Research Article Keggin-Type Heteropolyacid for Ring ...downloads.hindawi.com/journals/ijps/2015/826512.pdf · Research Article Keggin-Type Heteropolyacid for Ring-Opening Polymerization

Research ArticleKeggin-Type Heteropolyacid for Ring-Opening Polymerizationof Cyclohexene Oxide Molecular Weight Control

Ahmed Aouissi1 Zeid Abdullah Al-Othman1 and Abdurrahman Salhabi2

1Department of Chemistry College of Science King Saud University PO Box 2455 Riyadh 11451 Saudi Arabia2King Abdulaziz City for Science and Technology PO Box 6086 Riyadh 11442 Saudi Arabia

Correspondence should be addressed to Ahmed Aouissi aouissedyahoofr

Received 20 April 2015 Accepted 7 June 2015

Academic Editor Jose Ramon Leiza

Copyright copy 2015 Ahmed Aouissi et alThis is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Polymerization of 12-cyclohexene oxide (CHO) in dichloromethane was catalyzed by 12-tungstophosphoric acid(H3PW12O40sdot13H2O) as a super solid acid The effect of polymerization parameters such as reaction time temperature and

catalyst amount was investigated The effect of acetic anhydride as a ring-opening agent was also investigated The resultingpoly(12-cyclohexene oxide) (PCHO) was characterized by Fourier transform infrared (FTIR) nuclear magnetic resonancespectroscopy (1HNMR) gel-permeation chromatography (GPC) and differential scanning calorimetry (DSC) It has been foundthat the PCHO prepared over H

3PW12O40sdot13H2O has a stereoregularity higher than that prepared over clay and Aluminium

alkoxide catalysts The 119879g value obtained is due to the microstructure but not to molecular weight The yield and the molecularweight of the polymer depend strongly on the reaction conditions Molecular weights can be readily controlled by changingreaction temperature reaction time and catalyst amount Contrary to most polymerization reactions the molecular weightincreases with the temperature increase Addition of acetic anhydride to the reaction medium increased the yield threefold

1 Introduction

Due to their high polarizability and flexibility polyethersconstitute a very important soft segment for producingthermoplastic elastomers Many of these polymers have beensynthesized by ring-opening polymerization (ROP) of cyclicether monomers [1] Among cyclic monomersrsquo ring-openingpolymerization that of cyclohexene oxide (epoxide) intopolycyclohexene oxide (polyether) has been the subject ofa large number of papers [2ndash5] This is due to the fact thatcyclohexene oxide (CHO) polymers are useful materials Infact they are used in the synthesis of various alicyclic targetmaterials including pesticides pharmaceuticals perfumeryand dyestuffs ROP of cyclic ethers could be initiated byelectrophilic agents such as Broslashnsted acids (HCl H

2SO4

HClO4 etc) and Lewis acids (AlCl

3 BF3OEt2 TiCl

4 etc)

However the protonic acid catalysts used are corrosive andnot recoverable and the Lewis acids required great amountto achieve acceptable polymer yields Because of increasing

environmental concerns in recent years a more effectivecatalytic process has been sought In this respect researchershave conducted studies on the development of solid acidsso that aggressive and dangerous homogeneous acids can bereplaced to overcome the problem of separating the catalystsfrom the products and from the disposal of solidliquidwasteSolid Broslashnsted acids with super acidic character such asthe Keggin-type heteropolyacids are known as highly activecatalysts [6ndash8] Due to their strong acidity these ldquosuperacidsrdquo catalyze various reactions much more effectively thanthe conventional protonic acids [9 10] In recent yearsheteropolyacids have been used as catalysts to induce thepolymerization of various monomers such as cyclic ethersstyrene acetals polyalcohols and lactones [11ndash13] In aprevious paper [14] we have reported the polymerization oftetrahydrofuran catalyzed by a series of heteropolyacids Ithas been found that H

3PW12O40was the efficient catalyst of

the series of heteropolyacids tested This fact prompted us toinvestigate the cationic ring-opening polymerization of CHO

Hindawi Publishing CorporationInternational Journal of Polymer ScienceVolume 2015 Article ID 826512 6 pageshttpdxdoiorg1011552015826512

