Homopolymer Formation Research Articles

Single molecule visualization of tropomyosin isoform organization in the mammalian actin cytoskeleton.

The actin cytoskeleton is composed of both branched and unbranched actin filaments. In mammals, the unbranched actin filaments are primarily copolymers of actin and tropomyosin. Biochemical and imaging studies indicate that different tropomyosin isoforms are segregated to different actin filament populations in cells and tissues, providing isoform-specific functionality to the actin filament. Intrinsic to this model is the prediction that single-molecule imaging of tropomyosin isoforms would confirm homopolymer formation along the length of single actin filaments, a knowledge gap that remains unaddressed in the cellular environment. We combined chemical labeling of genetically engineered tropomyosin isoforms with electron tomography to locate individual tropomyosin molecules in fibroblasts. We find that the organization of two non-muscle tropomyosins, Tpm3.1 with Tpm4.2, can be distinguished from each other using light and electron microscopy. Visualization of single tropomyosin molecules associated with actin filaments supports the hypothesis that tropomyosins form continuous homopolymers, instead of heteropolymers, in the presence of all physiologically native actin-binding proteins. This is true for both isoforms tested. Furthermore, the data suggest that the tropomyosin molecules on one side of an actin filament may not be in register with those on the opposite side, indicating that each tropomyosin polymer may assembly independently.

Synthesis of Amidoxime Adsorbent by Radiation-Induced Grafting of Acrylonitrile/Acrylic Acid on Polyethylene Film and Its Application in Pb Removal.

In the aquatic environment, heavy metals such as lead ions Pb (II) are of particular importance. These are due to Pb (II) being toxic at concentrations over 0.01 mg/L, when taken continuously over an extended length of time. Organs including the heart, gut, and kidneys are seriously harmed by Pb (II) intoxication. The neurological, reproductive, and bone systems are also affected. The removal of Pb (II) from aquatic environments is, therefore, crucial. Low density Polyethylene (LDPE) is grafted by radiation with Acrylonitrile and acrylic acid (PE-g-AN/AAc) for the adsorption of Pb (II). Factors that control the grafting process for optimum conditions, such as the effect of solvents, the air atmosphere, inhibitors, comonomer concentration, and composition and irradiation dose, are studied to obtain a high grafting yield without homopolymer formation and a higher water uptake. The results showed that the addition of 2.5% by wt% ferric chloride salt effectively inhibits homoploymerization of a mixture of 30% methanol and 70% H2O used as a solvent in nitrogen. The highest graft yield obtained was 320% at a 25 kGy radiation dose with an 80/20 monomer composition and 60% comonomer concentration. The resulting composite films were characterized by XRD to analyze the dispersion properties of the material, SEM for the surface morphology, FTIR analysis for the functional groups, TGA, DSC for the thermal stability and elongation, and tensile strength for the mechanical properties. The uptake of Pb (II) from lead nitrate aqueous solution by (PE-g-AN/AAc) was observed under different conditions of the degree of grafting, contact time, metal ion concentration, and pH. The results obtained suggest LDPE-g-p (AN/AAc) as a superabsorbent for the Pb (II) ion’s removal from an aqueous solution.

Structural Modification of Starch Nanoparticles Via Graft Copolymerization Using KMnO4, HClO4 and HNO3 Redox Pair

The novelty addressed here is commenced with a view to use our formerly prepared starch nanoparticles (SNPs) of size around 80–100 nm as a starting substrate for grafting meth acrylic acid (MAA) using KMnO4, HClO4 in presence of HNO3 as innovative redox pair in aqueous medium. This was done to see the effect of SNPs with respect to well-dispersed nanosized particles, large surface areas, biodegradability and reactivity on the rate and extent of grafting. Besides; maximize the graft yield and graft reaction efficiency and reduce the homopolymer formation to lower extent. This could be accomplished via an in-depth assessment into the chief factors affecting the polymerization reaction such as initiator, monomer, SNPs and acid concentrations, time and temperature of polymerization, and liquor ratio. The results obtained indicate that the magnitude of the polymer yield including graft yield, graft reaction efficiency and homopolymer formation are determined by these factors. The structure of the resultant copolymers was confirmed instrumentally by Fourier transforms infrared spectroscopy; while both the surface morphology, crystalline structure and thermal properties were characterized by scanning electron microscopy, X-ray diffraction and thermal gravimetric analysis. Furthermore, the resultant copolymers were evaluated as environmental remediation materials via cadmium ions and cationic dyes removal from their solutions with different extent; in addition to higher swelling and chemical resistance in water as polar solvent and hydrochloric acid as acidic solution. The anticipated mechanisms involved in the synthesis are reported.

