Synthesis and Characterization of Carboxymethyl Chitosan Grafted Methacrylic Acid Initiated by Ceric Ammonium Nitrate

O-carboxymethyl chitosan (CMCH) was prepared and characterized by FTIR spectroscopy and X-ray diffraction. Grafting of methacrylic acid (MA) onto CMCH using ceric ammonium nitrate (CAN) as an initiator was carried out under nitrogen atmosphere in aqueous solution. Evidence of grafting was confirmed by comparison of FTIR spectra of CMCH and the grafted copolymer as well as scanning electron micrograph (SEM) and X-ray diffraction of the products. The effects of concentration of CAN, MA, reaction time and temperature on graft copolymerization were studied by determining the grafting percentage and grafting efficiency. Keeping other conditions constant, the optimum grafting conditions were obtained as follows: CMCH = 2 gm, CAN = 0.2 M and MAA = 0.581 mol/L, reaction temperature = 40°C and reaction time = 4.5 hr.     

Graft copolymerizaztion of methyl acrylate onto chitosan initiated by potassium diperiodatocuprate (III)

A novel redox system, potassium diperiodatocuprate [Cu (III)–chitosan], was employed to initiate the graft copolymerization of methyl acrylate (MA) onto chitosan in alkali aqueous solution. The effects of reaction variables such as monomer concentration, initiator concentration, pH and temperature were investigated. By means of a series of copolymerization reactions, the grafting conditions were optimized. Cu (III)–chitosan system was found to be an efficient redox initiator for this graft copolymerization. The structures and the thermal stability of chitosan and chitosan‐g‐poly(methyl acrylate) (PMA) were characterized by infrared spectroscopy (IR) and thermogravimetric analysis (TGA). In this article, a mechanism is proposed to explain the formation of radicals and the initiation. Finally, the graft copolymer was used as the compatibilizer in blends of poly(vinyl chloride) (PVC) and chitosan. The scanning electron microscope (SEM) photographs and differential scanning calorimetry (DSC) thermograms indicate that the graft copolymer improved the compatibility of the blend. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2283–2289, 2003     

Chemically induced graft copolymerization of 4-vinyl pyridine onto carboxymethyl chitosan

A novel super absorbent polymer was prepared by graft copolymerization of 4-vinyl pyridine (4VP) onto the chains of carboxymethyl chitosan in aqueous solution using potassium persulphate (KPS) as initiator. The effect of monomer and initiator concentration, reaction temperature, and time on the grafting yield has been investigated. The maximum grafting yield was achieved at [KPS] = 4 × 10⁻² mol/L, [M] = 2.5 mol/L at reaction temperature = 60 °C within reaction time = 3 h. The molecular structure of the graft copolymer was confirmed by FTIR, surface morphology before and after the polymerization was examined by SEM. Different analyses were done for the graft copolymer such as X-ray diffraction, solubility tests, and thermal analysis. Different applications were done on the graft copolymer such as swell ability in different pH solutions, dye, and metal uptake.     

Synthesis and characterization of graft copolymer (guar gum–g–N‐vinyl‐2‐pyrrolidone) and investigation of metal ion sorption and swelling behavior

Graft copolymer of N‐vinyl‐2‐pyrrolidone with guar gum was synthesized and its reaction conditions were optimized for better yield using potassium peroxymonosulfate (PMS) and glycolic acid (GA) as a redox initiator. The effect of PMS, GA, hydrogen ions, guar gum, and N‐vinyl‐2‐pyrrolidone (NVP) along with reaction time and temperature were studied by determining the grafting parameters: grafting ratio, efficiency, conversion, add‐on, homopolymer, and rate of grafting. It was observed that the maximum yield occurred at with a time of 120 min at a temperature of 45°C and a guar gum concentration of 0.4 g/L concentration. The graft copolymer was characterized by infrared spectroscopy and thermal analysis. The activation energy for the grafted and ungrafted gum was calculated. It was observed that the graft copolymer was thermally more stable than the pure gum. The swelling and metal ion sorption behavior of guar gum and guar gum‐g‐N‐vinyl‐2‐pyrrolidone also were studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2480–2489, 2006     

Synthesis and characterization of polysaccharide based graft copolymer by using potassium peroxymonosulphate/ascorbic acid as an efficient redox initiator in inert atmosphere

