Graft copolymers of starch and poly(ethyl acrylate) dilution effects

Graft copolymerization of ethyl acrylate onto starch initiated by ceric ion in an aqueous medium was studied at 29°C. It was found that the grafting frequencies and molecular weights of grafted poly(ethyl acrylate) changed from 2 graft polymer molecules per 10⁴ anhydroglucose units (AGU) and 3.03 · 10⁵ to 34 and 6.80 · 10⁵, respectively, when the starch content was varied from 1.0 wt.-% to 0.2 wt.-%. The influence of dilution of ceric ion on the extent and rate of graft polymerization of ethyl acrylate onto starch was also examined.     

Synthesis and characterization of butyl acrylate graft sodium salt of partially carboxymethylated starch

Graft copolymers were synthesized by graft copolymerization of butyl acrylate (BA) onto sodium salt of partially carboxymethylated starch (Na‐PCMS). Ceric ammonium nitrate (CAN), a redox initiator, was used for initiation of graft copolymerization reaction. All the experiments were run with Na‐PCMS having degree of substitution, DS = 0.35. The grafting reaction was characterized by parameters such as % total conversion (%Ct), % grafting (%G), % grafting efficiency (%GE), and % add‐on. Graft copolymers were characterized by infrared spectral analysis and scanning electron microscopy. Variables affecting graft copolymerization reaction such as nitric acid concentration, reaction time, reaction temperature, and ceric ion concentration were investigated. The results revealed that 0.3M CAN as initiator, 0.3M HNO₃, with reaction time 4–4.5 h at 25–30°C were found as suitable parameters for maximum yield of graft copolymerization reaction. © 2006 Wiley Periodicals, Inc. JAppl Polym Sci 102: 3334–3340, 2006     

Ceric(IV) ion‐induced graft copolymerization of acrylamide and ethyl acrylate onto cellulose

Graft copolymerization of acrylamide (AAm) and ethyl acrylate (EA) onto cellulose has been carried out from their binary mixtures using ceric ammonium nitrate (CAN) as an initiator in the presence of nitric acid at 25 ± 1 °C. The extent of acrylamide grafting increased in the presence of the EA comonomer. The composition of the grafted chains (F_AAm = 0.52) was found to be constant during the feed molarity variation from 7.5 × 10^?2 to 60.0 × 10^?2 mol L^?1, whereas the composition of the grafted chains (F_AAm) was found to be dependent on feed composition (f_AAm) and reaction temperature. The effects of ceric(IV ) ion concentration, reaction time and temperature on the grafting parameters have been studied. The grafting parameters showed an increasing trend up to 6.0 × 10^?3 mol L^?1 concentration of CAN at a feed molarity of 30.0 × 10^?2 mol L^?1 and showed a decreasing trend on further increasing the concentration of CAN (>6.0 × 10^?3 mol L^?1) at a constant concentration of nitric acid (5.0 × 10^?2 mol L^?1). The composition of the grafted chains (F_AAm) was determined by IR spectroscopy and nitrogen content and the data obtained then used to determine the reactivity ratios of the acrylamide (r₁) and ethyl acrylate (r₂) comonomers by using a Mayo and Lewis plot. The reactivity ratios of acrylamide and ethyl acrylate were found to be r₁ = 0.54 and r₂ = 1.10, respectively, and hence the sequence lengths of acrylamide (m?M₁) and ethyl acrylate (m?M₂) in the grafted chains are arranged in an alternating form, as the product of the reactivity ratios of acrylamide and ethyl acrylate (r₁ × r₂) is less than unity. The rate of graft copolymerization of the comonomers onto cellulose was found to be dependant on the ‘squares’ of the concentrations of the comonomers and on the ‘square root’ of the concentration of ceric ammonium nitrate. The energy of activation (ΔE_a) of graft copolymerzation was found to be 5.57 kJ mol^?1 within the temperature range from 15 to 50 °C. On the basis of the results, suitable reaction steps have been proposed for the graft copolymerzation of acrylamide and ethyl acrylate comonomers from their mixtures. Copyright © 2005 Society of Chemical Industry     

Graft copolymerization of methyl acrylate onto sago starch using ceric ammonium nitrate as an initiator