Comprehensive Structural Assessment of Linear Block Polymers by NMR and SEC

Block polymers are an important class of materials offering unique and useful properties different from random polymers. Because of their tailored structure, these materials present synthetic challenges. For this reason, it is necessary to provide a thorough structural analysis to drive the synthetic effort. We describe an analytical methodology that includes size exclusion chromatography (SEC), quantitative 13C NMR, and 1H pulsed gradient spin echo (PGSE) NMR coupled with direct exponential curve resolution algorithm (DECRA) data analysis. The combination of these complementary techniques provides a comprehensive assessment of the chemical structure of the final polymeric material, including the detection and quantification of homopolymer formation, compositional heterogeneity with molecular weight, and monomer sequencing. We present work on two different linear block polymers: poly(styrene-b-allyl methacrylate) and poly[styrene-b-(styrene-alt-maleic anhydride)].

Tailor-made ultra-crystalline, high molecular weight poly(ε-caprolactone) films with improved oxygen gas barrier and optical properties: a facile and scalable approach

The work presents a facile and scalable approach for fabricating tailor-made ultra-crystalline, high molecular weight biodegradable polymer poly(ε-caprolactone) [PCL] through ring-opening polymerization. Linear homopolymer of PCL were fabricated by tuning the molar ratio of monomer: initiator: catalyst in associated with organometallic catalyst (tin octoate) and a non-toxic and structurally symmetric initiator ethylene glycol (EG). High molecular weight PCL homopolymer formation with molecular weight higher than 90,000 Da was examined by FTIR, NMR and GPC. The ultra-crystalline characteristics (percent crystallinity, %Xc >70%) and unique crystal morphology of PCL were thoroughly scrutinized using DSC, XRD, HRTEM, SAED patterns and POM analysis. The developed protocol for the solvent-free technology allows high conversion ~99% at lowest possible reaction time of 1 h suggesting it a cost effective process, which is scalable to larger volume (5000 mL) without compromising the final product properties. The fabricated ultra-crystalline, high molecular weight PCL films showed good oxygen barrier property (~197 cm3 mm−1 day−1), surface free energy (133.7 mN/m) and optical transparency, recommending its niche in envisioned applications like low temperature flexible packaging and biomedical field.

Free-Radical Graft Polymerization onto Starch as a Tool to Tune Properties in Relation to Potential Applications. A Review

Grafting of acrylic monomers onto the renewable feedstock starch via free radical polymerizations has been investigated for many years. Many potential applications have been studied, such as superabsorbents, flocculants, thickening agents and so forth. It is expected that size and spacing of the grafts have a large influence on the performance of such polymers. Yet, information upon the structure-property relationships is only scarcely found in literature. Moreover, there is no clear overview of how reaction variables can be used to influence the grafted structure. In this review, an assessment has been made of the relation between the architecture of the grafts and potential applications. Then, from a selection of relevant literature data it is demonstrated that reaction variables such as the relative concentrations of initiator and monomer, have a large impact on the average size and spacing of the grafts. The emergence of controlled radical polymerizations, like Atom Transfer Radical Polymerization (ATRP) and Reversible Addition-Fragmentation chain Transfer (RAFT), is discussed, both the current status and future prospects. These methods are promising in the future of starch grafting, especially for systems where homopolymer formation may be a problem. Nevertheless, higher costs and other related issues make these advanced methods more suitable in high added-value products.

