Highest Grafting Percentage Research Articles

Sodium Salt of Partially Carboxymethylated Sodium Alginate-g-Poly(acrylonitrile): I. Photo-Induced Synthesis, Characterization, and Alkaline Hydrolysis.

An efficient redox initiating system, ceric ammonium nitrate/nitric acid, has been employed for the first time to carry out photo-induced graft copolymerization of acrylonitrile (AN) onto sodium salt of partially carboxymethylated sodium alginate, having an average degree of substitution value to be 1.10. The photo-grafting reaction conditions for maximum grafting have been systematically optimized by varying the reaction variables such as reaction time, temperature, the concentration of acrylonitrile monomer, ceric ammonium nitrate, and nitric acid, as well as the amount of the backbone. The optimum reaction conditions are obtained with a reaction time of 4 h, reaction temperature of 30 °C, acrylonitrile monomer concentration of 0.152 mol/L, initiator concentration of 5 × 10-3 mol/L, nitric acid concentration of 0.20 mol/L, amount of backbone of 0.20 (dry basis) and the total volume of the reaction system of 150 mL. The highest percentage of grafting (%G) and grafting efficiency (%GE) achieved are 316.53% and 99.31%, respectively. The optimally prepared graft copolymer, sodium salt of partially carboxymethylated sodium alginate-g-polyacrylonitrile (%G = 316.53), has been hydrolyzed in an alkaline medium (0.7N NaOH, 90-95 °C for ~2.5 h) to obtain the superabsorbent hydrogel, H-Na-PCMSA-g-PAN. The chemical structure, thermal characteristics, and morphology of the products have also been studied.

Synthesis of Cassava Starch-Grafted Polyacrylamide Hydrogel by Microwave-Assisted Method for Polymer Flooding

Cassava starch-grafted polyacrylamide (CS-g-PAM) hydrogels were synthesized using a microwave-assisted method and K2O8S2 (KPS) as an initiator. In this study, we studied the influence of the amount of acrylamide and irradiation time on the properties of CS-g-PAM. The characterization of CS-g-PAM obtained was shown by Fourier-transform infrared (FTIR) and Scanning Electron Microscope (SEM) analysis. To predict the behavior of the samples under reservoir conditions, the properties of CS-g-PAM, such as swelling ratio, water-solubility, and viscosity were determined as a function of temperature, salt concentration, and aging time. The FTIR spectra and SEM analysis of the CS-g-PAM confirmed that the polyacrylamide chains were successfully grafted onto the cassava starch backbone. The results showed that the increasing amount of acrylamide and the longer irradiation time improved the properties of CS-g-PAM. Preparation of CS-g-PAM with 10 g of acrylamide and 180 s of irradiation time resulted in the highest grafting percentage and water solubility, which was 1565.53 and 96.06%, respectively. Its viscosity also exceeded 97% after 15 days of aging. The results showed that CS-g-PAM expressed properties such as good thickening, temperature resistance, and salt resistance according to reservoir conditions. This finding indicated that CS-g-PAM has good potential for oil recovery applications.

Influence of phosphonic acid as a functional group on the adsorption behavior of radiation grafted polypropylene fabrics for Co(II) removal

The efficiency of new adsorbents, including polypropylene nonwoven fabrics by radiation grafting polymerization in the removal of cobalt (II) from aqueous solution, was in the batch experiments. The composition of the acrylonitrile and acrylic acid monomers was used in mutual irradiation grafting, and phosphonic acid was applied as a functional group. Factors affecting the grafting process as well as the adsorption percentage were studied, such as radiation dose (10–40 kGy), monomer concentration, adsorption time (2–24 h), solvent type (dioxane, and dimethylformamide), initial aqueous pH (0.5–6.5), temperature (25–65 °C), and adsorbent mass (0.01–0.1 g). Also, the synthesized adsorbent for the adsorption of various heavy metals such as nickel, cobalt, and zinc was studied. The outcomes revealed that the nonwoven fabrics could act as the excellent adsorbents of enough adsorption sites for cobalt ions or other heavy metals, mainly due to the high grafting percentage of 125.3% and adsorption percentage 99.78%. In this way, the synthesis adsorbents with high efficiency, protected, valuable and financial attributes could be novel potential materials applied in the heavy metal removal.

