Graft Copolymerization of Pyrrolidone onto Copolymers of N-Acryloyl Pyrrolidone and Vinyl Monomers

The copolymerizations of N-acryloyl pyrrolidone (NAP) with vinyl monomers methyl methacrylate (MMA), acrylonitrile (AN) and acrylamide (AA) were carried out in dimethylformamide at 65°C using 2,2′-azobisisobutyronitrile(AIBN) as an initiator. The resulting copolymers were used as a polymeric initiator of the anionic graft copolymerization of 2-pyrrolidone. The percent grafting of 2-pyrrolidone onto vinyl copolymer backbone chain involving N-acyllactam groups was found best with copoly(NAP-co-MMA) when the KOH concentration was 0.03 M. The presence of crown ether increased the viscosity of graft copolymers and accelerated the initial rate of anionic graft copolymerization.     

Graft polymerization of acrylamide on chitosan: Copolymer structure and properties

Graft copolymers have been prepared through the free-radical polymerization of acrylamide in water-acetic acid solutions of chitosan in the presence of ammonium persulfate as an initiator. The effect of temperature, pH of a medium, and concentrations of initiator, chitosan, and acrylamide on the grafting kinetics and efficiency has been established. The local concentration of acrylamide in the reaction zone increases due to intermolecular hydrogen bonding between polysaccharide and monomer molecules. Copolymer films are characterized by better mechanical properties compared to those of polysaccharide. Hydrogels with good viscoelastic properties have been obtained when grafting was performed in the presence of N,N-methylenebisacrylamide as a crosslinking agent.     

Effect of Ce4+ pretreatment on swelling properties of cellulosic superabsorbents

Cellulosic superabsorbents are prepared by pretreating the wood pulp (WP) with Ce⁴⁺ initiator, followed by the graft copolymerization of acrylamide (AM) monomer onto Ce⁴⁺‐pretreated WP (Ce⁴⁺ · WP) in acidic medium and in the presence of N,N′‐methylenebisacrylamide (MBAM) cross‐linker. The rate of AM copolymerization of Ce⁴⁺ · WP is significantly faster than that of the untreated WP. The obtained polyAM (PAM)‐grafted cellulosic copolymers (PAM‐g‐Ce⁴⁺ · WP copolymers) are alkaline‐hydrolyzed to produce the water‐absorbents. As PAM grafting yield increases, the absorbency increases rapidly and reaches the maximum value at a yield of 210–240%. The maximum water and saline absorbencies are around 2500 and 50 g g^?1, respectively. The optimum feed concentration of Ce⁴⁺ pretreatment on the maximum water and saline absorbencies is 5.0 × 10^?3 mol L^?1. The water and saline absorbencies of the PAM‐g‐Ce⁴⁺ · WP water‐absorbents are remarkably higher in comparison with that of the untreated WP (with a similar grafting yield) due to uniform PAM‐grafting onto Ce⁴⁺ · WP specimen. In addition, as the amount of cross‐linker increases, the grafting yield is not changed whereas the water and saline absorbencies are remarkably decreased. Copyright © 2008 John Wiley & Sons, Ltd.     

Grafting of poly(vinyl pyrrolidone) onto gelatin and its application as synthetic plasma expander

Grafting of N-vinyl pyrrolidone onto gelatin is reported using α,α'-azobisisobutyronitrile as initiator. The effects of various variables like initiator concentration, monomer concentration, time and temperature are reported. These variables appreciably affect the percentage grafting, grafting efficiency and molecular weight of the grafted chain. The graft copolymers were characterized by i.r. spectroscopy and ninhydrin tests. Sulphathiazole was coupled to these graft copolymers using a diazotization technique. Blood compatibility of these graft copolymers of different side chain molecular weight was found to be satisfactory.     