Towards Synthesis, Characterization and Properties of Smart Material Based on Chitosan Using Mn-IV Itaconic Acid as a Novel Redox Pair

The precipitation technique of Mn-IV/itaconic acid redox pair was chosen for grafting meth acrylic acid onto chitosan. This was done to maximize the graft yield and minimize the homopolymer formation to lower extent in addition to prepare water soluble chitosan instead of non-eco friendly acid soluble one. Evidence of grafting was confirmed instrumentally by (FTIR, SEM, and TGA), titrimetrically using carboxyl content and gravimetrically using dry weight method. The mechanism of grafting and factors affected grafting reaction were studied in details, and the optimum reaction conditions were obtained at [chitosan] 2 g, [MnO2] 25.9 mmol/100 g sample, [itaconic acid],100 mmol/L, [MAA] 50% bows,[liquor ratio], 25, reaction time, 2 h, and [reaction temperature], 65 °C. It is also seen from the obtained results that, the resultant copolymer showed the following findings: (a) only nitric acid solutions are proved to be a superior solvent for the grafted product; (b) superabsorbent towards water (197 g H2O/g polymer) and saline absorbency (60 g saline solution/g polymer) after cross-linked with epichlorohydrin, (c) higher water solubility (21%) at 48% graft yield and (d) 73.5% copper ion removal in comparison with 41% for chitosan.

Synthesis of novel grafted hyaluronic acid with antitumor activity

In our study, we aimed to synthesize novel grafted hyaluronic acid with cationic biodegradable polymer, poly (N-vinyl imidazole) (PVI), through free radical polymerization using potassium persulfate as initiator. The effect of various grafting factors including initiator and monomer concentrations, reaction time and temperature was studied on the percentage of grafting parameters such as; graft yield (% GY), grafting efficiency (% GE) and amount of homopolymer formation (% H). Maximum grafted HA was% GY = 235% and%GE = 83% obtained on optimum conditions at [In] = 17.5 mmol L−1, [M] = 1.25 mol L−1, Temp. = 50 °C, time = 1.5 h and [HA] = 0.025 mol L−1. The structure of grafted HA (HA-g-PVI) was elucidated via various analysis tools such as; elemental analyses, FTIR, 1H NMR, XRD, TGA and Field emission scanning electron microscopy (FE-SEM). Hepatic and breast cancers are two common cancer types threatening people worldwide, so, the antitumor activity of two grafted HA samples (% GY = 155% and 235%) was studied against hepatic cancer (HepG-2) and breast cancer cell lines (MCF-7) compared to unmodified HA and PVI. The results showed that antitumor activity of grafted samples was more than unmodified HA and increased with increasing the grafting percentage of PVI onto HA chains, also, the antitumor activity of tested samples against HepG-2 cell lines was higher than MCF-7 cell lines.

Dextran and poly(butyl methacrylate) graft copolymers as non-adherent materials for vascular applications

