Graft copolymerization of acrylic acid onto guar gum

The graft copolymerization of acrylic acid (AA) onto guar gum (GOH) was carried out by a peroxydiphosphate (PDP)–silver(I) system. Grafting ratio, efficiency, add‐on, and conversion increase upon increasing the concentration of PDP and acrylic acid, whereas they decrease upon increasing the concentration of guar gum. Upon increasing the concentration of silver and hydrogen ions up to 2.0 × 10⁻³ and 4.87 × 10⁻² mol dm⁻³, respectively, the grafting ratio and efficiency increase but decrease upon further increasing the concentration. The increase in temperature from 30 to 45°C increases the grafting ratio but the conversion efficiency decreases. The optimum time period for graft copolymerization was found to be 2 h. The graft copolymers were characterized by infrared spectroscopy and thermogravimetric analysis. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 39–44, 2000     

Homogeneous and heterogeneous grafting of 4‐vinylpyridine onto chitosan

Modification of chitosan by grafting with 4‐vinylpyridine (VP) was carried out both in homogeneous and heterogeneous phases, using potassium persulfate (K₂S₂O₈) and sodium bisulfite (NaHSO₃) as redox initiators. The effect of monomer concentration, initiator concentration and redox ratio, time and temperature on the extent of grafting (G%), homopolymer formation, and the efficiency of grafting were studied. Values of grafting percentages up to 96% were reached in heterogeneous conditions and up to 130% in homogeneous conditions (in 5% acetic acid). The grafting was confirmed by FTIR and ¹H NMR spectroscopy. The grafted samples were characterized by scanning electron microscopy, X‐ray diffraction, and thermogravimetric analysis. The crystallinity of the used chitosan was not affected by grafting, it even increased slightly. 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 grafted copolymers are soluble with difficulty in warm acetic acid solution. The quaternized graft copolymer was found to be soluble in water. The biological activity of the quaternized graft copolymers (G = 130 and 80%) was investigated and was found to have an inhibition effect on both the Azotobacter fungus and the bacterium Fusarium oxysporium. The effect on the micro organisms is proportional to the amount of VP in the graft copolymer. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3308–3317, 2006     

Cu+2/mandelic acid redox pair initiated graft copolymerization acrylamide onto guar gum

The effect of reaction conditions on the grafting parameters during the grafting of acrylamide (ACM) onto guar gum (GOH) by using a Cu⁺²–mandelic acid (MA) redox couple was studied. On increasing the Cu⁺² ion concentration (0.5 × 10⁻² to 1.0 × 10⁻² mol dm⁻³), an increase in total conversion of monomer, grafting ratio, efficiency, and add on was observed. Grafting ratios increased with an increase in concentration of mandelic acid and reaches its maximum value at 0.8 × 10⁻² mol dm⁻³. It was observed that grafting onto guar gum takes place efficiently when monomer and hydrogen ion concentrations are 20.0 × 10⁻² and 2.2 × 10⁻² mol dm⁻³, respectively. Optimum temperature and time for obtaining a maximum grafting ratio and efficiency was found to be 35 ± 0.2°C and 2 h, respectively. The plausible mechanism of grafting was suggested. The graft copolymer was characterized by infrared spectroscopy and thermogravimetric analysis. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 739–745, 1999     

Studies of graft copolymerization of acrylamide onto guar gum using peroxydiphosphate–metabisulphite redox pair

The effect of reaction conditions on the grafting parameter during grafting of acrylamide onto guar gum has been studied using peroxydiphosphate–metabisulphite redox pair at 35 °C. Grafting ratio, efficiency and add‐on all increase as the concentrations of peroxydiphosphate and acrylamide increase up to 40.0 × 10⁻³ mol dm⁻³ and 40.0 × 10⁻² mol dm⁻³, respectively. It has been observed that the optimum concentrations of metabisulphite and guar gum for obtaining high grafting ratio, efficiency, add‐on and conversion are 6.0 × 10⁻³mol dm⁻³ and 91.7 × 10⁻² g dm⁻³, respectively. © 2000 Society of Chemical Industry     

Comparative studies on the flocculation characteristics of polyacrylamide grafted guar gum and hydroxypropyl guar gum

