Research Article 1-Butyl-3-methylimidazolium Salts as New ...downloads.hindawi.com/journals/ijps/2014/607341.pdfResearch Article 1-Butyl-3-methylimidazolium Salts as New Catalysts

Research Article1-Butyl-3-methylimidazolium Salts as New Catalysts to ProduceEpoxy-anhydride Polymers with Improved Properties

Mikhail S Fedoseev1 Matvey S Gruzdev2 and Lubov F Derzhavinskaya1

1 Institute of Technical Chemistry of Ural Branch of the RAS Perm 614013 Russia2 GA Krestov Institute of Solution Chemistry of the RAS Ivanovo 153045 Russia

Correspondence should be addressed to Lubov F Derzhavinskaya lfderzhavinskayamailru

Received 6 February 2014 Accepted 14 April 2014 Published 13 May 2014

Academic Editor Jose Ramon Leiza

Copyright copy 2014 Mikhail S Fedoseev et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

We report the curing process of epoxy oligomers by using isomethyltetrahydrophthalic anhydride catalyzed with 1-butyl-3-methylimidazolium salts Catalytic action has been ascertained to be dependent on the nature of anion Salts with (Brminus) and (PO

4

minus)

anions appeared to be most active Formation of salt adducts with epoxy resin and anhydride is shown Polymers having highervalues of strength and glass transition temperaturemdashas compared with similar epoxy systems cured in the presence of tertiaryamines as catalystsmdashare prepared

1 Introduction

Epoxy-anhydride hot curing binding agents and polymers onthe basis are widely applicable in the composite materialsrsquoproduction in particular in production of multipurposeorgano- nano- and coal-plastic products [1] Unlike aminecuring binding agents and to binding agents produced inaccordance with homopolymerization mechanism epoxy-anhydride binding agents have more advanced technologi-cal properties However they are effectively cured only inthe presence of catalysts such as tertiary amines Mannichbases Lewis acids boron fluoride complexes with ani-line monoethanolamine and a-naphthylamine [2ndash4] Manyamines used in production processes are volatile and toxicmatters and do not meet modern ecological requirementsIn addition tertiary amines being active compounds cat-alyze the polyaddition reaction of epoxy groups immediatelyafter reaction components are mixed thus leading to theirincreased viscosity and to shortened pot life In a numberof cases this phenomenon troubles technological processesof massive production It has been ascertained also thatpolymeric materials based on widely used diglycidyl ether ofdiphenylolpropane (ED-20 resin) produced in the presenceof tertiary amines are not sufficiently heat resistant [5 6]

whereas polymers produced by means of cation polymeriza-tion in the presence of boron fluoride complexes are not heatresistant [4 7 8]

Imidazoles appear to be promising curing catalysts [9ndash11] It has been shown in [10 12] that polymers synthesizedusing imidazole catalysts and curing agents have larger heatresistance adhesion and water resistance While investigat-ing kinetics and interactionmechanism of epoxides with acidanhydrides in the presence of imidazoles these imidazoleswere shown to be comparablewith tertiary amines in catalyticaction For example 2-ethyl-4-methylimidazole being highlyactive curing agent while blended with epoxy resins doesnot provide necessary pot life This fact makes the use of thiscompound impossible in production of single-package com-positions (long-lived at room temperature blends comprisedepoxy resin anhydride and a catalyst) [13]

To resolve this technological problem imidazole adductsand their salts withmetals (Cu Ni and Co) were synthesizedThe mentioned compounds have latent reactivity (latency)at low temperatures and disintegrate at high temperaturesinto initial constituents of adducts while catalyzing curingreactions of polymers [12ndash14] 13-Dialkylimidazole salts asbeing ionic liquids can arguably also be regarded as adductsof this kind In line with up-to-date ideas ionic liquids based

Hindawi Publishing CorporationInternational Journal of Polymer ScienceVolume 2014 Article ID 607341 8 pageshttpdxdoiorg1011552014607341

2 International Journal of Polymer Science

on imidazolium salts are permolecular polymeric structureswith a high degree of self-organization These ionic liquidsare comprised only of ions and have lipophilic properties in awide temperature diapason [15]

Recently one of priority trends of the modern ldquogreenchemistryrdquo is the use of ionic liquids as promising medi-ums for organic reactions [16] The use of ionic liquids ascatalysts and curing agents for epoxy resins and productionof multipurpose materials is one of trends in this field[17ndash22] For example the work [23] describes a uniqueresult attained by using ionic liquid An ionic liquid typeimidazolium catalyst enhanced the conductivity of epoxy-anhydride resin based electrical conductive adhesives (ECAs)by more than two orders of magnitude compared with com-mon imidazole compounds Percolation growth dynamicsstudy combined with epoxy curing kinetics results indicatesthat the enhancement of conductivity was attributed to thehigher percolation efficiency within ionic liquid catalyzedECAs In work [24] ionic liquids differing in the lengthof alkyl chain at imidazolium cation (butyl or decyl) withvarious ions for example N(CN)

