Microwave initiated synthesis of polymethylmethacrylate grafted guar (GG-g-PMMA), characterizations and applications

Guar gum was grafted with polymethylmethacrylate (PMMA) by microwave initiated method. The synthesis was optimized for highest percentage grafting, by varying the microwave irradiation time and monomer (methyl methacrylate) concentration. The various grades of grafted product (GG-g-PMMA) were characterized through standard physicochemical characterization techniques (intrinsic viscosity measurement, elemental analysis, FTIR spectroscopy & SEM morphology study). Further, flocculation efficacy of this grafted polysaccharide was studied by standard 'Jar test' procedure in 0.5% kaolin suspension, to assess its application as flocculating agent for wastewater treatment and mineral ore beneficiation. Correlation between percentage grafting and intrinsic viscosity was also studied for the possibility of using it as a tool to control the intrinsic viscosity in the final product. This leads to the possibility of application of the grafted product as superior viscosifier than guar gum.     

A novel polymeric flocculant based on polyacrylamide grafted carboxymethylstarch

Novel functionalized polymeric flocculants based on polyacrylamide grafted carboxymethylstarch (CMS-g-PAM) have been successfully synthesized via conventional method (using ceric ammonium nitrate as free radical initiator, in an inert atmosphere) as well as by using microwave irradiation (‘microwave initiated’ synthesis). Under optimal grafting conditions, 50% grafting has been observed in case of the microwave irradiation based method and 47% grafting has been observed in case of the conventional process. The synthesized graft copolymers have been characterized by elemental analysis, FTIR spectroscopy, intrinsic viscosity measurement, molecular weight determination, ¹³C NMR spectroscopy and scanning electron micrograph (SEM); taking carboxymethylstarch (CMS) as reference. The effects of reaction parameters onto the percentage of grafting have been studied. Further, the applicability of these grafted polymers as flocculants for the treatment of municipal sewage wastewater has also been investigated.     

Microwave initiated synthesis of polyacrylamide grafted Psyllium and its application as a flocculant

This paper reports a novel microwave initiated method for synthesis of polyacrylamide grafted Psyllium (Psy-g-PAM). Psyllium was modified through grafting of polyacrylamide (PAM) chains on it using microwave radiations only, in absence of any other free radical initiator. The grafting was confirmed by intrinsic viscosity study and characterization techniques like FTIR spectroscopy, elemental analysis (C, H, N, O and S) and SEM morphology study. Further, the flocculation efficacy of the synthesized graft copolymers was studied in kaolin and coal fine suspension through standard 'Jar test' procedure.     

Polyacrylamide grafted Agar: Synthesis and applications of conventional and microwave assisted technique

Polyacrylamide grafted Agar (Ag-g-PAM) has been successfully synthesized by conventional method and microwave assisted method. The former method employs ceric ammonium nitrate (CAN) as the free radical initiator while the latter uses the combination of ceric ammonium nitrate (CAN) and microwave irradiation. The synthesized graft copolymers have been characterized by elemental analysis (C, H, N, O and S), FTIR spectroscopy, intrinsic viscosity measurement and scanning electron micrograph (SEM); taking agar as a reference. Flocculation efficacy of synthesized graft copolymers was studied in kaolin suspension and in waste water through 'Jar test' procedure. In the present investigation, we have observed that polyacrylamide grafted agar synthesized by microwave assisted technique shows superior properties than conventional technique. These properties are reported in terms of intrinsic viscosity, flocculation efficacy and pollutant load reduction of waste water.     

Microwave assisted synthesis of polyacrylamide grafted agar (Ag-g-PAM) and its application as flocculant for wastewater treatment

Grafting of polyacrylamide (PAM) chains was performed onto the backbone of Agar by microwave assisted method, using microwave radiation in synergism with ceric ammonium nitrate (CAN) as the chemical free radical initiator. The intended grafting of the PAM chains were confirmed through intrinsic viscosity study, FTIR spectroscopy and elemental analysis (C, H, N, O & S). Further characterization of the grafted product was done in form of SEM morphology and TGA study. Flocculation efficacy of the synthesized graft copolymers was studied in kaolin suspension, through ‘Jar test’ procedure. Further, flocculation efficacy of the ‘best grade’ (as determined by ‘jar test’ in kaolin suspension) in wastewater was studied for possible application in reduction of pollutant load of wastewater.     