Biochar Grafted on CMC-Terpolymer by Green Microwave Route for Sustainable Agriculture

The deficiency of water sources and the environmental disposal of large amounts of biomass waste (orange peels) produces economic and environmental problems, though its conversion into biochar by a pyrolysis procedure might be used to improve soil productivity. In the current study, we investigated the performance of superabsorbent biochar composite grafted on CMC as a low-cost, alternative, and biodegradable terpolymer composite (IPNCB) for soil water retention capacity. The IPNCB composite was synthesized by both microwave and conventional routes. The optimal reaction parameters proved that the microwave route has a high grafting percentage (%G) and short reaction time compared to the conventional route. The superabsorbent composite was characterized using different methods: FTIR, TGA, and SEM. The results show that the equilibrium water swelling (EW) of the IPNCB composite was improved at a 2% biochar concentration. The incorporation of biochar (BC) into the polymer network improved the water holding capacity (WHC) to 57.6% and water retention (WR) to 9.1% after 30 days. The degradation test indicates the IPNCB composite has a good degradability rate. Mixing soil with the prepared IPNCB composite can improve plant growth and reduce water consumption through the irrigation of arid lands. The IPNCB composite is a candidate in sustainable agriculture applications.

Reactive Extrusion of Maleic-Anhydride-Grafted Polypropylene by Torque Rheometer and Its Application as Compatibilizer.

This study is based upon the functionalization of polypropylene (PP) by radical polymerization to optimize its properties by influencing its molecular weight. Grafting of PP was done at different concentrations of maleic anhydride (MAH) and benzoyl peroxide (BPO). The effect on viscosity during and after the reaction was studied by torque rheometer and melt flow index. Results showed that a higher concentration of BPO led to excessive side-chain reactions. At a high percentage of grafting, lower molecular weight product was produced, which was analyzed by viscosity change during and after the reaction. Percentage crystallinity increased by grafting due to the shorter chains, which consequently led to an improvement in the chain’s packing. Prepared Maleic anhydride grafted polypropylene (MAH-g-PP) enhanced interactions in PP-PET blends caused a partially homogeneous blend with less voids.

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: ci = 0.08 mol/L, cm = 0.8 mol/L, cp = 8 g/L, tr = 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.

Preparation of macroporous polyvinyl alcohol formaldehyde based hydrogels and their dual thermo- and pH-responsive behavior

Dual thermo- and pH-responsive polymer hydrogels have broad potential applications due to their unique responsive behavior to environmental stimuliregulatedby more than one mechanism. Herein, the dual thermo- and pH-responsive polyvinyl alcohol formaldehyde (PVF) based hydrogels were successfully prepared via redox grafting polymerization by incorporating respectively poly(N-isopropylacrylamide) (PNIPAM) and poly(acrylic acid) (PAA) moieties onto PVF backbone. These hydrogels retain an interconnected macroporous structure with high porosity (~83.0%), facilitating rapid penetration and diffusion of water molecules. The sizes of pore and pore walls are in micrometer scale, significantly reducing the characteristic time of swelling or deswelling. Besides, these hydrogels possess the thermo-responsiveness even in high grafting percentage of PAA (60.8%), overcoming the inhibition effect of PAA moieties in a high content on thermal sensitivity of traditional poly(NIPAM-co-AA) copolymers. Their pH-responsiveness and excellent repeated absorption performance are determined by measuring the absorption capacities of hydrogels in water and different buffer solutions. Moreover, these hydrogels exhibit rapid deswelling kinetics on the minute time scale by detecting water retention in pH 3 buffer solution at 50 °C. In addition, the deswelling behavior leads to the noticeable changes of macroscopic dimensions of hydrogels; we anticipate potential applications in dual thermal and pH sensors.

