trihydrate

This study deals with the preparation of temperature-sensitive chitosan/hydroxypropyl cellulose-graft-polyacrylamide (CS/HPC-g-PAAm) blend microspheres as a controlled drug release system. For this purpose, HPC-g-PAAm copolymers of hydroxypropyl cellulose (HPC) with acrylamide (AAm) were synthesized using cerium (IV) ammonium nitrate as initiator. The HPC-g-PAAm copolymers were characterized by using Fourier transform infrared spectroscopy (FTIR), elemental analysis, and differential scanning calorimetry (DSC). Lower critical solution temperatures (LCST) of the synthesized copolymers were determined. Temperature-sensitive blend microspheres of HPC-g-PAAm and chitosan were prepared by emulsion cross-linking method using glutaraldehyde (GA) as a cross-linker in the hydrochloric acid catalyst (HCl) and they were used to achieve controlled release of amoxicillin trihydrate (AMX), an antibiotic drug. The microspheres were characterized by DSC, X-ray diffraction (X-RD), and FTIR spectroscopy. In addition, surfaces of empty and drug-loaded microspheres were examined by scanning electron microscopy (SEM). The effects of variables such as CS/HPC-g-PAAm ratio, drug/polymer ratio, amount of cross-linker, and reaction time of grafting on AMX release were investigated at three different pH environments (1.2, 6.8, 7.4) at 25 °C, 37 °C, and 50 °C. The release results showed that the microspheres had temperature sensitivity and the AMX release was slightly more controlled by especially increasing graft yield (%).

Radiation induced graft polymerization of glycidyl methacrylate onto sepiolite

Radiation induced graft polymerization (RIGP) was used to develop glycidyl methacrylate (GMA) grafted nanohybrid polymer. The absorbed dose and monomer concentration significantly affect the degree of grafting on vinyl modified sepiolite (VMS). Maximum grafting of 665% was achieved at optimized absorbed dose and monomer concentration. Post-polymerization modification of the nanohybrid with maximum grafting was carried out with sodium sulfite. Structural studies by ATR-FTIR and XRD analysis of the synthesized nanohybrids confirmed modification at different stages. The morphological changes studied by field emission scanning electron microscopy (FESEM) showed the conversion of sepiolite fiber into globular structure. Thermal gravimetric analysis (TGA) revealed an increase in thermal stability of the GMA grafted nanohybrid with the increase in grafting yield. The sulfonated form of the nanohybrid showed highest adsorption for Cu(II) at 4 pH value which indicates its potential as metal ion adsorbent for the recovery of metals from wastewater.

Synthesis and EMI shielding studies of polyaniline grafted conducting nanohybrid

AbstractPolyaniline (PANI) grafted conducting nanohybrids are successfully synthesized by emulsion graft polymerization. Maximum grafting of 644% is obtained on sepiolite at optimized concentrations and reaction conditions. The Fourier transform infrared (FT‐IR) spectra of sepiolite grafted polyaniline (MS‐g‐PANI) nanohybrid revealed the presence of stretching vibrations of C=C bonds of polyaniline at 1580 and 1490 cm−1 along with the characteristic peaks of sepiolite. Increased thermal stability of the nanohybrid is observed with the increase in polyaniline grafting. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are used to study the structural changes caused by grafting. A progressive increase in electrical conductivity is observed with the increase in grafting yield. Maximum electrical conductivity of 0.427 Scm−1 is observed in the nanohybrid having 644% grafting. 24.2 dB (>99% attenuation) EMI shielding effectiveness has been exhibited by the developed nanohybrids in X‐band frequency range.

Facile synthesis and properties of a cation exchange membrane with bifunctional groups prepared by pre-irradiation graft copolymerization.

