reactivity of glycidyl methacrylate grafted cellulose film prepared by grafting under ultrasonic...

Reactivity of Glycidyl Methacrylate Grafted Cellulose FilmPrepared by Grafting Under Ultrasonic Irradiation

TAKASHI KONDO, HITOSHI KUBOTA, RYOICHI KATAKAI

Department of Chemistry, Gunma University, Kiryu, Gunma 376-8515, Japan

Received 3 November 1998; accepted 15 May 1999

ABSTRACT: Ultrasonic irradiation largely accelerated ceric salt initiated grafting ofglycidyl methacrylate (GMA) on regenerated cellulose film (cellophane thickness 5 20mm) at 60°C in air. The grafting under ultrasonic irradiation was characterized by ahigher percent of grafting and graft efficiency and a lower density of GMA-graftedchains in the surface layer of the grafted films compared to the unirradiated system,which was obtained by attenuated total reflectance IR measurements. The grafted filmswere subjected to amination with ethylenediamine (En) at 70°C for 3 h in N,N-dimethylformamide. The amount of epoxy groups in the grafted films, which partici-pated in the reaction with En, reached about 50–60 mol % and was slightly lower forthe grafted film prepared in the irradiated system than that prepared in the unirradi-ated one. Adsorption of cupric ions with the aminated samples was performed at pH 5.0using Clark–Lubs buffer solution and cupric chloride. The adsorption was extremelyretarded for the aminated sample prepared using the unirradiated sample compared tothat prepared using the irradiated one. The retarded adsorption phenomenon is dis-cussed in terms of a larger formation of crosslinked structures on the surface layer ofthe former sample during the amination. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci74: 2462–2469, 1999

Key words: ceric salt initiated grafting; ultrasonic irradiation; regenerated cellulosefilm; glycidyl methacrylate

INTRODUCTION

In our previous study1 we investigated the effectof ultrasonic irradiation on ceric salt initiatedgrafting of methyl methacrylate (MMA) on cellu-lose film (cellophane) under an air atmosphere.We observed that the ultrasonic irradiation accel-erates the grafting remarkably, which is charac-terized by a higher percent of grafting and graftefficiency than those in the system without theirradiation. The accelerating effect of the graftingreaction by ultrasonic irradiation is due to thefunctions of ultrasound such as mass transfer and

diffusion induced by the cavitation phenomenon.Based on attenuated total reflectance IR (ATR-IR) studies of MMA-grafted films prepared in thesystems without and with the irradiation, thedensity of MMA-grafted chains in the surfacelayer of the grafted films was lower for the irra-diated sample compared to that of the unirradi-ated one, showing easier penetration of MMA-grafted chains into the film substrate in the irra-diated system. It is conceivable that the reactivityof the grafted film may be greatly influenced bythe location of the grafted chains in the film sub-strate. The functions of grafted polyethylene film,such as moisture permeability,2,3 catalytic activ-ity,4,5 and pH6 and temperature7 responsive char-acters, were found to closely relate to the distri-bution of grafted chains in the cross section of the

Correspondence to: H. Kubota.Journal of Applied Polymer Science, Vol. 74, 2462–2469 (1999)© 1999 John Wiley & Sons, Inc. CCC 0021-8995/99/102462-08

2462

film substrate. Therefore, this article deals withthe reactivity of glycidyl methacrylate (GMA)-grafted cellulose film prepared by grafting underultrasonic irradiation.

GMA was selected as a monomer component tointroduce into the film substrate because it has astructure similar to the MMA monomer and anepoxy group with high reactivity to amines. Thereactivity8–13 of the epoxy group has been utilizedin the introduction of functions into polymericmaterials. In the present study, in order to un-derstand the reactivity of GMA-grafted cellulosefilm prepared by grafting under ultrasonic irradi-ation, the grafted film was examined in terms of areaction with ethylenediamine (En) and the ad-sorption of cupric ions (Cu21) with the aminatedcellulose film in comparison with that prepared inthe unirradiated system.