2 International Journal of Polymer Science

by this catalyst The effect of reaction temperature reactiontime catalyst amount and acetic anhydride proportion onthe polymerization was investigated

2 Materials and Methods

21 Catalyst Preparation H3PW12O40was prepared accord-

ing to a now well-known method [15] that is 100 g ofNa2WO4sdot2H2O was dissolved in 100mL of warm distilled

water and then successively 85 H3PO4(5mL) and 375

HCl (22mL) were added slowly to the solution The mixturewas concentrated to three quarters of its initial volume byheating and then after that it was cooled to room temperatureThe cooled mixture was extracted with diethyl ether inhydrochloric acid medium The product formed with etherwhich settled down at the bottom was separated from theaqueous phaseThewhite crystals ofH

3PW12O40sdot13H2Owere

dried at room temperature

22 Polymerization Procedure Polymerization reactions ofCHO were carried out in dichloromethane in a glass reactorfitted with a condenser The temperature of the reactor wasadjusted by a heating jacket Typically a fixed amount ofH3PW12O40

as catalyst was added to CHO (10mL) anddichloromethane (4mL) mixture under stirring at a desiredtemperature Polymerization was terminated with additionof a saturated NaOH aqueous solution and still stirred for5min At the end of the reaction the resulting PCHOpolymer was precipitated in methanol and then filtrated offfor characterization and molecular weight measurements

23 Catalyst and Polymer Characterization The Kegginstructure of the catalyst (H

3PW12O40) was checked by means

of FTIR IR spectrum was recorded with an infrared spec-trometer GENESIS II FTIR (4000ndash400 cmminus1) as KBr pellets

The polymer was characterized by using FTIR spec-troscopy NMR spectroscopy differential scanning calorime-ter (DSC) and molecular weight measurements 1H NMRspectra were recorded on a Bruker Avance 400MHz spec-trophotometer using 5mm NMR tubes using deuteratedacetone-D6 as solvent DSC model DSC-60 made by Shi-madzu was utilized here The specimens weigh about 12mgeach Each specimen was placed in aluminum pan The panwas placed in the DSCrsquos oven in air at atmospheric pressureSpecimens were heated at a constant heating rate of 5∘Cminto 300∘C Molecular weight measurements were determinedby means of a HT-GPC Model 430 Viscotek Houston TXUSA gel-permeation chromatograph (GPC) with CLM6210column

3 Results and Discussion

31 Characterization of the Catalyst Infrared spectrum of 12-tungstophosphoric acid H

3PW12O40sdot13H2O (abbreviated as

H3PW12O40) is shown in Figure 1 According to [16] the

main characteristic features of the Keggin structure observedat 1080ndash1060 cmminus1 (]as P-Oa) at 990ndash960 cm

minus1 (]as Mo-Od)

20

16

12

8

4

Tran

smitt

ance

()

4000 3500 3000 2500 2000 1500 1000 500

Wavenumbers (cmminus1)

Figure 1 IR spectrum of H3PW12O40

3500 3000 2500 2000 1500 1000 500

110

100

90

80

70

60

50

40

30

20

CH2

C O

Tran

smitt

ance

()

O

Wavenumber (cmminus1)

Figure 2 IR spectrum of poly(CHO) Polymerization catalyzed by02 g of H

3PW12O40at 40∘C during 3 hours in CH

2Cl2

at 900ndash870 cmminus1 (]a Mo-Od-Mo) and at 810ndash760 cmminus1 (]asMo-Oc-Mo) were obtained

32 Polymer Characterization The cationic ring-openingpolymerization of cyclohexene oxide was catalyzed byH3PW12O40

solid super acid catalyst in dichloromethane at40∘C (Scheme 1)

The IR spectrum of PCHO is shown in Figure 2 Thebands present at 2932 (120574as CH2) 2859 (120574s CH2 120574 CH) 1449(120575 CH

2) 1366 (120575 CH

2) 1158 1090 (C-O-C antisymmetric

stretching) 895 850 and 756 (120575 CH out-of-plane) Theseassignments for PCHOagree well with those of Yahiaoui et al[2] and Suga and Aoyama [17] for the PCHO prepared withan acid-exchanged montmorillonite clay catalyst