A new type of a cation exchange membrane named ETFE-g-poly(AA-co-SSS) with bifunctional groups was synthesized by a one-step method. Its preparation by an electron beam-induced pre-irradiation grafting method and the effects of reaction temperature, monomer concentration, pH value of the grafting solution, storage time and temperature of the irradiated poly(ethylene-alt-tetrafluoroethylene) (ETFE) films on the grafting yield were studied. A total concentration of 2 mol L−1 of monomers was found to be beneficial for acrylic acid (AA) and sodium styrene sulfonate (SSS) co-grafting onto the ETFE films. Infrared spectroscopic analysis of the grafted membrane confirmed the existence of sulfonate and carboxylic acid groups. The contact angle of the grafted membrane decreased from 94.3 to 46.7° with the increase in grafting yield. The higher the grafting yield, the faster the response and recovery rate with respect to humidity. AFM images showed that the diameter of the grafted chains on the surface of ETFE membranes was about 30 nm. The voltage of the grafted membrane was stable after 100 cycles of charge–discharge; thus, the prepared membranes have great potentials to be used as separators in secondary batteries.

Synthesis of novel biodegradable antibacterial grafted xanthan gum

Xanthan gum (XG) is natural polysaccharides used in food industries as stabilizers and thickener agents. The problem is that some food products are found to be contaminated by pathogenic bacteria such as Escherichia coli (E. coli) and Staphyloccus aureus (S. aureus) that reduce their shelf life. This research aims to synthesize biodegradable antibacterial XG-grafted-poly(N-vinyl imidazole) PVI and the effect of reaction parameters were studied on grafting yield (G), grafting efficiency (GE), total conversion (TC) and homopolymer (H) %. XG-g-PVI was characterized via various analysis tools. Thermal analysis showed that grafted XG was more thermally stable than unmodified XG and their stability increased with increasing PVI%. XG-g-PVI was acting as antibacterial agent against (E. coli and S. aureus) bacteria that cause food borne diseases. Their activity increases with increasing grafting yield%. Surface morphology showed change from irregular lobules shape in XG to smooth surface in its graft with PVI.

Ethylene vinyl acetate based radiation grafted hydrophilic matrices: Process parameter standardization, grafting kinetics and characterization

A transparent, elastomeric, grafted matrix for several potential applications was synthesized by single-step simultaneous radiation grafting of methacrylic acid onto ethylene vinyl acetate (EVA). CuSO4 was found to be the most suitable homo-polymerization inhibitor among different inhibitors tried. The grafting kinetics was found to be a strong function of dose rate (D) and monomer content (M) and an equation relating grafting rate Rg=Kg [M]1.13D0.23 was deduced. Crystallinity of the grafted matrices as assessed from XRD and DSC measurements indicated decrease in crystalline content with increase in grafting yield, suggesting crystalline domain of EVA get disrupted on grafting. Elastic modulus increased linearly with the increase in grafting yield, though elongation at break decreased precipitously from 900% to 30% at even ~9% grafting. Thermo-gravimetric analysis showed three step weight loss of the grafted EVA matrix. The grafting of MAA resulted in increase in surface energy mainly due to enhanced polar component.

Synthesis of Graft Copolymers for Green Composite Films and Optimization of Reaction Parameters using Taguchi (L16) Orthogonal Array

Oleic acid was graft copolymerized onto barley husk (BH) using a redox initiator. Samples of natural and grafted BH were characterized by fourier transform infrared spectroscopy, scanning electron microscopy (SEM), x-ray diffraction, thermal analysis, swelling (%) and moisture absorption (%). SEM analysis revealed that the surface of the BH became rough after grafting. Reaction time, temperature, amount of solvent, monomer concentration and initiator molar ratio were optimized using conventional as well as Taguchi L16 (orthogonal array) design to get maximum percentage graft yield. At optimized conditions, the maximum graft yield was 55.3% by conventional method, whereas it was 56.82% by Taguchi method. Analysis of variance revealed that the reaction temperature and reaction time were the most and the least influential factors, respectively. Swelling (%) and moisture absorption (%) decreased with the increase in percentage graft yield. Grafted BH showed more chemical and thermal resistance as compared to natural BH. Synthesized graft copolymers were used as reinforcing material in poly vinyl alcohol composite films and rendered higher mechanical properties.