The synthesis of two polysaccharide‐based graft copolymers with acrylamide, guar gum grafted polyacrylamide (GG‐g‐PAM) and hydroxypropyl guar gum grafted polyacrylamide (HPG‐g‐PAM) is described. The graft copolymers have been characterized by viscometry, infrared spectroscopy and thermal analysis. The flocculation characteristics of the graft copolymers have been studied in kaolin, iron ore, and silica suspensions. For the base polysaccharides guar gum (GG) and hydroxypropyl guar gum (HPG), it is observed that GG exhibits better performance than HPG in all three suspensions. For the graft copolymers, HPG‐g‐PAM shows better performance than GG‐g‐PAM. The flocculation characteristics of the best performing graft copolymer (HPG‐g‐PAM) are compared with various commercially available flocculants in the three suspensions mentioned above. © 2001 Society of Chemical Industry     

Ultraviolet‐radiation‐induced graft copolymerization of methyl acrylate onto the sodium salt of partially carboxymethylated guar gum

In an attempt to modify the sodium salt of partially carboxymethylated guar gum (Na‐PCMGG; degree of substitution = 0.291), we studied the ultraviolet‐radiation‐induced graft copolymerization of methyl acrylate with ceric ammonium nitrate as a photoinitiator. The influence of the grafting yield was studied as a function of the different reaction parameters, and the optimum reaction conditions for photografting were determined. The various reaction parameters included the photoinitiator, nitric acid, and monomer (methyl acrylate) concentrations, the reaction time, the temperature, and the amount of the substrate. A kinetic scheme for photografting copolymerization was proposed, and the results were in good agreement with the kinetic scheme. The graft copolymerization of methyl acrylate onto Na‐PCMGG (degree of substitution = 0291) in the presence and absence of ultraviolet radiation was also carried out for the study of the efficiency of the photoinitiator. The influence of carboxymethyl groups added to the guar gum molecule on its behavior toward ultraviolet‐radiation‐induced grafting with methyl acrylate was also investigated. The evidence of photografting was ascertained with IR spectroscopy and scanning electron microscopy techniques. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1977–1986, 2005     

Grafting of polyacrylonitrile onto guar gum under microwave irradiation

Using microwave (MW) irradiation grafting of polyacrylonitrile (PAN) onto guar gum in water was done without using any radical initiator or catalyst within a very short reaction time. The extent of grafting could be adjusted by controlling the reaction conditions and maximum percentage grafting (%G) of about 188% was obtained under optimum conditions in 1.66 min. The average molecular weight of the grafted PAN chains and water‐retention power of the alkali hydrolyzed MW‐grafted gums were also determined and compared with those of the conventionally synthesized (cs) graft copolymer. A representative MW‐grafted copolymer, guar‐g‐polyacrylonitrile was characterized by IR, NMR, XRD, TGA, and elemental analysis. A plausible mechanism for the grafting under MW was proposed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1569–1575, 2004     

Multifunctional,pH‐responsive graft copolymer prepared from deproteinized natural rubber and 4‐vinylpyridine via emulsion polymerization

We investigated the synthesis of a pH‐responsive graft copolymer of natural rubber and 4‐vinylpyridine. The grafting reaction was carried out using deproteinized natural rubber (DPNR) latex, with potassium persulfate as a free radical initiator. The pH responsiveness of the graft copolymer was investigated using water swelling and contact angle measurements, and was compared with that of pure DPNR. The graft copolymer was found to become responsive in solution at a pH of around 4. Indigo carmine adsorption studies identified the Langmuir isotherm, suggesting monolayer coverage. The adsorbed indigo carmine, a model anionic drug, and carbon dots, an emerging nanosized fluorophore, could be released from the graft copolymer by lowering the pH of the solution. The graft copolymer was tested as a heavy metal adsorbent, and demonstrated selectivity to copper(II) ions. The graft copolymer of 4‐vinylpyridine and DPNR developed in this study is therefore a multifunctional, pH‐responsive material with a wide range of potential applications, including sensing and catalysis, as a biomedical material and as an adsorbent. © 2017 Society of Chemical Industry     

Modification of guar gum through grafting of 4‐vinyl pyridine using potassium peroxymonosulphate/ascorbic acid redox pair

In the present article, the graft copolymerization of 4‐vinyl pyridine onto guar gum initiated by potassium peroxymonosulphate/ascorbic acid redox pair in an aqueous medium was studied gravimetrically under a nitrogen atmosphere. Grafting ratio, grafting efficiency, and add on increased on increasing the concentration of potassium peroxymonosulphate from 5.0 × 10^?4 to 10 × 10^?4 mol/L and ascorbic acid concentration from 0.4 × 10^?3 to 2.0 × 10^?3 mol/L. On increasing the hydrogen ion concentration from 2.5 × 10^?3 to 10.0 × 10^?3 mol/L, grafting ratio, efficiency, add on and conversion were increased. Maximum grafting was obtained when guar gum and monomer concentration were 1.0 g/L and 20.0 × 10^?2 mol/L, respectively. An increase in temperature from 30 to 35°C increased the grafting ratio, but conversion and homopolymer decreased. The graft copolymers were characterized by IR spectroscopy and thermogravimetric analysis. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis and characterization of grafted carboxymethyl guar gum