Figure 3 shows different peaks the methylene groups(cyclohexane CH

2-) at 10ndash20 ppm and methine groups

(CH2-CHO) at 32ndash36 ppm The signal of the methine

protons appears in the form of two peaks (328 and 333 ppm)which we attribute respectively to triads isotactic (mm) andheterotactic (mr and rm)These assignments for PCHO agreewell with those of Ling et al [5] for the PCHO prepared overrecyclable scandium triflate in room temperature ionic liquidcatalyst

International Journal of Polymer Science 3

O

Olowast

lowast

nH3PW12O40

40∘C CH2Cl2

Scheme 1 Reaction scheme for the synthesis of PCHO by ring-opening polymerization of CHO over H3PW12O40catalyst

40 20 030 1050 minus10

ab

c

nO c2

b2

c1

b1mm

mr + rm

lowast

120575 (ppm)

Figure 3 1HNMR spectrum of PCHO Polymerization catalyzed by02 g of H

3PW12O40sdot13H2O at 40∘C during 3 hours in CH

2Cl2

10 20 30 40 50 60 700

5

10

15

20

25

30

35

40

45

50

Yiel

d (

)

3500

4000

4500

5000

5500

6000

6500

Temperature (∘C)

Mw

(gm

ol)

Figure 4 Yield and Mw of PCHO as a function of reaction tem-perature Polymerization catalyzed by 02 g of H

3PW12O40during 3

hours in CH2Cl2

33 Effect of Reaction Temperature The effect of the reactiontemperature on the yield molecular weight and 119879g of thePCHO was investigated The reactions were carried out in atemperature ranging from 15∘C to 70∘C in dichloromethanesolvent Figure 4 shows the effect of the temperature onthe yield and on the molecular weight It can be seen thatboth the yield and the molecular weight increased withthe increase of the temperature This result is in agreementwith that reported in the literature [2] The increase of theyield with temperature is an expected result but the increaseof the molecular weight is unexpected In fact in mostpolymerization reactions the molecular weight decreases

Hea

t flow

(Wg

)

Temperature (∘C)000 5000 10000

70∘C

60∘C

50∘C

40∘C

30∘C

35∘C

25∘C

20∘C

Figure 5 Typical DSC thermograms of the prepared PCHOobtained at a heating rate of 20∘Cmin Polymerization catalyzed by02 g of H

3PW12O40during 3 hours in CH

2Cl2

with the increase of the temperature owing to the fact that thetemperature accelerates the rate of chain transfer reactionswhich in turn decreases themolecular weight [18] In the caseof CHO polymerization the increase of the molecular weightcan be explained by the fact that the HO- group bound to arigid cyclohexene ring cannot approach sufficiently close tothe oxygen atom to allow for the interchange reaction [19]

The effect of the temperature reaction on the PCHO 119879gis shown in Figure 5 It can be seen that the 119879g values areranging between 23 and 37∘C These 119879g values are differentfrom that observed by Yahiaoui et al (119879g = 7523∘C) overa clay catalyst [2] As for the PCHO prepared by Zevacoet al over Aluminium alkoxides catalyst [20] the authorsreported that they have not observed a clear glass transitiontemperature but a broad endotherm between 66 and 100∘C(max at 70∘C) which they have attributed to a melting pointof their resulting polymer The difference in the 119879g valuebetween our polymer and that of Yahiaoui et al and Zevacoet al might be due to the difference in the microstructureof the prepared polymer Indeed our PCHO which wasprepared by a super acid (Keggin heteropolyacid) has adifferent stereoregularity than that prepared by these authorsIn fact the 1H NMR spectrum of our PCHO showed onlytwo peaks (328 and 333 ppm) for the signals of the methine


001 002 003 004 0050

10

20

30

40

50

60

70

80

90

Yield

Catalyst amount (g)

Yiel

d (

)

4000

5000

6000

7000

8000

9000

10000

Mw

(gm

ol)

Mw

Figure 6 Effect of catalyst amount on the molecular weight andyield for the polymerization of CHO in CH

2Cl2at 40∘C over

H3PW12O40

protons which we have attributed respectively to triadsisotactic (mm) and heterotactic (mr and rm) whereas theNMRof the PCHOprepared by Yahiaoui et al [2] and Zevacoet al [20] showed three peaks (33 34 and 35 ppm) and(366 378 and 388 ppm) respectively which they attributerespectively to triads isotactic (mm) heterotactic (mr andrm) and syndiotactic (rr)

