Study on the self-polymerization and co-polymerization properties of gadolinium methacrylate

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1 Proceedigs of the th IIE Iteratioal Coferece o Idustrial pplicatio Egieerig 7 Study o the self-polymerizatio ad co-polymerizatio properties of gadoliium methacrylate ChuhogWag a, Mig Zhag a,* a School of Chemistry ad Chemical Egieerig, Yagzhou Uiversity, Yagzhou, Chia *Correspodig bstract Gadoliium methacrylate (Gd(M) ) was sythesized through the reactio of gadoliium oxide ad methacrylic acid ad characterized by FT-IR spectroscopy, DSC ad TG. The o-isothermal ad isothermal aalysis were used to study the kietics of self-polymerizatio of Gd(M). The moomer reactivity ratios of MM/Gd(MM) were calculated by K-T method. The results showed that Gd(M) could be iduced to self-polymerizatio iitiated by thermal ad free radical ad the activatio eergy of polymerizatio was.kj/mol i solid state ad 8.kJ/mol i aqueous solutio. The rate of polymerizatio uder low coversio was govered by the expressio at 6 : Rp=K[M] [I].. The values of r (MM) ad r (Gd(M) ) were. ad.. Keywords: gadoliium methacrylate; thermal aalysis; kietics of the polymerizatio; moomer ratios..itroductio Rare earth elemets called idustrial moosodium glutamate with the special f electroic structures have widely applicatios i the field of fluorescece [], magetism [], hydroge storage [], ad catalysis []. Recetly rare earth-cotaiig polymer as a kid of fuctioal material has bee received more ad more attetio, because it combies with the uique properties of the rare earth ad the special properties of the polymer, such as light weight, excellet mechaical behavior ad varied preparatio method [-6]. Geerally rare earth ca be iduced ito the polymer matrix by physical bledig or chemical attachmet [7]. Physical bledig is a simple way to produce rare earth-cotaiig polymer, but most rare earth compouds have a bad compatibility with polymer ad ueve dispersio which will cause poor mechaical properties. The chemical attachmet method cosists of two parts: (Ⅰ) the iteractio of rare earth io with liear fuctioalized(such as carboxyl-cotaiig) polymers; (Ⅱ) the polymerizatio ad copolymerizatio of rare earth moomers. Okamoto had produced a lot of rare earth cotaiig polymers through method (Ⅰ) as the first time i 98 [8]. They foud that the fluorescece itesities of the rare earth cotaiig polymers were icrease liearly with the rare earth io cotet. However the disadvatage of method (Ⅰ) is reflected i the low rare earth cotet ad hard to quatify. The advatage of Method (Ⅱ) is that high rare earth cotet ca be get ad easy to quatify. ut the rare earth moomer should be sythesized first. Util ow few papers have studied the self-polymerizatio ad co-polymerizatio properties of the rare earth moomers. Ⅰ: CH CHCH CHCH CH + ReX COOH COOH COOH polymerizatio Ⅱ: CH CH C O O ReX - CH CH C O O ReX - CH CHCH CHCH CH COOH C O COOH ReX - I this paper, gadoliium methacrylate (Gd(M) ) as a example of rare earth moomers was sythesized ad its polymerizatio kietics was studied through the thermal aalysis. The reactivity ratio of Gd(M) ad methyl methacrylate was ivestigated ad calculated by K-T method.. Materials. Experimetatio Gadoliium oxide (Gd O, 99.99%) was purchased from Shaghai Yuelog Chemical Factory, methacrylic acid (M, CP), ethaol (R), N,N-dimethylformamide DOI:.79/iciae7. 9 7The Istitute of Idustrial pplicatios Egieers, Japa.