EXPERIMENTAL

Materials

Commercially available regenerated cellulosefilm (cellophane) with a thickness of 20 mm wasused as a film sample (3 3 10 cm), which wasextracted with hot methanol for 24 h to removeadditives. Ceric ammonium nitrate (Ce41), En,triethylenetetramine, b-alanine, N,N-dimethyl-formamide (DMF), and cupric salts such as cupricchloride (CuCl2 z 2H2O) and cupric acetate[Cu(CH3COO)2] were reagent grade. GMA waspurified by distillation under reduced pressure.

Grafting

Grafting was carried out at 60°C under an airatmosphere in a Pyrex glass tube containing thefilm sample, 24 mL of water, 1 mL of GMA (7.6mmol), and 5 mL of an aqueous solution of nitricacid (5 mmol) in which 30 mmol of Ce41 wasdissolved. Ultrasonic irradiation was carried outusing an ultrasonic cleaning bath (model NS80-1.5u) from Nihonseiki Seisakusho Ltd. (150 3 1353 100 mm bath size, 28-kHz nominal frequency,80-W power output). The grafting was carried outunder stirring at 600 rpm using the film sample,which was cut in small pieces (about 10 3 10mm), under an air atmosphere in the systemwithout ultrasonic irradiation.

Photografting was carried out in a Pyrex glasstube containing xanthone-coated film (which wasprepared by immersing the film sample in an

acetone solution containing 0.3 wt % xanthone atroom temperature, removing it from the solution,and then drying under reduced pressure at roomtemperature), 29 mL of water, and 1 mL of GMAunder a nitrogen atmosphere without ultrasonicirradiation. Irradiation with a high-pressure mer-cury lamp (400 W) was performed at 60°C for 30min using a Riko rotary photochemical reactor(RH400-10W).

Polymerized film was extracted with methylethyl ketone for 24 h to remove homopolymers ofpoly(GMA). The percent of grafting and graft effi-ciency were calculated by the following equations:

grafting (%) 5weight of grafts

weight of original film 3 100

graft efficiency (%)

5weight of grafts

weights of grafts and homopolymer 3 100

Measurement of ATR-IR Spectra of Grafted Film

ATR-IR spectra of the surface layer of the graftedfilm were measured with an IR Nicolet spectrom-eter (model Magna-IR 750). The absorbance ratioof the carbonyl peak (1728 cm21 stretching) of theGMA-grafted chains to the ether peak (1050 cm21

stretching) of the cellulose was obtained.

Reaction with En

A given amount of GMA-grafted film was added to30 mL of DMF in which known concentrations ofEn were dissolved, and then a reaction was car-ried out at 70°C for 3 h. After the reaction theamount of En residue introduced into the sub-strate was subjected to a measurement with anelemental analyzer (model PE2400 Series II, Per-kin Elmer). The aminated epoxy group was de-fined as the amount of the epoxy group that par-ticipated in the reaction with En and is expressedby the following equation:

aminated epoxy group (mol %)

5amount of En residue

initial amount of epoxy group 3 100

Adsorption of Cu21

A given amount of the aminated sample, whichwas prepared by the reaction of the GMA-grafted

GMA-GRAFTED CELLULOSE FILM REACTIVITY 2463

sample with En, was added to 50 mL of aqueousCuCl2 z 2H2O solution with known concentrationswhose pH was adjusted to 5.0 by Clark–Lubsbuffer solution; the adsorption was carried out at30°C for 24 h. The adsorbed amount of Cu21 wasdetermined by measuring the concentration ofCu21 in the solutions before and after the adsorp-tion using an inductively coupled argon plasmaatomic emission spectrophotometer (model ICAP-575, Nippon Jarrell–Ash).

Electron Probe Microanalysis (EPMA)

The distribution profile of Cu21 in the cross sec-tion of the aminated film was measured with elec-tron probe microanalyzer (model EPM-810 ofShimazu).