34 Effect of Catalyst Amount To investigate the effect of theamount of catalyst on the polymerization yield andmolecularweight we carried out the polymerization reaction of CHO(10mL) in dichloromethane (4mL) at 40∘C during 3 hoursThe results obtained are reported in Figure 6 It can beseen that the polymer yield increases as the mass of thecatalyst increases whereas the molecular weight decreasesThe highestmolecular weight (9100 gmolminus1) was obtained forthe lowest amount used of catalyst (10mg) The inverse pro-portionality between themolecular weight and the amount ofcatalyst can be explained by the fact that when the amount ofthe catalyst increased the number of initiating active respon-sible sites (H+) for inducing polymerization increased andconsequently the number of chains increased which is obvi-ously at the expense of the length of the chains The decreaseinmolecular weightmight be due also to the increase in waterwhich increased with the increase of catalyst amount

35 The Effect of Reaction Time Effect of reaction time onthe yield and the molecular weight of the polymer wereexamined The polymerization reactions were catalyzed by002 g of catalyst at 40∘C in dichloromethane solvent Theresults (Figure 7) show that both the yield and molecularweight of the polymer increase with increasing reaction timeThe increase of the yield and the molecular weight was rapidfor short reaction times whereas for long time reactions aslight variation is observed A yield of 64 and a molecular

0 4 8 12 16 20 24 280

10

20

30

40

50

60

70

Yield

Time (h)

Yiel

d (

)

4000

5000

6000

7000

8000

9000

Mw

(gm

ol)

Mw

Figure 7 Effect of reaction time on the conversion and molecularweight of PCHO in CH

2Cl2at 40∘C over H

3PW12O40

000 005 010 015 020 025 030 035 040 045 05020

30

40

50

60

70

80

90Yi

eld

()

Acetic anhydride (volume ratio)

Figure 8 Effect of acetic anhydride proportion on PCHO yieldReaction conditions T = 40∘C reaction time = 3 h

weight of 8300 gmolminus1 are reached after 21 hours of reactionThe stagnation of the molecular mass may be due to the factthat at higher yields and higher molecular weights theviscosity of the medium increased and therefore the reactionbecame kinetically slow So there was a stagnation of themolecular weight and yield

36 Effect of Acetic Anhydride Proportion Acetic anhydridehas been used for the ring-opening of many heterocycliccompounds and it has been found that the yield of thepolymer depends on its used proportion [21ndash23] That is whywe have tried to study its effect on the ring-opening of CHOTo achieve this different volumes are added to the solutionCHOCH

2Cl2 The reactions were carried out at 40∘C for

three hours The results obtained (Figure 8) showed that theyield of the polymer depends strongly on the acetic anhydrideproportion In fact when the volume ratio varies from 0 to


C

O

OO

CH3CO H2PW12O40 +

+CH3CO H2PW12O40 + H2PW12O40

CH3COOH

CH3

(CH3CO)2O + H3PW12O40

Initiation

Propagation

Termination

O OC

O

C

O

O

O

CH3 CH3 lowast

n

n

O O C

O

C

O

+

H2PW12O40

H3PW12O40CH3COOHCH3 CH3

n + 1

Scheme 2 Mechanism for the ring-opening polymerization of cyclohexene oxide in the presence of acetic anhydride over H3PW12O40

catalyst

030 the yield increased by 20 to 60 This shows that theinitial value has tripled When the volume ratio of the aceticanhydride added is beyond 03 the yield decreased Thedecrease of the yield at high acetic anhydride volume ratiomight be due to consumption of heteropolyacid protons bythe acetic anhydride leading to acetic acid (a weak acid) or toan increase in the number of methyl groups at the extremitiesof the chains that block the growth of polymer chains In factlarge addition of acetic anhydride to themixture creates chainends unable to take part in polymerization

37 Polymerization Mechanism The ring-opening polymer-ization of PCHO can be achieved by addition of aceticanhydride via a cationic pathway According to the obtainedresults we propose a cationic mechanism for the poly-merization initiated by protons provided by H

