Greffage de l'acide methacrylique sur des films de poly(chlorure de vinyle) par la methode radiochimique directe

Since PVC films do not swell in pure methacrylic acid (MAA) the films were subjected to gamma-rays while dipped in various mixtures MAACHCl₂. Under such conditions, the grafting proceeds smoothly and its rate exhibits a flat maximum for the mixture containing ca. 50% (molar) monomer. The rate satisfies the relationship Rate = KI^0.6 and the over-all activation energy of the process is 4 kcal/mole. MAA grafted PVC films do not swell in solvents for PMAA (such as water or methanol) even for high grafting ratios. This result is unexpected since PTFE films grafted with either acrylic or methacrylic acid swell to a large extent in water and are excellent membranes. The swelling of the grafted PVC films was investigated in mixtures 1,2-dichloroethylene -methanol. It was found that the extent of swelling was highest in the mixture containing 35% methanol. The unusual swelling properties of these grafted films are attributed to strong polar interactions between PVC and PMAA chains.     

Antibacterial modification of cellulose fibers by grafting β-cyclodextrin and inclusion with ciprofloxacin

Antibacterial-modified cellulose fiber was prepared by covalently bonding β-cyclodextrin (β-CD) with cellulose fiber via citric acid (CA) as crosslinking agent, followed by the inclusion of ciprofloxacin hydrochloride (CipHCl) as antibiotic. Effects of reaction time, temperature, concentration of β-cyclodextrin citrate (CA-β-CD) and pH on the grafting reaction were investigated, and the grafting ratio of β-CD onto cellulose fibers was 9.7 % at optimal conditions; the loading and releasing behaviors of CipHCl into/from β-CD grafted cellulose fibers were also revealed, the load amount of CipHCl into grafted cellulose fibers increased remarkably, and the release of CipHCl from the grafted cellulose fibers was prolonged. The microstructure, phase and thermal stability of modified cellulose fibers were characterized by FT-IR, ¹³C CPMAS NMR, X-ray diffraction and TGA. Considerably longer bacterial activity against E. coli and S. aureus was observed for grafted fibers loading CipHCl compared to virgin ones. Optical and mechanical properties of the paper sheets decreased generally with more antibacterial-modified fibers added.     

Characterization of methylcellulose produced from sugar cane bagasse cellulose: Crystallinity and thermal properties

In the present work, methylcellulose produced from sugar cane bagasse was characterized by FTIR, WAXD, DTA and TGA techniques. Two samples were synthesized: methylcellulose A and methylcellulose B. The only difference in the process was the addition of fresh reactants during the preparation of methylcellulose B. The ratio between the absorption intensities of the C-H stretching band at around 2900 cm⁻¹ and O-H stretching at around 3400 cm⁻¹ for methylcellulose B is higher than for methylcellulose A, indicating that methylcellulose B showed an increase in the degree of substitution (DS). Methylcellulose A presents a more heterogeneous structure, which is similar to the original cellulose as seen through FTIR and DTA. Methylcellulose B showed thermal properties similar to commercial methylcellulose. The modification of methylcellulose preparation method allows the production of a material with higher DS, crystallinity and thermal stability in relation to the original cellulose and to methylcellulose A.     

Preparation, characterization, and antimicrobial property of cotton cellulose fabric grafted with poly (propylene imine) dendrimer

Two generations of poly (propylene imine) dendrimer with amino terminated groups (G2- and G5-PPI-NH₂) were grafted on cotton cellulose fabric using cross linking agents (citric or glutaric acids). Fourier transform infrared (FTIR) spectroscopy identified ester groups which were formed between hydroxyl groups of the cotton fabric and carboxylic groups of the cross linking agents. Also, attenuated total reflectance-FTIR (ATR-FTIR) analysis confirmed formation of amide groups between the carboxylic groups of the cross linking agents and the amino end groups of the dendrimers. Nitrogen content (N-content) analysis revealed the presence of the dendrimers on the cotton fabric even after 5 washing cycles. In order to study the dispersion of the PPI dendrimers on the surface of the cotton fabric, field emission scanning electron microscopy (FE-SEM) was performed. The particle size distribution of the G2- and G5-PPI-NH₂ aqueous solutions was also determined by dynamic light scattering (DLS) analysis. Antimicrobial activity of the PPI dendrimer aqueous solutions and the cotton cellulose fabric grafted with the dendrimers was evaluated both quantitatively and qualitatively against Gram-positive bacterium (Staphylococcus aureus), Gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli) and fungus (Candida albicans). The dendrimer grafted cotton cellulose fabric exhibited a 99 % reduction in bacterial counts against S. aureus, E. coli and C. albicans. The antimicrobial activities of the grafted cotton cellulose fabric with the PPI dendrimers were maintained even after 5 washing cycles.     