RESULTS AND DISCUSSION

Grafting Behavior

Figure 1 shows the effect of ultrasonic irradiationon Ce41-initiated grafting of GMA on cellulosefilm. The grafting proceeded easily even under anair atmosphere and the percent of grafting in theunirradiated system reached about 100% withinthe reaction time of 5 min. The percent of graftingin the irradiated system was much higher thanthat of the unirradiated system, showing that theultrasonic irradiation markedly accelerates Ce41-initiated grafting of GMA on cellulose film. The

graft efficiency was also higher for the irradiatedsystem than for the unirradiated one, althoughthe value considerably decreased at the earlierstage of polymerization. Thus, the grafting ofGMA on cellulose film under ultrasonic irradia-tion was characterized by a higher percent ofgrafting and graft efficiency than those of theunirradiated system. In our previous article1 onCe41-initiated grafting of MMA on cellulose film,we considered that the accelerating effect of thediffusion of Ce41 and MMA monomer into a filmsubstrate by ultrasound results in a higher per-cent of grafting and graft efficiency in the irradi-ated system compared to the unirradiated one.The promoted grafting reaction due to ultrasonicirradiation observed in the present system alsoseems to be based on the functions of ultrasoundsuch as mass transfer and diffusion.

GMA-grafted chains of the surface layer of theresulting grafted films were examined by ATR-IRmeasurements, and the results are shown in Fig-ure 2. The vertical axis of the figure is the absor-bance ratio of the carbonyl peak of GMA-graftedchains at 1728 cm21 to the ether peak of thecellulose substrate at 1050 cm21. The absorbanceratio increased with an increase in the percent ofgrafting, indicating that the surface layer of thegrafted film becomes rich in the GMA-graftedchains compared to the cellulose components. Themagnitude of the increase was lower for the irra-diated sample than for the unirradiated one, sug-gesting easier penetration of GMA-grafted chains

Figure 2 Changes in the absorbance ratio of the car-bonyl peak at 1728 cm21 to the ether peak at 1050cm21 with the percent of grafting in GMA-grafted cellu-lose film: (E) without irradiation, (F) with irradiation.

Figure 1 Ce41-initiated grafting of glycidyl methac-rylate onto cellulose film under ultrasonic irradiation:[GMA] 5 0.33 mol/L, [Ce41] 5 5.0 mmol/L, (E, ‚)without irradiation; (F, Œ) with irradiation.

2464 KONDO, KUBOTA, AND KATAKAI

into the film substrate in the irradiated system.Thus, we found that the distribution of GMA-grafted chains in the cross section of the graftedfilm may differ between the two grafted films, theunirradiated and irradiated samples.

Reaction with En

The reaction of GMA-grafted films such as theunirradiated and irradiated samples with En wasexamined to compare the reactivity of the twosamples toward En, and the results are shown inFigure 3. The concentration of En in the systemranges from 2 to 20 times as much as the epoxygroup content, which is calculated from the per-cent of grafting of the GMA-grafted film. The am-inated epoxy group increased with increasing con-centration of En in the system, and the value wasslightly lower for the irradiated sample comparedto the unirradiated one. Similar values were re-corded for the system with the reaction time of24 h. These results may closely relate to the dif-ference in the location of GMA-grafted chains inboth samples: that is, the grafted chains of theirradiated sample may distribute the film insidecompared to those of the unirradiated one, result-ing in a lower aminated epoxy group.

In the present system the amination is conceiv-ably a main reaction, which is schematically

shown in eq. (1), where R denotes GMA-graftedchains.

About 40–50 mol % of the initial amount of epoxygroups may remain unreacted after the amina-tion reaction, although some parts of the epoxygroups are decomposed by the hydrolysis reactionaccording to eq. (2). The existence of the epoxygroups, which do not participate in the amination,was examined by FTIR measurement using ATRand transmittance methods (Fig. 4). There was noabsorption peak due to the epoxy group at 850cm21 in the IR spectra measured with the ATRmethod, which was commonly observed for theunirradiated and irradiated samples. This sug-

Figure 4 Absorption spectra of aminated GMA-grafted cellulose film measured by FTIR. ATR method:(1) without irradiation, GMA-grafted film (74.5% graft-ing); (2) without irradiation, aminated film (aminatedepoxy content 5 55.9 mol %); (3) with irradiation, am-inated film (aminated epoxy content 5 51.7 mol %).Transmittance method: (4) without irradiation, ami-nated film (aminated epoxy content 5 55.9 mol %); (5)with irradiation, aminated film (aminated epoxy con-tent 5 51.7 mol %).

