Cellulose graft copolymers. II. Graft copolymerization of ethyl acrylate with γ-irradiated cellulose from acetone–water systems

Ethyl acrylate was graft-copolymerized from acetone–water systems with γ-irradiated, purified cotton cellulose. The scavenging of the free radicals in the irradiated cellulose by water, acetone, and water–acetone systems was determined by electron spin resonance spectroscopy. The ESR spectra of free radicals, scavenged by water and acetone, were recorded by the use of a time-averaging computer attached to the ESR spectrometer, in which the ESR spectrum of the irradiated cellulose, which had been immersed in water and/or acetone, was electronically subtracted from the ESR spectrum of the irradiated cellulose control. For both water and acetone, the ESR spectra of the scavenged free radicals were singlets. This indicated that free radical sites formed on carbon C₁ or C₄ on radiation-initiated depolymerization, which would generate singlet ESR spectra, were readily accessible to these solvents. The maximum scavenging of the radicals was observed when irradiated cellulose was immersed in acetone–water solution which had a composition of 25/75 vol-%. The scavenging of the free radicals in irradiated cellulose when immersed in acetone–water solutions was less than when immersed in methanol–water solutions. Also, the extent of graft copolymerization of ethyl acrylate from acetone solutions with irradiated cellulose was less than that of ethyl acrylate from methanol solutions. These differences were probably due to differences in the diffusion rates of acetone and methanol into the cellulosie structure. The Trommsdorff-type effect in the acetone solutions would be less than in the methanol solutions, since acetone is a better solvent for poly(ethyl acrylate) than methanol.     

Cellulose graft copolymers. I. Graft copolymerization of ethyl acrylate with γ-irradiated cellulose from methanol–water systems

Ethyl acrylate was graft-copolymerized with γ-irradiated, purified cotton cellulose from methanol–water systems. The accessibility of the free radicals in the irradiated cellulose to water, methanol, ethyl acrylate, and methanol–water solutions was determined by electron spin resonance spectroscopy. The maximum scavenging of the radicals was recorded with the irradiated cellulose was immersed in methanol–water solution which had a composition of 50/50 vol-%. When ethyl acrylate was added to methanol–water solution (50/50 vol-%), maximum grafting on the irradiated cellulose occurred at a concentration of ethyl acrylate of about 20 vol-%. As the concentration of ethyl acrylate was decreased, maximum grafting occurred in solutions containing less than 50 vol-% methanol. It was also noted that maximum grafting of ethyl acrylate in methanol–water solutions to irradiated cellulose occurred at boundry conditions, that is, conditions where the ternary mixture was still one phase, slightly different from compositions which caused the mixture to separate into two phases. From methanol solution, maximum grafting occurred at a concentration of ethyl acrylate of 80 vol-%. The extent of grafting from methanol was less that obtained from methanol–water solutions at lower concentrations of ethyl acrylate. The accelerative effects of water was considered to be due to the Trommsdorff effect.     

Cellulose graft copolymers. IV. Graft copolymerization of methacrylonitrile with γ-irradiated cellulose from DMSO–, acetone–, and methanol–water systems

Methacrylonitrile was graft-copolymerized from DMSO–, acetone–, and methanol–water systems with γ-irradiated, purified cotton cellulose. The relative extents of scavenging of the free radicals in the irradiated cellulose after immersion in the solvents for 3 min at 25°C, as determined by electron spin resonance spectroscopy, were: methanol (77%) > water (70%) ? acetone (5%) > DMSO (0%). After immersion of irradiated cellulose in the solvents for 60 min at 25°C, the relative extents of scavenging of the radicals were: methanol, water (80–85%) > DMSO (80%) > acetone (62%). From these data, it would appear that the overall rates of diffusion of methanol and water into the fibrous macrostructure were greater than the rates of diffusion of DMSO and acetone into the structure. The relative radiochemical yields of the graft copolymerization reactions of methacrylonitrile with irradiated cellulose in the different solvents were: water ? DMSO > methanol ? acetone. The addition of water to the systems increased the yields of the reactions.     

Ionic graft copolymerization. II. Graft copolymerization of β-propiolactone onto acrylonitrile–sodium acrylate copolymer

Polyacrylonitrile–β-propiolactone (βPL) graft copolymer was synthesized by means of ionic polymerization, in which polymerization of βPL was initiated by polyacrylonitrile containing a small amount of some reactive groups such as ? COOK, ? COONa, ? COOLi, and ? COOH. Lower electronegativity of the countercation favored higher total conversion and higher grafting percentage. The grafting percentage increased with the reaction time and concentration of reactive groups in the trunk polymer, but grafting efficiency varied very little under these conditions. In the bulk polymerization at 60°C., grafting efficiency was about 60%, but in the solution polymerization in toluene or dioxane, grafting efficiency was higher than in bulk or nitrobenzene.     