3PW12O40

(Scheme 2) Initiation The first stage is the protonation ofacetic anhydride by H

3PW12O40 leading to the formation

of acetyl polyoxometalate salt Then there is a nucleophilicattack of the oxygen of cyclohexene oxide on the carbon atomof the acetyl species The formed oxonium ion undergoes anucleophilic attack on the carbon by the oxygen of the cyclo-hexene oxide of the chains in growth Propagation In thisstage the protonated oxonium ion undergoes a nucleophilic

attack by a molecule of cyclohexene oxide Termination Thelast stage is a nucleophilic attack of the oxygen of the aceticacid formed in the first stage on the carbon in alpha ofpositively charged oxygen of the chains in growth

4 Conclusions

From the results it can be concluded that Keggin-type het-eropolyacid (H

3PW12O40) is an effective catalyst of the ring-

opening polymerization of cyclohexene oxide owing to itsstrong Broslashnsted acidity

The microstructure of the resulting PCHO is differentfrom that prepared over clay and alumina alkoxide catalystsThe low119879g value of the PCHO is due to themicrostructure butnot to molecular weight Contrary to most polymerizationreactions the molecular weight and the yield increase withthe increase of the temperature

The decrease in the molecular weight with the increaseof the amount of catalyst might be due to the increase ofthe amount of water which increased with the increase ofcatalyst amount or to the increase of the number of initiatingactive sites (H+) which increases the number of chains at theexpense of the length of the chains


Controlled low molecular weight of the PCHO overH3PW12O40can find various applications It can be used for

preparing soft segments for thermoplastic elastomersThe use of H

3PW12O40

as a solid acid catalyst insteadof the usual soluble inorganic acids is a contribution to areduction of waste

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The authors extended their appreciation to the Deanship ofScientific Research at King Saud University for funding thework through the research group Project no RGP-VPP-116

References

[1] O Nuyken and S D Pask ldquoRing-opening polymerization-anintroductory reviewrdquo Polymers vol 5 no 2 pp 361ndash403 2013

[2] A Yahiaoui M Belbachir J C Soutif and L Fontaine ldquoSynthe-sis and structural analyses of poly (1 2 cyclohexene oxide) oversolid acid catalystrdquoMaterials Letters vol 59 no 7 pp 759ndash7672005

[3] Y Zhang D Wang K Wurst and M R Buchmeiser ldquoRing-opening polymerization of cyclohexene oxide by a novel dica-tionic palladium catalystrdquo Designed Monomers and Polymersvol 8 no 6 pp 571ndash588 2005

[4] H Yasuda and E Ihara ldquoLiving polymerizations of polar andnonpolar monomers by the catalysis of organo rare earth metalcomplexesrdquo Bulletin of the Chemical Society of Japan vol 70 no8 pp 1745ndash1767 1997

[5] J Ling L You Y Wang and Z Shen ldquoRing-opening poly-merization of cyclohexene oxide by recyclable scandium triflatein room temperature ionic liquidrdquo Journal of Applied PolymerScience vol 124 no 3 pp 2537ndash2540 2012

[6] L A Allaoui and A Aouissi ldquoEffect of the Broslashnsted acidity onthe behavior of CO

2methanol reactionrdquo Journal of Molecular

Catalysis A Chemical vol 259 no 1-2 pp 281ndash285 2006[7] NMizuno andMMisono ldquoHeterogeneous catalysisrdquoChemical

Reviews vol 98 no 1 pp 199ndash217 1998[8] I V Kozhevnikov ldquoCatalysis by heteropoly acids andmulticom-

ponent polyoxometalates in liquid-phase reactionsrdquo ChemicalReviews vol 98 no 1 pp 171ndash198 1998

[9] E F Kozhevnikova and I V Kozhevnikov ldquoA calorimetricstudy of the acidity of bulk and silica-supported heteropoly acidH3PW12O40rdquo Journal of Catalysis vol 224 no 1 pp 164ndash169

2004[10] M Misono I Ono G Koyano and A Aoshima ldquoHeteropoly-

acids Versatile green catalysts usable in a variety of reactionmediardquo Pure and Applied Chemistry vol 72 no 7 pp 1305ndash13112000

[11] Y Chen G L Zhang and H Z Zhang ldquoControl of molecularweight in tetrahydrofuran polymerization initiated by het-eropolyacidrdquo Journal of Applied Polymer Science vol 82 no 2pp 269ndash275 2001