Figure 3 Reaction of GMA-grafted film with ethyl-enediamine: (E) without irradiation, 75.7% grafting,amination at 70°C for 3 h; (‚) without irradiation,75.7% grafting, amination at 70°C for 24 h; (F) withirradiation, 77.1% grafting, amination at 70°C for 3 h;(Œ) with irradiation, 77.1% grafting, amination at 70°Cfor 24 h.


gests that epoxy groups on the surface layer ofboth the samples participate in the amination. Onthe other hand, the absorption peak at 850 cm21

was recorded for the two grafted samples by thetransmittance method, although the absorbancewas relatively low. Thus, we confirmed that someof the epoxy groups, which exist in the film inside,remain unreacted after the amination.

Adsorption of Cu21

In the present amination reaction it is supposedthat primary amino groups in the En residueintroduced into the film substrate may partici-pate in a further reaction with the epoxy groupsthat results in a crosslinking reaction as shown ineq. (3).

The resultant crosslinked structure may affectthe reactivity of the aminated samples. So, theadsorption reaction of Cu21 with the aminatedsamples prepared by the reaction of the unirradi-ated and irradiated samples with En was exam-ined, and the results are shown in Figure 5. Theadsorption was carried out at pH 5.0 using Clark–Lubs buffer solution because the pH is suitable

for the adsorption13,14 of Cu21. The amount ofadsorbed Cu21 was expressed by the number ofmoles of adsorbed Cu21 per 1 mol of En residue inthe sample. The amount of the irradiated sampleincreased with the increasing concentration ofCu21 and reached about 0.4 when a Cu21 concen-tration of 10.0 mmol/L was used. The value of 0.4implies that 80% of the En residues in the sampleparticipate in the adsorption reaction of Cu21. Onthe other hand, the amount of the unirradiatedsample was much lower in the whole range ofCu21 concentrations examined than that of theirradiated sample, showing that the amount of Enresidues, which participated in the adsorption re-action, was less than 20%. Thus, the adsorptionreaction of Cu21 with the unirradiated samplewas largely retarded.

Figure 6 shows the distribution profiles of Cu21

in the cross section of the aminated film samples,which were subjected to the adsorption of Cu21,measured by EPMA. We found that Cu21 ad-sorbed with the unirradiated sample localizesonly at the film surface while that adsorbed withthe irradiated sample distributes the film inside.Thus, with the unirradiated sample it is difficultfor the Cu21 to permeate into the film inside,resulting in the retarded adsorption. This sug-gests a larger formation of a crosslinked structureon the surface layer of the unirradiated samplethan the irradiated one. It is plausible that thecrosslinking reaction at the film surface proceedseasily in the former sample with grafted chainslocated densely at the film surface compared tothe latter sample, which distribute homoge-neously in the film substrate.

Figure 6 Distribution profiles of Cu21 in the crosssection of an aminated film measured by EPMA: (a)without irradiation, amount of adsorbed Cu21 5 0.08mol/mol En; (b) with irradiation, amount of adsorbedCu21 5 0.42 mol/mol En.

Figure 5 Adsorption of Cu21 with aminated samplesin the system using Clark–Lubs buffer solution: ad-sorption at pH 5.0 and 30°C for 24 h, [En residue] 5 2.0mmol/L, (E) without irradiation, (F) with irradiation.


Figure 7 presents the relationship between theamount of adsorbed Cu21 and the absorbance ra-tio of the carbonyl peak at 1728 cm21 to the etherpeak at 1050 cm21 obtained by ATR-IR measure-ment of GMA-grafted samples, which were pre-pared in various grafting systems. The graftedsamples were subjected to the amination with Enfollowed by the adsorption of Cu21 with the re-sulting aminated samples. The amount of ad-sorbed Cu21 decreased with an increasing absor-bance ratio. It was confirmed thusly that the ad-sorption tends to be retarded for the aminatedsample where GMA-grafted chains locate denselyat the film surface.