Graft copolymers of carboxymethyl guar gum (CMGG) and polyacrylamide (PAM) have been synthesized by grafting polyacrylamide chains onto carboxymethyl guar gum backbone using a ceric‐ion‐induced solution polymerization technique. By varying the amount of initiator, three different grades of graft copolymers are synthesized. The characterization of graft copolymer is carried out by FTIR, NMR, intrinsic viscosity measurement, SEM, SLS, DTG, and rheology. A comparison of flocculation efficiency of CMGG and its graft copolymer shows that the graft copolymer exhibits better flocculation performance. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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     

黄原胶与丙烯酰胺接枝共聚反应的研究

以过硫酸铵为引发剂,在氮气保护下,研究了黄原胶与丙烯酰胺的接枝共聚反应。考察了单体浓度、引发剂浓度、反应温度和反应时间等因素对接枝率及接枝效率的影响,探讨了过硫酸铵引发黄原胶接枝丙烯酰胺共聚反应的基本规律。采用红外光谱、X射线粉末衍射对接枝共聚物的结构进行研究,用热重分析法表征了产物的热性能,并初步探讨了接枝机理。结果表明,过硫酸铵能有效地引发黄原胶与丙烯酰胺的接枝共聚反应,并且接枝率和接枝效率随单体浓度、引发剂浓度、反应温度的变化出现极大值,随反应时间的延长不断上升,直至基本不变。     

Radiation‐induced graft copolymerization of 2‐vinylpyridine and styrene onto isotactic polypropylene fiber

Isotactic polypropylene fiber (IPP) was graft‐copolymerized using 2‐vinyl pyridine (2‐VP) and styrene (sty) as the monomers by the mutual irradiation method in air. The percentage of grafting was determined as a function of various reaction parameters and it was found that the maximum grafting of 2‐VP (114%) and sty (76%) was obtained at an optimum dose of 1.08 × 10⁴ and 0.64 × 10⁴ Gy using 1.8 × 10⁻² mol of 2‐VP and 4.3 × 10⁻² mol of sty, respectively. The graft copolymers were characterized by differential scanning calorimetric analysis and isolation of the grafted chains from the grafted iPP samples. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2959–2969, 1999     

A study toward the physicochemical properties of graft copolymer (partially carboxymethylated guar gum‐g‐N,N′‐dimethylacrylamide): Synthesis and characterization

Unreported graft copolymer of N,N′‐dimethylacrylamide (DMA) with partially carboxymethylated guar gum (CmgOH) has been synthesized and the reaction conditions have been optimized for affording maximum grafting using a potassium peroxymonosulphate (PMS)/thiourea (TU) redox initiators under nitrogen atmosphere. The study of graft copolymerization has been performed to observe maximum value of grafting parameters except percentage of homopolymer by varying the concentrations of DMA, PMS, and TU. The grafting parameters increase continuously on increasing the concentration of DMA from 8 × 10^?2 to 24 × 10^?2 mol dm^?3, PMS from 5 × 10^?3 to 21 × 10^?3 mol dm^?3, and TU from 1.6 × 10^?3 to 4.8 × 10^?3 mol dm^?3. The optimum temperature and time for grafting of DMA onto CmgOH were found to be 35°C and 120 min, respectively. The water‐swelling capacity of graft copolymer is investigated. Flocculation property for both coking and noncoking coals is studied for the treatment of coal mine waste water. The graft copolymer is characterized by Fourier transform infrared spectroscopy and thermogravimetric analysis. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

瓜尔胶/丙烯酰胺的反相乳液接枝共聚及其性能研究

以硝酸铈铵/硝酸为引发剂,在反相乳液中引发瓜尔胶/丙烯酰胺的接枝共聚反应。考察了单体丙烯酰胺/瓜尔胶（AM/GG）,引发剂浓度,反应温度和反应时间对接枝聚合的影响规律。实验结果显示：当AM/GG=3:2,引发剂浓度为4mmol/l,反应时间为4h,反应温度为45℃时,接枝共聚反应的接枝率和单体转化率分别为147.05%和87.7%。接枝共聚物的最大分子量可达到1.73?06.红外光谱(IR)和扫描电镜(SEM)分析证明了AM确实接枝到GG分子链上,热重分析(TGA)显示接枝的AM单体并未影响GG的热稳定性。     