Microwave assisted synthesis of polyacrylamide grafted starch (St-g-PAM) and its applicability as flocculant for water treatment

Polyacrylamide grafted starch (St-g-PAM) was made by a novel method of synthesis, involving combination of microwave radiation and a chemical free radical initiator (ceric ammonium nitrate) to initiate grafting reaction. This method (microwave assisted synthesis) is quick, highly reliable, reproducible and yields high quality product as compared to the conventional method (which uses a chemical free radical initiator alone to initiate the grafting reaction).The St-g-PAM grades synthesized were characterized by various physicochemical techniques. Further, its application as flocculant for wastewater treatment was investigated.     

Microwave initiated synthesis of polyacrylamide grafted carboxymethylstarch (CMS-g-PAM): Application as a novel matrix for sustained drug release

This paper reports the investigation of microwave initiated synthesized polyacrylamide grafted carboxymethylstarch (CMS-g-PAM) as matrix for sustained drug release. ‘In vitro’ release of a model drug (5-amino salicylic acid) from CMS-g-PAM matrix has been studied. It is evident that higher the percentage grafting, more sustained is the rate of drug release. Further, the percentage grafting vs. t₅₀ value (i.e. time taken for release of 50% of the enclosed drug) correlation has been successfully studied for the first time. This correlation will lead to the possibility of a programmable drug release matrix based on grafted polysaccharide. In this matrix, the rate of release of the enclosed drug can be precisely programmed simply by adjustment of percentage grafting during synthesis.     

Synthesis of graft copolymer (k-carrageenan-g-N,N-dimethylacrylamide) and studies of metal ion uptake, swelling capacity and flocculation properties

Graft copolymer of k-carrageenan and N,N-dimethylacrylamide has been synthesized by free radical polymerization using peroxymonosulphate/glycolic acid redox pair in an inert atmosphere. The grafting parameters i.e. grafting ratio, add on and efficiency decrease with increase in concentration of k-carrageenan from 0.6 to 1.4 g dm⁻³ and hydrogen ion from 3 × 10⁻³ to 7 × 10⁻³ mol dm⁻³, but these grafting parameters increase with increase in concentration of N,N-dimethylacrylamide from 16 × 10⁻² to 32 × 10⁻² mol dm⁻³, and peroxymonosulphate from 0.8 × 10⁻² to 2.4 × 10⁻² mol dm⁻³. The metal ion sorption, swelling behaviour and flocculation properties have been studied. The intrinsic viscosity of pure and grafted samples has been measured by using Ubbelohde capillary viscometer. Flocculation capability of k-carrageenan and k-carrageenan-g-N,N-dimethylacrylamide for both coking and non-coking coals has been studied for the treatment of coal mine waste water. The graft copolymer has been characterized by Infrared (IR) spectroscopy and thermogravimetric analysis.     

Grafting of cellulose fibers with poly(epsilon-caprolactone) and poly(L-lactic acid) via ring-opening polymerization

In this study, ring-opening polymerization (ROP) of epsilon-caprolactone (epsilon-CL) and L-lactide (L-LA) has been performed from cellulose fibers. The hydroxyl groups on cellulose act as initiators in the polymerization, and the polymers are covalently bonded to the cellulose fiber. As an attempt to introduce more available hydroxyl groups on the surface, and thereby obtain higher grafting efficiency in the ROP of epsilon-CL and L-LA, unmodified paper was modified with xyloglucan-bis(methylol)-2-methylpropanamide (XG-bis-MPA) and 2,2-bis(methylol)propionic acid (bis-MPA), respectively. The grafted substrates were characterized via Fourier transform infrared spectroscopy (FTIR), contact angle measurement, atomic force microscopy, and enzymatic degradation. The results showed a successful grafting of poly(epsilon-caprolactone) (PCL) and poly(L-lactic acid) (PLLA) from the cellulose fiber surfaces. Furthermore, the results showed an improved grafting efficiency after activation of the cellulose surface with bis-MPA, and showed that the amount of grafted polymer could be controlled by the ratio of added free initiator to monomer.     

