Grafting Vinyl Monomers onto Silk Fibers. V. Graft Copolymerization of Methyl Methacrylate onto Silk with Potassium Permanganate as Initiator

The graft copolymerization of methyl methacrylate onto silk fibers in aqueous solution with the use of manganese (IV) ions as initiator was investigated. The rate of grafting was determined by varying monomer, acidity of the medium, temperature, nature of silk, and the reaction medium. The graft yield increases significantly with increase of manganese (IV) concentration up to 15 meq/liter; with further increase of manganese (IV) concentration, the graft yield decreases. The effect of the increase of monomer concentration brings about a significant enhancement in the graft yield up to 7%, and with further increase of monomer concentration the graft yield decreases. The graft yield is considerably influenced by chemical modification prior to grafting. The effect of some inorganic salts and anionic surfactants on the rate of grafting has been investigated.     

Grafting Vinyl Monomers onto Tussah Silk Fiber. I. Graft Copolymerization of Methyl Methacrylate onto Nonmulberry Tussah Silk by Tetravalent Cerium Ion

The graft copolymerization of methyl methacrylate onto nonmulberry natural tussah silk fibers was investigated in aqueous solution using tetravalent cerium as initiator. The rate of grafting was determined by varying the monomer concentration, the cerium (IV) concentration, the temperature, and the nature of the silk. With increasing monomer concentration the graft yield increased (up to 0.657 M) and thereafter decreased. The graft yield also increased with increasing cerium (IV) concentration. The graft-on was influenced by chemical modification of the tussah silk prior to grafting. The effect of certain inorganic salts on the rate of grafting was investigated.     

Grafting of Vinyl Monomers onto Silk Fibers

Abstract

Graft copolymerization onto textile fibers is a challenging field of research with unlimited future prospects [1–6]. This is attractive to chemists as a means of chemical modification of natural macromolecules since, in general, degradation could be minimized. Thus it is hoped to retain the desirable properties of the natural material and give it additional properties through the added polymer. Means of forming copolymers with natural macromolecules are now well understood because the techniques of polymer chemists are usually applicable. A vast number of combinations of composition and conformation is possible for each copolymer, and the properties of each copolymer may vary with the mode of formation employed.     

Grafting Vinyl Monomers onto Silk Fibers: Graft Copolymerization of Vinyl Monomers onto Silk Using the Vanadyl Acetylacetonate Complex

Abstract

The graft copolymerization of methyl methacrylate (MMA) onto mulberry silk fibers was studied in aqueous solution using the acetylacetonate oxovanadium (IV) complex. The rate of grafting was investigated by varying the concentration of the monomer and the complex, the acidity of the medium, the solvent composition of the reaction medium, the surfactants, and the inhibitors. The graft yield increases with increasing concentration of the initiator up to 8.75 × 10^?5 mol/L, of the monomer up to 0.5634 mol/L, and thereafter it decreases. Among the various vinyl monomers studied, MMA was found to be most suitable for grafting. Grafting increases with increasing concentration of HCIO₄ and with increasing temperature. Inhibitors like picryl chloride and hydroquinone significantly decrease the extent of grafting. Alcoholic solvents at a solvents/water ration of 10:90 seem to constitute the most favorable medium for grafting. A suitable reaction scheme has been proposed, and the activation energy calculated from the Arrhenius plots.     

Graft Copolymerization of Vinyl Monomers onto Silk Fibers

Modification of the properties of textile fibers in order to get a fiber of improved textile performance is the subject of study of several groups of scientists and technologists [1–4]. Of the several methods available, grafting promises to be a potentially effective means of altering the fiber properties through the added polymer formed in situ without destroying the basic properties of the parent fiber. Copolymerization is attractive to chemists as a means of modifying macromolecules since, in general, degradation can be minimized. The desirable properties of the polymer are retained and copolymerization provides additional properties through the added polymer. The added polymer may be formed in situ by polymerization of a monomer or monomers, by condensation of reactants, or by the deposition of preformed polymer.     

