graft copolymerization

The preparation of SRC-g-PAA was carried out through chemical modification of semi- refined -carrageenan that was prepared from K. alvarezii (Doty) Doty ex P. Silva,by introducing vinyl monomer on the carrageenan through free-radical graft copolymerization method.The optimization process was performed in order to study the effect of crosslinker, monomer, initiator and alkaline hydrolysis on the swelling behaviour of SRC-g- PAA.

Contour plot of the two most significant parameters that contribute to the results shown in Figure 3 suggests that the results are not optimized yet and need further improvement for optimization. A large number of work on radiation-induced graft copolymerization (Chauhan, Guleria et al.,2005, Kang, Jeun et al.,2007, Seko, Ninh et al.,2010, Wojnárovits, Földváry et al.,2010, Nasef and Güven,2012, Madrid, Nuesca et al.,2013, Mohamed, Tamada et al.,2013, Sharif, Mohamad et al.,2013) reported that percentage of grafting increase with the increasing of irradiation dose as shown in Figure 4. This is mainly due to the formation of more free radicals at higher irradiation doses which increasing the accessibility of monomer towards the active sites (Nasef and Güven,2012). Madrid, Nuesca et al. (2013) also evidenced the same phenomena where the percentage of grafting of GMA onto water hyacinth increase with the increase of irradiation dose(Madrid, Nuesca et al.,2013). The scanning electron microscopy images of grafted material in Fig. 5(B) show a smooth surface and the evidence of thick coating of GMA on the fiber. Raw kenaf in Fig. 5(A) is characterized with a rough, dirty surface and glued together because it is coated with non-cellulose compound. Fig. 6 shows the FTIR spectra of raw kenaf fiber, NaClO 2 treated kenaf and GMA grafted kenaf. As shown in the spectrum of GMA grafted

The fibers were immersed in water before the graft-copolymerization process to activate the reaction sites on the fiber surface. After that the known amount of ascorbic acid was mixed with hydrogen peroxide and the mixture was poured into the reaction vessel containing the fibers. The monomers MMA and ANwere added into different reaction vessels containing fibers along with the initiators. The reaction vessel was placed in a microwave at 70 watt power which was having a microwave (IFB 20PGI) frequency of 2450 MHz. The reaction parameters were determined to get the maximum graft yield.

chitosan and it is considered to be a promising approach for designing a wide variety of molecular matrices. Graft copolymerization of acrylamide on chitosan using ammonium persulfate as an initiator, was prepared [15]. The effect of temperature, pH of the medium and concentrations of initiator, chitosan and acrylamide on grafting kinetics and efficiency were established. Graft copolymerization of mixtures of acrylic acid and acryla- mide onto chitosan using potassium per sulphate as initia- tor and methylenebisacrylamide as a cross-linker was carr- ied [16]. Semi-interpenetrating polymer network hydrogel was pre-pared to recognize hemoglobin, by molecularly imprinted method, in mild aqueous media of chitosan and acylami-de in the presence of N, N’-methylenebisa- crylamide as the cross linking agent [17].

The present work focused on the design of drug delivery system (DDS) based on a pH-sensitive hydrogel. The hydrogels were prepared via graft copolymerization of acrylonitrile (AN) monomer was directly grafted onto alginate using ammonium persulfate (APS) as an initiator and sodium hydroxide (NaOH) as a crosslinking agent under an inert atmosphere. Porous structure of hydrogel was essential in this system to yield a large surface area so that Metronidazole release could be facilitated. Due to the reversible swelling behavior of the hydrogels, the synthesized networks can sense the environmental pH change and achieve an oscillatory release pattern. The concentration of released Metronidazole loaded was monitored at 278 nm on the UV spectrophotometer.

In this study, the degree of the microfi brillation of cellu- lose achieved by ultra high-pressure counter-collision treat- ment was studied by scanning electron microscopy (SEM). Using the resultant micropulverized cellulose emulsion, we attempted compositing with vinyl polymers through knead- ing as well as graft copolymerization of methyl methacrylate (MMA) onto the activated cellulose by using ceric ammo- nium nitrate (CAN) as initiator, and evaluated the effects of the counter-collision treatment. This newly developed approach offers new opportunities for creating innovative products derived from biomass.