2 (DMF,R), methyl methacrylate (MM, CP), azodiisobutyroitrile (IN, CP), ad ammoium persulphate (PS, R) were obtaied from Sipharm Chemical Reaget Co., Ltd. MM was washed by sodium hydroxide solutio ad distilled water to elimiate the ihibitor ad IN was recrystallizatio before used. Gadoliium oxide (Gd O, 99.99%) was purchased from Shaghai Yuelog Chemical Factory, methacrylic acid (M, CP), ethaol (R), N,N-dimethylformamide (DMF,R), methyl methacrylate (MM, CP), azodiisobutyroitrile (IN, CP), ad ammoium persulphate (PS, R) were obtaied from Sipharm Chemical Reaget Co., Ltd. MM was washed by sodium hydroxide solutio ad distilled water to elimiate the ihibitor ad IN was recrystallizatio before used.. Sythesis of gadoliium methacrylate (Gd(M) ) Gd(M) was prepared by addig Gd O, M ad H O with the molar ratio of :: ito a -ml three-ecked flask. The reactio was carried out at 9 for h util all the powders had bee dissolved ad the solutio became trasparet. The solutio was filtered while still hot, ad the filtrate was cocetrated by distillig water. white precipitate was obtaied by addig ethyl alcohol i excess to the filtrate ad leavig it overight. The solid was filtered off, washed with ethyl alcohol ad dried uder vacuum. The fial product was obtaied i about 8% yield.. Polymerizatio Self-polymerizatio of Gd(MM) was carried out i a ml vessel usig water as a reactio medium ad PS as a iitiator ad the exothermic process of polymerizatio was directly detected by the micre-dsc. Copolymerizatio of MM ad Gd(MM) was carried out i a three-ecked flask at 7 uder itroge atmosphere usig DMF as a reactio medium ad IN as a iitiator. I the reactio system, the total moomer cocetratio was wt%, ad the iitiator cocetratio was wt% (o the basis of total moomers). Good agitatio was used i the polymerizatio process to throw off the reactio heat istataeously. The copolymerizatio was termiated at a low coversio of % to keep the copolymerizatio at a steady reactio stage. The the precipitate mixture was isolated by filtratio, washed successively with water ad ethyl alcohol, ad dried uder vacuum at. The low coversios were measured by weighig method.. Characterizatios The Fourier trasform ifrared (FT-IR) spectra of samples were recorded at a resolutio of cm - o a Varia Cary spectrometer. The thermal characteristics of Gd(M) was obtaied by DSC (PerkiElmer, DSC 8) ad TG(PerkiElmer, Pyris TG ). The aalyses were performed at a heatig rate of /mi i itroge atmosphere. No-isothermal aalysis by DSC (PerkiElmer, DSC 8) was used as a alterative way of calculatig the self-polymerizatio activatio eergy of Gd(M) i the solid state kow as the Kissiger method [9]. Kissiger method is based o a liear relatioship betwee the logarithmβ/tp with the iverse of the edothermic peak through the followig expressio: l l () where βis the heatig rate( /K), Tp is the edothermic peak temperature(k), R is ideal gas costat. Isothermal aalysis by micro-dsc (Setaram,C8 ) was used to study the kietics of the radical polymerizatio of Gd(M) i aqueous solutio usig ammoium persulphate as iitiator. With the presumptio that the heat flow, dh/dt, was proportioal to the rate of reactio dα/dt, it is possible to determie the extet of coversio, α, directly from the experimetal curve by partial itergratio []: α dt () where HT stads for the total heat of polymerizatio. The depedece of polymerizatio rate o iitiator ad cocetratio was determied by varyig cocetratio of oe species while keepig the other costat ad vice versa. The effect of temperature o the coversio was ivestigated at costat momer ad iitiator cocetratios. Elemet aalysis method was used to calculate moomer reactivity ratios of MM/Gd(M). The gadoliium (Gd) cotets of the copolymer were obtaied by ash determiatio method.. Results ad discussio Fig. shows the FT-IR spectra of M ad Gd(M). The bads characteristic of the oioized carboxyl groups ν(c=o) that lies i the iterval 69-7 cm - i fig. disappear ad ew bads appeare i the regios -8 cm - ad 9- cm - respectively

3 which belog to the stretchig vibratiosνas(coo-) adνs(coo-) of carboxylate io i fig.. It meas the gadoliium io ad carboxyl groups have coordiatio reactio with each other. The frequecies of stretchig vibratios ν(c=c) does ot chage sigificatly betwee M ad Gd(M), that sigify Gd(M) had the ability of polymerizatio. T waveumber/cm - --M --Gd(M) Fig. FT-IR spectra of () M; () Gd(M) I order to cofirm the polymerizatio ability of Gd(M), the thermal aalysis is take as showed i fig.. Two sharp edothermic peaks at ad 9 i fig. ca be related to the meltig of Gd(M) crystals. Geerally rare earth io has a large coordiatio umber, so that there may be two differet kids of crystallie structure i the Gd(M) powder []. There is a sigificat exothermic peak at - i fig.. The TG curve i fig.c exhibit almost o mass loss from -. Therefore, the exothermic peak may be attributed to the self-polymerizatio of Gd(M) rather tha the decompositio of Gd(M). What s more, edothermic peaks ad exothermic peaks are all disappeared i fig.. It also proves that Gd(M) has bee self-polymerizatio at - durig the first heat up process. Gd(M) is chaged to be the poly(gd(m) ) because of the self-polymerizatio which breaks the crystal structure of Gd(M) leadig to the disappearace of edothermic peaks i fig.. mg edo up 7 8 Fig. Thermal aalysis curves of Gd(M) : () DSC for the first heat up; () DSC for the secod heat up; (C) TG T/ C mass/% It has cofirmed that Gd(M) ca be iduced self-polymerizatio iitiated by thermal at - from above aalysis. s show i fig., Tp is raised from 8. to.9 alog with the heatig rate from to /mi ad the activatio eergy (Ea) of polymerizatio is.kj/mol calculated by Eq (). - - : /mi : /mi : /mi : /mi edo up l(p y=-x+. R= x -.7x -.7x -.7x -.8x -.8x -.8x - Tp - /K - T/ Fig. DSC curves of Gd(M) at differet heatig rates:() ;() ;() ; () /mi.iset: Kissiger method plot for activatio eergy determiatio of Gd(M) Most of previous workers used the dilatometer ad gravimetry techique to study the radical chai polymerizatio [-]. Here isothermal aalysis by micro-dsc is used to study the kietics of the radical polymerizatio of Gd(M) i aqueous solutio. The coversio-time curves are geerally S-shaped as show i fig.. t the very begiig of the polymerizatio, coversio ad time are appeared approximate liear relatioship. s the reactio goig, the poly(gd(m) ) is precipitated from the solutio that cause the gel effect ad icrease the polymerizatio rate rapidly. Geerally the depedece of polymerizatio rate o moomer ad iitiator cocetratios isa importat part of the kietic study. The polymerizatio rate, Rp, is obtaied from the slope of the coversio versus time curve. The relatioship of Rp with moomer ad iitiator cocetratio is obtaied by plottig the l[rp] versus l[m] ad l[i], ad the form Rp [M] [I]. is obtaied from the lie of the slope as show i fig.. The polymerizatio kietics equatio of Gd(M) is quite cosistet with the classical kietic theory. The effect of temperature o polymerizatio rate is show i fig.6. s the temperature icreased, the rate of productio of primary free radicals icreased, thus icreasig the polymerizatio rate []. The activatio eergy is 8.kJ/mol determied by plottig l[rp] versus /T(K). This value correspods well with the typical activatio eergies of propagatio i free radical polymerizatio [] ad it reveal that Gd(M) was easier