Event Abstract Back to Event Dextran and poly(butyl methacrylate) graft copolymers as non-adherent materials for vascular applications Eléonore Michel1, 2, Pascale Chevallier1, Caroline Loy1, Lucie Lévesque1, Didier Letourneur2 and Diego Mantovani1 1 CHU de Québec Research Center, Laval University, Lab. Biomaterials and Bioengineering, CRC-I, Dept Min-Met-Materials Eng., Canada 2 Institut Galilée, Université Paris 13, Sorbonne Paris Cité, INSERM, U1148, Laboratory for Vascular Translational Science, France Introduction: Various polymers have been investigated and developed to resist to non-specific adhesion to avoid or limit adsorption of proteins, cells, bacterial or platelets adhesion, known to lead to inflammation, infections and to be the main responsible for the eventual failure of the implant. Thus, a major challenge in the field aims to decrease the hydrophobicity for enhancing the biocompatibility in an effort for compromising biological and mechanical properties. Polysaccharides, polyacrylates and their derivatives have been reported in many biomedical fields as potential candidates for antifouling, tissue engineering or hemocompatible applications[1]-[3]. This work aimed to develop and investigate copolymers of carboxymethyldextran and polybutylmethacrylate which are susceptible to show interesting mechanical and non-adherent properties especially suitable for vascular applications. Material and Methods: Graft copolymers (CMD-PBMA) have been synthesized by radical copolymerization with Ce(IV) ions, from butyl methacrylate monomers (BMA) and carboxymethyldextran (CMD) (Table 1)[4],[5]. Synthesis were characterized by mass balance, and copolymers by solid state 13C-NMR, FTIR as well as by SEC/HPLC after acid hydrolysis allowing to differentiate PBMA and CMD chains. Films have been prepared by dispersion of CMD-PBMA (50 mg/mL) in THF/water (90:10) poured in a mold and placed under THF atmosphere with CaCl2 overnight. Relaxation assay (ɛ = 3 %) were performed on dumbbell-shaped films with an Instron 5944 system, at 10 mm/min, until 25% of deformation and then up to rupture. Cytotoxicity and proliferation assays were performed with 3T3 fibroblast (15000 cells/cm²) and HUVEC (40000 cell/cm²). Cytotoxicity was investigated after 24h by resazurin with 1 and 7 days extracts. Cells viability was tested with resazurin prior observation of proliferation by fluorescence microscopy after 1, 4 and 7 days. Clotting assay was evaluated after 25 min of contact with whole blood by measuring free hemoglobin in absorbance. Results and Discussion: NMR and FTIR spectra of copolymers clearly evidenced the characteristic peaks of both CMD and PBMA. Whatever the copolymer considered, they were mostly made of PBMA chains (80-90%) which were 10 times larger than CMD ones as seen in Table 1. Furthermore, the reaction yield was quite low mainly due to PBMA homopolymer formation. It has been noticed that for both ratios of CMD/BMA used, CMD 0.2 led to higher yields than CMD 0.4, due to more available substitution sites (less COOH) for radical copolymerization. Latest observations, get along with the polymerization scheme involving PBMA macro-radicals formation and their recombination on the CMD backbone. Despite these differences, all copolymers films showed equivalent composition after XPS analyses and higher hydrophilicity than PBMA (80° vs 95°). Mechanical relaxation assays on CMD-PBMA films showed quasi-total relaxation of stress and elongations to fracture up to 60% whereas PBMA films were too brittle to be unmolded. Copolymer films did not induce cytotoxicity and HUVECs and 3T3 fibroblasts did not adhere, therefore no further proliferation has been observed (Figure 1). No difference in hemocompatibility was observed between copolymers and PBMA. Conclusions: The presence of CMD in the copolymer lead to increase mechanical resistance while antifouling properties of PBMA are preserved, as no cells adhere, and non-cytotoxicity is shown. Regardless the substitution degree of CMD and the BMA/CMD ratio considered, copolymers exhibit similar biological and mechanical properties. Therefore, these copolymers appear as promising materials for non-adherent coatings or polymers for vascular applications. This work was supported by Inserm-FRSQ, FP7 european program PRESTIGE, the Natural Science and Engineering Research Council of Canada, the Quebec Ministry for International Relations, the Centre Franco-Québecois de Coopération Universitaire, Centre d’Études et de Recherche sur les Matériaux Avancés (CERMA-ULaval), the CHU de Québec Research Center, the Centre Franco-Québecois de Coopération Universitaire, and the Research Center of CHU de Québec. The authors would like to express their gratitude to all the volunteers who donated blood and all technicians involved.