Water-soluble copolymers. III. Dextran-g-poly(acrylamides) control of grafting sites and molecular weight by Ce(IV)-induced initiation in homogeneous solutions

Model graft copolymers were synthesized by grafting acrylamide onto dextran (M_w = 500,000) utilizing an initiation method in which a Ce(IV)/HNO₃ solution was added to the dextran solution in order to allow coplexation prior to monomer addition. Three synthetic reaction parameters were optimized on the basis of conversion and solution viscosity: monomer concentration, dextran concentration, and nitric acid concentration. Molar ratios of [Ce(IV)]/[dextran] were changed systematically to affect the number and length of the acrylamide grafts. The number of grafting sites and graft chain lengths, determined by selective hydrolysis of the carbohydrate backbone, were in good agreement with those theortically predicted from knowledge of initiation efficiency and monomer conversion. Rheological studies of the model graft copolymers were conducted in aqueous solutions as a function of temperature, added salt, and copolymer concentration.     

Synthesis and characterization of hydrophobically modified polyacrylamides and some observations on rheological properties

Hydrophobically modified polyacrylamide (PAM) polymers were synthesized by means of an aqueous micellar copolymerization, the di-alkyl substituted acrylamides di-n-propylacrylamide (DPAM) and di-n-octylacrylamide (DOAM) being used as hydrophobic comonomers. The number of hydrophobic blocks was varied using three different comonomer contents (f=1, 3 and 5 wt.%). The length of hydrophobic blocks, i.e. the number of hydrophobes per micelle, N_H, was controlled by the sodium dodecyl sulphate surfactant concentration. The effect of the type of hydrophobic comonomer and the number and length of hydrophobic units on the composition of the copolymer and its solubility and rheological properties were studied. The results indicate that the average copolymer composition is independent of the degree of conversion and surfactant concentration. Solubility and rheological measurements lead to a number of conclusions. First, DPAM is a weak hydrophobic monomer, all DPAM/AM (AM=acrylamide) copolymers being water soluble. Second, there is no strong hydrophobic interaction between DPAM units, in particular for low polymer concentration and N_H, and thus no strong associative thickening behaviour. Third, DOAM is a strong hydrophobic comonomer. Incorporation of a small amount of DOAM into PAM causes a dramatic enhancement in viscosity due to hydrophobic interactions. The properties of the copolymers are strongly dependent on the N_H values, most DOAM/AM copolymers being insoluble in water.     

New Grafted Copolymers Carrying Betaine Units Based on Gellan and N-Vinylimidazole as Precursors for Design of Drug Delivery Systems

New grafted copolymers possessing structural units of 1-vinyl-3-(1-carboxymethyl) imidazolium betaine were obtained by graft copolymerization of N-vinylimidazole onto gellan gum followed by the polymer-analogous reactions on grafted polymer with the highest grafting percentage using sodium chloroacetate as the betainization agent. The grafted copolymers were prepared using ammonium persulfate/N,N,N′,N′ tetramethylethylenediamine in a nitrogen atmosphere. The grafting reaction conditions were optimized by changing one of the following reaction parameters: initiator concentration, monomer concentration, polymer concentration, reaction time or temperature, while the other parameters remained constant. The highest grafting yield was obtained under the following reaction conditions: c_i = 0.08 mol/L, c_m = 0.8 mol/L, c_p = 8 g/L, t_r = 4 h and T = 50 °C. The kinetics of the graft copolymerization of N-vinylimidazole onto gellan was discussed and a suitable reaction mechanism was proposed. The evidence of the grafting reaction was confirmed through FTIR spectroscopy, X-ray diffraction, ¹H-NMR spectroscopy and scanning electron microscopy. The grafted copolymer with betaine structure was obtained by a nucleophilic substitution reaction where the betainization agent was sodium chloroacetate. Preliminary results prove the ability of the grafted copolymers to bind amphoteric drugs (cefotaxime) and, therefore, the possibility of developing the new sustained drug release systems.     