4 to polymerizatio i solutio state tha i solid state. - exo up t/mi :[M] =.7mol/L :[M] =.mol/l :[M] =.mol/l :[M] =.mol/l t/mi - exo up t/mi :[I]=.6 - mol/l :[I]=6. - mol/l :[I]=9. - mol/l :[I]=.8 - mol/l Fig. micro-dsc curves recorded for the polymerizatio of Gd(M). Iset: polymerizatio coversio of Gd(M) as a fuctio of time. : [M] =.7-.mol/l, [I]=7.7 -mol/l ad T=6 : [I]= mol/l, [M] =.mol/l ad T=6 t/mi should be better. Table Parameters for copolymerizatio of MM/Gd(M) MM/Gd(M) (w/w) 9/ 8/ 8/ 7/ 7/ X (mol/mol) Coversio (%) Gd cotet (wt%) Y (mol/mol) G H τ l[rp] - y=x-8.66 R =.98 l[rp] y=.x-6.7 ε Ps:α H H l[m] l[i] Fig. the depedece of Rp [M] () ad [I] () uder low coversio l[rp] -9. y=-7.x+.88 R = x -.8x -.9x -.9x -.9x -.9x -.9x -.x - t/mi T - /K - :6 :7 :7 :8 Fig.6 Polymerizatio coversio of Gd(M) as a fuctio of time. T=6-8,[M] =.mol/l, [I]=7.7 -mol/l.iset: the depedece of Rp o T uder low coversio O the basis of the elemet aalysis results of gadoliium (Gd), the reactivityratios of MM/Gd(M) ca be calculated by K-T method [6]. Parameters for copolymerizatio are detailed i Table. Fig.7 is the plot of τ vs. ε used to calculate the moomer reactivity ratios by K-T method. The values of r (MM) ad r (Gd(M) ) are. ad., which imply that both the growig radical ~~~MM ad ~~~Gd(M) prefer to combie with the Gd(M) uit. That may because that the gadoliium io has a large coordiatio umber ad the carboxylic group of ~~~MM ca supply loe pair electros to attract the Gd(M) moomer, so that the growig radicals are more likely to combie with the Gd(M) uit. s a result, i order to obtai the copolymer with uiform distributed gadoliium io, addig the Gd(M) moomer ito the solutio drop by drop Fig.7 The plot of τ vs. ε related to the moomer reactivity ratios of MM/Gd(M) calculated by K-T method. Coclusios I summary, Gadoliium methacrylate as a kid of ew moomer ca be sythesized through the reactio of gadoliium oxide ad methacrylic acid with a quite high yield. s the existece of C=C bod, Gd(M) ca be self-polymerizatio iitiated by thermal ad free radical. The characteristic of polymerizatio i aqueous solutio uder low coversio is quite cosistet with the classical kietic theory. Gd(M) moomer also shows a quite high reactivity copolymerizatio with MM by the iferred from the values of moomer reactivity ratios. The purpose of this paper is to add the basic polymerizatio parameters of the rare earth moomer ad provide a little help to produce a kid of fuctioal rare earth-cotaiig polymer material i the comig future.

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