The Effect of Temperature on the Grafting of Acrylic Acid onto Carboxymethyl Cellulose

SummaryThe grafted copolymer CMC‐g‐PAA has been prepared by graft copolymerization reaction using 10% w/w carboxymethyl cellulose (CMC), acrylic acid (AA), 2.5% w/w benzoyl peroxide (BPO) as initiator, 3.75% w/w methylenbisacrylamide (MBA) as crosslinking agent in distilled water at 30, 50, 70, and 90 °C during reaction periods of 30 to 300 min and composited with 10% w/w montmorillonite for 5 h.The grafted copolymer CMC‐g‐PAA and homopolymer were dried in the oven at 40 °C, then washed with distilled water and aceton. After that the hydrogel material was dried, and subjected to Soxhlet extraction with dioxane to separate the homopolymer, poly(acrylic acid), from the graft copolymer, CMC‐g‐PAA. The water absorption capacities and grafting values of grafted CMC were also determined. The graft copolymer CMC‐g‐PAA obtained at 30 °C has high conversion rate of AA (87.6%). The maximum grafting yield (99.181%) and the lowest of homopolymer formation (0.819%) were obtained at 50 °C. It was observed that polyacrylic acid‐grafted CMC produced at 90 °C had the highest water retention capacity (55.03%). The graft copolymer was characterized by infra‐red spectroscopy to determine the structure of the graft chains.

Effect of some parameters on the synthesis and the physico-chemical properties of new amphiphilic starch-g-copolymers

The detailed studies on the graft copolymerization of phenyl methacrylate onto gelatinized potato starch in water using potassium persulfate as radical initiator were presented. The different reaction parameters such as effect of initiator concentration, starch to monomer ratio, reaction temperature and reaction time were studied in terms of grafting efficiency, grafting percent and percent homopolymer formation. It was found that grafting process of aromatic methacrylate monomer onto potato starch backbone allowed obtaining new amphiphilic copolymers with different physicochemical properties as compared to non-modified starch. The influence of the copolymer structure on the swelling behavior in polar and non-polar solvents, moisture absorbance, gelatinization properties, acid and base resistance, surface morphology and thermal properties was discussed.

Tunable hydrophylicity/hydrophobicity of fluorinated carbon nanotubes via graft polymerization of gaseous monomers

In order to further change the surface chemistry of fluorinated single-walled carbon nanotubes (SWCNTs), gas-phase grafting of monomers onto their surface was performed thanks to the presence of long-lived radicals resulted from the fluorination. Such a two-step process, i.e. fluorination followed by monomer vapor exposure, used here for the first time, resulted in a fast graft polymerization without any solvent using. The total treatment duration does not exceed 4–5 h, contrary to the other reported routes in solvent, and the grafted SWCNTs are ready for use without any purification step. The grafting of monomers from a gaseous phase allows to avoid the homopolymer formation on the tube surface. Grafting drastically changes the SWCNTs surface chemistry. The hydrophilicity/hydrophobicity character may be adjusted according to the monomer nature. Poly(acrylic acid) grafting is resulted in enhanced hydrophilicity, and consequently a better dispersion in water and ethanol. On the contrary, grafted polystyrene improves the dispersion in low-polarity organic solvents because of more hydrophobic nature. Once dispersed in an adequate solvent (commonly used in “wet” chemistry, low hazard and low toxic), the grafted fluorinated nanotubes can be then used for further uses, e.g. incorporation into nanocomposites.

Functionalization of lignin: Fundamental studies on aqueous graft copolymerization with vinyl acetate

The second most abundant natural polymer, lignin, an under-valued co-product from the pulp and paper, and biofuel industry has a great potential to be utilized to engineer value-added, green products. Graft copolymerization of vinyl acetate (VAc) on lignin was performed using potassium persulfate as an initiator and ammonium iron (II) sulfate as a catalyst. Aqueous reaction medium is used for the preparation of graft copolymer as a cost effective and greener route. The effects of reaction conditions were studied to obtain optimal grafting percentage with very low homopolymer formation. The effects of various factors like temperature, initiator concentration, amount of monomers, and volume of catalyst found to have considerable effects on grafting efficiency. Highest grafting of 60% was observed for 1:1.5 ratio of lignin and vinyl acetate at 70°C in presence of 9.24×10−2mol/L initiator and 5.1×10−4mol/L of catalyst concentration. Graft copolymerization was identified from the new absorption peaks at wavelengths around 1720cm−1 and 1210cm−1 (Fourier transform infrared spectroscopy), and the new degradation peak observed at 339°C (thermogravimetric analysis). Reinforcing or blending of VAc-g-lignin with desirable polymers can yield value-added greener products.