Figure 8 shows the adsorption of Cu21 with theaminated samples in the system of pH 4.8 withoutClark–Lubs buffer solution. We observed that theamount of adsorbed Cu21 increases with the con-centration of Cu21 and reaches about 0.5 even inthe unirradiated sample. With the adsorption sys-tem with Clark–Lubs buffer the Cu21 forms acomplex with the phthalate component in thebuffer and the resulting complex may be too bulkyto diffuse into the film inside through thecrosslinked structure on the film surface, leadingto a lower amount of adsorbed Cu21 in the unir-radiated sample where grafted chains locate

densely at the film surface. The formation of aCu21–phthalate complex was confirmed by aspectroscopic study on the aqueous solution con-sisting of cupric chloride and potassium hydrogenphthalate with various concentrations of both thecomponents where two phthalate molecules arecoordinated with one Cu21. With the adsorptionsystem without the buffer, on the other hand,Cu21 may easily diffuse into the film inside be-cause of no complex formation with a bulky struc-ture and it can coordinate with the En residue,resulting in a higher amount of adsorbed Cu21

even in the unirradiated sample.The retarded adsorption was also recorded for

the aminated samples prepared using triethyl-enetetramine in place of En, which is shown inTable I. The table also includes the results of theadsorption with the aminated sample preparedusing b-alanine. The amount of adsorbed Cu21

was nearly equal between the aminated samplesprepared using the unirradiated and irradiatedsamples. This may have originated in the forma-tion of aminated samples without the crosslinkedstructure due to the amination. The reaction ofGMA-grafted film with b-alanine conceivably pro-ceeds according to eqs. (4) and (5).

Figure 8 Adsorption of Cu21 with aminated samplesin the system without Clark–Lubs buffer solution (pH4.8). [En residue] 5 2.0 mmol/L, grafting 5 115–125%.

Figure 7 Relationship between the amount of ad-sorbed Cu21 and the absorbance ratio of the carbonylpeak at 1728 cm21 to the ether peak at 1050 cm21 inthe GMA-grafted films: (E) without irradiation, (F)with irradiation, (h) grafting under stirring (600 rpm),(3) photografting. Adsorption was carried out at 30°Cfor 24 h in the system using Clark–Lubs buffer solution(pH 5.0). [En residue] 5 2.0 mmol/L, [Cu21] 5 10.0mmol/L, grafting 5 100–120%.


Ikeda et al.15 examined the reaction of epoxy-activated cellulose with glycine and succinic acidat 70°C for 24 h in a water medium; they observedthat the amount of the epoxy group, which par-ticipated in the reaction, is higher for glycine thanfor succinic acid. The results suggest that theamino group preferentially participates in the re-action of epoxy-activated cellulose with glycinecompared to the carboxyl group. In order to con-firm the existence of the carboxyl group intro-duced into the aminated sample according to eq.(4), FTIR measurements using the ATR methodwere carried out, and the results are shown inFigure 9. In Figure 9(a) an absorption peak due tothe carbonyl of the carboxyl group at 1725 cm21 issuperimposed on that due to the carbonyl of theGMA-grafted chains at 1735 cm21. Figure 9(b)presents a spectrum of the aminated sample,which was treated with a 0.1 mol aqueous solu-tion of sodium hydroxide. Absorption peaks due tothe sodium salt of the carboxyl group were ob-served at 1400 and 1572 cm21 (stretching vibra-tion). The absorption peaks were confirmed tohave disappeared by treating the alkali-treatedsample with a 0.1 mol aqueous solution of hydro-chloric acid. Accordingly, it is plausible that eq.(4) may preferentially proceed in the reaction ofGMA-grafted film with b-alanine compared to eq.(5), resulting in less formation of the crosslinked

structure. Adsorption of Cu21 was also performedusing cupric acetate in the system without thebuffer. As shown in Table I, the amount of ad-sorbed Cu21 was nearly equal for the two ami-nated samples, indicating that the Cu21–acetatecomplex can permeate inside the film through thecrosslinked structure on the surface layer in theunirradiated sample.

