High Grafting Degree Research Articles

Uranium Adsorbent Fibers Prepared by Atom-Transfer Radical Polymerization (ATRP) from Poly(vinyl chloride)-co-chlorinated Poly(vinyl chloride) (PVC-co-CPVC) Fiber

The need to secure future supplies of energy attracts researchers in several countries to a vast resource of nuclear energy fuel: uranium in seawater (estimated at 4.5 billion tons in seawater). In this study, we developed effective adsorbent fibers for the recovery of uranium from seawater via atom-transfer radical polymerization (ATRP) from a poly(vinyl chloride)-co-chlorinated poly(vinyl chloride) (PVC-co-CPVC) fiber. ATRP was employed in the surface graft polymerization of acrylonitrile (AN) and tert-butyl acrylate (tBA), precursors for uranium-interacting functional groups, from PVC-co-CPVC fiber. The [tBA]/[AN] was systematically varied to identify the optimal ratio between hydrophilic groups (from tBA) and uranyl-binding ligands (from AN). The best performing adsorbent fiber, the one with the optimal [tBA]/[AN] ratio and a high degree of grafting (1390%), demonstrated uranium adsorption capacities that are significantly greater than those of the Japan Atomic Energy Agency (JAEA) reference fiber in ...

The effect of epoxy and tetramethyl thiuram disulfide on melt‐grafting of maleic anhydride onto polypropylene by reactive extrusion

ABSTRACTIn this report, melt grafting of maleic anhydride (MAH) and epoxy resin onto polypropylene (PP) by peroxide‐initiated reactive extrusion has been investigated. As evidenced by Fourier transform infrared spectroscopy, both MAH and epoxy resin were successfully grafted onto PP through the reactions of MAH with PP and epoxy resin with MAH. It was found that tetramethyl thiuram disulfide could promote the grafting of MAH and inhibit the degradation of PP, as revealed by chemical titration and melt flow experiments, through prolonging the lifetime of the macroradical; meanwhile, epoxy resin could reduce the sublimation of MAH and the maximum grafting degree of MAH. Furthermore, the introduction of grafted products was found to enhance the mechanical properties of PP/glass fiber composites, and this influence was very significant at high grafting degrees with a high content of epoxy resin, which could be interpreted in terms of improved compatibility and adhesion at the interface. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43422.

Coordinated pH/redox dual-sensitive and hepatoma-targeted multifunctional polymeric micelle system for stimuli-triggered doxorubicin release: Synthesis, characterization and in vitro evaluation

Multifunctional polymeric micelles self-assembled from a DOX-conjugated methoxypolyethylene glycols-b-poly (6-O-methacryloyl-d-galactopyranose)-disulfide bond-DOX (mPEG-b-PMAGP-SS-DOX) copolymer were prepared as an antitumor carrier for doxorubicin delivery, of which the chemical modification with disulfide bonds and hydrazone bonds allowed micelles to release doxorubicin (DOX) selectively at acidic pH and high redox conditions. The resulting micelles exhibited coordinated pH/redox dual-sensitive and hepatoma-targeted multifunction with sustaining stability in aqueous media. The multifunctional micelles showed spherical shapes with a mean diameter of 93±2.08nm, a low polydispersity index (PDI) of 0.21, a low CMC value of 0.095mg/mL, a high drug grafting degree of 56.9% and a drug content of 39.0%. Remarkably, in vitro drug release studies clearly exhibited a pH and redox dual-sensitive drug release profile with significantly accelerated drug release treated with pH 5.0 and 10mM GSH (88.4% in 72h) without drug burst release. The tumor proliferation assays indicated that DOX-grafted micelles, along with low cytotoxicity and well biocompatibility to normal cells up to a concentration of 10μg/mL, inhibited the proliferation of HepG2 cells in a formulation-, time- and concentration-dependent manner in comparison with MCF-7 cells which was similar to free DOX. Anticancer activity releaved that the disulfide-modified micelles possessed much higher anti-hepatoma activity with a low IC50 value of 1.1μg/mL following a 72h incubation. Furthermore, the intracellular uptake tested by CLSM and FCM demonstrated that multifunctional polymeric micelles could be more efficiently taken up by HepG2 cells compared with MCF-7 cells, agreed well with MTT assays, suggesting these well-defined micelles provide a potential drug delivery system for dual-responsive controlled drug release and enhanced anti-hepatoma therapy.