Study of modified polypropylene nonwoven cloth. I. graft copolymerization of 4‐vinylpyridine onto polypropylene nonwoven cloth by preirradiation method

Polypropylene (PP) nonwoven cloth was grafted with 4‐vinylpyridine (4‐VP) by a preirradiation method. The effects of preirradiation conditions on the mechanical properties of preirradiated PP nonwoven cloth and the percentage of grafting (Pg) of 4‐VP onto the preirradiated PP nonwoven cloth were systematically investigated. The results indicated that the mechanical properties of preirradiated PP nonwoven cloth decreased with increasing irradiation dose and that the Pg was greatly affected by the concentration of monomer, irradiation dose, grafting reaction temperature, and the addition of inhibitor and inorganic acid in the grafting reaction system. The grafted nonwoven cloth samples were characterized using IR spectroscopy and SEM. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1861–1868, 2000     

Photo‐induced graft copolymerization of acrylonitrile onto sodium salt of partially carboxymethylated guar gum

Photo‐induced graft copolymerization of acrylonitrile (AN) onto sodium salt of partially carboxymethylated guar gum (Na‐PCMGG, = 0.291) was carried out in an aqueous medium using ceric ammonium nitrate (CAN) as photo‐initiator to synthesize a novel graft copolymer, Na‐PCMGG‐g‐PAN, which may find potential application as a superabsorbent hydrogel. Studying the influence of concentrations of photo‐initiator (CAN), nitric acid, monomer (AN) as well as reaction time, temperature, and amount of substrate on the grafting yields, the reaction conditions for optimum grafting were evaluated. Maximum values of the grafting yields achieved were %G = 285.77 and %GE = 70.76 at optimized conditions. The proposed kinetic scheme could explain very well the experimental results. The influence of different kind of acids on the grafting yields was also studied. Grafting process was confirmed with the help of FTIR, thermal (TGA/DSC), and SEM techniques. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41371.     

Nitroxide‐mediated homopolymerization and copolymerization of 2‐vinylpyridine with styrene

Homopolymerization and copolymerization of 2‐vinylpyridine (2VP) with styrene (S) at 125°C in the presence of 2,2,6,6‐tetramethyl piperidin‐1‐yloxyl (TEMPO) radicals have been studied. The homopolymerization was carried out with 2,2′‐azobis(isobutyronitrile) (AIBN) as a thermal initiator or without AIBN in the initial reaction mixture. In the copolymerization initiated with AIBN, the molar fraction of 2VP in the feed, F_2VP, varied in the range of 0.1–0.9; F_2VP = 0.65 was found to be the azeotropic composition. The linear semilogarithmic time–conversion plots demonstrated a pseudoliving nature of the polymerizations under study. The molecular weight–conversion dependences indicated the participation of side reactions, diminishing the number of TEMPO‐terminated polymer chains. The synthesized homopolymers and copolymers were characterized using size‐exclusion chromatography (SEC), nitrogen analysis, and NMR spectroscopy. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2024–2030, 2001     

Functionalization of crosslinked polyacrylamide through γ‐radiation‐induced grafting of 4‐vinylpyridine

Crosslinked polyacrylamide beads were irradiated in air with a Co⁶⁰ γ‐radiation source. The preirradiated beads were graft‐copolymerized through heating with 4‐vinylpyridine in the presence of benzoyl peroxide. Grafting was studied as a function of various reaction parameters and was determined from the increase in the weight of the original polymer and the estimation of pyridine pendants in the homopolymer‐free graft copolymer. Although making the polymer basic in character, this modification retained the hydrophilic nature of polyacrylamide. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2613–2620, 2002     

Preparation and catalytic application of poly 4‐vinylpyridine microspheres

Poly 4‐vinylpyridine (P4VP) microspheres between 170 and 728 nm were synthesized by Emulsifier‐Free Emulsion Polymerization. The monomer concentration, ionic strength, and initiator concentration affected the microsphere size and size distribution. The increasing monomer concentration led to the increase of microsphere size, whereas the size distribution of the resultant P4VP microspheres increased with the increasing ionic strength of the reaction systems. Mo(O₂)₂O·2DMF was successfully anchored onto the P4VP microspheres by ligand exchange, and the heterogeneous catalyst showed high‐catalytic activity for epoxidation of cis‐cyclooctene with environmentally friendly hydrogen peroxide. The size and morphology of the supported microspheres has important influence on the catalytic activity. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010