Controlled grafting of MMA onto cellulose and cellulose acetate

Homogeneous graft copolymerization of methyl methacrylate onto cellulose and cellulose acetate was carried out in various solvents and solvent systems taking ceric ammonium nitrate, tin (II) 2-ethyl hexanoate [Sn(Oct)2] and benzoyl peroxide as initiators. The effect of solvents, initiators, initiator and monomer concentration, on graft yield, grafting efficiency and total conversion of monomer to polymer were studied. Formation of Ce3+ ion during grafting in presence of CAN enhances the grafting efficiency. Methylene blue was used as a homopolymer inhibitor and controlled the molecular weight of the grafted polymer and its effect on grafting was also studied. In presence of MB, amount of PMMA homopolymer formation reduced and consequently grafting efficiency increased. The number average molecular weights and polydispersity indices of the grafted PMMA were found out by gel permeation chromatography. The products were characterized by FTIR and 1H-NMR analyses and possible reaction mechanisms were deduced. Finally, thermal degradation of the grafted products was also studied by thermo-gravimetric and differential thermo-gravimetric analyses.

Oxygen plasma-induced graft polymerization of acrylic acid on polycaprolactone monofilament

Plasma-induced graft polymerization of acrylic acid was carried out on polycaprolactone filament using low pressure oxygen plasma. The degree of grafting was studied by varying parameters such as the medium of grafting, reaction temperature, monomer concentration and storage conditions. Addition of ferrous sulphate suppressed the homopolymer formation but resulted in a lower degree of grafting. However, the presence of methanol increased the graft yield. The equilibrium degree of grafting exhibited strong dependence on monomer concentration, reaction temperature and active centers’s concentration created upon plasma exposure. From the reaction kinetics, the order of dependence on the monomer concentration was found to be 1.1. The degree of grafting was strongly dependent on storage temperature following plasma treatment. At very low temperature, significant concentrations of active centers could be preserved for graft polymerization. Graft polymerization on the surface led to the filling of valleys by grafted polymer chains resulting in increased hydrophilicity and topographical changes as measured by contact angle, SEM and AFM experiments.

The grafting of acrylic acid onto biosorbents: Effect of plant components and initiator concentration

Acrylic acid was grafted onto raw and Fenton's reagent treated pine cone using KMnO4 as initiator to determine the effect of plant organic components on grafting process. Concentration of the KMnO4 was varied between 0.0005 and 0.0200mol/dm3 and progress of the initiation process monitored using ORP and change in hydrogen ion concentration (ΔH+).The optimum ratio for Fenton's modification was Fe2+/H2O2=1/50 which corresponds to the highest leaching of plant components and having the least bulk density, ORP and ΔH+. It was observed that increasing KMnO4 concentration, reduced the MnO2 deposited on the pine surface, increased Mn3+ production in bulk solution while reducing grafting efficiency but increasing homopolymer formation. Radical formation on the raw pine cone was found to be lower as seen from the lower ORP and ΔH+ values observed at similar grafting conditions.Plant organic components was observed to affect the grafting efficiency and monomer conversion as observed from the weight increase, surface charge and FTIR analysis of the acrylic acid grafted Fenton's reagent treated pine and the raw pine.Optimum dye removal did not correspond to highest grafting efficiency.

Multi functionalization of polypropylene with controlled degradation and its structure characterization

The multi functionalization of isotactic polypropylenes (iPP) with glycidyl methacrylate (GMA) was carried out by in situ chlorinating graft copolymerization (ISCGC), in which chlorine (Cl2) is used as a radical initiator as well as a radical scavenger. The molecular weight measurement indicates that functionalized iPP with controlled degradation could be obtained because the unstable radicals that induce iPP degradation could be terminated quickly by chlorine. Owing to the unique allyl-containing structure of GMA, multi functionalized iPP could be synthesized under the effect of chlorine, which contained both epoxy groups and C=C double bonds as well as trace amount of chlorine atoms in the functionalized polymer structure. The structure of both the functionalization polymer and homopolymer formed in this system were analyzed by FTIR and 1H NMR. The mechanism of grafting reaction, iPP chain degradation, and GMA homopolymer formation scheme in ISCGC were proposed. The thermal properties of the functionalized polymer are also discussed.