Graft copolymerization is an attractive means for modifying base polymers because grafting frequently results in the superposition of properties relating to the backbone and pendant chains. Considerable interest has been focused on chemical modification by free radical graft copolymerization of hydrophilic and hydrophobic vinyl monomers biopolymers such as polysaccharides 1-3 . These biodegradable and low

As the present study was confined to granular starch, the temperature was not allowed to exceed the gelatinization temperature. The result obtained for the graft copolymerization at temperature between 30 and 50°C are tabulated in Table 3. Table 3, shows the effect of polymerization temperature on the %GE and %G. It is observed that higher the temperature, the higher the %GE and %G. This favorable effect of temperature on grafting could be ascribed to (1) increase in the mobility of monomer molecules and their collision with starch macro radicals, and (2) increased propagation of starch grafts.

A doubly modified cellulose, St-g- polyacrylonitrile, was prepared using ceric-initiated graft polymerization of acrylonitrile (AN) onto starch. The study of FTIR spectra and thermogravimetric analysis provide that the graft copolymerization takes place. the synthetic conditions were systematically optimized through studying the influential factors including temperature, concentration of the initiator, the monomer AN, and the substrate. The effect of the individual factors was investigated by calculating the grafting parameters, i.e., grafting ratio (Gr), add- on value, homopolymer content (Hp), and conversion. Under optimum conditions (starch 3.0 wt%, AN 0. 5 molL -1 , CAN 0.004 molL -1 , reaction

PAAm was simultaneously grafted onto CMC in a homogenous medium using Ceric Ammonium Nitrate as a radical initiator under an inert atmosphere.The initiator, polysaccharide and the monomer concentration, as well as the reaction temperature four important variables affected on graft copolymerization, were investigated. The mechanism of copolymerization of AAm onto CMC is shown in Scheme 1. At the first step, a complex between the Ce 4+ ion with the oxygen atom at the

Some natural occurring as well as synthetic polymers has commercial application 1-3 . The modification of polymers has received much attention recently. Graft copolymerization is one of the most promising techniques to impart a variety of functional groups to a polymeric back bone. Chemically modified natural fibres through graft copolymerization are useful in many applications in diverse fields 4-8 . In continuation of our earlier reported work of modification of natural polymers by grafting technique, we have grafted binary mixtures of vinyl monomers onto silk fibre. Literature survey reveals that grafting of vinyl monomers onto the polymeric fibre backbones improves their chemical resistance, moisture repellency and dye uptake 9-17 . In literature a number of initiators like ceric ammonium nitrate (CAN) 18 , benzoyl peroxide 19 , KMnO 4 -oxalic

An unreported graft copolymer was synthesized by carrying out ceric ammonium nitrate initiated graft copolymerization of acrylonitrile onto sodium salt of partially carboxymethylated sodium alginate. The synthetic conditions were systematically optimized through studying the effective reaction parameters including reaction time, temperature and concentrations of monomer, initiator and nitric acid as well as amount of substrate. The influence of these reaction parameters on graft copolymer yields was investigated. A possible initiation mechanism of grafting was proposed and the experimental data of the graft copolymerization were found to agree well with the proposed kinetic scheme. The overall activation energy for the grafting was estimated to be 13.02 kJ/mole. The products of grafting were characterized by FTIR, TGA and SEM data.

becomes evident from this figure that %G increases with the rise of temperature from15 o C to 40 o C beyond which it decreases with further increase in temperature. The behaviour of variation of %G with temperature, in the temperature range of 15 o C to 40 o C, can be ascribed to the fact that with the initial rise in temperature, as the kinetic energy of the molecules increases, more and more radicals get drifted at a faster rate to the Na-PCMSA backbone, resulting in the increasing in %G. However, after reaching the optimum temperature, with further increase in temperature, a considerable amount of homopolymer is formed, which results in an increase in the viscosity of the reaction medium and it provides a hindrance for the radicals to move forward to the active sites of Na-PCMSA backbone resulting in the decrease in the grafting yields. In addition, at higher temperature, the substantial increase in the rate of chain transfer and chain termination reactions between grafted chains and monomer molecules also would lead to the observed decrease in %G as well as %GE. Similar results are also reported in the literature[7, 10, 14, 26-28]. Thus, from the above discussion the optimal reaction conditions evaluated in the case of graft copolymerization of EA on to Na-PCMSA ( DS = 605) are: Na-PCMSA ( DS = 0.605) = 1.5 g (dry basis); [CAN] = 0.04 mol.L -1 ; [HNO 3 ] = 0.40 mol.L -1 ;

A general procedure for chemically graft copolymerization of Acrylamide (AAm) and 2- Acrylamido-2-methyl propan sulfonic acid (AMPS) onto gelatin backbones was conducted as follows. Gelatin (1.0 g) was added to a three-neck reactor equipped with a mechanical stirrer (Heidolph RZR 2021, three blade propeller type, 300 rpm), including 35 mL doubly distilled water. The reactor was immersed in a thermostated water bath preset at a desired temperature (70 o C). Then 0.10 g of APS as