Surface modification PVA hydrogel with zwitterionic via PET‐RAFT to improve the antifouling property

ABSTRACTTo improve the antifouling property, polyvinyl alcohol hydrogel was successfully grafted with [2‐(methacryloyloxy) ethyl] dimethyl‐(3‐sulfopropyl) ammonium hydroxide (MEDSAH) via photoinduced electron transfer–reversible addition–fragmentation chain transfer (PET‐RAFT) polymerization under a 10 W blue (450–460 nm) light‐emitting diodes. It is surprising that the reaction could be performed in the presence of oxygen, which meant that the reaction has a great prospect of industrialization. The highest grafting percentage (GP) was 55.77% by adding triethylamine and changed the MEDSAH usage in the absence of oxygen. Thermal gravimetric analysis exhibited that grafted MEDSAH affects the thermal property of PVA hydrogel. Also, there was no influence on the ultraviolet–visible transmittance, and the PVA‐g‐pMEDSAH hydrogel became hydrophilicity after grafting. Moreover, in vitro cytotoxicity of both PVA and PVA‐g‐pMEDSAH hydrogel was noncytotoxic according to ISO 10993‐2009. The antifouling property of PVA‐g‐pMEDSAH hydrogel was increased about 53.05%. Thus, the PVA‐g‐pMEDSAH hydrogel can be an ideal optical biomaterial candidate. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47653.

Characterization and properties of biodegradable thermoplastic grafted starch films by different contents of methacrylic acid

Due to poor mechanical and thermal properties of native starch (NS) film; in the present work; NS was modified by graft copolymerization. Thermoplastic starch (TPS) grafted by methacrylic acid (MAA) with different percentage of grafting, i.e., 0%, 18.3%, 36.3%, 52.1% and 89.7% were prepared and tested. The result demonstrated that the intensity of IR peak of acrylic group increased with the increasing percentage of grafting. The higher graft copolymerization with MAA also significantly reduced degree of crystallinity. The strain at maximum load of TPS film grafted by MAA increased with the increasing percentage of grafting. However, water uptake of TPS film grafted by MAA reduced with high percentage of grafting (52.1% and 89.7%). In addition, different TPS films grafted by MAA were also examined for morphology, water vapor permeability, thermal property and biodegradable property by soil buried test.

Synthesis of palygorskite/polystyrene nanocomposites without crosslinked network via in-situ radical bulk polymerization technique

Abstract Clay/polymer nanocomposites have attracted more and more attention owing to their superior performance for potential applications. The in-situ polymerization has been regarded as the promising strategy for the mass production of the clay/polymer nanocomposites with well-defined interfacial property. However, the gelation usually accompanies with the grafting reaction during the polymerization especially for the high aspect ratio nanomaterials, resulting to crosslinked network. In order to solve the problem, the thoil-modified palygorskite nanorods (Pal-SH) were prepared as clay-based chain transfer reagent for the radical bulk polymerization of styrene, as an example. With different dosages of the Pal-SH nanorods from 0.5% to 1.0% and 2.0%, well-defined polystyrene grafted palygorskite nanorods (Pal-PS) were obtained without crosslinked network, with high grafting percentage (PG%) of 40.0, 43.2, and 51.3% respectively. The proposed approach provides a promising technique for the mass production of high aspect ratio nanomaterials-based polymer nanocomposites with well-defined interfacial property, especially avoiding crosslinked network.

Synthesis of hydrophilic carbon nanotubes by grafting poly(methyl methacrylate) via click reaction and its effect on poly(vinylidene fluoride)-carbon nanotube composite membrane properties