Polysaccharide based graft copolymer (xanthan gum‐g‐4‐vinyl pyridine) was synthesized using potassium peroxymonosulphate/ascorbic acid redox initiator in inert atmosphere at 40°C. By studying the effect of the concentration of monomer, peroxymonosulphate (PMS), ascorbic acid (AA), xanthan gum (XOH), hydrogen ion along with effect of time and temperature on grafting characteristics: grafting ratio (%G), add on (%A), conversion (%C), efficiency (%E), homopolymer (%H), and rate of grafting (Rg), the reaction conditions for optimum grafting were determined. The optimum concentration of AA, H⁺ ion, 4‐VP for maximum grafting were found to be 10.0 × 10^?3 mol dm^?3, 2.5 × 10^?2 mol dm^?3, 10.0 × 10^?3 mol dm^?3, respectively. Maximum %G was obtained at minimum concentration of xanthan gum i.e., at 40.0 × 10^?2 g dm^?3 and at maximum concentration of PMS i.e., at 10.0 × 10^?3 mol dm^?3. The optimum temperature and time duration of reaction for maximum % of grafting were found to be 45°C and 120 min respectively. The synthesized graft copolymer was characterized by FTIR analysis. Thermogravimetric analysis showed that the xanthan gum‐g‐4‐vinyl pyridine is thermally more stable than pure gum. A probable mechanism was suggested for the graft copolymerization. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and characterization of ultra‐low molecular weight poly(vinyl alcohol) graft copolymer

Graft reaction of acrylamide (AM) and 4‐vinyl pyridine (4‐VP) onto ultra‐low molecular weight poly(vinyl alcohol) by ceric (IV) ion initiation had been systematically investigated; and the graft conditions were optimized by studying the effect of monomer/initiator concentration, solvents composition, reaction time and temperature. At optimized conditions, the maximum grafting efficiency and grafting ratio was ～ 50% and 51%, respectively with the presence of AM, whereas they decreased to 19% and 23%, respectively, without the presence of AM. Thermogravimetric analysis showed that as‐resulted graft copolymer had a lower thermal stability than homopolymer PVA. FTIR and ¹H‐NMR confirmed chemical structure of as‐synthesized graft copolymer. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Grafting of methyl methacrylate onto cellulose nitrate initiated by benzoyl peroxide

It has been observed that grafting of vinyl monomers onto cellulose nitrate in solution takes place using benzoyl peroxode. The graft copolymer was isolated from the unreacted backbone and homopolymer by selective solvent extraction. The effect of variables, such as the initiator concentration, the monomer concentration and the reaction time on the percent grafting and the grafting efficiency, were discussed. A probable mechanism for grafting of vinyl monomers to cellulose nitrate in solution has been proposed.     

Homogeneous grafting reaction of vinyl pyrrolidone onto chitosan

Modification of chitosan by grafting of vinyl pyrrolidone (VP) was carried out in homogeneous phase using potassium persulfate as redox initiator. The effect of the reaction variables on the extent of grafting was studied systematically. Values for grafting percentages up to 290% were reached. It was observed that the solubility of chitosan was markedly reduced after grafting with vinyl pyrrolidone. The grafted product is insoluble in common organic solvents as well in dilute organic and inorganic acids. However, the solubility of the grafted chitosan after adsorption of copper ions changed substantially, becoming completely soluble in dilute hydrochloric acid. This was attributed to the effect of complex formation produced by coordination of amino groups of chitosan with copper ions. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1321–1326, 1997     

两亲性接枝共聚物PVA-g-PBA的合成与表征

以过硫酸钾 (KPS)为引发剂 ,将丙烯酸丁酯 (BA)接枝到聚乙烯醇 (PVA)上 ,制得两亲性接枝共聚物 PVA-g-PBA。用红外光谱、X射线衍射表征了接枝物 ,研究了引发剂浓度、单体浓度及反应时间对单体转化率、接枝率和接枝效率和接枝率对共聚物吸水性能的影响。结果表明在水介质中 ,氮气保护下 ,70℃时 ,以过硫酸钾 (KPS)为引发剂 ,将丙烯酸丁酯 (BA)接枝到聚乙烯醇 (PVA)上 ,[PVA]为 2 .5× 1 0 -4mol/ L,[BA]为 0 .63 mol/ L、[KPS]为 5 .5 5× 1 0 -4时 ,反应 5 h,能获得较高 CM、G和 Ge的接枝物。接枝物的接枝率越高 ,吸水率越低 ,吸水 1 0 h达平衡 ,最大平衡吸水率为 1 88.8%。     