Synthesis and Non-Isothermal Crystallization Behaviors of Maleic Anhydride onto High Density Polyethylene

The grafting reaction for maleic anhydride (MA) onto high density polyethylene (HDPE) was investigated from solution process with initiators. The chemical modification of neat HDPE was carried out with various contents of MA (3-21 wt.%) and initiator (0.2-1 wt.%) at different temperature (80-130℃). The grafting degree was obtained from the titration and the highest grafting degree was 3.1%. The grafting degree increased as the content of MA and initiator increased, however, the highest grafting degree was demonstrated for a particular content of MA and initiator. In the non-isothermal crystallization kinetics, the Ozawa model was unsuitable method to investigate the crystallization behavior of MA onto HDPE, whereas the Avrami and Liu models found effective. The crystallization rate was accelerated as the cooling rate increased, but postponed by combination of MA onto neat HDPE backbone.

Surface functionalization of rubber latex nanoparticles with sulfidosilane moieties

ABSTRACTPolybutadiene latex particles were functionalized with bis[3‐(triethoxysilyl) propyl] tetrasulfide (TESPT) in the presence of zinc oxide as an activator and ethanol as a co‐solvent. The success of this reaction was confirmed both by the peaks attributed to Si‐O groups at 1085 and 1110 cm−1 and C‐S bond at 630 cm−1 which appeared after reaction in Attenuated Fourier Transform Infrared (ATR‐FTIR) Spectra and also by increasing in the particle size diameter of latex particles (from 95 to 127 nm) in Dynamic Light Scattering analysis. X‐ray Diffraction results also showed changes in crystalline structure of the modified particles (as a strong decrease in the intensity of peak at 2θ=19.54). The effect of reactant concentration in a constant amount of TESPT (by varying the water and ethanol content), reaction time, activator size (micro and nanoparticles), and pH (≈7, 8.5) were investigated on degree of grafting (obtained from thermogravimetric analysis and ATR‐FTIR spectra), particle size diameter, cross‐link density, and swelling ratio of the samples. The amounts of silane grafting and cross‐link density of polymer particles were increased by an increase in the reaction time. The highest grafting degree was observed at low concentration of TESPT. Silane functionalization was also improved in a slight basic condition (pH=8.5) rather than neutral pH. The grafting reaction took place such as sulfur pre‐vulcanization and the possible mechanism of this reaction was discussed. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43268.

Design and preparation of matrine surface-imprinted material and studies on its molecule recognition selectivity

A matrine molecule surface-imprinted material was designed and prepared using an effective surface-imprinting technique developed by our group, and its molecular recognition performance and mechanism were investigated in depth. Monomer glycidyl methacrylate (GMA) was first graft-polymerized on the surfaces of micron-sized silica gel particles in surface-initiated graft polymerization manner, obtaining the grafted particles PGMA/SiO2 with high grafting degree. Subsequently, the ring-opening reaction of the epoxy groups of the grafted macromolecules PGMA with 5-aminosalicylic acid (5-ASA) was carried out, resulting in the functional grafted particle SA-PGMA/SiO2, on whose surfaces salicylic acid as functional group was chemically bonded. By right of the mutual strong secondary bond forces, electrostatic interaction and hydrogen bonding, SA-PGMA/SiO2 particles produced strong adsorption for matrine. Finally, with this strong adsorption, matrine molecule surface imprinting was carried out on the surfaces of SA-PGMA/SiO2 particles with ethylene glycol diglycidyl ether as cross-linking agent, resulting in the matrine molecule surface-imprinted material MIP-SAP/SiO2. The binding characteristic of MIP-SAP/SiO2 toward matrine was investigated in depth with both batch and column methods and using oxymatrine and cytisine as two contrast alkaloids. The experimental results show that MIP-SAP/SiO2 has special recognition selectivity and excellent binding affinity for matrine. Relative to oxymatrine and cytisine, the selectivity coefficients of MIP-SAP/SiO2 for matrine are 5.66 and 11.17, respectively.