The graft copolymerization of methyl acrylate onto sago starch was carried out by a free radical initiating process. The free radicals were produced by the chemical initiation method in which ceric ammonium nitrate was used as an initiator. It was found that the percentages of grafting, grafting efficiency, and rate of grafting were all dependent on the concentration of ceric ammonium nitrate (CAN), methyl acrylate (MA), sago starch (AGU), mineral acid (H₂SO₄), and reaction temperature and period. The variables affecting the graft copolymerization were thoroughly examined. The optimum yield of grafting was obtained when the concentration of CAN, MA, AGU, and H₂SO₄ were used at 8.77 × 10⁻³, 0.803, 0.135, and 0.175 mol L⁻¹, respectively. The optimum reaction temperature and period were 50°C and 60 min, respectively. The rate of graft polymerization was explored on the basis of experimental results and reaction mechanism. The evidence of grafted copolymers was investigated by using FTIR spectroscopy, TG, and DSC analysis. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 516–523, 2000     

Graft copolymerization of starch with methyl acrylate: An examination of reaction variables

Starch-g-poly(methyl acrylate) (S-g-PMA) copolymers containing 55–60% PMA were prepared from cornstarch, high amylose cornstarch, and waxy cornstarch with ceric ammonium nitrate initiation. Graft copolymers were characterized with respect to % PMA homopolymer, % conversion of monomer to polymer, grafted PMA content, grafting frequency, and the molecular weight and molecular weight distributions of PMA grafts. Variables investigated in the graft copolymerization reaction were nitric acid concentration, ceric ion-to-starch ratio, reaction time, gelatinization of the starch, and reactant concentration in water. At high reactant concentrations, high conversions of methyl acrylate to grafted PMA could be obtained in less than 0.5 h at 25°C. © 1993 John Wiley & Sons, Inc.     

Preparation,characterization, and properties of cellulose–polyacrylamide graft copolymers

Graft copolymers of acrylamide on cellulose materials (α‐cellulose 55.8%, DP 287.3) obtained from Terminalia superba wood meal and its carboxymethylated derivative (DS 0.438) were prepared using a ceric ion initiator and batch polymerization and modified batch polymerization processes. The extent of graft polymer formation was measured in graft level, grafting efficiency, molecular weight of grafted polymer chains, frequency of grafting as a function of the polymerization medium, and initiator and monomer concentrations. It was found that the modified batch polymerization process yielded greater graft polymer formation and that graft copolymerization in aqueous alcohol medium resulted in enhanced levels of grafting and formation of many short grafted polymer chains. Viscosity measurements in aqueous solutions of carboxymethyl cellulose‐g‐polyacrylamide copolymer samples showed that interpositioning of polyacrylamide chains markedly increased the specific viscosity and resistance to biodegradation of the graft copolymers. The flocculation characteristics of the graft copolymers were determined with kaolin suspension. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 913–923, 2003     

Graft copolymerization of acrylamide–methylacrylate comonomers onto cellulose using ceric ammonium nitrate

The graft copolymerization of acrylamide–methylacrylate comonomers was carried out using ceric ammonium nitrate as initiator in the presence of nitric acid at 25 ± 1°C. The effects of feed molarity, feed composition, reaction time, and temperature on graft yield (%G) and other grafting parameters were investigated. The determination of rate of ceric (IV) ions disappearance as a function of feed molarity and reaction time was useful in the determination of the rate of ceric (IV) ions consumption during graft copolymerization. The graft yield (%G) in the presence of acrylamide increases because of the synergistic effect of acrylamide comonomer. The composition of the grafted chains (F_AAm) varies on varying the feed composition and reaction temperature but is almost constant during feed molarity variation. The Mayo and Lewis method was used to determine the reactivity ratios of acrylamide (r₁) and methylacrylate (r₂), which are 0.65 and 1.07, respectively. The product of reactivity ratio (r₁ r₂) is less then unity; hence, an alternate arrangement of comonomer blocks in the grafted copolymer chain is proposed. The rate of graft copolymerization of comonomers onto cellulose is second power to the concentration of comonomers and square root to the concentration of ceric ammonium nitrate. Suitable reaction steps for graft copolymerization of comonomers onto cellulose are proposed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2631–2642, 2002     

Graft copolymerization of acrylamide onto cellulose in presence of comonomer using ceric ammonium nitrate as initiator