Figure 6 portrays the effect of lignin content of banana fiber on grafting yield. The grafting yield depicts a decreasing trend with increase in lignin content. Grafting was found to be in negligible amount on virgin banana fibers which denotes that the existence of lignin naturally inhibits graft copolymerization. Grafting yield obtained at mild delignification happens to be little and this might be due to the trapping of growing polymer radical in lignin network. Therefore, the possibilities of grafting chain propagation remains limited (Rizk et al, 1984). Fibers with residual lignin ranging 3.9-1.4% are capable of generating high grafting yield because they are highly reactive and proficient of accessible surface area by crystal regions of cellulose exposure at secondary layer (Ghosh et al, 1998). In agreement, fibers with 2.86% of lignin residue had generated grafting yield about 308%. The occurrence of grafting was confirmed with FTIR analysis (Figure 7). Apart from the common peaks which exist in fibers, there was seen an elongated peak at 1733cm -1 which was assigned to C=O vibration indicating the presence of ester group –COO- contribution from gma having been used. Appearance of epoxy characteristic peak at 1237 and 901 cm -1 in grafted fibers suggests successful grafting of gma onto banana fibers as well. Few researchers had reported the presence of these three peaks in their studies on radiation grafting too (Jordan et al, 2013; Wojnarovits et al, 2010). Another prominent evidence of grafting is clearly shown on SEM images in Figure 8. The grafted delignified fibers were coated with a thin layer of gma copolymer.

Original citation: Bao, Xianyang, Yu, Long, Simon, George P., Shen, Shirley, Xie, Fengwei, Liu, Hongsheng, Chen, Ling and Zhong, Lei2018 Rheokinetics of graft copolymerization of acrylam[r]

The effect of temperature on the graft yield was more pronounced than that of the initiator concentration. When the reaction temperature was increased from 23˚C to 50˚C and 80˚C, the graft yield greatly increased. That could be attri- buted to the increase in temperature leading to more grafting sites being pro- duced on the surface of the silk fibers, and consequently to the increase in graft yield. On the other hand, increasing the temperature also increased the rate of bi-radical termination. Therefore, when the temperature was further increased from 50˚C to 80˚C, the graft yield decreased again.

Temperature-responsive poly(N-isopropylacrylamide) (PNIPAM) was grafted onto Polystyrene (PS) surfaces via atmospheric plasma treatment of NIPAM monomer coated PS surface. The PS was pretreated by plasma before coating. Fourier Transform Infrared Spectroscopy (FTIR) confirms the grafting of PNIPAM on PS surface. AFM images revealed distinctly different surface topographies of PNIPAM grafted PS compared to original and plasma treated PS. Water contact angles for PNIPAM grafted PS surface increased dramatically approximately at 32 o C, confirming the temperature sensitivity of the PNIPAM grafted surfaces. The effects of grafting parameters on the graft yield, i.e., pre-plasma treatment time, post-plasma treatment time, and coated monomer amount, were studied. The plasma pretreatment activated the surface and was beneficial to the graft copolymerization. However, more than 1 or 2 min pretreatment time decreased the graft yield indicating that plasma surface activation is not linearly related the treatment time. The post-plasma treatment induces the graft copolymerization. However, etching occurred and decreased the graft yield at higher post-treatment time (>2 min). 55% monomer solution higher than 109 µl decreased the graft yield

A novel biosuperabsorbent hydrogel was prepared by simultaneously graft copolymerization of acrylic acid and acrylonitrile onto CMC in the presence of a crosslinking agent. The resultant superabsorbent had a large degree of water absorbency. Evidence of grafting was obtained by comparison of FTIR ,TGA and SEM spectra of initial substrates and biosuperabsorbent hydrogel. The study of FTIR spectra shows that in the hydrogel spectrum a new absorptions bands at 1715 cm -1

The water soluble polymers have wide application in industries due to its unique properties[1]. Since they are biodegradable, their utilization is restricted. Chemical modification of conventional polymers can provide a potential route for significantly altering their physical and chemical properties. The modification is brought about by graft copolymerization technique.[2] Grafting techniques are successful in modifying some of the properties of natural[3] and synthetic polymers. Various initiators are employed for grafting technique.[4,5] The graft polymerization occurs either through abstraction of hydrogen atom from the backbone polymer containing a hydroxyl group or an amino group.[6,7]