Effects of amylose/amylopectin ratio on starch-based superabsorbent polymers

Biodegradable superabsorbent polymers (SAPs) were prepared by grafting acrylamide onto starches then crosslinking with N,N′-methylene-bisacrylamide. This work focused on the effects of the amylose/amylopectin ratio of starches from the same source (corn) on the grafting reactions and performance of the resultant starch-based SAPs. To characterise each SAP, the acrylamide groups grafted onto the starch were detected by FTIR; grafting ratio and grafting efficiency were evaluated by a gravimetric method; and graft position and the length of the grafted segment were investigated by NMR. The relationships between the microstructures of the starches, and the graft reactions and performance of the SAPs were studied based on the amylose content in the starches. It was found that under the same reaction conditions, the grafting ratio and efficiency increased with increasing amylose content, which corresponds with water absorption ratio. NMR results indicated that the acrylamide group mainly grafted onto C6, and that the length of the grafted segment decreased with increasing amylopectin content in general, and in particular for waxy starch. The high molecular weight and branched structure of amylopectin reduced the mobility of the polymer chains and increased viscosity, which could explain the graft reactions and performance of the starch-based SAPs.     

Graft copolymerization of acrylamide on chitosan-co-chitin and its application for immobilization of Aspergillus sp. RL2Ct cutinase

The synthesis of chitosan (Chs) and chitin (Chi) copolymer and grafting of acrylamide (AAm) onto the synthesized copolymer have been carried out by chemical methods. The grafted copolymer was characterized by FTIR, SEM and XRD. The extracellular cutinase of Aspergillus sp. RL2Ct (E.C. 3.1.1.3) was purified to 4.46 fold with 16.1% yield using acetone precipitation and DEAE sepharose ion exchange chromatography. It was immobilized by adsorption on the grafted copolymer. The immobilized enzyme was found to be more stable then the free enzyme and has a good binding efficiency (78.8%) with the grafted copolymer. The kinetic parameters K_M and V_max for free and immobilized cutinase were found to be 0.55 mM and 1410 μmol min⁻¹ mg⁻¹ protein, 2.99 mM and 996 μmol min⁻¹ mg⁻¹ protein, respectively. The immobilized cutinase was recycled 64 times without considerable loss of activity. The matrix (Chs-co-Chi-g-poly(AAm)) prepared and cutinase immobilized on the matrix have potential applications in enzyme immobilization and organic synthesis respectively.     

Modification of Okra mucilage with acrylamide: Synthesis, characterization and swelling behavior

In the present communication, the synthesis and characterization of Okra mucilage, a food grade and water-soluble polysaccharide, based-materials are described. Okra mucilage has been modified by grafting acrylamide (AAm) for developing the new green polymeric materials of specialty applications. Grafting has been done under N₂ atmosphere using redox initiator and hydrogels were prepared by using N,N-methylenebisacrylamide (NN-MBAAm) as crosslinker. The effect of monomer concentration, initiator concentration, reaction time and temperature in terms of grafting efficiency (%GE), percent grafting (PG) and percent gel (%G) has been investigated. The grafted polymers and hydrogels were characterized by SEM, XRD and FTIR techniques to study various structural aspects. The swelling behavior of the crosslinked polymeric material has also been studied as a function of time, temperature and pH. The application area of these polymers is varied from biomaterials to the wastewater treatment.     

Effects of alkyl chain lengths of gallates upon enzymatic wool functionalisation

The covalent grafting of alkyl gallates on wool through a laccase catalysed reaction in 80/20 (v/v, %) aqueous–ethanol mixture provided in a one-step process a multifunctional textile material with antioxidant, antibacterial and water repellent properties. Gallic acid and its alkyl esters ethyl, propyl, octyl and dodecyl gallate have been enzymatically grafted on wool fibres in order to study the effect of alkyl chain length on wool functional modification. The capacity of laccase to oxidise these phenolic compounds in an aqueous–organic medium has been verified by electrochemical techniques. The increase of CH₂, CH₃ groups in the FTIR spectra, together with the XPS analysis of the enzymatically modified fabrics confirmed the covalent grafting of ester gallates on wool. The result obtained in this work for antibacterial, water repellent as well as antioxidant properties show that the length of the alkyl chain of gallates molecule play an important role on wool functionalisation.     