The uranium recovery from aqueous solutions using amidoxime modified cellulose derivatives. III. Modification of hydroxypropylmethylcellulose with amidoxime groups

Grafting of acrylonitrile on hydroxypropyl methylcellulose films has been carried out by means of ⁶⁰Co-γ radiation, using a constant amount of hydroxypropyl methylcellulose films, at different concentrations of acrylonitrile in dimethylformamide. Grafting percentage—dose curves were obtained. 63 % of grafting yield were reached at around 3 kGy dose. Conversion of nitrile groups to amidoxime groups were achieved by aqueous solutions of NH₂OH·HCl–NaOH at 50 °C. The amidoxime conversion was followed by using FTIR spectrophotometer and determined as percentage. 98 % amidoxime conversion was achieved within 50 h. The structural, morphological and thermal evaluations of acrylonitrile grafted hydroxypropyl methylcellulose films, before and after amidoxime conversion, were performed using FTIR, AFM, Contact Angle, SEM and TGA analyses.     

Quantum mechanical calculations on cellulose–water interactions: structures,energetics, vibrational frequencies and NMR chemical shifts for surfaces of Iα and Iβ cellulose

Periodic and molecular cluster density functional theory calculations were performed on the Iα (001), Iα (021), Iβ (100), and Iβ (110) surfaces of cellulose with and without explicit H₂O molecules of hydration. The energy-minimized H-bonding structures, water adsorption energies, vibrational spectra, and ¹³C NMR chemical shifts are discussed. The H-bonded structures and water adsorption energies (ΔE_ads) are used to distinguish hydrophobic and hydrophilic cellulose–water interactions. O–H stretching vibrational modes are assigned for hydrated and dry cellulose surfaces. Calculations of the ¹³C NMR chemical shifts for the C4 and C6 surface atoms demonstrate that these δ¹³C4 and δ¹³C6 values can be upfield shifted from the bulk values as observed without rotation of the hydroxymethyl groups from the bulk tg conformation to the gt conformation as previously assumed.     

Heterogeneous grafting on polymers containing chlorine: Grafting of amide groups in water suspension and the reactivity of the new polymer towards epoxy resins

Heterogeneous grafting on polyvinylchloride suspended in water was carried out using N-butyl-3-mercaptopropionamide as nucleophile. Over 50% graft was obtained by using a small amount of solvent as a swelling agent and tricapryl methyl ammonium chloride as a phase transfer catalyst. Elemental analysis of the grafted polymer shows that the chlorine displaced from the polymers is replaced by the thio-amide group. The above conclusion is supported by NMR and IR analysis. The kinetics of the chlorine displacement from PVC by the thio amide group obeys the Shell progressive mechanism. The rate at which an individual spherical particle reacts depends on the diffusion through the reacted layer. The grafted polymer is soluble in tetrahydrofuran or nitrobenzene. The films obtained from the grafted material are brittle due to excessive internal hydrogen bonding. The electrostatic charge which is a characteristic surface phenomena in PVC is diminished in the grafted polymer which may be due to the existence of the amide group near the surface. The amide groups attached to the side chains on the polymer may participate in various reactions, e.g., with epoxy resins. IR analysis of the cured film indicates the disappearance of the oxiran band at 913 cm^?1 and an increase in the hydroxyl band around 3300 cm^?1. Thus, grafting of amide groups on PVC enables us to further modify PVC by epoxy resins.     