Synergistic compatibilization and reinforcement of HDPE/wood flour composites

ABSTRACTMulti‐monomer grafted copolymers, high‐density polyethylene‐grafted‐maleic anhydride‐styrene (HDPE‐g‐(MAH‐St)) and polyethylene wax‐grafted‐ maleic anhydride ((PE wax)‐g‐MAH), were synthesized and applied to prepare high‐performance high‐density polyethylene (HDPE)/wood flour (WF) composites. Interfacial synergistic compatibilization was studied via the coordinated blending of high‐density polyethylene‐grafted‐maleic anhydride (MPE‐St) and polyethylene wax‐grafted‐ maleic anhydride (MPW) in the high‐density polyethylene (HDPE)/wood flour (WF) composites. Scanning electron microscopy (SEM) morphology and three‐dimensional WF sketch presented that strong interactive interface between HDPE and WF, formed by MPE‐St with high graft degree of maleic anhydride (MAH) together with the permeating effect of MPW with a low molecular weight. Experimental results demonstrated that HDPE/WF composites compatibilized by MPE‐St/MPW compounds showed significant improvement in mechanical properties, rheological properties, and water resistance than those compatibilized by MPE, MPE‐St or MPW separately and the uncompatibilized composites. The mass ratio of MPE‐St/MPW for optimizing the HDPE/WF composites was 5:1. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42958.

Preparation and properties of a novel environmentally friendly film from maleated poly(vinyl alcohol) grafted with chitosan in solution form: the effect of different production factors

A maleated poly(vinyl alcohol) (PVAM)-g-chitosan (CS) (PVAM-g-CS) film was prepared in solution form using potassium persulfate (K2S2O8) as an initiator. The influence of the PVAM:CS ratio, the reaction time and temperature and the concentration of K2S2O8 on the properties of the PVAM-g-CS were investigated. Ether linkage of the PVAM-g-CS was observed at 1154 and 1089 cm−1 by ATR-FTIR. The conditions for grafting CS to PVAM were developed and optimized. The highest degree of grafting was observed at a ratio of 9:1 PVAM:CS. The optimum grafting conditions were found to be 50 °C for a reaction time of 1 h, with a ratio of PVAM:CS of 9:1 and a concentration of 0.5 % K2S2O8. The maximum and minimum swelling ratios were 150 and 330 %, respectively. The tensile strength of the PVAM was enhanced after the incorporation of CS in the PVAM. The highest tensile strength of 24 MPa was found at a ratio of 5:5 PVAM:CS. The PVAM-g-CS shows a high efficiency of controlling capsaicin release in base–acid medium and was easily biodegradable in natural soil especially with high proportions of CS.

Grafting of Linear Low Density Polyethylene (LLDPE) onto Tallow via Anhydride: Effect of Residence Time

Grafting polymerization by reactive small molecules involves the formation of graft copolymers from a reaction between polymers and monomers. Monomer units can be propagated onto the polymer backbone to form a graft structure. In the polymer processing industry, the internal mixer is the most important piece of machinery. The study used the internal mixer as a reactor to make a reactive process with the interest in residence time,as the residence time is importance in the chemical reaction. By increase the residence time, the optimum degree of grafting may be occurred. The objectives of this study are to increase the knowledge and understanding of the internal mixer process, determine optimum residence time process variables for grafting LLDPE and study the effect of the residence time toward the LLDPE grafting process. Several residence times was choosing for the specified sample, to study the effect of the residence time which were 60 s, 120 s, 180 s, 240 s, 300 s and 600 s. Degree of grafting (DOG) was calculated to determine the grafting of LLDPE grafted copolymers and a series of samples in which degrees of grafting had been determined by chemical titration. Residence time at 300 s produces the optimum DOG of monomer onto polymer. Longer residence time will produce high degree of grafting but will cause other issues such as increasing in gel content and lower the mechanical properties of the grafted polymer.