Preparation of hemocompatible cellulosic paper based on P(DMAPS)-functionalized surface

The surface-modification of paper substrates with functional layers is gaining increasing interest, both from academic and industrial research. In this case, the cellulosic paper (CP) surface was functionalized with zwitterionic poly-(3-dimethyl(methacryloyloxyethyl) ammoniumpropane sulfonate) (CP-g-P(DMAPS) via surface-initiated atom transfer radical polymerization (ATRP) technique for enhancing blood compatibility. An obvious increase in graft yield of the functional P(DMAPS) with polymerization time was observed. The new CP-g-P(DMAPS) produced was investigated for its hemocompatibility. The hemocompatibility studied including platelet and whole blood ceels adhesion tests, hemolysis assay, morphological changes of red blood cells (RBCs), coagulation time tests, and complement activation, platelet activation at the molecular level. Most assays had remarkable differences in the presence of the new zwitterionic CP, indicated the importance of the zwitterion for hemocompatibility of CP.

Amination of glycidyl methacrylate-grafted polystyrene particles and their adsorption capacity for Nd3+ and Cd2+

A new chelating adsorbent was prepared by grafting glycidyl methacrylate (GMA) onto polystyrene (PS) particles using simultaneous radiation technique and amination of graft copolymers by reacting with diethylenetriamine. The effects of various parameters such as, irradiation doses, inhibitor concentrations, amination temperature, and reaction time were investigated. The grafting yield increased with irradiation dose to reach its maximum value at 15 kGy. The accelerative effect of solvent medium on the grafting yield was higher in THF than DMF. The addition of 0.001 % (wt) inhibitor to the reaction medium led to a sharp increase of grafting yield. The best conversion ratio was obtained at 115 °C during 24 h. By using a column separation technique, the adsorption behaviors of the adsorbent toward Cd2+ and Nd3+ in aqueous solution were examined. The adsorption amount of both Cd2+ and Nd3+ increased with initial ions concentration. The maximum equilibrium of Cd2+ and Nd3+ adsorbed ions were 18.1 and 17.58 mg/g, respectively. It was observed that the functionalized GMA-g-PS was reusable by desorbing with 0.1 M nitric acid almost without losing their adsorption capacity. FTIR test indicates that epoxide and amine groups were introduced onto GMA-g-PS and aminated GMA-g-PS, respectively. The Tg of graft copolymer slightly decreased, and that of aminated GMA-g-PS was higher than graft copolymer.

Polymer‐based metal adsorbents via graft copolymerization of polyvinyl alcohol with diaminomaleonitrile: A green chemistry approach

AbstractSynthesis, characterization, and amidoximation of diaminomaleonitrile‐functionalized polyvinyl alcohol (PVA) grafts were studied. Ceric ammonium nitrate (CAN) was used as an initiator in an aqueous nitric acid medium under N2 atmosphere. Optimum conditions for grafting were as follows: monomer concentration [DAMN] = 1.4M, [CAN] = 16 × 10−2 mol/L, T = 50°C, and t = 2 h. Water uptake of the PVA graft films increased with the increase of grafting yield. The imparted cyano group of the grafted PVA polymer chains (with degree of grafting up to 136%) was converted into amidoxime group by the reaction with hydroxylamine hydrochloride. The grafted polymers were characterized by FTIR spectroscopy, differential scanning calorimetry, and thermal gravimetric analysis. The grafted PVA films are more thermally stable than the ungrafted PVA membrane, because the grafted membrane showed a single degradation pattern despite having two components. A decrease in Tg values is observed as the grafting yield of copolymers increases indicating the incorporation of polydiaminomaleonitrile chains in amorphous copolymers with higher thermal stability. The prepared amidoximated DAMN136‐g‐PVA was investigated for its properties in removing heavy toxic metals, such as Pb2+, Cd2+, Zn2+, Fe3+, Cu2+, Ni2+, and Co2+ from water. The amidoximated film is characterized by a considerably greater binding ability with respect to heavy metals. The nature of the metal ion also has great importance in the amount binding to the polymeric material. The kinetics of the sorption/desorption process for Co2+, Ni2+, and Zn2+ were investigated. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Synthesis, characterization, and amidoximation of diaminomaleodinitrile-functionalized polyethylene terephthalate grafts for collecting heavy metals from wastewater