Ce(Ⅳ)盐引发丙烯酰胺在聚乙烯醇微球表面接枝聚合的研究

以硫酸铈铵为引发剂,采用水溶液聚合体系,在酸性介质中实施了丙烯酰胺(AM)在聚乙烯醇交联微球(CPVA)表面的接枝聚合,制备了接枝微粒CPVA-g-PAM,重点研究了各种因素对接枝聚合的影响规律,探讨了铈盐引发接枝聚合的机理.实验结果表明,在Ce(Ⅳ)盐的氧化作用下,在含有大量羟基的CPVA微球表面会产生自由基,顺利地实现丙烯酰胺的自由基接枝聚合反应.PAM的接枝度首先取决于水介质中硫酸的浓度,接枝度随硫酸浓度的增大呈现先增大后减小的变化规律,当H+离子浓度为0.36mol/L时,PAM的接枝度最高,酸浓度对接枝度的影响反映了铈盐引发接枝聚合的微观机理.引发剂Ce4+盐的浓度过大,将会促进氧化终止过程,降低接枝度,适宜的Ce4+盐浓度为5.98×10-3mol/L.在接枝聚合过程中,单体丙烯酰胺浓度和反应温度也会对接枝聚合产生影响.在本研究所确定的适宜条件下,可制得PAM接枝度为27.13g/100g的接枝微粒CPVA-g-PAM.     

Graft Copolymerization of Methyl Methacrylate on Potato Starch Using Potassium Trioxalatomanganate,K3[Mn(C2O4)3], as Initiator

Graft copolymerization of methyl methacrylate on potato starch was carried out in methanol-water medium at 35°C in the dark using potassium trioxalatomanganate, K₃[Mn(C₂O₄)₃], as initiator. The effect of different methanol-water ratios (v/v), the temperature of polymerization, the initiator concentration, the monomer concentration, the starch content, and the time of polymerization were studied. Percent total conversion, % grafting, and grafting efficiency (%) under different conditions were evaluated and compared. High grafting efficiency (～80%), high % total conversion (～85%), and high % grafting (-95%) were readily obtained. The reaction mechanism for graft copolymer formation is discussed.     

Synthesis and characterization of poly(phenylene oxide) graft copolymers by atom transfer radical polymerizations

A series of comb-like poly(phenylene oxide)s (PPO) graft copolymers with controlled grafting density and length of grafts were synthesized by atom transfer radical polymerization (ATRP). The α-bromo-poly(2,6-dimethyl-1,4-phenylene oxide)s (BPPO) were used as macroinitiators to polymerize vinyl monomers and the graft copolymers carrying polystyrene (PS), poly(p-acetoxystyrene) (PAS), and poly(methyl methacrylate) (PMMA) as side chains were synthesized and characterized by NMR, FTIR, GPC, DSC and TGA. The composition-dependent glass-transition temperatures (T_g) of PPO-g-PS exhibited good correlation with theoretical curve in Couchman equations except for the cases of low PS content (<40 mol%) copolymers in which a positive deviation was observed due to enhanced molecular interactions. The increase in monomer/initiator ratio led to the increase of degree of polymerization and the decrease of polydispersity. Despite the immiscibility nature between PPO and PMMA, the PPO-g-PMMA exhibited enhanced compatibilization as apparent single T_g in a wide temperature window throughout various compositions revealing an efficient segmental mixing on a molecular scale due to grafting structure.     

Polymer–Metal Complexes Obtained by Radiation‐Induced Grafting Process onto Polyester Fabrics

Abstract

This paper reports the preparation of chelating copolymers via grafting of acrylic acid, and/or acrylamide onto polyester microfiber (PETMF) fabrics using a γ‐radiation technique. The effect of monomer concentration on the grafting process at irradiation dose 20?kGy was studied. The prepared graft chains (PETMF‐g‐AA), (PETMF‐g‐AAm), and (PETMF‐g‐PAAc/PAAm) acted as chelating sites for some selected transition metal ions. The effect of grafting on mechanical properties of PETMF and its copolymer–metal complexes was investigated. The prepared chelating copolymers and their metal complexes were characterized using x‐ray (energy dispersive x‐ray, EDX), differential scanning calorimeter (DSC), color parameters, and electrical conductivity measurements. The possibility of practical uses for such prepared graft copolymer–metal complexes was discussed and determined. The observed results showed that the electrical conductivity of the grafted copolymers and their metal complexes are thermally activated. Moreover, the degree of grafting enhanced the conductivity values of the grafted and non‐complexed copolymer up to three orders of magnitude, on the other hand, the conductivity of the copolymer–metal complexes slightly increased.     