Preparation and characterization of hybrid cationic hydroxyethyl cellulose/sodium alginate polyelectrolyte antimicrobial films

This study aimed to develop polyelectrolyte‐structured antimicrobial food packaging materials that do not contain any antimicrobial agents. Cationic hydroxyethyl cellulose was synthesized and characterized by Fourier‐transform infrared, ¹H NMR, and ¹³C NMR spectroscopy. Its nitrogen content was determined by Kjeldahl method. Polyelectrolyte‐structured antimicrobial food packaging materials were prepared using hydroxyethyl cellulose, cationic hydroxyethyl cellulose, and sodium alginate. Antimicrobial activity of materials was defined by inhibition zone method (disc diffusion method). Thermal stability of samples was evaluated by thermal gravimetric analysis and differential scanning calorimetry. Surface morphology of samples was investigated by SEM. The obtained results prove that produced food packaging materials have good thermal and antimicrobial properties, and they can be used as food packaging material in many industries.     

Synthesis and characterization of photosensitive cinnamate-modified cellulose acetate butyrate spin-coated or network derivatives

The photochemical behavior of photosensitive materials obtained by spin-coating or network synthesis of a cellulosic polymer bearing photo-cross-linkable cinnamate groups was investigated. First, cinnamate groups were grafted on a cellulose acetate butyrate polymer, with different grafting densities. The photochemical properties of the polymers were studied in solution by UV–visible and ¹H NMR spectroscopy. Then spin-coated films and networks were prepared and characterized as a function of the number of cinnamate groups per cellulosic unit. The water-wetting properties of both surfaces were studied by dynamic contact angle measurements, before and after photoirradiation, and subsequent heating. The surfaces obtained by the two methods have significantly different behaviors that can be assigned to the distinct photochemical pathways of the cinnamate groups upon irradiation depending on the sample preparation. Indeed, dimerization reaction is evidenced as the main process in the spin-coated films while the expected isomerization is predominant at the surface of the polymer networks.     

One-pot synthesis,characterization, and drug loading of polysaccharide-based nanoparticles with carboxy functional groups

Herein, various polysaccharide-based nanoparticles were synthesized from dextran, hydroxypropyl cellulose, and hydroxyethyl cellulose, respectively, by a self-assembly assisted approach. This approach enables us to prepare stable polysaccharide-based nanoparticles with carboxy functional groups directly from monomers without using any surfactant and organic solvent. The existence of abundant carboxyls in these polysaccharide-based nanoparticles provides them obvious pH sensitivity as verified by ¹H nuclear magnetic resonance as well as the potential in loading cationic drug.     

Graft copolymerization ofN‐vinyl‐pyrrolidone and acrylamide on cellulose derivatives: synthesis,characterization and study of their biological effect

Graft copolymers of carboxymethyl cellulose and hydroxyethyl cellulose with N‐vinyl‐2‐pyrrolidone and acrylamide have been synthesized by grafting copolymer of N‐vinyl‐2‐pyrrolidone and acrylamide onto a mixture of carboxymethyl cellulose and hydroxyethyl cellulose by a solution polymerization technique using a redox initiation system. The graft copolymers were characterized by ¹³C‐NMR spectroscopy and scanning electron microscopy. These graft copolymers have been tested for their biodegradability and biological activity. None of the graft copolymer solutions shows any microbial degradation up to 10 days. The reported results are evidence of the possibility of anti‐fungi effect. Copyright © 2002 John Wiley & Sons, Ltd.     

Cellulose Functionalization via ATRP Grafting of Glycidyl Methacrylate for Cr（VI） Adsorption

Cellulose was first grafted with glycidyl methacrylate （GMA） in an ionic liquid via atom transfer radical polymerization （ATRP） and then the introduced epoxy groups were reacted with ethanediamine （EDA） to obtain an amino adsorbent. The grafting copolymer and the obtained adsorbent were characterized by FTIR, aH NMR, TEM and SEM. The results showed that the grafted copolymers had grafted polymer chains with well-controlled molecu- lar weight and polydispersity, the polymerization was a controlled system. The cellulose adsorbent had numerous micropores on the surface and showed high performance for Cr（VI） adsorption. The adsorption behavior was pH dependent and the sorption equilibrium was achieved within 2 h on the adsorbent.     