[12] A Aouissi ldquoCationic polymerization of 23 Dihydro-4H pyranusing H

3PW12O40

as a solid acid catalystrdquo Journal of AppliedPolymer Science vol 117 no 3 pp 1431ndash1435 2010

[13] Q Wu L Li Y Yu and X Tang ldquoThe linear relations andliving feature in cationic ring-opening copolymerization ofepoxyTHF systemrdquo Colloid and Polymer Science vol 286 no6-7 pp 761ndash767 2008

[14] A Aouissi S S Al-Deyab and H Al-Shehri ldquoCationic ring-opening polymerization of tetrahydrofuran with Keggin-typeheteropoly compounds as solid acid catalystsrdquo Chinese Journalof Polymer Science vol 28 no 3 pp 305ndash310 2010

[15] C Rocchiccioli-Deltcheff M Fournier R Franck and RThouvenot ldquoVibrational investigations of polyoxometalates 2Evidence for anion-anion interactions in molybdenum(VI)and tungsten(VI) compounds related to the keggin structurerdquoInorganic Chemistry vol 22 no 2 pp 207ndash216 1983

[16] C Rocchiccioli-Deltcheff and M Fournier ldquoCatalysis by poly-oxometalates Part 3mdashinfluence of vanadium(V) on the ther-mal stability of 12-metallophosphoric acids from in situ infraredstudiesrdquo Journal of the Chemical Society Faraday Transactionsvol 87 no 24 pp 3913ndash3920 1991

[17] S Suga and H Aoyama ldquoFree-radical-induced polymerizationof epoxides in the presence of maleic anhydriderdquo Journal ofPolymer Science Part A-1 Polymer Chemistry vol 7 no 5 pp1237ndash1245 1969

[18] E J Goethals ldquoCyclic oligomers in the cationic polymerizationof heterocyclesrdquo Pure and Applied Chemistry vol 48 no 3 pp335ndash341 1976

[19] P Kubisa and S Penczek ldquoCationic activated monomer poly-merization of heterocyclic monomersrdquo Progress in PolymerScience vol 24 no 10 pp 1409ndash1437 1999

[20] T A Zevaco J K Sypien A Janssen O Walter and E Din-jus ldquoSynthesis structural characterisation of new oligomericalkyl aluminium (221015840-methylene-p-chloro-bisphenoxides) andapplication as catalysts in polymerisation reactions involvingcyclohexene oxiderdquo Journal of Organometallic Chemistry vol692 no 10 pp 1963ndash1973 2007

[21] A Aouissi S S Al-Deyab and H Al-Shahri ldquoThe cationicring-opening polymerization of tetrahydrofuran with 12-tungstophosphoric acidrdquoMolecules vol 15 no 3 pp 1398ndash14072010

[22] M I Ferrahi and M Belbachir ldquoPreparation of poly(oxybuty-leneoxymaleoyl) catalyzed by a proton exchanged montmoril-lonite clayrdquoMolecules vol 9 no 11 pp 968ndash977 2004

[23] T Diao X Sun R Fan and J Wu ldquoUnexpected ring-openingreaction of aziridine with acetic anhydride in DMFrdquo ChemistryLetters vol 36 no 5 pp 604ndash605 2007

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materials


Journal ofNanomaterials


by this catalyst The effect of reaction temperature reactiontime catalyst amount and acetic anhydride proportion onthe polymerization was investigated

2 Materials and Methods

21 Catalyst Preparation H3PW12O40was prepared accord-

ing to a now well-known method [15] that is 100 g ofNa2WO4sdot2H2O was dissolved in 100mL of warm distilled

water and then successively 85 H3PO4(5mL) and 375

HCl (22mL) were added slowly to the solution The mixturewas concentrated to three quarters of its initial volume byheating and then after that it was cooled to room temperatureThe cooled mixture was extracted with diethyl ether inhydrochloric acid medium The product formed with etherwhich settled down at the bottom was separated from theaqueous phaseThewhite crystals ofH