Graft copolymerization of 2-hydroxyethylmethacrylate onto carboxymethyl chitosan using CAN as an initiator

O-Carboxymethyl chitosan (CMCH) was prepared and characterized by FTIR spectroscopy. Graft copolymerization of 2-hydroxyethylmethacrylate (HEMA) onto CMCH using ceric ammonium nitrate (CAN) as an initiator was carried out in an aqueous solution. Evidence of grafting was confirmed by comparison of FTIR spectra of CMCH and the grafted copolymer as well as scanning electron micrograph (SEM) of the products. The effects of concentration of CAN, HEMA, reaction time and temperature on graft copolymerization were studied by determining the grafting percentage, grafting efficiency. With keeping other condition constant, the optimum grafting conditions was obtained as following: CMCH, 2 g; CAN, 0.2 M; and HEMA, 0.384 mol/l; reaction temperature, 40 °C; and reaction time, 4.5 h.     

Synthesis and Characterization of Starch-Poly(vinyl Acetate) Graft Copolymers and their Saponified Form

A redox initiation system based on potassium persulfate/acetone sodium bisulphite (KPS/ASBS) was developed to initiate the graft copolymerization of vinyl acetate (VAc) monomer onto corn starch in aqueous solution. The grafting reaction was studied with respect to grafting yield (GY), grafting efficiency (GE) and total conversion (TC) and results obtained were compared with those a well-established redox initiation system namely potassium persulfate/sodium bisulphite (KPS/SBS). The effect of reaction variables such as redox initiator concentration, liquor ratio, reaction time and temperature as well as VAc concentration were investigated. The GY, GE and TC increased significantly with increase of the redox initiation concentration up to 8/16 mmol/l irrespective of the initiation system used. Moreover, optimal grafting was obtained at 60 ^○C for KPS/ASBS redox system and 70 ^○C for KPS/SBS redox system. Saponification of poly (vinyl acetate)-starch graft copolymers were effected using NaOH in three different bath media (n-hexane, acetone or methanol) to convert starch-g-poly(vinyl acetate) to starch-g-poly(vinyl alcohol). Higher extent of solubility in hot water of the saponified form was achieved by using a bath containing n-hexane/sodium hydroxide; however, increasing the graft yield higher than 26.3% decreases the solubility. The structures and thermal stability of starch, grafted starch copolymer and saponified grafted starch copolymer were characterized by infrared spectroscopy and thermogravimetric analysis. Moreover, the rheological behavior as well as sizing performance of the saponified grafted starch copolymers were evaluated and compared with the native starch and commercial polyvinyl alcohol.     

Synthesis and characterization of xanthan gum‐g‐N‐vinyl formamide with a potassium monopersulfate/Ag(I) system

A xanthan gum‐g‐N‐vinyl formamide graft copolymer was synthesized through the graft copolymerization of N‐vinyl formamide (NVF) onto xanthan gum with an efficient system, that is, potassium monopersulfate (PMS)/Ag(I) in an aqueous medium. The effects of the concentrations of Ag(I), PMS (KHSO₅), hydrogen ion, xanthan gum, and NVF along with the time and temperature on the graft copolymerization were studied by the determination of the grafting parameters (grafting ratio, add‐on, conversion, grafting efficiency, and homopolymer) and the rate of grafting. The maximum grafting ratio was obtained at a 0.6 g/dm³ concentration of xanthan gum. All the parameters showed an increasing trend with an increasing concentration of peroxymonosulfate, except the homopolymer percentage, which showed a decreasing trend. The grafting ratio, add‐on conversion, grafting efficiency, and rate of grafting increased with the concentration of Ag(I) increasing from 0.8 × 10^?2 to 1.2 × 10^?2 mol/dm³. The optimum time and temperature for the maximum degree of grafting were 90 min and 35°C, respectively. The graft copolymer was characterized with IR spectral analysis, thermogravimetric analysis, and differential calorimetry analysis. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1637–1645, 2006     

Graft polymerization of vinyl acetate onto starch. Saponification to starch–g–poly(vinyl alcohol)