Surface initiated ring-opening polymerization of l-proline N-carboxy anhydride from single and multi walled carbon nanotubes

Ring-opening surface initiated polymerization of l-proline N-carboxyanhydride was performed from amine functionalized single (SWNTs) and multi walled carbon nanotubes (MWNTs). The primary amines were grafted on the surfaces via a well-studied Diels–Alder cycloaddition. The initiator attachment helped the debundling of carbon nanotubes as shown by atomic force microscopy (AFM) studies where only small aggregates were observed. Thermogravimetric analysis revealed high wt% of grafted polyproline on the carbon nanotubes surface after the ring-opening polymerization. AFM studies showed a rather uniform layer of grafted polyproline from both MWNTs and SWNTs. The grafting of PLP on the surface was also verified by FTIR and Raman spectroscopy as well as ¹H NMR in CDCl₃/d-TFA. The polyproline grafted carbon nanotubes (CNTs) were readily dissolved in organic solvents in contrast to the insoluble pristine and amine-functionalized CNTs.     

Protein immobilization on the surface of poly-L-lactic acid films for improvement of cellular interactions

To covalently immobilize gelatin or collagen type I on poly-L-lactic acid (PLLA) film surfaces poly(hydroxyethyl methacrylate) (PHEMA) or poly(methacrylic acid) (PMAA) was grafted via photooxidization and subsequent UV-induced polymerization [Makromol. Chem. 186 (1985) 1533.1]. For films grafted with PHEMA, methyl sulfonyl chloride was used to activate the hydroxyl groups and for films grafted with PMAA 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide was used to activate the carboxyl groups. Gelatin and collagen were finally reacted with the activated hydroxyl or carboxyl groups to obtain covalently immobilized protein layers. Grafting of PHEMA, PMAA and protein on the surfaces was confirmed using ATR-IR and XPS. Surface wettability of the modified films was improved. The protein immobilized PLLA may be widely used as a biocompatible material.     

Superabsorbent materials derived from hydroxyethyl cellulose and bentonite: Preparation,characterization and swelling capacities

Superabsorbent polymers (SAPs) and composites (SAPCs) were prepared entirely by graft copolymerization of polyacrylamide (PAM) onto hydroxyethyl cellulose (HEC), using potassium persulfate (KPS) as an initiator, and N,N′-methylenebisacrylamide (MBA) as a crosslinker, in an aqueous solution. The extent of grafting was evaluated from % grafting efficiency (%GE) for various HEC/AM ratios, and a near optimal ratio was determined. Influences of various preparation parameters, i.e., the ratio of HEC/AM, amount of initiator and crosslinker, reaction temperature and time, and amount of filler on water swelling capacity of SAPs and SAPCs were studied. An FT-IR determination confirmed that the PAM was successfully grafted onto the HEC backbone, by showing absorption bands of the HEC backbone and new absorption bands from the grafted copolymer. The swelling capacity of SAPs and SAPCs depended strongly on different parameters, and the maximum swelling capacity was over 426 g/g and 538 g/g for the SAPs and SAPCs, respectively.     

Synthesis and thermoreversible gelation of diblock methylcellulose analogues via Huisgen 1,3-dipolar cycloaddition

A novel synthetic method to link acetylated cellulose derivatives with methylated cellulose derivatives via Huisgen 1,3-dipolar cycloaddition was developed to produce 1,2,3-triazole-linked diblock copolymers consisting of hydrophilic cellobiose or low-molecular-weight cellulose and a hydrophobic 2,3,6-tri-O-methyl-cellulose. Huisgen 1,3-dipolar cycloaddition had the advantage over glycosylation reaction of being able to connect a hydrophilic block having higher molecular weight than cellobiose with a hydrophobic 2,3,6-tri-O-methyl-cellulose block. As a consequence, 2.0 wt% aqueous solutions of the 1,2,3-triazole-linked diblock methylcellulose analogues exhibited the thermoreversible gelation in water at around 25 °C as same as that of β-(1 → 4)-linked diblock methylcellulose. Differential scanning calorimetry measurements of 2.0 wt% aqueous solutions of the diblock copolymers revealed that an important structural factor for its thermoreversible gelation was not a β-(1 → 4)-glycosidic linkage between hydrophilic and hydrophobic blocks of diblock methylcellulose, but a sequence of anhydro 2,3,6-tri-O-methyl-glucopyranosyl units and that of unmodified glucopyranosyl ones.     