Synthesis, characterization, and amidoximation of diaminomaleodinitrile-functionalized polyethylene terephthalate (PET) grafts were studied. Azobisisobutyronitrile (AIBN) was used as an initiator. Optimum conditions for grafting were as follows: monomer concentration [DAMN] = 0.5M, [AIBN] = 1.50 × 10−3 mol/L, T = 80°C and t = 3 h. Water uptake of the grafted-PET film increased with the increase of grafting yield. The imparted cyano group of the grafted polymer chains (with degree of grafting up to 83%) was converted into amidoxime group by reaction with hydroxylamine. The unique advantage of this polymer is that it contains double amidoxime groups per repeating unit and an additional diethylene spacer unit between neighboring amidoxime groups in each monomeric unit. The grafted-PET films were characterized by FTIR spectroscopy, differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA). The grafted-PET films are more thermally stable than the ungrafted-PET membrane, since the grafted membrane showed a single degradation pattern despite having two components. A decrease in Tg values is observed as the grafting yield of copolymers increases indicating the incorporation of polydiaminomaleodinitrile chains in amorphous copolymers with higher thermal stability. The prepared amidoximated DAMN83-g-PET was investigated for its properties in removing heavy toxic metals, such as Pb2+, Cd2+, Zn2+, Fe2+, Cu2+, Ni2+, Co2+, and Ag1+ from waste water. The amidoximated-film is characterized by a considerably greater binding ability with respect to heavy metals. The nature of the metal ion also has great importance in the amount binding to the polymeric material. The kinetics of the sorption/desorption process for Co2+, Ni2+, and Zn2+ are investigated. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Novel Materials Procured from Surface Modification of Biomass

Hibiscus sabdariffa (Roselle) stem fiber has 73.9% cellulose and is present in abundance though-out the world. It has a low therapeutic potential but lesser weight and high tensile strength promotes it to serve as an effective backbone for graft copolymerization. This renewable biomass was graft copolymerized with efficient acrylate as principal monomer while incorporating the secondary monomers in addition, to enhance the graft yield. The increase in graft yield affected the properties and behavior of the fiber. The morphological transformations in the graft co-polymers were characterized by FTIR, SEM, TG–DTA and XRD. The modified fiber were found to be physico-chemico-thermally resistant, hydrophobic whereas, percentage crystallinity, crystallinity index decreased with increase in percentage grafting. The use of raw fiber and graft copolymers as reinforcement in phenol–formaldehyde polymer matrix based bio-composites improved the physico-chemico-thermal properties and the mechanical strengths like the flexural strength/modulus of rupture, young’s modulus/modulus of elasticity, stress at the limit of proportionality and hardness. These advanced materials could be useful in various scientific and industrial applications and serve as pioneer for the development of technology.

Improvement of Hemocompatibility of Polycaprolactone Film Surfaces with Zwitterionic Polymer Brushes

Polycaprolactone (PCL) has been widely adopted as a scaffold biomaterial, but further improvement of the hemocompatibility of a PCL film surface is still needed for wide biomedical applications. In this work, the PCL film surface was functionalized with zwitterionic poly(3-dimethyl(methacryloyloxyethyl) ammonium propane sulfonate) (P(DMAPS)) brushes via surface-initiated atom transfer radical polymerization (ATRP) for enhancing hemocompatibility. Kinetics study revealed an approximately linear increase in graft yield of the functional P(DMAPS) brushes with polymerization time. The blood compatibilities of the modified PCL film surfaces were studied by platelet adhesion tests of platelet-rich plasma and human whole blood, hemolysis assay, and plasma recalcification time (PRT) assay. The improvement of hemocompatibility is dependent on the coverage of the grafted P(DMAPS) brushes on the PCL film. Lower or no platelet and blood cell adhesion was observed on the P(DMAPS)-grafted film surfaces. The P(DMAPS) grafting can further decrease hemolysis and enhance the PRT of the PCL surface. With the versatility of surface-initiated ATRP and the excellent hemocompatibility of zwitterionic polymer brushes, PCL films with desirable blood properties can be readily tailored to cater to various biomedical applications.