Radiation-chemical effect of helium ions on kinetics of styrene accumulation in polymer matrix of proton-exchange membrane

The degree of grafting of styrene monomer to a polyvinylidene fluoride (PVDF) polymer film matrix by bombardment with 27-MeV helium ions has been studied. The grafting of styrene was carried out by two methods, the direct irradiating with helium ions the polymer immersed in a styrene monomer solution and using the a “postradiation effect” when the polymer has been irradiated in a vacuum, air, or argon atmosphere. The experimental dependences of the degree of grafting on the absorbed dose, irradiation medium, and grafting-solution the composition are presented. The results of microscopic, IR and UV spectroscopic investigations are reported. It has been shown that the direct grafting of styrene onto the PVDF films results in higher degrees of grafting compared with those obtained using the postradiation effect.

Grafting of poly (lactic acid) with maleic anhydride using supercritical carbon dioxide

The aim of this work was to modify poly lactic acid (PLA) via free radical grafting with maleic anhydride (MA) by using supercritical carbon dioxide (SCCO2). Benzoyl peroxide (BPO) was used as an initiator. The solubility of MA in SCCO2 was first determined to estimate the suitable grafting conditions and equilibrium. From the solubility study of MA in SCCO2, it was found that the solubility of MA in SCCO2 increased with the increasing pressure and dissolution time. PLA films were first prepared by compression molding. The ratio of MA to BPO was 2:1. The reaction temperature and pressure were 70°C and 100 bar respectively. The grafting reaction and the degree of grafting were characterized by nuclear magnetic resonance (NMR) spectroscopy and titration, respectively. Scanning electron microscope (SEM) technique and contact angle were used to confirm the changes in physical properties of PLA film grafted MA. NMR spectrum indicated that the grafting of MA onto PLA was successively achieved. Degree of grafting by using SCCO2 was as high as 0.98%. This provided rather high grafting degree compared with other processes. SEM pictures showed the rough surface structure on modified PLA film. In addition, contact angle results showed an improvement of the hydrophilicity by maleic anhydride grafting onto polymers.

Modification of poly(lactic acid) using itaconic anhydride by reactive extrusion

Itaconic anhydride (IA) was grafted onto poly(lactic acid) (PLA) using dicumyl peroxide (DCP) as radical initiator using free-radical grafting. Different concentrations of monomer (2–6wt.%) and initiator (0.5–0.75wt.%) at 180 and 200°C were used for chemical modification. Grafting was confirmed using titration and the highest degree of grafting was 0.75%. The degree of grafting increased gradually with increasing IA and DCP concentration, with minimal chain scission. Reaction kinetics showed that the initial rate of reaction was between 0.024 and 0.03 (l/mols)1/2, depending on temperature. Grafted PLA showed a significant change in enthalpy of crystallization, enthalpy of fusion as well as increased tensile strength and elongation at break accompanied by a reduction in stiffness.

Direct capture of His₆-tagged proteins using megaporous cryogels developed for metal-ion affinity chromatography.