Surface modification of azide-decorated multiwalled carbon nanotubes (MWCNTs) with well-defined alkyne-terminated poly(methyl methacrylate) (PMMA) chains was accomplished via the combination of reversible addition fragmentation chain transfer (RAFT) and “click” chemistry. Successful attachment of PMMA onto MWCNT was confirmed by Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA), gel permeation chromatography, Raman spectroscopy, and transmission electron microscopy. The highest grafting percentage (GP) of the PMMA chains (GP=23.3%) was calculated using TGA. The effect of the PMMA-grafted-MWCNTs (MWCNTs-g-PMMA) content on the performance of the poly(vinylidene fluoride) (PVDF)-MWCNTs-g-PMMA composite membrane was studied. The MWCNTs-g-PMMA was found to be well dispersed in the PVDF composite membrane matrix because of the excellent compatibility between the PMMA and PVDF chains. The composite membranes showed improved porosity, hydrophilicity, water flux, β-PVDF content, and mechanical properties at an optimal amount of 2wt% MWCNTs-g-PMMA incorporated in the PVDF membrane matrix. In contrast, the hydroxyl functionalized MWCNTs (MWCNTs-OH) showed limited enhancement in the water flux and mechanical strength, which is mainly due to the poor dispersion of MWCNT because of the weak interaction between the MWCNT and PVDF chains. This study reveals the excellent prospect of the MWCNT-based ultrafiltration membrane with enhanced properties in water treatment applications.

Properties and Biodegradability of Thermoplastic Starch Obtained from Granular Starches Grafted with Polycaprolactone

Granular starches grafted with polycaprolactone (St-g-PCL) were obtained using N-methylimidazole (NMI) as a catalyst. The effect of the starch/monomer ratio and catalyst content was studied to obtain different levels of grafted PCL. The highest grafting percentage (76%) and addition (43%) were achieved for reactions with a starch/monomer ratio of 50/50 and 25% catalyst. The grafting of PCL on the starch granule was verified by the emergence of the carbonyl group in the FTIR spectra and the increased diameter of the grafted starch granule. Thermoplastic starch from ungrafted starch (TPS) and grafted starch (TPGS) was obtained by mixing ungrafted or grafted starch granules with water, glycerol, or sorbitol in a mixer. TPS and TPGS behave as plastic materials, and their mechanical properties depend on the type of plasticizer used. Materials with glycerol as the plasticizer exhibited less rigidity. The presence of starch-g-PCL results in a dramatic increase in the elongation of the thermoplastic material. The starch present in the TPS or TPGS was completely biodegraded while the grafted PCL was partially biodegraded after the enzymatic degradation of the materials.

Surface-initiated polymerization of styrene from one-step prepared thiol-functionalized organoclays

A polystyrene–organoclay composite material was prepared by surface-initiated radical polymerization of styrene from the surface of thiol-functionalized organoclays synthesized in a one-step process. Characterizations of the composite by infrared spectroscopy (FTIR) and powder X-ray diffraction (PXRD) confirmed a direct covalent bonding between the polystyrene and the clay layers and an essentially exfoliated structure. The significant amount of SH reactive sites present in the organoclay resulted in a high grafting percentage (PG%, 49.8%) and in a high content of grafted polystyrene in the material (35.8wt%), indicating that such polystyrene-grafted organoclays could be easily used as polymer fillers for incorporation in various polymeric matrices.

Graft Copolymerization of Chitosan with L-Lactide under Microwave Irradiation

Poly (L-lactide) was grafted onto chitosan by ring-opening copolymerization under microwave irradiation in the presence of tin octoate (Sn (Oct)2) as catalyst. The chemical structure and physical properties of the copolymers with different feeding ratios were discussed by FTIR, DTG and X-RD, taking pure chitosan as reference. The results showed that the application of microwave irradiation in the reaction could achieve the copolymer with high grafting percentage in a short time and low temperature. The thermal stability and crystallinity were decreased with the feeding ratio increasing, attributing to the increasing of grafting percentage.