Ionic graft copolymerization. III. Graft copolymerization of β-propiolactone onto polyacrylonitrile containing diketene units

Polyacrylonitrile (PAN)–β-propiolactone (βPL) graft copolymer was synthesized by means of the ionic polymerization of βPL in the presence of polyacrylonitrile containing diketene units by using basic catalysts. A graft copolymer was produced by the copolymerization of βPL with the lactone ring in the trunk polymer. In this graft copolymerization method, the grafting efficiency was low. However, grafting efficiency increased with the mole ratio of polymeric lactone to βPL; also higher molecular weight of PβPL favored higher grafting efficiency. The reactivity ratio of polymeric lactone to βPL was estimated to be in the range of 0.1–0.3.     

Ceric(IV) ion‐induced graft copolymerization of acrylamide and ethyl acrylate onto cellulose

Graft copolymerization of acrylamide (AAm) and ethyl acrylate (EA) onto cellulose has been carried out from their binary mixtures using ceric ammonium nitrate (CAN) as an initiator in the presence of nitric acid at 25 ± 1 °C. The extent of acrylamide grafting increased in the presence of the EA comonomer. The composition of the grafted chains (F_AAm = 0.52) was found to be constant during the feed molarity variation from 7.5 × 10^?2 to 60.0 × 10^?2 mol L^?1, whereas the composition of the grafted chains (F_AAm) was found to be dependent on feed composition (f_AAm) and reaction temperature. The effects of ceric(IV ) ion concentration, reaction time and temperature on the grafting parameters have been studied. The grafting parameters showed an increasing trend up to 6.0 × 10^?3 mol L^?1 concentration of CAN at a feed molarity of 30.0 × 10^?2 mol L^?1 and showed a decreasing trend on further increasing the concentration of CAN (>6.0 × 10^?3 mol L^?1) at a constant concentration of nitric acid (5.0 × 10^?2 mol L^?1). The composition of the grafted chains (F_AAm) was determined by IR spectroscopy and nitrogen content and the data obtained then used to determine the reactivity ratios of the acrylamide (r₁) and ethyl acrylate (r₂) comonomers by using a Mayo and Lewis plot. The reactivity ratios of acrylamide and ethyl acrylate were found to be r₁ = 0.54 and r₂ = 1.10, respectively, and hence the sequence lengths of acrylamide (m?M₁) and ethyl acrylate (m?M₂) in the grafted chains are arranged in an alternating form, as the product of the reactivity ratios of acrylamide and ethyl acrylate (r₁ × r₂) is less than unity. The rate of graft copolymerization of the comonomers onto cellulose was found to be dependant on the ‘squares’ of the concentrations of the comonomers and on the ‘square root’ of the concentration of ceric ammonium nitrate. The energy of activation (ΔE_a) of graft copolymerzation was found to be 5.57 kJ mol^?1 within the temperature range from 15 to 50 °C. On the basis of the results, suitable reaction steps have been proposed for the graft copolymerzation of acrylamide and ethyl acrylate comonomers from their mixtures. Copyright © 2005 Society of Chemical Industry     

Electron spin resonance studies of γ-irradiated cellulose. I. Free radicals in decrystallized cellulose

The types of free radicals formed in decrystallized cellulose prepared from cellulose I and II after γ-irradiation in nitrogen atmosphere at room temperature were studied by ESR spectroscopy. X-Ray diffraction revealed that decrystallized cellulose I and II have the same microstructure. The ESR spectra obtained with the γ-irradiated decrystallized samples are simple. By contacting the irradiated sample with moisture in nitrogen atmosphere, the ESR spectrum changed to a narrow singlet, which gradually decreased in intensity until the spectrum completely disappeared. It was found that the types of free radicals generated in the decrystallized cellulose by γ-irradiation consist of the overlap of singlet and doublet. The singlet spectrum is mainly attributed to alkoxyl radical formed by the rupture of glycosidic linkage at the C 1 or C 4 position, and the doublet spectrum is ascribed to radical formed by hydrogen abstraction from the C 1 position in cellulose molecule.     