Immobilized metal-ion affinity chromatography (IMAC) has been developed for the rapid isolation and purification of recombinant proteins. In this chapter, megaporous cryogels were synthesized having metal-ion affinity functionality, and their adsorptive properties were investigated. These cryogels have large pore sizes ranging from 10 to 100 μm with corresponding porosities between 80 and 90%. The synthesized IMAC-cryogel had a total ligand density of 770 μmol/g. Twelve milligram of a His6-tagged protein (NAD(P)H-dependent 2-cyclohexen-1-one-reductase) can be purified from a crude cell extract per gram of IMAC-cryogels. The protein binding capacity is increased with higher degrees of grafting, although a slight decrease in column efficiency may result. This chapter provides methodologies for a rapid single-step purification of recombinant His6-tagged proteins from crude cell extracts using IMAC-cryogels.

High-energy, stable and recycled molecular solar thermal storage materials using AZO/graphene hybrids by optimizing hydrogen bonds.

An important method for establishing a high-energy, stable and recycled molecular solar heat system is by designing and preparing novel photo-isomerizable molecules with a high enthalpy and a long thermal life by controlling molecular interactions. A meta- and ortho-bis-substituted azobenzene chromophore (AZO) is covalently grafted onto reduced graphene oxide (RGO) for solar thermal storage materials. High grafting degree and close-packed molecules enable intermolecular hydrogen bonds (H-bonds) for both trans-(E) and cis-(Z) isomers of AZO on the surface of nanosheets, resulting in a dramatic increase in enthalpy and lifetime. The metastable Z-form of AZO on RGO is thermally stabilized with a half-life of 52 days by steric hindrance and intermolecular H-bonds calculated using density functional theory (DFT). The AZO-RGO fuel shows a high storage capacity of 138 Wh kg(-1) by optimizing intermolecular H-bonds with a good cycling stability for 50 cycles induced by visible light at 520 nm. Our work opens up a new method for making advanced molecular solar thermal storage materials by tuning molecular interactions on a nano-template.

The optimized synthesis of starch-g-lactic acid copolymer with high grafting degree catalyzed by sulfuric acid

The starch-g-lactic acid copolymer was synthesized with catalysis of sulfuric acid by onestep process, and the structure of starch-g-lactic acid copolymer was characterized by means of IR, 13C-NMR, HMBC, XRD, and SEM. The experimental results show that the maximum grafting degree of starch can reach 75% when the starch-g-lactic acid copolymer is activated at 80 °C for 2 h and reacted with lactic acid at 90 °C for 4 h in vacuum.

Synthesis of starch-g-lactic acid copolymer with high grafting degree catalyzed by ammonia water.

The study of starch-g-lactic acid copolymer has gained much attention for its completely degradable property, but its intricate synthetic procedure and low graft degree inhibited its further application. In this work, the synthesis of starch-g-lactic acid copolymer was attempted via the catalysis of ammonia water by one-step process, and the structure of starch-g-lactic acid copolymer was characterized by means of IR, (13)C NMR and HMBC. The synthetic conditions were optimized as follows, the starch was activated for 2h at 80°C at first, starch and lactic acid with weight ratios of 1:4 reacted for 4h at 90°C in vacuum. The starch-g-lactic acid copolymer can be finally obtained with graft degree of starch 58.9%.

Microwave-Assisted Synthesis and Characterization of Poly(2-(dimethylamino)ethyl methacrylate) Grafted Gellan Gum

Poly(2-(dimethylamino)ethylmethacrylate) was grafted on gellan gum (GG) in aqueous medium under microwave irradiation using ammonium persulfate and N,N,N′N′-tetramethylethylenediamine as the initiation system. Grafted copolymers were characterized by FT-IR, TGA, and SEM techniques. The influence of microwave power, exposure time, and composition of the reaction mixture on extent of grafting was studied. Conditions for obtaining the highest degree of grafting were optimized. The rate of grafting was determined from weight measurements. The overall activation energy for grafting is found to be 31.2 kJ/mol, indicating the occurrence of the grafting process with absorption of low thermal energy.