Preparation, characterization and transfection efficiency of nanoparticles composed of alkane-modified polyallylamine

Objective(s): Although viral vectors are considered efficient gene transfer agents, their board application has been limited by toxicity, immunogenicity, mutagenicity and small gene carrying capacity. Non-viral vectors are safe but they suffer from low transfection efficiency. In the present study, polyallylamine (PAA) in two molecular weights (15 and 65 kDa) was modified by alkane derivatives in order to increase transfection activity and to decrease cytotoxicity. Materials and Methods: Modified PAA was synthesized using three alkane derivatives (1bromobutane, 1-bromohexane and 1-bromodecane) in different grafting percentages (10, 30 and 50). The condensation ability of modified PAA was determined by ethidium bromide test. The prepared polyplexes, complexes of modified PAA and DNA, were characterized by size and zeta potential. Transfection activity of polyplexes was checked in Neuro2A cells. The cytotoxicity of vector was examined in the same cell line. Results: DNA condensation ability of PAA was decreased after modification but modified polymer could still condense DNA at moderate and high carrier to plasmid (C/P) ratios. Most of polyplexes composed of modified polymer had mean size less than 350 nm. They showed a positive zeta potential, but some vectors with high percentage of grafting had negative surface charge. Transfection efficiency was increased by modification of PAA by 1bromodecane in grafting percentages of 30 and 50%. Modification of polymer reduced polymer cytotoxicity especially in C/P ratio of 2. Conclusion: Results of the present study indicated that modification of PAA with alkane derivatives can help to prepare gene carriers with better transfection activity and less cytotoxicity.

Grafting Efficiency of Lignin-Grafted-Polyacrylic Acid

Agriculture biomasses have been successfully converted into value-added products such as biocomposite plastics, furniture, papers and textiles. However, only the cellulose parts of these lignocellulosic materials are being used while other components such as lignin and wax are discarded. For a tropical country like Malaysia, banana stem is one of the sources of biomasses. Like other biomasses-based products, only cellulose part of banana stem is used while the lignin portion is discarded due to overly hydrophilic character. This water-loving property of lignin can be manipulated into specific application such as water absorbent for waste treatment. This research is aimed to synthesis water absorbent-based lignin from banana stem. The lignin had been extracted from banana stem using Kraft process prior to grafted with acrylic acid monomer (AA) in order to increase its water absorbency. The reaction was carried out via free radical polymerization in the presence of hydrogen peroxide (H2O2) as initiator and ammonium iron (II) sulfate hexahydrate as catalyst. The reaction temperature was set at 60°C. Grafting efficiency of polyacrylic acid (PAA) onto lignin backbone was determined by varying the amounts of AA monomer, lignin and initiator. The highest grafting percentage was acquired at 60% with the amount of 6ml acrylic acid, 2ml initiator and 0.2g lignin respectively.

A simple approach for producing highly efficient DNA carriers with reduced toxicity based on modified polyallylamine.

Nowadays gene delivery is a topic in many research studies. Non-viral vectors have many advantages over viral vectors in terms of safety, immunogenicity and gene carrying capacity but they suffer from low transfection efficiency and high toxicity. In this study, polyallylamine (PAA), the cationic polymer, has been modified with hydrophobic branches to increase the transfection efficiency of the polymer. Polyallylamine with molecular weights of 15 and 65kDa was selected and grafted with butyl, hexyl and decyl acrylate at percentages of 10, 30 and 50. The ability of the modified polymer to condense DNA was examined by ethidium bromide test. The complex of modified polymer and DNA (polyplex) was characterized for size, zeta potential, transfection efficiency and cytotoxicity in Neuro2A cell lines. The results of ethidium bromide test showed that grafting of PAA decreased its ability for DNA condensation but vectors could still condense DNA at moderate and high carrier to DNA ratios. Most of polyplexes had particle size between 150 and 250nm. The prepared vectors mainly showed positive zeta potential but carriers composed of PAA with high percentage of grafting had negative zeta potential. The best transfection activity was observed in vectors with hexyl acrylate chain. Grafting of polymer reduced its cytotoxicity especially at percentages of 30 and 50. The vectors based of PAA 15kDa had better transfection efficiency than the vectors made of PAA 65kDa. In conclusion, results of the present study indicated that grafting PAA 15kDa with high percentages of hexyl acrylate can help to prepare vectors with better transfection efficiency and less cytotoxicity.

Preparation of corn starch-g-polystyrene copolymer in ionic liquid: 1-ethyl-3-methylimidazolium acetate.