The graft copolymerization of acrylamide (AAm) and ethylmethacrylate (EMA) monomers onto cellulose has been carried out using ceric ammonium nitrate (CAN) as initiator in presence of nitric acid at (25 ± 1)°C and varying feed molarity from 7.5 × 10^?2 mol dm^?3 to 60.0 × 10^?2 mol dm^?3 at fixed feed composition (f_AAm = 0.6). The graft yield (%G_Y) has shown a linear increasing trend upto a feed molarity of 37.5 × 10^?2 mol dm^?3. The composition of grafted copolymer chains was found to be constant (F_AAm = 0.56) during feed molarity variation but shown variations with feed composition (f_AAm) and reaction temperature. The grafting parameters have shown increasing trends up to 7.5 × 10^?3 mol dm^?3 concentration of ceric (IV) ions and decreased on further increasing the concentration of ceric (IV) ions beyond 7.5 × 10^?3 mol dm^?3. The IR and elemental analysis data were used to determine the composition of grafted chains (F_AAm) and reactivity ratio of acrylamide (r₁) and ethylmethacrylate (r₂) comonomers. The reactivity ratio for acrylamide (r₁) and ethylmethacrylate (r₂) has been found to be 0.7 and 1.0 respectively, which suggested for an alternate arrangement of average sequence length of acrylamide (mM?₁) and ethylmethacrylate (mM?₂) in grafted chains. The rate of graft copolymerization of comonomers onto cellulose was found to be proportional to square concentration of comonomers and square root to the concentration of ceric (IV) ions. The energy of activation (ΔEa) of graft copolymerization was found to be 9.57 kJ mol^?1 within the temperature range of 20–50°C. On the basis of experimental findings, suitable reaction steps have been proposed for graft copolymerization of selected comonomers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2546–2558, 2006     

Preparation of conductive nylon 6 film

Electrically conducting nylon 6 films was prepared by introducing amide group or cyan group into the nylon 6 film and then introducing Cu_xS, which is known as the p-type semiconductor, into the grafted nylon films. The graft copolymerization of acrylamide (AM) and acrylonitrile (AN) onto nylon 6 film was investigated using ceric salt as the initiator. The graft yield was influenced by the concentration of ceric salt, sulfuric acid and monomer, and the reaction time. The optimum conditions for the introducing of Cu_xS were studied. Electrical conductivity of Cu_xS-treated nylon film was found to be higher by order of 10⁹ than that of the original nylon 6 film, and then properties of the resulting modified films were investigated.     

Grafted polysaccharides based on acrylamide and N,N‐dimethylacrylamide: Preparation and investigation of their flocculation performances

The graft copolymerization of N,N‐dimethylacrylamide (DMA) and acrylamide (AM) were carried out onto different polysaccharide backbones separately. The graft copolymers were synthesized by ceric ion induced redox polymerization technique. Three polysaccharides were used, namely hydroxyethyl starch (HES), hydroxyethyl cellulose (HEC) and Amylopectin (AP), for the grafting reactions. Among the three polysaccharides, HEC has linear structure, while HES and AP have a branch one. The graft copolymers were characterized by intrinsic viscosity measurements, FTIR spectroscopy, NMR (both ¹H and ¹³C) spectroscopy, and thermal analysis. Flocculation performances of the graft copolymers were evaluated in 1 wt % kaolin and in 0.25 wt % iron ore suspensions. A detailed comparative study of the flocculation properties of the synthetic graft copolymers was also made. It showed that graft copolymers based on DMA were better flocculants than those based on AM. Among the synthetic graft copolymers, HES‐g‐Poly (DMA) performed best when compared with the other synthetic graft copolymers as well as to the commercial flocculants in the same suspensions. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Graft copolymerization of acrylonitrile on kenaf fibers by ceric ion in the presence of allyl compounds

Graft copolymers of acrylonitrile on kenaf fibers were obtained in an aqueous medium by the use of allyl alcohol and allyl chloride in combination with ceric ion as redox pairs. The graft copolymerization reactions showed distinct features that were associated with different initiating species derived from the redox pairs. For a ceric–allyl-chloride-initiated reaction, a minimum graft yield was observed, accompanied by an enhanced graft yield. This suggested the existence of two kinetically controlled grafting reactions arising from two different initiating species. For the ceric–allyl-alcohol-initiated reaction, the grafting profile showed a maximum yield and suggested the presence of one active initiating species. High concentrations of acrylonitrile were favorable to grafting with values of up to 150%, but they also resulted in decreased efficiency in monomer conversion to grafted polymer. The frequency of grafting increased with the concentration of allyl alcohol but the molecular weight of grafted polymer of up to 4.46 × 10⁴ decreased by a factor of one and half over the concentration range 1.8–9.0 × 10⁻⁴M of the latter. The presence of 10% (v/v) N,N′-dimethylformamide resulted in zero graft, but the same vol % of formic acid had no apparent effect on the graft yield. A negative temperature dependence in the graft yield was found in the temperature range of 50–70°C. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1757–1761, 1999     

Macromonomers by activated polymerization of oxiranes. Synthesis and polymerization