Synthesis of poly(styrene-graft-ethylene oxide) by ethoxylation of amide group containing styrene copolymers

Graft copolymers containing poly(ethylene oxide) side chains on a polystyrene backbone have been synthesized. Styrene copolymers synthesized by free radical mechanism and containing between 5 and 15 mol % acrylamide or methacrylamide were used as backbones. The amide groups in the copolymers were ionized by using potassium tert-butoxide or potassium naphthalene, and grafting was achieved by utilizing the amide anions as initiator sites for the polymerization of ethylene oxide in 2-ethoxyethyl ether at 65°C. The graft copolymers were characterized with respect to molecular weight and composition using elemental analysis, NMR, gel permeation chromatography, IR, and viscosity measurements. The size of the side chains were between 600 and 2000 g/mol. GPC results from a hydrolyzed graft copolymer sample suggest a narrow size distribution for the poly(ethylene oxide) grafts. Solution properties of the graft copolymers were investigated in different toluene/methanol mixtures. The intrinsic viscosities of the graft copolymers were found to depend primarily on the poly(ethylene oxide) content rather than the graft density or the poly(ethylene oxide) chain length. © 1993 John Wiley & Sons, Inc.     

Graft copolymerization. I. Grafting of hydroxyalkyl methacrylates on poly(vinyl alcohol)

New graft copolymers were synthesized by grafting hydroxyethyl methacrylate and hydroxpropyl methacrylate on poly(vinyl alcohol) in aqueous solution with Ce⁺⁴ions as initiator. The dependence of the percentage of grafting and monomer conversion on the concentration of the monomer, on the concentration of the initiator, on the total concentration of the reactants, and on temperature and duration of the reaction were investigated. Some basic properties of the graft copolymers and some preliminary permeation measurements of water vapors through films, made from these copolymers, are also reported.     

Water-Soluble Copolymers. II. Synthesis and Characterization of Model Dextran-g-Acrylamides by Ce(lV)/HNO3-lnduced Initiation

In order to develop polymers useful as mobility control agents in enhanced oil recovery processes, water-soluble acrylamide grafted polysaccharide copolymers have been synthesized in water at 25° C using a ceric ammonium nitrate/nitric acid system. The effects of varying concentrations of ceric ion, monomer, and substrate on conversion, graft length, and molecular structure of the reaction products have been examined. The crude reaction products were purified by fractional precipitation and then were analyzed for nitrogen content using a micro-Kjeldahl method. The chemical structures of the graft copolymers were studied by selective hydrolysis of the carbohydrate backbones. Intrinsic viscosity and grafting length data were used to predict solution behavior of the graft copolymers prepared under controlled conditions. Aqueous size exclusion and viscosity studies showed direct correlations between hydrodynamic volume and length of the polyacrylamide side-chain grafts.     

Grafting of Acrylamide On 1, 1, 2, 2-Tetra-Chloroethane Preswelled Polyethylene Terephthalate) Films Using Azobisisobutyronitrile Initiator

Abstract

Graft polymerization of acrylamide (AAm) on 1, 1, 2, 2 tetrachloro-ethane (TCE) preswelled poly(ethylene terephthalate) (PET) films were performed with chemical initiation method using asobisiso-butyronitrile (AIBN) initiator. Temperature was found to have a greater effect on the swelling then the swelling time. Variation of the graft yield with polymerization temperature, time, AIBN concentration, AAm concentration, AIBN and AAm inclusion times were investigated. The optimum temperature for grafting was found to be 70°CC. The graft yield was observed to increase with polymerization time, AAm concentration, initiator and monomer diffusion time up to a saturation graft yield and then leveled off. An increase in AIBN concentration first enhanced the percent grafting then showed a decrease. The addition of some salts (Ni²⁺, Cr³⁺, Co²⁺, Cu²⁺) on the rate of grafting was also investigated. From the temperature dependence of the initial rate of grafting, the overall activation energy was found to be 4. 1 kcal/mol and relevant rate equation have been derived. The effect of grafting on film propities, such as water absorption capacity, intrinsic viscosity were determined. Grafted films were characterized by FTIR spectros-copy and scanning electron microscopy (SEM).     