2

minus (BF4

minus

) and (Clminus) wereused as curing agents for epoxy compositions By usingvarious physical methods thermal and thermomechanicalproperties of polymers were ascertained to be influenced bythe nature and by concentration of an anionThe highest glasstransition temperature (170∘C) was attained for materialscross-linkedwith ion liquid containing dicyandiamide anionMolecular ionic liquid that is 1-ethyl-3-methylimidazoliumchloride ([EMIM]Cl) and eutectic mixture of imidazole withcholine chloride (IM + ChCl) have been used as epoxyresin hardeners An influence of [EMIM]Cl and IM + ChClcontent on pot life of epoxy compositions and runs of cross-linking process has been evaluated using DSC and ARESrheometry techniques Epoxy compositions with [EMIM]Clshowed latent properties (pot life up to 50 days) while thesystems with IM + ChCl gelled after few days Compositeepoxy materials cross-linked with [EMIM]Cl exhibited moreelastic properties (lower 119879

119892

and higher tan120575 values) andgenerally better mechanical features than those hardenedwith imidazole + choline chloride eutectic mixture [25]

This work aims at investigating 1-butyl-3-methyl imida-zolium salts as latent catalysts for anhydride-cured epoxyoligomers and at studying the properties of polymers pro-duced on their basis

2 Experimental Method

Preparation of epoxy polymers was performed by usingchemical interaction of epoxy oligomers diphenylolpropanediglycidylether (ED-20 resin) and oligodienetetraurethanediepoxide (PDI-3AK) with isomethyltetrahydrophthalicanhydride (IMTHPA) under the action of catalysts (saltsof 1-butyl-3-methylimidazolium hereinafter as SBMI) inaccordance with general formula as follows

H3C N N+

CH3Xminus

(1)

where X stands for Br BF4

PO4

and HSO4

The mentioned salts with various ions were synthesizedon the basis of 1-methylimidazole in accordance with theupgraded method described in [26]

Epoxy-anhydride compositions comprised epoxy oligo-mer curing agent (IMTHPA) taken in equimolar ratio andcatalyst (05ndash1 wt) were mixed in laboratory mixer at 40ndash50∘C under vacuum for 15ndash20min The reaction mix wascasted into metallic fill-out forms and kept in thermostatuntil complete curing The curing was performed at tem-perature values determined from reaction kinetics by usingthe DSC method on the DSC 822e calorimeter (MettlerToledo Switzerland) in dynamic mode at 5∘Cmin heatingrate in temperature interval of 25ndash300∘C Initial temperature(119879initial) temperature of maximal heat-evolution (119879max) andheat-evolution power versus time were registered in tem-perature profiles These data resulted in calculation of heatefficiency of the reaction (based on peak area) and of theeffective activation energy (E)

Strain-strength characteristics of the cured polymersnamely tensile strength and relative elongation were deter-mined at a set-point temperature and at 0056 sminus1 stretchingrate on the Instron 3565 universal testing machine (InstronGreat Britain)

The glass transition temperature 119879119892

was determined bythe method of thermomechanical analysis on the UIP-70device (Russia) in temperature interval 20ndash200∘C at thescanning rate 5∘Cmin in the dilatometry regime

Thermal characteristics of polymers were determinedon the MOMQ-1500D (Paulik-Paulik-Erdey) derivatographThe programmed heating was performed at 5∘Cmin rate ininterval of 20ndash1000∘C in the air Aluminium oxide was usedas a standard Heat resistance of polymers was appraised from5 and 10 loss of mass

The water uptake of polymers was appraised from anincrease in a specimenrsquos mass in water at 25∘C for 24 h

Pot life 119905lowast (inductive effect) of mixed reaction composi-tions was appraised from a variation in viscosity while usingthe rotational rheotest-2 viscometer (Germany) with cone-plate unit at constant 180 sminus1 shear rate at 25 plusmn 05∘C

Chemical interaction between 1-butyl-3-methylimidazo-lium salts and epoxy compositionrsquos components (ED-20 PDI-3AK and IMTHPA) was investigated by means of FTIR-spectroscopy method using IFS-66 spectrometer (BrukerGermany)

3 Results and Discussions

Due to availability of pyridine and pyrrole atoms in thestructure of imidazole molecules these molecules exhibitboth acid and basic properties This fact enables using thesecompounds in various chemical reactions In [27 28] reac-tions of mono- and diepoxy compounds with various imi-dazoles are investigated also a bimodal curing mechanismfor polymers supposing formation of intermediate adducts(epoxide-imidazole) being true catalysts of curing reactionsis offered Recently [10] the nonsubstituted imidazoles wereascertained to form adducts also with acid anhydrides cat-alyzing polyaddition reaction of oligomerrsquos epoxy group with