Graft polymerizations of vinyl acetate onto granular corn starch were initiated by cobalt-60 irradiation of starch-monomer-water mixtures, and ungrafted poly(vinylacetate) was separated from the graft copolymer by benzene extraction. Conversions of monomer to polymer were quantitative at a radiation dose of 1.0 Mrad. However, over half of the polymer was present as ungrafted poly-(vinyl acetate) (grafting efficiency less than 50%), and the graft copolymer contained only 34% grafted synthetic polymer (34% add-on). Lower irradiation doses produced lower conversions of monomer to polymer and gave graft copolymers with lower % add-on. Addition of minor amounts of acrylamide, methyl acrylate, and methacrylic acid as comonomers produced only small increases in % add-on and grafting efficiency. However, grafting efficiency was increased to 70% when a monomer mixture containing about 10% methyl methacrylate was used. Grafting efficiency could be increased to over 90% if the graft polymerization of vinyl acetate-methyl methacrylate was carried out near 0°C, although conversion of monomers to polymer was low and grafted polymer contained 40-50% poly(methyl methacrylate). Selected graft copolymers were treated with methanolic sodium hydroxide to convert starch–g–poly(vinyl acetate) to starch–g–poly(vinyl alcohol). The molecular weight of the poly(vinyl alcohol) moiety was about 30,000. The solubility of starch–g–poly(vinyl alcohol) in hot water was less than 50%; however, solubility could be increased by substituting either acid-modified or hypochlorite-oxidized starch for unmodified starch in the graft polymerization reaction. Vinyl acetate was also graft polymerized onto acid-modified starch which had been dispersed and partially solubilized by heating in water. A total irradiation dose of either 1.0 or 0.5 Mrad gave starch–g–poly(vinyl acetate) with about 35% add-on, and a grafting efficiency of about 40% was obtained. A film cast from a starch–g–poly(vinyl alcohol) copolymer in which homopolymer was not removed exhibited a higher ultimate tensile strength than a comparable physical mixture of starch and poly(vinyl alcohol).     

Synthesis and properties of chitosan‐modified poly(vinyl acetate)

A redox initiator, cerium ammonium nitrate, was used to initiate the graft copolymerization of vinyl acetate (VAc) onto the chitosan chain in a dispersion polymerization at 60°C. With an addition of 0.5–7.5 g of chitosan based on 50 g of VAc, the monomer conversion was found to be between 70 and 80% after 2 h of reaction. The grafting efficiency increased with the amount of chitosan added; yet, the grafting ratio increased slightly and then decreased. After the reaction, a stable dispersion system was observed and the surface of the latex particles was found to be rich in chitosan. All the experimental results indicated that the chitosan molecules not only took part in the graft copolymerization, but also served as a surfactant, providing the stability of the dispersion particles. If the dispersion aqueous solution was oven‐dried, a particulate membrane was formed. The experimental results indicated that the incorporation of poly(vinyl acetate) to the chitosan chains increased the toughness and decreased the water absorption of the chitosan material. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3057–3063, 2002     

Radiation Grafting of N-Isopropylacrylamide onto Poly(vinyl chloride) tubes by Gamma Irradiation

Summary Grafted copolymer of poly(vinyl chloride) (PVC) with N-isopropylacrylamide (NIPAAm) was prepared by radiation-grafting method using γ-ray source. NIPAAm was graft polymerized from its aqueous solution onto PVC tubes by preirradiation method, all samples were exposed in the presence of air at room temperature to ⁶⁰Co. Conditions for achieving maximum grafting yield were observed between 0.5 and 1 moldm^-3 of monomer concentration, pre-irradiation dose of PVC from 5 to 110 kGy, and reaction temperature of 323 and 333 K. Characterization of the grafted copolymer was conducted by various methods: FTIR-ATR, TGA, and SEM. The temperature-responsive behavior of grafted copolymer was studied by swelling at various temperatures and pH 6.8.     

Graft Copolymerization of Chitosan with Butyl Acrylate and Application of the Copolymers to Cotton Fabric

Graft polymerization of butyl acrylate (BuA) onto chitosan using potassium persulfate (KPS) as initiator was studied under different conditions. The grafting percentage (G%) and the grafting efficiency (GE%) increase by increasing KPS concentration up to 40 mmol/L then decrease thereafter. Another trend was observed with BuA concentration where G% increases significantly as BuA concentration increases within the range studied, i.e., 10%–100%, based on weight of chitosan sample (ows), meanwhile GE% exhibits a maximum at BuA concentration of 50% ows. Temperature acts in favor of grafting up to 65°C where maxima for both G% and GE% could be achieved. The grafting reaction is characterized by an initial fast rate during the first 60 minutes then levels off thereafter. Poly (BuA)-chitosan graft copolymers were applied to cotton fabric in presence and absence of low formaldehyde cross-linking agent. Introduction of the copolymer and the cross-linking agent to cotton fabric enhances the performance of the latter to a great extent provided that the copolymer and the cross-linking agent are applied in two subsequent steps. Fabric performance was assessed through monitoring, nitrogen content, crease recovery angle, tensile strength and elongation at break.     