Macromonomers were obtained by cationic polymerization of propylene oxide and epichlorohydrin proceeding by the activated monomer mechanism with hydroxyethyl acrylate as initiator. Up to DP _n ～ 15 for propylene oxide and DP _n ～ 20 for epichlorohydrin, polymerization proceeds as a living process, giving with quantitative yields macromonomers with functionality equal to one, controlled molecular weight and narrow molecular weight distribution (M _wM _n<1.2) free of side products. In the higer molecular weight region, side reactions become increasingly noticeable. Propylene oxide macromonomers undergo radical homopolymerization. Homopolymerization of macromonomer with M _n = 8×10² gives graft copolymers with M _n up to 7.2×10³ in copolymerization with styrene, completely soluble graft copolymers with M _n ～ 2×10⁴ were obtained. Radical copolymerization of epichlorohydrin macromonomers with styrene gives initially soluble products with M _n ～ 6×10⁴ were obtained. Radical copolymerization of epichlorohydrin macromonomers with styrene gives initially soluble products with M_n～ 6×10⁴, which are converted in the later stages into insoluble gels, apparently due to the chain transfer to chloromethly groups of the polyepichlorohydrin chains.     

Graft copolymers of starch with mixtures of acrylamide and the nitric acid salt of dimethylaminoethyl methacrylate

Mixtures of acrylamide and the nitric acid salt of dimethylaminoethyl methacrylate (DMAEMA·HNO₃) have been graft polymerized onto unmodified wheat starch with ferrous ammonium sulfate–hydrogen peroxide initiation. Graft polymerizations were carried out with both unswollen starch granules and granules that had been swollen by heating in water to 60°C. Ungrafted synthetic polymers were removed from graft copolymers by cold-water extraction and were characterized by their M?_n and DMAEMA·HNO₃ content. Graft copolymers were characterized with respect to per cent add-on, M?_n and DMAEMA·HNO₃ content of grafted polymer, and grafting frequency. Ungrafted synthetic polymers contained a mole percentage of DMAEMA·HNO₃ equal to or greater than that present in the initial monomer mixtures; whereas in most grafted polymers the mole-% DMAEMA·HNO₃ in the grafted branches was less than that in the starting monomers. At all monomer ratios examined, polymer grafted to swollen starch granules contained a higher percentage of DMAEMA·HNO₃ then polymer grafted to unswollen starch. The influence of starch granule swelling on the molecular weight and frequency of grafted branches was correlated with the composition of the initial monomer mixture. It was determined that the effect of granule swelling on graft copolymer structure would be minimal when 25–30 mole-% DMAEMA·HNO₃ was used. In an acetonitrile–water solvent system, reactions with 20 and 50 mole-% DMAEMA·HNO₃ produced graft copolymers with less DMAEMA·HNO₃ in grafted branches than corresponding graft polymerizations run in water. The flocculation of 3% aqueous suspensions of diatomaceous silica was examined with selected starch graft copolymers.     

Internal plasticization of poly(vinyl chloride) by grafting acrylate copolymers via copper-mediated atom transfer radical polymerization

Internal plasticization of poly(vinyl chloride) (PVC) was achieved in one-step using copper-mediated atom transfer radical polymerization to graft different ratios of random n-butyl acrylate and 2–2-(2-ethoxyethoxy)ethyl acrylate copolymers from defect sites on the PVC chain. Five graft polymers were made with different ratios of poly(butyl acrylate) (PBA) and poly(2–2-(2-ethoxyethoxy)ethyl acrylate) (P2EEA); the glass transition temperatures (T_g) of functionalized PVC polymers range from − 25 to − 50°C. Single T_g values were observed for all polymers, indicating good compatibility between PVC and grafted chains, with no evidence of microphase separation. Plasticization efficiency is higher for polyether P2EEA moieties compared with PBA components. The resultant PVC graft copolymers are thermally more stable compared to unmodified PVC. Increasing the reaction scale from 2 to 14 g produces consistent and reproducible results, suggesting this method could be applicable on an industrial scale.     

Graft copolymerization onto protein by the ceric ion method. Studies on grafting site

Graft copolymerization of methyl methacrylate and acrylamide onto ovalbumin was carried out with redox system with ceric ion. Initiation of grafting occurred very rapidly, and the number of grafting sites reached a maximum after about 2 min. regardless of initial ceric ion concentration. The grafted polymer chains were separated by selective hydrolysis of the protein backbone with hydrochloric acid or protease in order to characterize the graft copolymers. The grafted polyacrylamide separated by the proteolytic digestion contained a carbohydrate residue at the end of the polymer molecule. The problem of grafting sites on ovalbumin is discussed.     