International Journal of Polymer Science 3

Exo

up

75 125 175 225 275

1

2

3

4

T (∘C)

Figure 1DSC curves of curing reaction of IMTHPA-curedED-20 resin in the presence of catalysts (1) 1-butyl-3-methylimidazoliumbromide(2) 1-butyl-3-methylimidazolium orthophosphate (3) 1-butyl-3-methylimidazolium tetrafluoroborate (4) 1-butyl-3-methylimidazoliumsulfate

Table 1 Kinetics parameters of interaction reaction of ED-20 resin and IMTHPA under the action of 1-butyl-3-methyl imidazolium saltswith various inorganic anions in molecule of 1-methyl imidazole and of 246-tris(dimethylaminomethyl)phenol

Catalyst 119879in∘C 119879pic

∘C 119876 Jg 119864 kJmol1-Butyl-3-methylimidazolium tetrafluoroborate 120 214 387 1001-Butyl-3-methylimidazolium sulfate 120 222 317 1021-Butyl-3-methylimidazolium phosphate 82 156 331 951-Butyl-3-methylimidazolium bromide 70 137 322 921-Methylimidazole 45 125 350 75246-Tris(dimethylaminomethyl)phenol 75 145 312 87

anhydride epoxy group followed by formation of a cross-linked polymer Investigation of interaction kinetics of ED-20andPDI-3AK epoxy oligomerswith IMTHPAcuring agent inthe presence of 1-butyl-3-methyl imidazolium salts by usingDSC method has shown these oligomers to be catalysts ofpolyaddition reaction Their catalytic activity is somewhatlower as compared with tertiary amines and imidazolesThe DSC temperature profiles (Figure 1) have enabled ascer-taining temperature-time conditions for the curing reactionKinetics parameters are presented in Table 1 As is apparentfrom the obtained data initial temperature of reaction andmaximal heat-evolution are dependent on the nature of anionin salt molecule 1-Butyl-3-methylimidazolium bromide and1-butyl-3-methylimidazolium phosphate proved to be mostactive catalysts (119879in = 70∘C and 82∘C resp) Salts with BF

4

and HSO4

anions start catalyzing the interaction reactionbetween resin and anhydride at a higher temperature (120∘C)1-Butyl-3-methylimidazolium bromide as the most activecatalyst was selected for further investigations

As expected catalytic action of 1-butyl-3-methylimidazo-lium bromide is lower as compared with that of 1-methy-limidazole being initial product of the given salt (Figure 2)This is attributed to the fact that the salt has latent propertiesto a greater extent as compared with 1-methylimidazole alsointeraction mechanism during synthesis of epoxy-anhydridepolymers has certain distinctions To ascertain these dis-tinctions interaction between 1-butyl-3-methylimidazolium

50 75 100 125 150 175 200

Exo

up

1

2

T (∘C)

Figure 2 DSC curves of curing reaction of IMTHPA-cured ED-20resin in the presence of catalysts (1) 1-methylimidazole (2) 1-butyl-3-methylimidazolium bromide

bromide and epoxy compositionsrsquo components (ED-20 PDI-3AK and IMTHPA oligomers) was investigated by using theFTIR-spectroscopy method The FTIR spectra of reactionmixes are presented in Figures 3 4 and 5 Analysis of thespectra has shown that on interaction between 1-butyl-3-methyl imidazolium bromide and IMTHPA at 100∘C thereaction proceeds with participation of anhydride group withsubsequent formation of oligoamides polyanhydrides and


0

05

1

700120017002200270032003700

Wavenumber (cmminus1)

Abso

rban

ce

123306

1776

1723

1846

1239

971

923

Figure 3 FTIR-spectrum of reaction mixture ldquo1-butyl-3-methyli-midazolium bromide ndash IMTHPArdquo (1) initial mixture (2) kept for5 h at 100∘C

700120017002200270032003700


0

05

15

1

Abso

rban

ce

2965

1796

1732

1508

1242

1

2

Figure 4 FTIR-spectrum of reaction mixture ldquo1-butyl-3-methyli-midazolium bromide ndash ED-20 resinrdquo (1) initial mixture (2) kept for5 h at 100∘C

ketones The produced adducts are stable viscous liquidsand active catalysts of the epoxy-anhydride binding agentrsquoscuring process (Figure 6) Most likely these adducts canbe regarded as complexes with the charge transfer Similarcomplexes were produced in [23] on interaction betweendicarboxylic acid anhydrides and tertiary amines They cantransform to polyanhydrides polyesters oligoamides andoligoalkyl(aryl)ketones with a system of conjugate bondsJudging from the DSC diagrams of the same type the curingreactionrsquos mechanism of catalysis in the presence of adductsproduced on the basis of 1-butyl-3-methylimidazolium bro-mide and on the basis of the earlier investigated 2-ethyl-4-methylimidazole [10] is the same mechanism