Removal of boron(III) by N-methylglucamine-type cellulose derivatives with higher adsorption rate

To obtain adsorbents for boron(III) derived from a natural polymer, two forms (powder and fiber) of N-methylglucamine-type cellulose derivatives were newly synthesized. After the graft polymerization of two forms of cellulose with vinyl monomer having epoxy groups, the N-methylglucamine-type cellulose derivatives were obtained by the reaction of the grafted cellulose with N-methylglucamine. The adsorption capacities of the cellulose derivatives for boron(III) were the same levels as that of a commercially available N-methylglucamine-type polystyrene resin. However, the cellulose derivatives adsorbed boron(III) more quickly than the polystyrene resin. The adsorption and desorption of boron(III) with a column method using the cellulose fiber were achieved at a higher flow rate than that using the polystyrene resin. In addition, the boron(III), adsorbed on the cellulose fiber column, was quantitatively recovered with dilute hydrochloric acid in 20- and 200-fold increased concentrations. Consequently, it was found that the cellulose derivatives were superior to the polystyrene resin as adsorbents for boron(III) for treatment of a large quantity of wastewater.     

Fonctionnalisation du polychlorure de vinyle: Greffage de fonctions plastifiantes (type ester d'éthyle-hexyle)

The grafting of plasticizing groups such as 2-ethyl-hexyl ester on PVC has been carried out either in solution or in the gel state through nucleophilic substitution of chlorine atoms, with the help of sodium salts of 2-ethyl-hexyl esters of o-mercaptobenzoic acid and thioglycollic acid. As with sodium thiophenate, the substitution of chlorine atoms is stereoselective with respect to iso and heterotactic triads. The glass transition temperature is lowered as the substitution rate increases and the plasticizing power of grafted 2-ethyl-hexyl ester groups of thioglycollic acid is greater than those introduced by o-mercaptobenzoic acid. Further the plasticizing power of 2-ethyl-hexyl ester groups is decreased when they are grafted on the polymer.     

Sorbents based on asbestos with a layer of an hydroxyethylcyclam derivative of PVC containing aquacomplexes of sulfuric acid or sodium hydroxide with aza-crown groups

Aquacomplexes of sulfuric acid and sodium hydroxide with aza-crown groups are synthesized in cavities of a sorbent from the porous layer of a PVC cyclam-derivative grafted onto fibers of asbestos fabric. The structure of sorbents with complexes is studied and their adsorption characteristics are determined. It is shown that the affinity of the developed surface toward ethanol, benzene, and hexane depends on the nature of complexes in the pore walls, and the volume of cavities formed as a result of the pores on the developed asbestos surface being coated with networks of aza-crown groups is larger than that of cavities with walls of aza-crown groups in the layers of a PVC cyclam derivative. Indicators of H⁺- and OH^–-conductivity of sorbents with complexes as electrochemical bridges are determined. It is shown that the major part of H⁺- and OH^–-ions moves through complexes with aza-crown groups in the region of cavities formed of pores on the surface of asbestos.     

Hydrogen ion-selective poly(vinyl chloride) membrane electrode based on a p-tert-butylcalix[4]arene-oxacrown-4

A hydrogen ion-selective poly(vinyl chloride) (PVC) membrane electrode was developed using p-tert-butylcalix[4]arene-oxacrown-4 as ionophore. Apart from the ionophore, plasticisers and lipophilic anions were blended, in various proportions, with PVC in tetrahydrofurane and mixtures so prepared were poured onto glass surfaces to form the membrane. 2-Nitrophenylpentylether has proved to be the best alternative as plasticiser and the lipophilic anions tried have turned out to have an adverse effect on the pH response. The electrode of the optimum characteristics had a composition of 2% p-tert-butylcalix[4]arene-oxacrown-4, 68.3% o-NPPE and 29.7% PVC. The electrode showed an apparent Nernstian response in the pH range 2-11 with a slope of 54.2±0.4 mV pH⁻¹ at 20±1 °C. It has a rapid potential-response to changes of pH, high ion selectivity towards lithium, sodium and potassium, and other characteristics comparable to those reported for the conventional pH glass membrane electrode. It appears to be a suitable potentiometric indicator electrode specifically for hydrofluoric acid solutions.