Spontaneous copolymerization of N‐butyl maleimide and ethyl α‐phenyl acrylate with high alternating tendency

The copolymerization of N‐butyl maleimide (BMI) and ethyl α‐phenyl acrylate (EPA) was successfully carried out without an initiator. A high alternating tendency was observed. The Q, e values were derived by Alfrey–Price equations: Q = 0.09, e = 0.81 for BMI and Q = 0.21, e = ?0.5 for EPA, and the monomer reactivity ratios were r_BMI = 0.15 ± 0.01 and r_EPA = 0.18 ± 0.08, respectively. In this system BMI was donor and EPA was acceptor. The maximum copolymerization rate and molecular weight appeared at 70 mol % (BMI) in the feed ratio. The spontaneous alternating copolymerization was considered to be completed by a contact‐type charge‐transfer complex formed by the monomer pairs. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 355–360, 2004     

Plasticization of cellulose diacetate by graft copolymerization of ε‐caprolactone and lactic acid

Graft copolymerization of ε‐caprolactone (CL) and lactic acid (LA) onto cellulose diacetate (CDA) at the residual hydroxyl positions was conducted to obtain thermoplastic CDA. The effects of the reaction temperature and time and the CL/LA molar ratio in the feed on the progress of the graft copolymerization were investigated. The molecular weight of CDA was increased by this graft copolymerization. The oxycaproyl and lactyl molar substitutions (MS_CL and MS_LA, respectively) in grafted CDA (g‐CDA) were determined through ¹H‐NMR spectral analysis. These MS values were controllable by changing the reaction conditions adequately. The flow temperature and melt viscosity of g‐CDA decreased with an increase in the total substitution of MS_CL and MS_LA, and transparent polymer sheets could be obtained from the resulting g‐CDA by hot pressing at around 200°C without adding any plasticizer. The mechanical properties of the molded g‐CDA samples varied widely, depending on the different combinations of the MS_CL and MS_LA values; the g‐CDA sheets became elastic when the MS_CL was larger than the MS_LA, and their tensile strengths were enhanced as the MS_LA was increased. It was thus found that CDA was successfully plasticized by this graft copolymerization. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2621–2628, 2002     

Corona-induced graft polymerization of ethyl acrylate onto cellulose film

Ethyl acrylate was readily grafted from an aqueous solution onto cellophane film previously treated in a corona discharge at atmospheric pressure. The effect was found when the corona treatment was carried out not only in air but also in pure nitrogen. The observed grafting was not promoted but depressed by the presence of ferrous ion, which indicated that peroxide radicals were not initiating the graft. A high grafting efficiency was obtained, and the grafted surface was covered with a smooth uniform layer of polymer.     

Effect of crystalline structure on the infrared spectra of γ-irradiated cotton cellulose

The effect of crystalline modifications on the infrared spectra of γ-irradiated cotton cellulose is presented. The crystalline modifications were brought about by treating cotton material with an aqueous solution of NaOH of various concentrations. The infrared spectra of the irradiated samples indicate an absorption band corresponding to the absorption of C?O groups. It was found that the intensity and frequency of this band depend on the crystalline structure. Thus, it appears at 1735 cm^?1 in the spectrum of cellulose I and at 1610 cm^?1 in the spectrum of cellulose II.     

Radiation‐induced graft copolymerization of α‐methyl styrene and butyl acrylate mixture into polyetheretherketone films

Radiation‐induced graft copolymerization of α‐methyl styrene (AMS), butyl acrylate (BA) monomers, and their mixture was investigated on poly(etheretherketone) films. The graft polymerization was carried out using ethyl methyl ketone as the medium for the copolymerization and the maximum degree of grafting of 27% was achieved. It was observed that the grafting is significantly influenced by the reaction conditions, such as reaction time, preirrradiation dose, monomer concentration, monomer ratio, and the reaction temperature. The degree of grafting increases as the monomer concentration increases up to 30%, beyond which a decrease in the grafting was observed. The degree of grafting showed a maximum at 40% BA content in the monomer mixture. The temperature dependence of the grafting process shows decreasing grafting with the increase in the reaction temperature. The presence of AMS and BA grafts in the film was confirmed by FTIR spectra. The relative change in the PBA/PAMS fraction with respect to the reaction temperature has been found in this study. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

羟乙基纤维素与丙烯酸-2-羟基丙酯的反应规律

以硝酸铈铵/乙二胺四乙酸(CAN/EDTA)为引发剂,研究了羟乙基纤维素(HEC)与丙烯酸-2-羟基丙酯(HPA)的接枝共聚反应,讨论了单体浓度、引发剂浓度、反应温度、反应时间等因素对接枝率的影响,试验结果表明:在引发剂CAN和EDTA为22mmol/L,单体HPA为0.31mol/L,反应温度为40℃,反应时间为4h时,接枝率和接枝效率值最佳,并用红外光谱对接枝共聚物结构进行了鉴定。     

Radiation degradation of α-substituted acrylate polymers and copolymers

Radiation degradation is observed in poly(methyl α-chloroacrylate), poly(methyl α-cyanoacrylate), and poly(α-chloroacrylonitrile) homopolymers and their respective MMA copolymers when γ-irradiated in vacuo. Polymer degradation susceptibilities are quantified in terms of G(scission radicals) and G(scission) ? G(crosslinks), measured by EPR and membrane osmometry, respectively, values by these two methods are compared. Higher G(rads) values ranging from 2 to 6 and [G(s) ? G(x)] values ranging from 2 to 11 are obtained for the substituted polymers and copolymers relative to the values for PMMA (1.6; 1.9), a standard e-beam positive resist, which suggests that these modified polymers are more sensitive e-beam resists than PMMA.     