3PW12O40sdot13H2Owere

dried at room temperature

22 Polymerization Procedure Polymerization reactions ofCHO were carried out in dichloromethane in a glass reactorfitted with a condenser The temperature of the reactor wasadjusted by a heating jacket Typically a fixed amount ofH3PW12O40

as catalyst was added to CHO (10mL) anddichloromethane (4mL) mixture under stirring at a desiredtemperature Polymerization was terminated with additionof a saturated NaOH aqueous solution and still stirred for5min At the end of the reaction the resulting PCHOpolymer was precipitated in methanol and then filtrated offfor characterization and molecular weight measurements

23 Catalyst and Polymer Characterization The Kegginstructure of the catalyst (H

3PW12O40) was checked by means

of FTIR IR spectrum was recorded with an infrared spec-trometer GENESIS II FTIR (4000ndash400 cmminus1) as KBr pellets

The polymer was characterized by using FTIR spec-troscopy NMR spectroscopy differential scanning calorime-ter (DSC) and molecular weight measurements 1H NMRspectra were recorded on a Bruker Avance 400MHz spec-trophotometer using 5mm NMR tubes using deuteratedacetone-D6 as solvent DSC model DSC-60 made by Shi-madzu was utilized here The specimens weigh about 12mgeach Each specimen was placed in aluminum pan The panwas placed in the DSCrsquos oven in air at atmospheric pressureSpecimens were heated at a constant heating rate of 5∘Cminto 300∘C Molecular weight measurements were determinedby means of a HT-GPC Model 430 Viscotek Houston TXUSA gel-permeation chromatograph (GPC) with CLM6210column

3 Results and Discussion

31 Characterization of the Catalyst Infrared spectrum of 12-tungstophosphoric acid H

3PW12O40sdot13H2O (abbreviated as

H3PW12O40) is shown in Figure 1 According to [16] the

main characteristic features of the Keggin structure observedat 1080ndash1060 cmminus1 (]as P-Oa) at 990ndash960 cm

minus1 (]as Mo-Od)

20

16

12

8

4

Tran

smitt

ance

()

4000 3500 3000 2500 2000 1500 1000 500

Wavenumbers (cmminus1)

Figure 1 IR spectrum of H3PW12O40

3500 3000 2500 2000 1500 1000 500

110

100

90

80

70

60

50

40

30

20

CH2

C O

Tran

smitt

ance

()

O

Wavenumber (cmminus1)

Figure 2 IR spectrum of poly(CHO) Polymerization catalyzed by02 g of H

3PW12O40at 40∘C during 3 hours in CH

2Cl2

at 900ndash870 cmminus1 (]a Mo-Od-Mo) and at 810ndash760 cmminus1 (]asMo-Oc-Mo) were obtained

32 Polymer Characterization The cationic ring-openingpolymerization of cyclohexene oxide was catalyzed byH3PW12O40

solid super acid catalyst in dichloromethane at40∘C (Scheme 1)

The IR spectrum of PCHO is shown in Figure 2 Thebands present at 2932 (120574as CH2) 2859 (120574s CH2 120574 CH) 1449(120575 CH

2) 1366 (120575 CH

2) 1158 1090 (C-O-C antisymmetric

stretching) 895 850 and 756 (120575 CH out-of-plane) Theseassignments for PCHOagree well with those of Yahiaoui et al[2] and Suga and Aoyama [17] for the PCHO prepared withan acid-exchanged montmorillonite clay catalyst

Figure 3 shows different peaks the methylene groups(cyclohexane CH

2-) at 10ndash20 ppm and methine groups

(CH2-CHO) at 32ndash36 ppm The signal of the methine

protons appears in the form of two peaks (328 and 333 ppm)which we attribute respectively to triads isotactic (mm) andheterotactic (mr and rm)These assignments for PCHO agreewell with those of Ling et al [5] for the PCHO prepared overrecyclable scandium triflate in room temperature ionic liquidcatalyst


O

Olowast

lowast

nH3PW12O40

40∘C CH2Cl2


40 20 030 1050 minus10

ab

c

nO c2

b2

c1

b1mm

mr + rm

lowast

120575 (ppm)



2Cl2

10 20 30 40 50 60 700

5

10

15

20

25

30

35

40

45

50

Yiel

d (

)

3500

4000

4500

5000

5500

6000

6500

Temperature (∘C)

Mw

(gm

ol)


3PW12O40during 3

hours in CH2Cl2


Hea

t flow

(Wg

)