A more complicated character is observed in interactionmechanism between 1-butyl-3-methylimidazolium bromideand ED-20 epoxy oligomers especially with PDI-3AK con-taining four urethane groups and two end-capped epoxygroups in its molecule This is attributed to peculiaritiesin their structure and to the difference in reactivity of

0

05

1

700120017002200270032003700


Abso

rban

ce

1

2

3045

1532

1446

Figure 5 FTIR-spectrum of reaction mixture ldquo1-butyl-3-methyli-midazolium bromide-PDI-3AKrdquo (1) initial mixture (2) kept for 5 hat 100∘C

Exo

up

1

2

75 100 125 150 175 200

T (∘C)

Figure 6 DSC curves of curing reaction of ED-20 resin withIMTHPA hardener in the presence of interaction products (1) 2-ethyl-4-methylimidazole + IMTHPA (2) 1-butyl-3-methylimida-zolium bromide + IMTHPA

the end-capped epoxy groups With this connection wehad set optimal temperature regimes for these reactions Itwas expedient to do this while also keeping in mind thatcompounds for electronic and radioengineering devices aswell as polymeric and sealing materials for various purposeswere designed on the basis of the given polymers [28ndash30]

Distinction in reactive capability of catalysts exerts appre-ciable influence on rheological properties of reaction mixesComparable results are presented in Figure 7 As is apparentfrom viscosity curves registered at room temperature reac-tion mixesrsquo pot life regarded as a period of time needed forthe mixes to attain viscosity value of 140 Pas was appreciablydependent on the nature of the catalyst The lowest pot life(119905lowast

1

= 30 h) has a composition containing tertiary aminemdash246-tris(dimethylaminomethyl)phenol The N-substituted1-methyl imidazole as a high-temperature catalyst enablesextending pot life of the epoxy-anhydride composition up to119905lowast

2

= 72 h at room temperature Pot life of the composition


50

100

150

200

250

300

0 50 100 150 200 250tlowast1 t

lowast2 t

lowast3

Time (h)

1 2

3

Visc

osity

(Pas

)

Figure 7 Dynamic viscosity variation of epoxy-anhydride compositions at T = 25∘C versus time in the presence of catalysts (1) 246-tris(dimethylaminomethyl)phenol (2) methylimidazole (3) 1-butyl-3-methylimidazolium bromide

with the SBMI-Br catalyst (119905lowast3

) attains 178 h that is thiscatalyst can be regarded as a latent catalyst

Action mechanism of the known amine catalyst namely246-tris(dimethylaminomethyl)phenol is represented in(2)

CC

C CC

C

C

CO

O

O

O

O

O

O O

O

O

O

O

O OO

NR3NR3

R998400

R998400

HCHC

CH2

CH2

CH2CH CH

C C

CC

O

OO

O

OO

O

O

O NR3

NR3 R998400 HC CH2CHH2C

R

R

R

R R

R

+

(2)

Formationaction mechanism of adducts with participa-tion of 1-substituted imidazoles differs from that of tertiaryamine In [28] formation outline of an adduct resulting fromreaction of 1-methylimidazole with phenyldiglycidyl ether at

1 1 ratio is represented In this reaction the epoxy group isattacked by more basic pyridine group of nitrogen

N NN

R

R

R998400

R998400

CHCH R998400998400 R998400998400CH2

O

ON+

+H2C (3)


Table 2 Rheological physic-mechanical thermal properties of epoxy polymers

Composition wt 119905lowast h Synthesis

conditions119879119892

∘CPhysic-mechanical properties

under stretchingWater

absorption 24 h25∘C mas

119879 ∘Cmass loss

120590 mPa 120576 5 10ED-20mdash555IMTHPAmdash440SBMI-Brmdash05

178 120∘C 3 h160∘C 3 h 135 60 12 017 330 360

ED-20mdash555IMTHPAmdash440246-Tris(dimethylaminomethyl)ahenolmdash05

30 120∘C 3 h160∘C 3 h 105 55 10 011 335 360

PDI-3AKmdash93IMTHPAmdash6SBMI-Brmdash1

240 80∘C 72 h120∘C 3 h minus82 4 415 mdash 300 340

PDI-3AKmdash93IMTHPAmdash6246-Tris(dimethylaminomethyl)ahenolmdash1

40 80∘C 72 h120∘C 3 h minus76 22 142 mdash 305 340

The adduct initiates further polymerization of phenyldi-glycidyl ether

The work [31] shows how reaction between ionic liquid(N1198731015840-dioctadecylimidazolium iodide) and bisphenol digly-cidylether A (DGEBA) forms adducts

R

R

R R

RR

R

R

RR

R

N N

N

N

N

N

N

N

N

H

H

H

HeatN +

N N +

other compounds

CH

CH

CH

CHCH O

O

O

CCH2

CH2

CH2CH2

CH2

CH2

OH

OH

OH

Iminus

Ominus

OH (4)