Pressure-Sensitive Adhesives from Renewable Triblock Copolymers

ABA triblock copolymers were prepared using the renewable monomers menthide and lactide, by sequential ring-opening polymerizations. Initially, hydroxy telechelic polymenthide was synthesized by the diethylene glycol-initiated and tin(II) ethylhexanoate-catalyzed polymerization of menthide. The resulting 100 kg mol−1 polymer was used as a macroinitiator for the tin(II) ethylhexanoate-catalyzed ring-opening polymerization of d,l-lactide. Two polylactide−polymenthide−polylactide triblock copolymers were prepared with 5 and 10 kg mol−1 polylactide end blocks. Transesterification between the two blocks, and polylactide homopolymer formation were minimized, and triblock copolymers with narrow molecular weight distributions were produced. Microphase separation in these systems was corroborated by differential scanning calorimetry and small-angle X-ray scattering measurements. The triblocks were combined with up to 60 wt % of a renewable tackifier, and the resulting mixtures were evaluated using probe tack, 180° peel adhesion, and shear strength tests. Maximum values of peel adhesion (3.2 N cm−1) and tack (1.1 N) were obtained at 40 wt % of tackifier. These new materials hold promise as renewable and hydrolytically degradable pressure-sensitive adhesives.

Grafting of acryloyl cyanoacetohydrazide onto chitosan

Chitosan was grafted with a novel monomer namely Acryloyl cyanoacetohydrazide (ACAH) which contains carbonyl and cyano groups. The graft copolymerization was conducted in heterogeneous phase using potassium persulfate (K2S2O8) and sodium bisulfite (NaHSO3) as redox initiators. The effect of monomer concentration, initiator concentration and ratio, time and temperature on the extent of grafting (G%) and the efficiency of grafting were studied. Homopolymer formation has not been observed under all the investigated conditions. The grafted samples were characterized by FTIR spectroscopy, X-ray diffraction and thermogravimetric analysis. The crystallinity of the used chitosan was reduced by grafting. Dye uptake of the grafted samples towards the different types of dyes (acidic, and basic) was investigated and was found to improve profoundly over the native chitosan with a higher uptake for the acidic dye. The grafted samples showed an increased swelling in water, which increased further upon quaternization of the graft copolymers. The extent of swelling is higher in acidic and basic media more than in neutral pH. The quaternized graft copolymer was found to be soluble in water. The fungicidal activity of the quaternized graft copolymers towards three soil-borne sugar beets pathogens was investigated in vitro. The effect on the micro organisms is proportional to the amount of ACAH in the graft copolymer.

Synthesis and characterization of (poly (N-vinyl formamide)—pregelled starch—graft copolymer

Bromate / cyclohexanone redox system was investigated as a novel initiator for graft copolymerization of N-vinyl formamide onto pregelled starch. A number of variables in the grafting reaction were investigated including N-vinyl formamide, cyclohexanone, bromate ion, sulphuric acid and pregelled starch concentrations, material to liquor ratio along with polymerization time and temperature. The graft copolymers were evaluated in terms of graft yield, graft reaction efficiency and homopolymer formation (%). The optimum conditions for grafting of N-vinyl formamide onto pregelled starch are: N-vinyl formamide 50% based on weight of substrate, cyclohexanone 15 mmol / l, bromate ion, 30 mmol / l, liquor ratio 10, pH 6, time 120 min., and temperature 40°C. On the other hand, characterizations of the resultant copolymers with respect to swelling capacity, solubility %, metal ion up-take and suitability as a sizing agent for cotton textiles were investigated. The results obtained reflect that, the resultant copolymer shows better results for the aforementioned properties in comparison with that obtained from native pregelled starch as a starting substrate.