Grafting of vinyl acetate–methyl acrylate mixture onto cellulose. Effect of inorganic salts

The effect of the addition of NaNO₃ and NaCl on the graft copolymerization of a mixture of vinyl acetate–methyl acrylate onto cellulose, using ceric ion as initiator, is examined. Several grafting parameters were measured. Presence of NaNO₃ affects the graft copolymerization by enhancing the cellulose oxidation, but it leaves almost unaffected the homopolymerization reaction. NaCl works similarly to NaNO₃. As a consequence of salt presence, ligand changes in the ceric ion complexes, as well increase in the ionic strength of the medium, are expected.     

Copolymers of methyl methacrylate and acrylate comonomers: Synthesis and characterization

Methyl methacrylate (MMA) has been copolymerized with n-butyl acrylate (n-BA), ethyl acrylate (EA), and 2-ethylhexyl acrylate (2-EHA) in solution at 70°C using benzoyl peroxide as free radical initiator. The copolymer composition was estimated by the ¹H-NMR spectroscopic technique. The copolymers were further characterized by IR, XRD, TGA, DTA, DSC, GPC, and solubility. The adhesive characteristics of the copolymers to cellulosic substrate are also reported. © 1995 John Wiley & Sons, Inc.     

Development and assessment of the advanced graft copolymers obtained from Hibiscus sabdariffa biomass

In this article, the morphological transformation in Hibiscus sabdariffa stem fiber through graft copolymerization with effective ethyl acrylate (EA) and its binary vinyl monomeric mixtures using ceric ammonium nitrate—nitric acid initiator system has been reported. Different reaction parameters such as temperature, time, initiator concentration, monomer concentration, and pH were optimized to obtain the maximum graft yield (117.3%). The optimized reaction parameters were then used to screen the additive effect of EA with n‐butyl acrylate (BA), acrylic acid (AA), and 4‐vinyl pyridine (4‐VP) in binary vinyl monomer mixtures on percentage grafting, properties, and the behavior of the fiber. The graft copolymers were characterized by FTIR, SEM, XRD, TGA, and DTA techniques and evaluated for physico‐chemical changes. With increase in the P_g a significant physico‐chemico‐thermal resistance, miscibility in organic solvents, hydrophobicity were found to increase, whereas crystallinity, crystallinity index, dye‐uptake, and hydrophylicity decreased, however, the cellulose form I remained unchanged. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Characterization of acrylamide polymers for enhanced oil recovery

Four different copolymers, of acrylamide and acrylic acid, acrylamide and 2‐acrylamido‐2‐methyl propane sulfonic acid, N,N‐dimethylacrylamide and acrylic acid, and N,N‐dimethylacrylamide and 2‐acrylamido‐2‐methyl propane sulfonic acid (sodium salts), were prepared. The copolymers were characterized by their intrinsic viscosities and monomer ratios and with IR, ¹H‐NMR, and X‐ray diffraction (XRD) spectroscopy. No crystallinity was observed by differential thermal analysis, and this was well supported by XRD. All the polymers showed low decomposition temperatures. A number of decomposition temperatures were observed in differential thermogravimetry thermograms because of the elimination of gases such as CO₂, SO₂, CO, and NH₃. The replacement of the acrylate group with a sulfonate group produced polymers that were more compatible with brine, whereas the replacement of acrylamide with a more hydrophobic group such as N,N‐dimethylacrylamide produced a more shear‐resistant polymer. A N,N‐dimethylacrylamide‐co‐sodium‐2‐acrylamido‐2‐methyl propane sulfonate copolymer was better with respect to thermal stability when the polymer solution was aged at 120°C for a period of 1 month. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1869–1878, 2003     

Radiation-induced graft copolymerization of mixtures of styrene and n-butyl acrylate onto cellulose and cellulose triacetate

Mixtures of styrene and n-butyl acrylate of various compositions were grafted onto cellulose and cellulose triacetate fibers preirradiated with γ-rays at 0°C in air. Monomer reactivity ratios of the grafted copolymers were found to be different from those of the nongrafted copolymers or those of AIBN-initiated copolymers. The active species initiating the graft copolymerization were trapped radicals for cellulose and peroxides for cellulose triacetate. Kinetic investigations of the graft copolymerization of styrene onto preirradiated cellulose triacetate fibers were also carried out, and it was found that the kinetic scheme for radical polymerization is also applicable to graft copolymerization in a heterogeneous system.