Nanocomposites Based on Chitosan-Graft-Poly(N-Vinyl-2-Pyrrolidone): Synthesis,Characterization, and Biological Activity

Organophilic montmorillonite (OMMT) was synthesized by cationic exchange between Na⁺-MMT and N-octyl-N-vinyl-2-pyrrolidonium bromide. Chitosan graft copolymer nanocomposites were synthesized by grafting N-vinyl-2-pyrrolidone onto chitosan in aqueous acetic acid in the presence of OMMT using free radical polymerization. The chemical structures were verified by FTIR. Scanning electron microscopy showed a surface roughness for chitosan graft nanocomposites. Wide-angle X-ray diffraction confirmed the intercalation of grafted chitosan chains between OMMT galleries. Thermogravimetric analysis indicated that the thermal stability of grafted chitosan was enhanced by OMMT incorporation. Preliminary studies showed that the nanocomposites exhibited antimicrobial activity compared with chitosan graft copolymer.     

Graft copolymerization of methyl acrylate onto chitosan initiated by potassium diperiodatoargentate (III)

A novel efficient redox system—potassium diperiodatoargentate [Ag(III)]‐chitosan—was employed to initiate the graft copolymerization of methyl acrylate (MA) onto chitosan in aqueous alkali solution. The effects of reaction variables such as monomer concentration, initiator concentration, reaction time, and temperature were investigated and the grafting conditions were optimized. The structures and the thermal stability of chitosan and chitosan‐g‐PMA were characterized by infrared spectroscopy (IR) and thermogravimetric analysis (TGA). The solubility of chitosan‐g‐PMA in some mixed solvent was tested. The graft copolymer was shown to be an effective compatibilizer in blends of poly(vinyl chloride) (PVC) and chitosan. Finally, a mechanism is proposed to explain the formation of radicals and the initiation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 799–804, 2006     

Polydimethylsiloxane-modified chitosan I. Synthesis and structural characterisation of graft and crosslinked copolymers

Graft and crosslinked polydimethylsiloxane (PDMS)-chitosan copolymers were prepared through the reaction between mono and difunctional glycidoxypropyl-terminated PDMSs and chitosan. The transformation of amino groups of chitosan through the reaction with epoxy groups was confirmed by FT-IR and ¹³C cross-polarization (CP) magic-angle spinning (MAS)-NMR analysis. Chitosan-based materials modified with about 40% and 60% hydrophobic polydimethylsiloxane were obtained, respectively. As proved by wide angle X-ray analysis, the crystallinity of chitosan was strongly decreased through the incorporation of PDMS sequences. However, both graft and crosslinked copolymers still present a partial crystalline structure. Their X-ray patterns are not only different as compared to chitosan but also as compared to each other. For the graft copolymer, three diffraction peaks were observed at 2θ = 8.4°, 11.2° and 21.2°, indicating the formation of a new partially crystalline phase and the modification of the interplanar distances for the phases similar to chitosan. The crosslinked copolymer is even less crystalline, the peak around 2θ = 20° being strongly decreased. Different thermal behaviour of siloxane modified chitosan was registered for graft and crosslinked copolymers; the graft sample is less stable than chitosan, while the crosslinked copolymer showed an intermediate stability between chitosan and polydimethylsiloxane precursors.     

Graft copolymerization of methacrylic acid onto guar gum,using potassium persulfate as an initiator

Graft copolymerization of methacrylic acid (MAA) onto guar gum (GG) was carried out by free radical initiation mechanism by using potassium persulfate (PPS) as an initiator. It was found that % grafting, grafting efficiency, and % conversion were all dependent on the concentration of PPS, MAA, reaction temperature, and reaction time. Using PPS, the maximum % grafting was ascertained to be 241 at the optimum conditions of 60°C reaction temperature, 3 h of reaction time, 1.1 mmol of PPS, and 0.058 mol of MAA. Plausible mechanism for grafting reaction was suggested. The graft copolymer formed was characterized by Fourier transform infrared and differential scanning calorimetry. The graft copolymer formed could find applications in drug delivery. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 618–623, 2006