Efficient Green Protocols for Preparation of Highly Functionalized β-Cyclodextrin-Grafted Silica

The modification and characterization of porous particles and matrices using cyclodextrins (CD) have attracted a large amount of interest in recent years. In fact, CDs are at the heart of this study that aims to graft β-CD onto silica particles by means of efficient protocols and nonconventional energy sources. In particular, the use of microwave irradiation, benign reaction media, and a solvent-free planetary ball mill has provided a high degree of grafting. The inclusive properties of β-CD-grafted silica were tested with phenolphthalein and its sorption capacity with methyl orange, and both tests confirmed the efficiency of the grafting protocols. Samples were extensively characterized by TGA, elemental analysis, IR, BET, and HRTEM. The green protocols herein reported can facilitate access to functionalized silica and pave the way for its use in novel applications.

Study on recognition and separation of rare earth ions at picometre scale by using efficient ion-surface imprinted polymer materials

The graft-polymerization of hydroxyethyl methylacrylate (HEMA) on micro-sized silica gel particles was first conducted by initiating of a surface-initiating system, which was constituted by the bonded amino groups on the modified silica gel particles and persulfate in the solution, obtaining the grafted particles PHEMA/SiO2 with a high grafting degree of 40g/100g. Subsequently, 8-hydroxyquinoline as a ligand with strong chelating ability for metal ions was bonded on the side chains of the grafted macromolecule PHEMA through the substitution reaction between 5-chloromethyl-8-hydroxyquinoline (CHQ) and the hydroxyl group of the grafted macromolecule PHEMA, preparing the functional grafted particles HQ-PHEMA/SiO2. On the basis of examining the chelating adsorption property of HQ-PHEMA/SiO2 particles for Pr3+ ion, the Pr3+ ion surface-imprinting was carried out by using the effective surface-imprinting technique of “pre-grafting and post-crosslinking/imprinting” established by our group. During the surface-imprinting process, Pr3+ ion was used as a template ion, and 2,2′-dichlorodiethyl ether was used crosslinked, resulting in the Pr3+ ion surface-imprinted material IIP-HQP/SiO2. The recognition and binding characters of IIP-HQP/SiO2 towards Pr3+ ion were investigated in-depth with La3+ and Ce3+ ions as two contrast ions. The experimental results show that the IIP-HQP/SiO2 particles possess special recognition selectivity and high binding ability for Pr3+ ion. The binding capacity of IIP-HQP/SiO2 for Pr3+ ion reaches 0.13mmol/g, and relative to La3+ and Ce3+ ions, the selectivity coefficients of IIP-HQP/SiO2 for Pr3+ ion are 5.22 and 5.12, respectively. La, Ce and Pr are three neighbouring rare earth elements, and the ion radius differences between La3+, Ce3+ and Pr3+ ions are only in a range of 2–5pm. Obviously, in this investigation, the mutual separation of La3+, Ce3+ and Pr3+ ions at picometre scale is realized successfully by using the ion surface-imprinted polymer material with high performance.

Nanofiltration hollow fiber membranes with high charge density prepared by simultaneous electron beam radiation-induced graft polymerization for removal of Cr(VI)

A novel kind of nanofiltration (NF) hollow fiber membranes with high density of negative charges and relative high permeate flux was prepared by grafting of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) onto a polysulfone (PSf) ultrafiltration hollow fiber membrane using the simultaneous electron beam radiation-induced method. ATR-FTIR and FESEM analyses revealed that the monomer was grafted on both the outer and inner surfaces of the membrane. The effects of irradiation dose and monomer concentration on the mean pore size and performance of the membranes were investigated. The prepared NF membranes were used for removal of Cr(VI) from aqueous solution under varying conditions such as pH value, initial Cr(VI) concentration and coexisting ions. The experimental results showed that Cr(VI) could be effectively removed by the resulting NF membranes when the pH of the solution was higher than 8 and the performance of Cr(VI) removal was nearly not affected by the presence of Na2SO4 and NaCl in the experimental range. It was indicated that the high negative charge density resulting from the high degree of grafting made the grafted membranes achieve nanofiltration performance at a relative large pore size.