PH responsive itaconic acid grafted alginate microspheres for the controlled release of nifedipine

A series of pH responsive alginate-g-poly(itaconic acid) (NaAlg-g-PIA) microspheres were prepared as drug delivery matrices of nifedipine cross-linked by glutaraldehyde (GA) in the hydrochloric acid catalyst. Graft copolymers of sodium alginate with itaconic acid were synthesized using ceric ammonium nitrate. The chemical stability of the nifedipine after encapsulation into microspheres was confirmed by FTIR, DSC and X-RD analysis. The preparation conditions of the NaAlg-g-PIA microspheres such as graft yield, GA concentration, exposure time to GA and drug amount were optimized by considering the percentage entrapment efficiency, particle size, swelling capacity and their release data. The results showed that NaAlg-g-PIA microspheres are pH responsive. The release of nifedipine from grafted microspheres was slower for the pH 1.2 solution than that of the pH 7.4 buffer solution. It has been observed that an increase in exposure time, drug amount, GA and NaAlg-g-PIA concentrations causes a decrease in the nifedipine release from the microspheres, whereas an increase in graft yield leads to an increase in the nifedipine release.

Preparation of chelating fabrics by radiation‐induced grafting of itaconic acid and acrylonitrile onto polypropylene nonwoven fabrics and subsequent amination of graft copolymer

AbstractA mixture of acrylonitrile (AN) and itaconic acid (IA) was cografted onto polypropylene (PP) nonwoven fabrics by preirradiation method. The effects of graft polymerization conditions such as temperature, reaction time, Mohr's salt concentration, solvent mixture ratio, and comonomer composition on the total grafting yield were investigated. The addition of AN as a comonomer increased the amount of IA that reacted with PP fabrics. An increase in the temperature from 40 to 60°C increased the grafting rate, but the final grafting yield decreased at high temperature. The addition of 0.01 wt % Mohr's salt to the reaction medium leaded to a sharp increase of grafting yield. The accelerative effect of solvent medium on the grating yield was higher in dimethylformamide (DMF) and methanol mixtures, when compared with DMF or methanol. Chelating fabrics was synthesized by subsequent amination of grafted fabric with ethylene diamine (EDA) and phenylhydrazine (PH). The conversion yield reached maximum value at about 90% for 80% PP‐g‐AN‐IA fabrics at 90°C. At same amination conditions, the conversion yield is higher when PP‐g‐AN‐IA fabrics react with EDA compared with PH. FT‐IR data indicate that amine groups were introduced onto PP‐g‐AN‐IA fabric through amide linkage between grafted AN or IA and EDA or PH. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Solvent effects in the polyethylene terephthalate surface modification by cold argon plasma‐induced grafting polymerization of methacrylic acid

AbstractWe studied the surface modification of polyethylene terephthalate (PET) by grafting with methacrylic acid (MAA) through plasma‐induced polymerization method. The results show that the grafting yield increases with the increase of reaction temperature. The grafting yield is in proportion to the increase of monomer concentration. The grafting yield increases along with the prolonging of reaction time. The solvent has great influence to the grafting reaction. The grafting yield increases with the increase of volume ratio R, which is defined by the volume of water to the volume of alcohol, when using alcohol and water as mixed solvent. The grafting yield is not zero when only using methanol, ethanol or isopropanol as the solvent. The red shift in UV spectrum could be ascribed to different reactive activities of MAA in different solvents, which also can explain the change trend of the grafting yield. The UV‐vis absorbance difference and the FTIR integrated peak area of the CO stretching increase steadily with the increase of grafting yield, which are almost linear relationship. It was confirmed that MAA was grafted onto the PET surface in terms of UV‐vis spectrophotometric, FTIR and atomic force microscopy analysis. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Characterization and Mechanical Properties of Cellulose-graft-Polyacrylonitrile Prepared by Using KMnO4/different Acids as Redox System

Cellulose-graft-polyacrylonitriles were prepared by using KMnO4/different acids redox system and the obtained samples were characterized by POM, SEM, 13C-NMR, XRD, TGA and their mechanical properties were investigated as a function of crystallinity degree (Cr%). In all cases, Cr decreased with increase of graft yield irrespective of acids species. Stress at break, strain at break and Young's modulus decreased with decreasing Cr%, which can be attributed to the increase of the amorphous region and the main chain rapture of cellulose. The mechanical properties of the samples prepared by strong acids became more poor than those for samples prepared by weak acids, indicating that more chain rupture occurred when strong acids are used.