70∘C

60∘C

50∘C

40∘C

30∘C

35∘C

25∘C

20∘C



2Cl2




001 002 003 004 0050

10

20

30

40

50

60

70

80

90

Yield

Catalyst amount (g)

Yiel

d (

)

4000

5000

6000

7000

8000

9000

10000

Mw

(gm

ol)

Mw


2Cl2at 40∘C over

H3PW12O40




0 4 8 12 16 20 24 280

10

20

30

40

50

60

70

Yield

Time (h)

Yiel

d (

)

4000

5000

6000

7000

8000

9000

Mw

(gm

ol)

Mw



3PW12O40

000 005 010 015 020 025 030 035 040 045 05020

30

40

50

60

70

80

90Yi

eld

()








C

O

OO

CH3CO H2PW12O40 +


CH3COOH

CH3


Initiation

Propagation

Termination

O OC

O

C

O

O

O

CH3 CH3 lowast

n

n

O O C

O

C

O

+

H2PW12O40


n + 1


catalyst



3PW12O40





4 Conclusions









3PW12O40




Acknowledgment


References
















3PW12O40




















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




O

Olowast

lowast

nH3PW12O40

40∘C CH2Cl2


40 20 030 1050 minus10

ab

c

nO c2

b2

c1

b1mm

mr + rm

lowast

120575 (ppm)



2Cl2

10 20 30 40 50 60 700

5

10

15

20

25

30

35

40

45

50

Yiel

d (

)

3500

4000

4500

5000

5500

6000

6500

Temperature (∘C)

Mw

(gm

ol)


3PW12O40during 3

hours in CH2Cl2


Hea

t flow

(Wg

)


70∘C

60∘C

50∘C

40∘C

30∘C

35∘C

25∘C

20∘C



2Cl2




001 002 003 004 0050

10

20

30

40

50

60

70

80

90

Yield

Catalyst amount (g)

Yiel

d (

)

4000

5000

6000

7000

8000

9000

10000

Mw

(gm

ol)

Mw


2Cl2at 40∘C over

H3PW12O40




0 4 8 12 16 20 24 280

10

20

30

40

50

60

70

Yield

Time (h)

Yiel

d (

)

4000

5000

6000

7000

8000

9000

Mw

(gm

ol)

Mw



3PW12O40

000 005 010 015 020 025 030 035 040 045 05020

30

40

50

60

70

80

90Yi

eld

()








C

O

OO

CH3CO H2PW12O40 +


CH3COOH

CH3


Initiation

Propagation

Termination

O OC

O

C

O

O

O

CH3 CH3 lowast

n

n

O O C

O

C

O

+

H2PW12O40


n + 1


catalyst



3PW12O40





4 Conclusions









3PW12O40




Acknowledgment


References
















3PW12O40




















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




001 002 003 004 0050

10

20

30

40

50

60

70

80

90

Yield

Catalyst amount (g)

Yiel

d (

)

4000

5000

6000

7000

8000

9000

10000

Mw

(gm

ol)

Mw


2Cl2at 40∘C over

H3PW12O40




0 4 8 12 16 20 24 280

10

20

30

40

50

60

70

Yield

Time (h)

Yiel

d (

)

4000

5000

6000

7000

8000

9000

Mw

(gm

ol)

Mw



3PW12O40

000 005 010 015 020 025 030 035 040 045 05020

30

40

50

60

70

80

90Yi

eld

()








C

O

OO

CH3CO H2PW12O40 +


CH3COOH

CH3


Initiation

Propagation

Termination

O OC

O

C

O

O

O

CH3 CH3 lowast

n

n

O O C

O

C

O

+

H2PW12O40


n + 1


catalyst



3PW12O40





4 Conclusions









3PW12O40




Acknowledgment


References
















3PW12O40




















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




C

O

OO

CH3CO H2PW12O40 +


CH3COOH

CH3


Initiation

Propagation

Termination

O OC

O

C

O

O

O

CH3 CH3 lowast

n

n

O O C

O

C

O

+

H2PW12O40


n + 1


catalyst



3PW12O40





4 Conclusions









3PW12O40




Acknowledgment


References
















3PW12O40




















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






3PW12O40




Acknowledgment


References
















3PW12O40




















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



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