一缩二乙醇二甲基丙烯酸酯对真丝接枝的反应性

研究了一缩二乙二醇二甲基丙烯酸酯在空气存在下，用过硫酸钾(KPS)在水液 中对真丝的接枝。对接枝的条件，如单体、引发剂、甲酸(FA)和乳化剂OP的浓度以 及温度和时间对接枝率的影响进行了测试。发现了较佳的接枝条件是：温度 = 80 ℃，时间 = 30 min，[KPS] = 1.85% (owm)，[OP] = 1% (owf)，[FA] = 0.2%。 接枝率的大小可以用单体浓度来调节，接枝活化能是86.94 kJ/mol。     

一缩二乙醇二甲基丙烯酸酯对真丝接枝的反应性

研究了一缩二乙二醇二甲基丙烯酸酯在空气存在下,用过硫酸钾(KPS)在水液 中对真丝的接枝。对接枝的条件,如单体、引发剂、甲酸(FA)和乳化剂OP的浓度以 及温度和时间对接枝率的影响进行了测试。发现了较佳的接枝条件是：温度 = 80 ℃,时间 = 30 min,[KPS] = 1.85% (owm),[OP] = 1% (owf),[FA] = 0.2%。 接枝率的大小可以用单体浓度来调节,接枝活化能是86.94 kJ/mol。     

Influence of Pigments on Graft Polymerization of Methacrylamide onto Wild Silk Fibers

Abstract

Graft polymerization of methacrylamide (MAA) onto wild silk fibers was performed and the influence of pigments on graft polymerization was investigated. The pigments of Chinese oak silk and Japanese oak silk inhibited the polymerization of MAA. The inhibitory power of the pigments of Chinese oak silk was serious as compared with the pigments of Japanese oak silk. Therefore, MAA polymer add-on of Chinese oak silk fibers became smaller than that of Japanese oak silk fibers.     

再生丝素固定葡萄糖氧化酶及其传感器应用

再生丝素固定葡萄糖氧化酶及其传感器应用钱江红，刘永成，刘海鹰，于同隐，邓家祺（复旦大学化学系高分子科学系，上海，２００４３３）关键词再生丝素，葡萄糖氧化酶，传感器，酶电极酶电报的各项性能在很大程度上取决于酶的固定比方法，葡萄糖氧化酶的固定化方法很多１...     

Graft Polymerization of 2-Hydroxyethyl Methacrylate onto Plasma Pretreated Cotton,Silk, and Polyester Fibers

Graft polymerization of 2-hydroxyethyl methacrylate was made onto plasma pretreated fabrics of cotton, silk, and polyester. Homopolymerization also took place during the graft polymerization, but the percent of the homopolymer formation was comparatively small. Therefore, kinetic analyses of graft polymerization were undertaken based on the first-order reaction of the monomer. Through a comparison of the rate constants which were obtained from the rate equation of the graft polymerization of 2-hydroxyethyl methacrylate, the dependence of plasma pretreatment on various factors and the resulting polymerization were clarified. Polymerizability was compared to that obtained with the Ce(IV) catalyst and without catalysts.     

Studies on graft copolymerization onto cellulose derivatives. XXVII. Photo-induced graft copolymerization onto nitrocellulose

Photo-induced graft copolymerization was investigated using nitrocellulose having a different nitrogen content, especially by a noncatalytic method. The effects of a sample nitrogen content, reaction temperature, and monomer, sample, solvent and photosensitizer concentrations on the degree of grafting, the grafting efficiency, and the apparent number of grafted chains were examined. Methyl methacrylate (MMA) and methyl acrylate (MA) easily polymerized, but acrylamide (AAm), vinyl acetate (VAc), and styrene (St) scarcely polymerized. The apparent activation energies were 4.1–11.5 kcal/mol, indicating the small value in the high nitrogen content sample. The degree of grafting and the apparent number of grafted chains increased with increasing monomer and sample concentrations. In every case, the grafting efficiency was at a high level, above 90%. The polymerization did not occur without the sample in the same condition. Furthermore, a part of nitro groups split off by the irradiation of light. With respect to these results, the mechanisms of the photo graft copolymerization was discussed.     

Reinforcing Silk Scaffolds with Silk Particles

Silk fibroin is a useful protein polymer for biomaterials and tissue engineering. In this work, porogen leached scaffolds prepared from aqueous and HFIP silk solutions were reinforced through the addition of silk particles. This led to about 40 times increase in the specific compressive modulus and the yield strength of HFIP‐based scaffolds. This increase in mechanical properties resulted from the high interfacial cohesion between the silk matrix and the reinforcing silk particles, due to partial solubility of the silk particles in HFIP. The porosity of scaffolds was reduced from ≈90% (control) to ≈75% for the HFIP systems containing 200% particle reinforcement, while maintaining pore interconnectivity. The presence of the particles slowed the enzymatic degradation of silk scaffolds.