By using the FTIR-spectroscopy the reaction betweenDGEBA and amine curing agent (441015840-methylenebis(3-chloro-26-diethylaniline) was shown to proceed at highertemperatures (140ndash180∘C)

Currently formationaction mechanism of SBMI-Bradducts namely of epoxy oligomer and of anhydride hasnot been studied Conditionally the following outline for thecuring of epoxy oligomers by means of acid anhydride underthe action of SBMI-Br can be presented On the first stagevariously comprised adducts of oligomer and of anhydridewith SBMI-Br catalyst are formed On the second stagecatalysis initiated by adducts occurs followed by formationof linear and branched polymers On the third stage thestructure of a cross-linked polymer and its physic-mechanicalproperties are finally formed

While using the SBMI-Br catalyst a number of polymerswere synthesized Their physic-mechanical thermal andthermal-physic properties as well as water-resistance wereinvestigated (Table 2)

Compositions with the 246-tris(dimethylaminomethyl)phenol are presented for comparison These data indicatephysic-mechanical thermal and thermal-physic propertiesof polymers synthesized using the SBMI-Br and 246-tris(dimethylaminomethyl)phenol catalysts to be approxi-mately at the same level

As regards the influence of catalysts on structure for-mation an increase in glass transition temperature by 30∘Cand respectively an increase in heat resistance of polymersproduced in the presence of the SBMI-Brwere revealedThusthe 1-butyl-3-methyl imidazolium bromide salt can also be


regarded as a structural modifier Strength and critical strainvalues of elastomer based on PDI-3AK and SBMI-Br increasealmost 2-fold as compared with an elastomer synthesized inthe presence of tertiary amine

The increase in strength is probably attributed to for-mation of strong intermolecular interaction within polymerin particular of donor-acceptor bonds with energy valuesattaining 40 kcalmol This phenomenon leads to an increasein cohesion and respectively in strength properties of poly-mers Glass transition temperature of polymers is minus76∘C andminus82∘C this fact enables classifying the given polymers asfrost-resistive

4 Conclusions

Results of investigations in 1-butyl-3-methylimidazoliumsalts (ionic liquids) as catalysts in synthesis of epoxy-anhydride polymers have enabled ascertaining the following(a) these salts are comparable with tertiary amines in catalyticaction (b) unlike tertiary amines they are latent catalystsDue to this pot life of reactive mixes containing the givensalts increases 5- to 6-fold at 20plusmn5∘C thus enabling producingthe so-termed single-package compositions featured by highstability Chemical interaction of one of most promisingsalt namely 1-butyl-3-methylimidazolium bromide with (a)ED-20 (b) oligodienetetraurethane diepoxide (PDI-3AK)and (c) IMTHPA as curing agents was investigated byDSC and FTIR-spectroscopy methods Formation of respec-tive adducts being true catalysts and curing agents forepoxy oligomers was shown Physic-mechanical thermaland structural characteristics of epoxy polymers curedwith 1-butyl-3-methylimidazolium bromide were determined ten-sile strength of polymers based on ED-20 resin IMTHPAand 1-butyl-3-methyl imidazolium bromidemdash60mPa rel-ative elongation 10ndash12 and glass transition temperatureminus135∘C Physic-mechanical characteristics are appraised asbeing at the level of polymers produced in the presence oftertiary amines for example in glass transition temperaturepolymers based on ionic liquid outperform these by 30∘C

Thus 1-butyl-3-methylimidazolium bromide can beregarded also as a structural modifier which duringsynthesis of polymer is embedded into polymeric chainwhile imparting more strength and density of package to itThis leads to an increase in glass transition temperature andrespectively in heat resistance The obtained results are inaccordance with literature data

Thermal properties of polymers judging from data ofdifferential thermal analysis are not dependent on the natureof the used catalyst but mainly depend on the nature of epoxyoligomer It was shown that polymers on the basis of thePDI-3AKwere frost-resisting elastomers with glass transitiontemperature minus76∘C divide minus82∘C

Conflict of Interests

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

References

[1] G Lubin EdHandbook of Composites VanNostrand ReinholdCompany 1982

[2] H Lee and K Neville Handbook of Epoxy Resins M EnergyMoscow Russia 1973 (Russian)

[3] R A Dickie S S Labana and R S Bauer Eds Cross-LinkedPolymers American Chemical Society Washington DC USA1988

[4] M A Sinelnikova E P Volkova and E M Shved ldquoTheinfluence of epoxy resin-catalyst ratio on the rate of anhydridecuring of ED-20 resin in the presence of boron trifluoride withbenzylaminerdquo Journal of Chemistry and Chemical Technologyvol 3 pp 115ndash118 2002