Coupled atom transfer radical coupling and atom transfer radical polymerization approach for controlled grafting from poly(vinylidene fluoride) backbone

A new “grafting from” strategy for grafting of different monomers (methacrylates, acrylates, and acrylamide) on poly(vinylidene fluoride) (PVDF) backbone is designed using atom transfer radical coupling (ATRC) and atom transfer radical polymerization (ATRP). 4‐Hydroxy TEMPO moieties are anchored on PVDF backbone by ATRC followed by attachment of ATRP initiating sites chosen according to the reactivity of different monomers. High graft conversion is achieved and grafting of poly(methyl methacrylate) (PMMA) exhibits high degree of polymerization (DPn = 770) with a very low graft density (0.18 per hundred VDF units) which has been increased to 0.44 by regenerating the active catalyst with the addition of Cu(0). A significant impact on thermal and stress–strain property of graft copolymers on the graft density and graft length is noted. Higher tensile strain and toughness are observed for PVDF‐g‐PMMA produced from model initiator but graft copolymer from pure PVDF exhibits higher tensile strength and Young's modulus. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 995–1008     

Poly(N-isopropylacrylamide) thermoresponsive cross-linked conjugates containing polymeric soybean oil and/or polypropylene glycol

Synthesis, characterization and solution properties of a new series of the PNIPAM-soybean oil and/or polypropylene glycol, PPG, conjugates (conjugates also referred to as co-networks) have been described. For this purpose free radical polymerization of NIPAM monomer was initiated by macroinitiators based on PSB and/or PPG in order to obtain PSB-g-PNIPAM, PPG-g-PNIPAM and PSB-g-PPG-g-PNIPAM cross-linked graft copolymers. The autooxidation of soybean oil under air at room temperature rendered waxy soluble polymeric soybean oil peroxide associated with cross-linked parts. The soluble polymeric oil macro-peroxide isolated from the cross-linked part was used to initiate the free radical polymerization of NIPAM to give PSB-g-PNIPAM cross-linked copolymer. To obtain PPG-macromonomeric initiator, PPG-MIM, PPG-bis amino propyl ether with Mn 400 (or 2000) Dalton was reacted with 4,4′-azo bis cyanopentanoyl chloride and methacryloyl chloride, respectively. PPG-MIM also initiated the free radical polymerization of NIPAM at 80 °C to yield PPG-g-PNIPAM cross-linked thermoresponsive product. In order to obtain PSB-g-PPG-g-PNIPAM cross-linked triblock copolymer, NIPAM was polymerized by using the mixture of two macroinitiators, PSB and PPG-MIM. PSB contents in the graft copolymers were calculated via elemental analysis of nitrogen in graft copolymers. Thermal analysis, SEM, FTIR and ¹H NMR techniques were used in the characterization of the products. The effect of polymeric soybean oil, PSB, and/or PPG on the thermal response rate of poly(N-isopropylacrylamide, PNIPAM, cross-linked-graft copolymers swollen in water has been investigated by means of swelling-deswelling and drug release behaviors against to temperature change. Lower critical solution temperatures (LCST) of the cross-linked PNIPAM conjugates (conjugates also referred to as co-networks) were determined from the curves of swelling degrees versus solution temperatures. The response temperature of the hydrophobically modified PNIPAM conjugates was reduced to 27 °C, 23 °C and 27 °C for PSB-g-PNIPAM, PPG-g-PNIPAM and PSB-g-PPG-g-PNIPAM, respectively. We have found that the graft copolymers were not pH-responsive. In addition, higher pH ranges cause the hydrolysis of the PSB ester linkages, quickly and makes the cross-linked graft copolymers soluble.The fastest shrinking of the gels was observed by loosing water between 65% and 98% at 50 °C.Methyl orange (MO), was used as a model drug, loaded into cross-linked graft copolymers to examine and compare the effects of controlled release at lower and higher temperatures of lower critical solution temperature (LCST).     