Synthesis,characterization and biocompatibility studies on chitosan-graft-poly(EGDMA)

Poly(ethylene glycol dimethacrylate), poly(EGDMA), was grafted onto chitosan by using a redox initiation system. Chitosan-graft-poly(EGDMA) products were characterized by DSC, TGA, FTIR and XRD techniques. Chitosan-graft-poly(EGDMA) was found to be enzymatically degradable in aqueous solutions of lysozyme, lipase and a mixture of α-amylase and protease. The biocompatibility of chitosan-graft-poly(EGDMA) with 871% grafting yield was investigated by studying its cytotoxicity, sensitization, irritation, acute systemic toxicity and hemolytic activity. The results of biocompatibility experiments showed that the product can potentially be used for external intervention devices on bone and other tissue.     

Photoinduced graft-copolymer synthesis and characterization of methacrylic acid onto natural biodegradable lignocellulose fiber

UV radiation induced graft copolymerization of methacrylic acid onto natural lignocellulose (jute) fiber was carried out both by "simultaneous irradiation and grafting" and by preirradiation methods using 1-hydroxycyclohexyl-phenyl ketone as a photoinitiator. In the "simultaneous irradiation and grafting" method, the variation of graft weight with UV-radiation time, monomer concentration, and the concentration of photoinitiator was investigated. In the case of the preirradiation method, the incorporation of 2-methyl-2-propene 1-sulfonic acid, sodium salt, into the grafting reaction solution played a most important role in suppressing the homopolymer/gel formation and facilitating graft copolymerization. The optimum value of the reaction parameters on the percentage of grafting was evaluated. In comparison, results showed that the method of graft-copolymer synthesis has significant influence on graft weight. The study on the mechanical and thermal properties of grafted samples was conducted. The results showed that the percentage of grafting has a significant effect on the mechanical and thermal properties in the case of grafted samples. Considering the water absorption property, the jute-poly(methacrylic acid)-grafted sample showed a maximum up to 42% increase in hydrophilicity with respect to that of the "as received" sample. Attenuated total reflection infrared studies indicate that the estimation of the degree of grafting could be achieved by correlating band intensities with the percent graft weight.     

Study of polyacrylamide grafted starch based algal flocculation towards applications in algal biomass harvesting

Microalgae may be the source of high amount of lipid and protein. It has the property for carbon dioxide sequestration, recycling and also can remove pollutants from wastewater. Using traditional methods, collection of algal biomass is either cost effective, time consuming or may be toxic due to use of chemical salts. The aim of this study is to harvest freshwater microalgae (Chlorella sp. CB4) biomass by using polymer. Polyacrylamide grafted starch (St-g-PAM) has been synthesized by microwave assisted method involving a synergism of microwave radiation and ceric ammonium nitrate (CAN) to initiate the grafting reaction. The synthesis was optimized in terms of CAN and monomer (acrylamide) concentration. The algal flocculation efficacy of all the grades of this graft copolymer was studied through standard 'Jar test' procedure. Effects of percentage grafting, pH and zeta potential on percentage recovery of algal biomass were thoroughly investigated.     

Graft polymers of eucalyptus lignosulfonate calcium with acrylic acid: Synthesis and characterization

The graft copolymerization of eucalyptus lignosulfonate calcium (HLS-Ca) from hardwood and acrylic acid (AA) was investigated by using Fenton agent as a coinitiator. The influences of reaction conditions on grafting parameters i.e. product yield (Y%), AA conversion (C%), grafting ratio (G%) and grafting efficiency (GE%) were carefully studied. The effects of the phenolic hydroxyl (Ph-OH) group on the polymerization of AA and grafting reaction were researched. Graft copolymers were identified by the new absorption at 1727 cm^?1, more homogenized morphology and higher decomposition temperature after grafted with AA, as illustrated in FTIR, SEM and TG spectra. The optimum synthesis conditions are as follows: H₂O₂ = 25.2 mol/L, FeCl₂ = 63.0 mol/L, T = 50 °C and t = 2 h and the optimum percentages of Y, C, G and GE are 97.61%, 95.23%, 71.29% and 78.85%, respectively. The Ph-OH group of HLS-Ca cannot inhibit the polymerization of AA and is involved in the grafting reaction as an active center.     