Lipases improve the grafting of poly(ethylene terephthalate) fabrics with acrylic acid

AbstractIn this study, poly(ethylene terephthalate) (PET) fabrics were modified with two types of commercial lipases, namely, Lipex and Lipolase, and grafted with acrylic acid (AA) to improve their absorption properties. The effects of the enzyme concentration, reaction temperature, time, and pH on the grafting of AA onto PET were investigated. The pretreatment of PET with lipases increased the amount of AA that was introduced to the PET fibers, whereas AA grafting onto the untreated PET fabrics led to lower graft yields. Fourier transform infrared spectroscopy and scanning electron microscopy were used to characterize the AA‐grafted pretreated polyester fabrics. A new band appearing at 1546 cm−1 in the Fourier transform infrared spectrum implied that AA was introduced onto the PET fabrics. The surfaces of the fabric fibers presented in scanning electron microscopy micrographs clearly indicated the formation of a layer of grafted poly (acrylic acid). The results show that the density of surface grafting was improved by the lipase pretreatment. The increase in grafting was higher for Lipex than for Lipolase. The highest graft yield was obtained with 1% Lipex and Lipolase for 30 min at pH values of 7 and 5, respectively. There were no significant changes in the tenacity or weight reduction of the fabrics. The moisture content of the samples increased linearly with increasing graft yield. This was higher for the pretreated fabrics grafted with Lipex. A higher color strength was obtained for grafted PET samples that were pretreated with Lipex when they were dyed in alkaline aqueous solutions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Hydrophilic modification of PET fabric via continuous photografting of acrylic acid (AA) and hydroxyethyl methacrylate (HEMA)

Poly(acrylic acid) and poly(hydroxyethyl methacrylate) were introduced onto PET fabrics by UV-induced photografting to improve its hydrophilicity. Several factors affecting the photografting were studied including irradiation energy, monomer, and photoinitiator (PI) concentrations. ATR and ESCA analyses proved successful grafting of the two monomers onto PET. Morphology of fabric surface was examined using FE-SEM. Both zeta potential and water wetting time of the grafted PET fabrics decreased with increasing grafting yield. Also cationic dyeability of the grafted PET fabrics increased because of the increased electrostatic interactions between the anionic dyeing sites and cationic dyes.

Investigation of styrene‐assisted free‐radical grafting of glycidyl methacrylate onto high‐density polyethylene using response surface method

AbstractIn this study, the free‐radical grafting of glycidyl methacrylate (GMA) onto high‐density polyethylene (HDPE) in the presence of styrene, as a comonomer, is investigated using a Brabender internal mixer. To optimize grafting level of GMA onto HDPE, response surface method (RSM) was exploited. Using RSM method of experimental design, it was possible to investigate the individual effects of various variables including dicumyl peroxide (DCP) concentration, GMA content, as well as reaction time, and their interactions on grafting efficiency. The fitted quadratic model obtained from statistical analysis is expressed by an approximating function to investigate the final torque as a responding variable over the experimental range of the independent variables. The grafting yield of GMA onto HDPE for the prepared samples was determined using titration/back‐titration technique and Fourier transform infrared spectroscopy (FTIR). According to the torque–time diagrams, increasing the DCP content led to an increase in GMA grafting yield. Also, it was found that the reaction time imparts minor effect on the final processing torque, and there exists an interaction between DCP and GMA content. The results of melt flow index (MFI) test showed that increasing the reaction time at constant DCP and GMA content enhances the MFI values of the samples, due to the more probability of chain scission phenomenon. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009