[5] P A Sitnikov A G Belykh M S Fedoseev I N Vaseneva andA V Kuchin ldquoModification of epoxy-anhydride polymers withaluminum oxiderdquo Russian Journal of Applied Chemistry vol 81no 5 pp 826ndash829 2008

[6] O I Petko and I P Petko ldquoEpoxy binding agents for productionof variously shaped fiberglass plastics and figures of revolutionrdquoPlastics vol 10 pp 38ndash39 2008

[7] V M Mikhalrsquochuk T V Kryuk and A N NikolaevskiildquoInhibition of thermal and thermo-oxidative destruction ofcation-polymerized epoxy polymers by oxides and metal saltsrdquoRussian Journal of Applied Chemistry vol 69 no 6 pp 1008ndash1013 1996

[8] V M Mikhalrsquochuk T V Kryuk and A N NikolaevskiildquoStabilization of epoxy polymers by synergetic mixtures ofphenol anti-oxidants and metalsrsquo compoundsrdquo Russian Journalof Applied Chemistry vol 69 no 6 pp 1354ndash1368 1996

[9] K Kowalczyk and T Spychaj ldquoIonic liquids as convenient latenthardeners of epoxy resinsrdquo Polimery vol 48 no 11-12 pp 833ndash835 2003

[10] M S Fedoseev L F Derzhavinskaya and V N StrelrsquonikovldquoCuring of epoxy-anhydride compositions in the presence ofimidazolesrdquo Russian Journal of Applied Chemistry vol 83 no8 pp 1303ndash1307 2010

[11] J M Barton ldquoAspects of epoxy resin curing reactionsrdquo Macro-molecular Symposia vol 7 no 1 pp 27ndash36 1987

[12] M S Fedoseev and I V Zvereva ldquoInvestigation in imidazoleand benzotriazole derivatives as catalysts for curing of epoxy-anhydride binding agentsrdquo Russian Journal of Applied Chem-istry vol 81 no 5 pp 799ndash802 2008

[13] F Wang J Xiao J-W Wang and S-Q Li ldquoA novel imidazolederivative curing agent for epoxy resin synthesis characteriza-tion and cure kineticrdquo Journal of Applied Polymer Science vol107 no 1 pp 223ndash227 2008

[14] A V Pocius Adhesion and Adhesives Technology An Introduc-tion Carl Hanser Munich Germany 2002

[15] A A Zanin ldquoIonic liquids in synthesis of nanoobjectsrdquo Progressin Chemistry Journal vol 79 no 6 pp 516ndash531 2010

[16] P J Dyson andT J GeldbachMetal Catalyzed Reactions in IonicLiquids Springer Dordrecht The Netherlands 2005

[17] J Lu F Yan and J Texter ldquoAdvanced applications of ionicliquids in polymer sciencerdquo Progress in Polymer Science vol 34no 5 pp 431ndash448 2009

[18] P Kubisa ldquoIonic liquids in the synthesis and modification ofpolymersrdquo Journal of Polymer Science A Polymer Chemistry vol43 no 20 pp 4675ndash4683 2005

[19] J P Pascault and R J J Williams Eds Epoxy Polymers Wiley-VCH Weinheim Germany 2010


[20] J Sanes F-J Carrion-Vilches and M-D Bermudez ldquoNewepoxy-ionic liquid dispersions Room temperature ionic liquidas lubricant of epoxy resin-stainless steel contactsrdquo e-Polymersvol 7 no 1 pp 48ndash59 2007

[21] J Sanes F J Carrion and M D Bermudez ldquoEffect of the addi-tion of room temperature ionic liquid and ZnO nanoparticleson the wear and scratch resistance of epoxy resinrdquo Wear vol268 no 11-12 pp 1295ndash1302 2010

[22] K Matsumoto and T Endo ldquoSynthesis of ion conductivenetworked polymers based on an ionic liquid epoxide having aquaternary ammonium salt structurerdquoMacromolecules vol 42no 13 pp 4580ndash4584 2009

[23] X Zhang H Sun C Yang K Zhang M M F Yuen andS Yang ldquoHighly conductive polymer composites from room-temperature ionic liquid cured epoxy resin effect of interphaselayer on percolation conductancerdquo RSC Advances vol 3 no 6pp 1916ndash1921 2013

[24] H Maka T Spychaj and R Pilawka ldquoEpoxy resinionic liquidsystems the influence of imidazoliumcation size and anion typeon reactivity and thermomechanical propertiesrdquo Industrial andEngineering Chemistry Research vol 51 no 14 pp 5197ndash52062012

[25] H Maka and T Spychaj ldquoEpoxy resin cross-linked with con-ventional and deep eutectic ionic liquidsrdquo Polimery vol 57 no6 pp 456ndash462 2012