     

Grafting onto wool. I. Ceric ion-initiated grafting of poly(methyl acrylate) onto wool

Poly(methyl acrylate) has been grafted onto wool by using ceric ion as redox initiator in an aqueous medium. Initiation by ceric ammonium nitrate (CAN) was carried out in the presence of nitric acid of varying concentration at 35, 45, and 50°C for a period of 1.5 or 3 hr. Percent grafting was found to be dependent on concentrations of acid and monomer, reaction time, and temperature. Above 45°C, a considerable amount of homopolymer was formed; at 35°C, very little grafting of poly(methyl acrylate) was observed. Nitric acid catalyzed the reaction and a concentration of 0.17–0.19M HNO₃ was found suitable.     

Molecular adsorption onto metallic quantum wires.

We have studied the adsorption of mercaptopropionic acid, 2,2'-bipyridine, and dopamine onto electrochemically fabricated Cu nanowires. The nanowires are atomically thin with conductance quantized near integer multiples of 2e(2)/h. Upon molecular adsorption, the quantized conductance decreases to a fractional value, due to the scattering of the conduction electrons by the adsorbates. The decrease is as high as 50% for the thinnest nanowires whose conductance is at the lowest quantum step, and smaller for thicker nanowires with conductance at higher quantum steps. The adsorbate-induced conductance changes depend on the binding strengths of the molecules to the nanowires, which are in the order of mercaptopropionic acid, 2,2'-bipyridine, and dopamine, from strongest to weakest. The sensitive dependence of the quantized conductance on molecular adsorption may be used for molecular detection.     

Silk Sericin Retards the Crystallization of Silk Fibroin

Summary: The thermal and structural analysis of silk fibroin (SF) and silk sericin (SS) blend films reveals that the crystallization of SF is retarded in the presence of SS. Although a phase separation was observed, there might be a strong interaction at the boundary of the SF and SS through intermolecular hydrogen bonding, which restricts the conformational transition of SF.

TEM image of the cross‐section of the SF/SS blend (75:25) film (magnification: ×15 000).     

Graft copolymerization onto rubber. V. Graft copolymerization of methyl methacrylate onto rubber using potassium peroxydiphosphate as initiator

The graft copolymerization of methyl methacrylate onto natural rubber (NR) is investigated using potassium peroxydiphosphate as the initiator. The rate of grafting is determined by varying monomer concentration, peroxydiphosphate concentration, and temperature. The graft yield increased with an increase in monomer concentration up to 1.4082M/L and thereafter the graft yield decreases. The graft yield increases significantly with an increase of peroxydiphosphate concentration up to 150 X 10^-1M/L and thereafter the graft yield decreases. The grafting reaction is temperature dependent. A suitable kinetic scheme is proposed and the rate equation is evaluated.     

Grafting onto wool. II. BPO-initiated grafting of polystyrene

Grafting of polystyrene (PS) onto wool has been carried out in aqueous medium by use of benzoyl peroxide (BPO) as initiator in the presence of an acetic acid–pyridine mixture which acted as a pH modifier. Percent grafting was found to be dependent on concentration of acetic acid and pyridine, concentration of monomer, concentration of BPO, and reaction temperature. The role of pH modifier upon BPO-initiated grafting is established by the observation that no grafting occurred when one of the components of the pH modifier was absent.     

Studies on graft copolymerization onto cellulose derivatives. XXIX. Photo-induced graft copolymerization of methyl methacrylate onto chitin and oxychitin

Graft copolymerization of methyl methacrylate (MMA) onto chitin and oxidized chitin was carried out by a noncatalytic photo-induced and a photo-sensitized method. The isolation method of grafted chains without a decrease in their degree of polymerization (DP) by sulfuric acid hydrolysis and the effects of some factors on the conversion and the grafted chain length have been studied. In case of the photo-induced graft copolymerization, if a small amount of dimethylformaldehyde (DMF) is added in the polymerization system, the induction period is shortened and the degree of grafting and the apparent number of grafted chains increase. The degree of grafting and the apparent number of grafted chains of the oxidized chitin containing a small amount of C?O groups are greater than those of the untreated chitin, but a further increase in C?O groups decreases these values. In the presence of this two species of the chitin samples, the polymerization reaction was carried out as functions of monomer and chitin concentrations. From these results, the mechanisms of the photo-induced graft copolymerization were discussed. It is also clear that the conversion and the apparent number of grafted chains by the noncatalytic photo-induced method are generally larger than those by the photo-sensitized method, and the grafting activity with hydrogen peroxide (HPO) is higher than that with azobisisobutyronitrile (AIBN).