Poly(acrylonitrile) grafted Ipomoea seed-gums: a renewable reservoir to industrial gums

Plants of Ipomoea genus are widely distributed in India as wild vegetation and are reported source for the seed gums. Seed gums from Ipomoea dasysperma, Ipomoea hederacea, and Ipomoea palmata plants were grafted with polyacrylonitrile (PAN) using potassium persulfate/ascorbic acid redox initiator for modifying their properties for potential industrial applications. Under identical grafting conditions, the extent of the grafting was observed to be dependent on the galactose-to-mannose ratio and the degree of the branching in the galactomannans. Viscosity, gel formation, film formation, and the shelf life of the grafted gum solutions and water and saline retention capacity of the grafted seed gums were determined and compared with the parent gums. Water retention of the alkalie hydrolyzed grafted seed gums were also studied. Grafted gums were characterized using FTIR, NMR, and XRD analysis.     

Effect of drying on the biological activities of a red microalgal polysaccharide

The red microalga Porphyridium sp. produces a polysaccharide exhibiting a variety of biological activities with potential for medical and cosmetic uses. For this reason, it is important that the drying process, which is the end point of production, should not destroy the natural characteristics of the material. The objective of this study was to evaluate the effect of drying at temperatures ranging from 40 to 140 degrees C on the bioactivities of the polysaccharide. Drying the polysaccharide at temperatures above 90 degrees C caused a significant decline in its biological activities (antiviral and anti-cell proliferation) and reduced elasticity, viscosity, and intrinsic viscosity relative to lyophilized polysaccharide and to the starting product. The relationship between molecular weight and intrinsic viscosity indicated that the polysaccharide takes a rigid coil conformation, which stiffens as a result of drying. FTIR analysis revealed that drying caused both significant conformational alterations in the polymer chains and changes in the interaction between the polysaccharide and the glycoprotein to which it is noncovalently associated. Differential scanning calorimetry analysis of the water adsorbed on the charged groups of the polysaccharide showed that drying at higher temperatures increased the bound water content due to dissociation of the polymer chains. Thus, it is recommended that the polysaccharide be dried in a two-step process in which free water is removed by convection and bound freezing water is removed by lyphophilization.     

Inhibition de l'adhérence de Porphyromonas gingivalis sur la surface de titane greffé de poly(styrène sulfonate de sodium)

Dental implant-associated infections as peri-implantitis represent one of the major causes of osteointegration failures of oral implants. Adhesion of Porphyromonas gingivalis, one of the bacterial strains mainly involved in such infections, is tightly dependent on the topographical and/or physico-chemical properties of the implant surfaces. As a matter of fact, we showed that the grafting of one bioactive polymer such as poly(sodium styrene sulfonate) onto titanium implant surfaces allowed a sensitive decrease of Staphylococcus aureus adhesion (> 40%). The aim of the study consists in evaluating the adhesion of P. gingivalis onto titanium surfaces grafted with poly(sodium stryrene sulfonate) in order to elaborate implants exhibiting appropriate inhibiting properties towards the adhesion of periodontal pathogens. The grafting of poly(sodium stryrene sulfonate) onto titanium surfaces is carried out in two steps: chemical oxydation of titanium to initiate radical species then grafting of poly(sodium stryrene sulfonate) by radical polymerization. Chemical characterization of the surfaces is achieved by Fourier transformed infrared spectroscopy (FTIR). Bacterial adhesion was studied on grafted and non grafted (control) titanium surfaces, preadsorbed or not by plasmatic proteins. Protein adsorption as well as bacteria adhesion is followed by fluorescence spectroscopy by using proteins or bacteria previously labelled with fluorescence probes; the quantification of adsorption and bacteria adhesion are performed by image analysis. Results showed that protein adsorption is more important (~3 times) and that P. gingivalis adhesion is strongly inhibited (~73%) onto poly(sodium styrene sulfonate) grafted surfaces when compared to titanium control. Moreover, the inhibition of bacterial adhesion on grafted surfaces preadsorbed with plasma proteins is comparable to that observed on grafted surfaces preadsorbed with fibronectin. In conclusion, the obtained results evidenced that the grafting of titanium surface by poly(sodium styrene sulfonate) led to significant inhibition of P. gingivalis adhesion and that this inhibitory activity involved adsorbed proteins. Poly(sodium styrene sulfonate) grafted titanium surfaces present a high interest for the elaboration of oral implants in various clinical dental applications.