[26] M S Gruzdev L M Ramenskaya U V Chervonova andR S Kumeev ldquoPreparation of 1-butyl-3-methylimidazoliumsalts and study of their phase behavior and intramolecularintractionsrdquo Russian Journal of General Chemistry vol 79 no8 pp 1720ndash1727 2009

[27] V Jisova ldquoCuring mechanism of epoxides by imidazolesrdquoJournal of Applied Polymer Science vol 34 no 7 pp 2547ndash25581987

[28] M Ghaemy and S Sadjady ldquoKinetic analysis of curing behaviorof diglycidyl ether of bisphenol a with imidazoles using dif-ferential scanning calorimetry techniquesrdquo Journal of AppliedPolymer Science vol 100 no 4 pp 2634ndash2641 2006

[29] M S Fedoseev V V Tereshatov and L F DerzhavinskayaldquoPolymeric materials on the basis of oligodieneurethane epoxyoligomersrdquo Russian Journal of Applied Chemistry vol 83 no 8pp 1261ndash1263 2010

[30] S N Gladkikh E N Basharina and L I Naumova ldquoNewcompounds for cold impregnation of spooled productsrdquo GluesSealants Technologies Journal vol 9 pp 26ndash30 2009

[31] B G Soares S Livi J Duchet-Rumeau and J-F GerardldquoSynthesis and characterization of epoxyMCDEA networksmodified with imidazolium-based ionic liquidsrdquoMacromolecu-lar Materials and Engineering vol 296 no 9 pp 826ndash834 2011

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Journal ofNanomaterials


on imidazolium salts are permolecular polymeric structureswith a high degree of self-organization These ionic liquidsare comprised only of ions and have lipophilic properties in awide temperature diapason [15]

Recently one of priority trends of the modern ldquogreenchemistryrdquo is the use of ionic liquids as promising medi-ums for organic reactions [16] The use of ionic liquids ascatalysts and curing agents for epoxy resins and productionof multipurpose materials is one of trends in this field[17ndash22] For example the work [23] describes a uniqueresult attained by using ionic liquid An ionic liquid typeimidazolium catalyst enhanced the conductivity of epoxy-anhydride resin based electrical conductive adhesives (ECAs)by more than two orders of magnitude compared with com-mon imidazole compounds Percolation growth dynamicsstudy combined with epoxy curing kinetics results indicatesthat the enhancement of conductivity was attributed to thehigher percolation efficiency within ionic liquid catalyzedECAs In work [24] ionic liquids differing in the lengthof alkyl chain at imidazolium cation (butyl or decyl) withvarious ions for example N(CN)

2

minus (BF4

minus

) and (Clminus) wereused as curing agents for epoxy compositions By usingvarious physical methods thermal and thermomechanicalproperties of polymers were ascertained to be influenced bythe nature and by concentration of an anionThe highest glasstransition temperature (170∘C) was attained for materialscross-linkedwith ion liquid containing dicyandiamide anionMolecular ionic liquid that is 1-ethyl-3-methylimidazoliumchloride ([EMIM]Cl) and eutectic mixture of imidazole withcholine chloride (IM + ChCl) have been used as epoxyresin hardeners An influence of [EMIM]Cl and IM + ChClcontent on pot life of epoxy compositions and runs of cross-linking process has been evaluated using DSC and ARESrheometry techniques Epoxy compositions with [EMIM]Clshowed latent properties (pot life up to 50 days) while thesystems with IM + ChCl gelled after few days Compositeepoxy materials cross-linked with [EMIM]Cl exhibited moreelastic properties (lower 119879

119892

and higher tan120575 values) andgenerally better mechanical features than those hardenedwith imidazole + choline chloride eutectic mixture [25]

This work aims at investigating 1-butyl-3-methyl imida-zolium salts as latent catalysts for anhydride-cured epoxyoligomers and at studying the properties of polymers pro-duced on their basis

2 Experimental Method

Preparation of epoxy polymers was performed by usingchemical interaction of epoxy oligomers diphenylolpropanediglycidylether (ED-20 resin) and oligodienetetraurethanediepoxide (PDI-3AK) with isomethyltetrahydrophthalicanhydride (IMTHPA) under the action of catalysts (saltsof 1-butyl-3-methylimidazolium hereinafter as SBMI) inaccordance with general formula as follows

H3C N N+

CH3Xminus

(1)

where X stands for Br BF4

PO4

and HSO4

The mentioned salts with various ions were synthesizedon the basis of 1-methylimidazole in accordance with theupgraded method described in [26]

Epoxy-anhydride compositions comprised epoxy oligo-mer curing agent (IMTHPA) taken in equimolar ratio andcatalyst (05ndash1 wt) were mixed in laboratory mixer at 40ndash50∘C under vacuum for 15ndash20min The reaction mix wascasted into metallic fill-out forms and kept in thermostatuntil complete curing The curing was performed at tem-perature values determined from reaction kinetics by usingthe DSC method on the DSC 822e calorimeter (MettlerToledo Switzerland) in dynamic mode at 5∘Cmin heatingrate in temperature interval of 25ndash300∘C Initial temperature(119879initial) temperature of maximal heat-evolution (119879max) andheat-evolution power versus time were registered in tem-perature profiles These data resulted in calculation of heatefficiency of the reaction (based on peak area) and of theeffective activation energy (E)