The copolymer of starch grafted with polystyrene (starch-g-PS) was synthesized with high grafting percentage by utilizing the ionic liquid 1-ethyl-3-methylimidazolium acetate ([EMIM]Ac) as solvent and potassium persulfate as initiator. The effect of various parameters upon the polymerization were studied including: initiator concentration, styrene:starch weight ratio, the reaction time and temperature. Grafting percentages were calculated using an FT-IR calibration method, with values up to 114%. The resulting copolymer was characterized using FT-IR, SEM, WAXD and TGA, which demonstrated that polystyrene side chains were evenly distributed on the starch backbone. Our results indicate that ionic liquid dissolution of starch, prior to polystyrene grafting, is a versatile methodology for the synthesis of amphiphilic, polysaccharide-based graft copolymers, having high grafting percent.

Optimization of Graft Polymerization and Performance of Carboxymethyl Chitosan / Polyacrylamide Flocculants

In this study, amphoteric graft copolymer-based flocculants were prepared by conventional peroxy graft copolymerization of acrylamide (AM) onto carboxymethyl chitosan (CMCH) using potassium persulphate (PPS) initiator. The optimization of grafting of AM onto CMCH was carried out by studying the influence of various process parameters including CMCH, acrylamide and PPS concentration, as well as reaction temperature and time on percent grafting. FTIR spectral and thermal analyses of polyacrylamide/carboxymethyl chitosan graft copolymer (CMCH-g-PAM) were studied to furnish evidence of grafting. By performing the grafting process via reacting carboxymethyl chitosan (2%), acrylamide (6%) in presence of PPS (0.1%), highest grafting percentage was found at reaction temperature of 55 ⁰C with reaction time of three hours. The flocculation of the kaolinite suspensions was investigated by studying the effect of CMCH-g-PAM dosage, treatment time and pH of suspensions. The graft co-polymer flocculants resultant in this study exhibited higher efficiency comparing with those obtained from homo-polymers of carboxymethyl chitosan or polyacrylamide. Furthermore, the flocculation efficiency of these grafted copolymers was significantly increased with increasing the grafting percentage, where the maximum efficiency (93%) was attained at the highest grafting percentage (146%).

Investigation of poly(methyl acrylate) grafted chitosan as a polymeric drug carrier

The graft copolymerization of methyl acrylate (MA) onto chitosan in aqueous medium was investigated using potassium persulfate (KPS) as initiator. The grafting conditions were optimized by studying the effects of the polymerization variables (the initiator concentration, the ratio of monomer to chitosan, and reaction temperature) on the percentage of grafting (PG). PG was found to depend on these variables, and the highest grafting percentage (256 %) could be obtained at chitosan = 1 g, KPS = 4.5 × 10−3 M, methyl acrylate monomer = 6 g, T = 60 °C and t = 180 min. The graft copolymer was characterized by Fourier transform infrared spectra analysis, thermogravimetry (differential thermogravimetry, differential scanning calorimetric), X-ray powder diffraction as well as CP-MAS 13C NMR spectroscopy. These analyses are highly confirmed the formation of poly(methyl acrylate) grafted chitosan (PMAGC). Furthermore, the gelation of the grafted polymers (PG 68, 122, 218 and 256 %) in distilled water has been studied, and the results revealed that the percentage of swelling number increase with increasing PG of the polymers. Controlled release of niacin (vitamin B3) from the hydrogel of the grafted polymers (PG 68, 122 and 256 %) in aqueous medium has been studied using ultraviolet absorption to follow quantities released at different times (for each experiment: PMAGC 100 mg, niacin 2.46 mg, distilled water 100 ml). The study was repeated again with same conditions except the using of 4.92 mg of niacin instead of 2.46 mg (PG of the grafted polymer is 256 %). The diffusion coefficient (D, cm2/h) of niacin from the hydrogel of the grafted polymer (PG 256 %) was calculated depending on Higuchi model (diffusion coefficient of the first load is 0.00194 cm2/h while 0.00255 cm2/h of the second load).