Based on the above investigations, we con-cluded that the use of ultrasonic irradiation in

Table I Adsorption of Cu21 with Aminated Samples

Amine Cupric Salt Buffer Solution

Amount of Adsorbed Cu21

(mol/mol Amine)

WithoutIrradiationa

WithIrradiationb

Ethylenediamine CuCl2 z 2H2O With (pH 5.0) 0.08 0.42Ethylenediamine CuCl2 z 2H2O Without (pH 4.8) 0.46 0.49Triethylenetetramine CuCl2 z 2H2O With (pH 5.0) 0.12 0.26b-Alanine CuCl2 z 2H2O With (pH 5.0) 0.19 0.19Ethylenediamine Cu(CH3COO)2 Without (pH 4.8) 0.30 0.31

[Amine residue] 5 2.0 mmol/L; [Cu21] 5 10.0 mmol/L; Clark–Lubs buffer at pH 5.0 and 30°C for 24 h.a Aminated samples were prepared using GMA-grafted films (100–120% grafting) obtained in the grafting system without

ultrasonic irradiation.b Aminated samples were prepared using GMA-grafted film (100–120% grafting) obtained in the grafting system with ultrasonic

irradiation.

Figure 9 ATR-IR spectra of GMA-grafted cellulosefilms aminated with b-alanine: (a) aminated film (am-inated epoxy content 5 50.0 mol %), (b) aminated filmtreated with a 0.1 mol aqueous solution of sodium hy-droxide.


Ce41-initiated grafting of GMA on cellulose film isa useful means for preparation of grafted cellu-lose samples with a homogeneous distribution ofgrafted chains. The resulting GMA-grafted sam-ple smoothly reacts with En in less formation ofcrosslinked structures in the surface layer ofgrafted chains compared to that prepared in theunirradiated system.

REFERENCES

1. Kondo, T.; Kubota, H.; Katakai, R. J Appl PolymSci 1999, 71, 251.

2. Kubota, H.; Koike, N.; Ogiwara, Y.; Hata, Y. JPolym Sci Polym Lett Ed 1987, 25, 273.

3. Kubota, H.; Sugiura, A.; Hata, Y. Polym Int 1994,34, 313.

4. Kubota, H. Eur Polym J 1992, 28, 267.5. Kubota, H. Eur Polym J 1993, 29, 551.

6. Imaizumi, M.; Kubota, H.; Hata, Y. Eur Polym J1994, 30, 979.

7. Kubota, H.; Nagaoka, N.; Katakai, R.; Yoshida, M.;Omichi, H.; Hata, Y. J Appl Polym Sci 1994, 51,925.

8. Iwakura, Y.; Kurosaki, T.; Uno, K.; Imai, Y. JPolym Sci 1964, C24, 673.

9. Haubl, G.; Wegscheioler, W.; Knapp, G. AngewMakromol Chem 1984, 121, 209.

10. Khalil, M. I.; Wally, A.; Kantouch, A.; Abo-Shosha,M. H. J Appl Polym Sci 1989, 38, 313.

11. Kondo, T.; Ishizu, A.; Nakano, I. J Appl Polym Sci1989, 37, 3003.

12. Allmer, K.; Hilborn, J.; Larsson, P. H.; Hult, A.;Rånby, B. J Polym Sci Part A Polym Chem 1990,28, 173.

13. Maekawa, E.; Kousaki, T.; Koshijima, T. Sen-iGakkaishi 1986, 42, T-460.

14. Kubota, H.; Ujita, S. J Appl Polym Sci 1995, 56, 25.15. Ikeda, I.; Tomita, H.; Suzuki, K. Sen-i Gakkaishi

1990, 46, 63.


reactivity of glycidyl methacrylate grafted cellulose film prepared by grafting under ultrasonic...

Documents