New wood-polymer composites containing ethyl α-hydroxymethyl acrylate polymers

Ethyl α-hydroxymethyl acrylate (EHMA) was synthesized and evaluated as a candidate for wood impregnation and in-situ polymerization. Southern Pine softwood was impregnated under a variety of conditions with EHMA alone and with various comonomers plus free radical initiator. Following thermal polymerization, the wood-polymer composites were tested for increased dimensional stability (water soaking swell resistance) and mechanical properties over untreated wood. The greatest increase in dimensional stability was attained using EHMA alone, while the maximum compression modulus was achieved by impregnating with 1:1 EHMA-styrene and styrene alone. The composites were further characterized by ¹³C CP/MAS solid state NMR and scanning electron microscopy.     

Effect of stirring on cellulose graft copolymerization. III. Acrylic and methacrylic monomers

Acrylate and methacrylate monomers were grafted onto dissolving pulp by the xanthate process. All the nine monomers tested showed a well-defined dependence of conversion on stirring speed. Total conversion and conversion to copolymer vs. agitator speed curves for each monomer were very similar in shape, but they varied widely from monomer to monomer. For the homologous series acrylate and methacrylate esters, optimum stirring speed was found to increase with increasing the size of the alkyl group. The breadth of the maximum also depended on the type of monomer. Monomers partially soluble in water forming water-insoluble polymers were found to be the most reactive.     

Thermal behavior of graft copolymers of cotton cellulose and acrylate monomers

Cotton cellulose yarn was grafted with methyl acrylate, ethyl acrylate, n-butyl acrylate, and methyl methacrylate at various percentages of grafting. The effects of concentration of the initiator, concentration of the acid, and of temperature on grafting was studied and the mechanism discussed. The effect of reactivity of the monomer on the percentage graft-on is pointed out. Thermal behavior of natural and grafted cotton yarn was studied using dynamic thermogravimetry in air at a heating rate of 6°C/min up to a temperature of 500°C. The thermal stabilities of the samples grafted with various acrylate monomers to various percentages of grafting were computed from their primary thermograms by calculating the values of IDT, IPDT, and E^*. The results show that the thermal stability increases with increase in graft-on per cent, and the thermal stabilities of natural cotton and cotton grafted with different monomers are in the order ethyl > methyl > natural cellulose > methyl methacrylate > n-butyl acrylate.     

Radiation-induced graft copolymerization of mixtures of styrene and n-butyl acrylate onto cellulose and cellulose triacetate

Mixtures of styrene and n-butyl acrylate of various compositions were grafted onto cellulose and cellulose triacetate fibers preirradiated with γ-rays at 0°C in air. Monomer reactivity ratios of the grafted copolymers were found to be different from those of the nongrafted copolymers or those of AIBN-initiated copolymers. The active species initiating the graft copolymerization were trapped radicals for cellulose and peroxides for cellulose triacetate. Kinetic investigations of the graft copolymerization of styrene onto preirradiated cellulose triacetate fibers were also carried out, and it was found that the kinetic scheme for radical polymerization is also applicable to graft copolymerization in a heterogeneous system.     

Electron spin resonance studies of γ-irradiated cellulose. II. Free radicals in accessible regions to water in cellulose I and cellulose II

The types of free radicals produced in the water-accessible regions of cellulose I and cellulose II fibers by γ-irradiation in nitrogen atmosphere at room temperature were studied by ESR spectroscopy. The ESR spectra of the irradiated cellulose I and II change by contacting the fibers with water, and after immersion in water the spectral shape depends on the orientation of the fiber axes to the magnetic field. These spectra are probably related to the free radicals generated in the highly ordered regions inaccessible to water in irradiated cellulosic fibers. The ESR spectrum of free radicals generated in decrystallized cellulose after irradiation consists of a singlet and a doublet. When the ESR spectra of free radicals formed in the highly ordered regions of cellulose I and II and the singlet and the doublet are combined in adequate ratio, the constructed spectra are similar to those of the radicals scavenged by water in the irradiated cellulose I and II fibers. From these facts, the spectra due to the free radicals in the water-accessible regions in irradiated cellulose I and II are considered to consist of the singlet and the doublet formed by free radicals in the typical amorphous regions and the spectra of other types of radicals generated in the semicrystalline regions.