Crystallization behavior, thermal property and biodegradation of poly(3-hydroxybutyrate)/poly(ethylene glycol) grafting copolymer

The poly(3-hydroxybutyrate)(PHB)/poly(ethylene glycol)(PEG) grafting copolymer was successfully prepared by PHB and acrylate groups ended PEGM using AIBN as initiator. The crystallization behavior, thermal stability and environmental biodegradability of PHB/PEG grafting copolymers were investigated with differential scanning calorimetry (DSC), Thermogravimetric analysis (TGA), wide angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), and Biodegradation test in vitro. In the results, all the grafting copolymers were found to show the X-ray diffraction arising from the PHB crystal lattice, while none of the PEG crystallized peaks could be found even though the graft percent reached 20%. This result indicated that PEG molecules were randomly grafted onto PHB chain. The thermal properties measured by DSC showed that the melting temperature(T_m) and glass transition temperature (T_g) were both shifted to lower temperature with the graft percent increasing, and this broadened the narrow processability window of PHB. According to TGA results, the thermal stability of the grafting copolymers is not changed compared to pure PHB. From the biodegradation test, it could be concluded that degradation occurred gradually from the surface to the inside and that the degradation rate could be adjusted by the PEG grafting ratio. In another words, the biodegradation profiles of PHB/PEG grafting copolymer can be controlled. These properties make PHB/PEG grafting copolymer have promising potential applications especially in agriculture fields.     

Potassium diperiodatonickelate‐initiated graft copolymerization of methyl acrylate onto organophilic montmorillonite

Using potassium diperiodatonickelate (Ni (IV)) as an efficient initiator, the graft copolymerization of methyl acrylate (MA) onto organophilic montmorillonite (OMMT) was successfully performed in an alkaline medium. Three grafting parameters were systematically evaluated as functions of the temperature, the initiator concentration, reaction time, pH value, and the ratio of MA to OMMT substrate. The structure of the titled graft copolymers (OMMT‐g‐PMA) were confirmed by Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and thermo‐gravimetric analysis (TGA). It was found that Ni (IV) was a highly efficient initiator for graft copolymerization of the MA onto OMMT, i.e., grafting efficiency is as high as 95% and grafting percentage can be facilely controlled within 700% in this study. In addition, the highest grafting efficiency and grafting percentage were obtained when temperature adopted was over 40°C and pH was about 10.3. A single‐electron‐transfer mechanism was proposed to illustrate the formation of radicals and the initiation reaction. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis, characterization and metal uptake capacity of a new carboxymethyl chitosan derivative

Chemical modification of chitosan (Cs) and its derivatives via graft copolymerization can enhance their properties and consequently expands their potential applications. Carboxymethyl chitosan (CMCs) was prepared and characterized by FTIR spectroscopy, elemental analysis and X-ray diffraction. Graft copolymerization of N-acryloylglycine (NAGly) onto CMCs using 2,2-dimethoxy-2-phenyl acetophenone (PI) as photoinitiator was carried out under nitrogen atmosphere in aqueous solution. Evidence of grafting was confirmed by comparison of FTIR spectra of CMCs and the graft copolymers as well as the 2D-X-ray diffraction patterns, elemental analysis and the difference in solubility profiles before and after grafting. The effects of concentration of NAGly, PI and reaction time on the extent of grafting were investigated by determining the grafting percentage and grafting efficiency. With other conditions kept constant, the obtained optimum grafting conditions were: CMCs = 0.1 g, NAGly = 0.4 g, PI = 0.02 g and reaction time = 1 h. A preliminary study was then carried out to evaluate the capacity of the prepared new graft copolymer to uptake copper ions from aqueous systems. This preliminary investigation of the prepared graft copolymers showed that they may be tailored and exploited to expand the utilization of these systems in metal ions uptake and treatment of wastewater.