Strain-strength characteristics of the cured polymersnamely tensile strength and relative elongation were deter-mined at a set-point temperature and at 0056 sminus1 stretchingrate on the Instron 3565 universal testing machine (InstronGreat Britain)

The glass transition temperature 119879119892

was determined bythe method of thermomechanical analysis on the UIP-70device (Russia) in temperature interval 20ndash200∘C at thescanning rate 5∘Cmin in the dilatometry regime

Thermal characteristics of polymers were determinedon the MOMQ-1500D (Paulik-Paulik-Erdey) derivatographThe programmed heating was performed at 5∘Cmin rate ininterval of 20ndash1000∘C in the air Aluminium oxide was usedas a standard Heat resistance of polymers was appraised from5 and 10 loss of mass

The water uptake of polymers was appraised from anincrease in a specimenrsquos mass in water at 25∘C for 24 h

Pot life 119905lowast (inductive effect) of mixed reaction composi-tions was appraised from a variation in viscosity while usingthe rotational rheotest-2 viscometer (Germany) with cone-plate unit at constant 180 sminus1 shear rate at 25 plusmn 05∘C

Chemical interaction between 1-butyl-3-methylimidazo-lium salts and epoxy compositionrsquos components (ED-20 PDI-3AK and IMTHPA) was investigated by means of FTIR-spectroscopy method using IFS-66 spectrometer (BrukerGermany)

3 Results and Discussions

Due to availability of pyridine and pyrrole atoms in thestructure of imidazole molecules these molecules exhibitboth acid and basic properties This fact enables using thesecompounds in various chemical reactions In [27 28] reac-tions of mono- and diepoxy compounds with various imi-dazoles are investigated also a bimodal curing mechanismfor polymers supposing formation of intermediate adducts(epoxide-imidazole) being true catalysts of curing reactionsis offered Recently [10] the nonsubstituted imidazoles wereascertained to form adducts also with acid anhydrides cat-alyzing polyaddition reaction of oligomerrsquos epoxy group with


Exo

up

75 125 175 225 275

1

2

3

4

T (∘C)






4

and HSO4



50 75 100 125 150 175 200

Exo

up

1

2

T (∘C)




0

05

1

700120017002200270032003700


Abso

rban

ce

123306

1776

1723

1846

1239

971

923


700120017002200270032003700


0

05

15

1

Abso

rban

ce

2965

1796

1732

1508

1242

1

2




0

05

1

700120017002200270032003700


Abso

rban

ce

1

2

3045

1532

1446


Exo

up

1

2

75 100 125 150 175 200

T (∘C)




1


2



50

100

150

200

250

300

0 50 100 150 200 250tlowast1 t

lowast2 t

lowast3

Time (h)

1 2

3

Visc

osity

(Pas

)





CC

C CC

C

C

CO

O

O

O

O

O

O O

O

O

O

O

O OO

NR3NR3

R998400

R998400

HCHC

CH2

CH2

CH2CH CH

C C

CC

O

OO

O

OO

O

O

O NR3


R

R

R

R R

R

+

(2)



N NN

R

R

R998400

R998400

CHCH R998400998400 R998400998400CH2

O

ON+

+H2C (3)










178 120∘C 3 h160∘C 3 h 135 60 12 017 330 360


30 120∘C 3 h160∘C 3 h 105 55 10 011 335 360


240 80∘C 72 h120∘C 3 h minus82 4 415 mdash 300 340


40 80∘C 72 h120∘C 3 h minus76 22 142 mdash 305 340



R

R

R R

RR

R

R

RR

R

N N

N

N

N

N

N

N

N

H

H

H

HeatN +

N N +

other compounds

CH

CH

CH

CHCH O

O

O

CCH2

CH2

CH2CH2

CH2

CH2

OH

OH

OH

Iminus

Ominus

OH (4)









4 Conclusions






References








































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




Exo

up

75 125 175 225 275

1

2

3

4

T (∘C)






4

and HSO4



50 75 100 125 150 175 200

Exo

up

1

2

T (∘C)




0

05

1

700120017002200270032003700


Abso

rban

ce

123306

1776

1723

1846

1239

971

923


700120017002200270032003700


0

05

15

1

Abso

rban

ce

2965

1796

1732

1508

1242

1

2




0

05

1

700120017002200270032003700


Abso

rban

ce

1

2

3045

1532

1446


Exo

up

1

2

75 100 125 150 175 200

T (∘C)




1


2



50

100

150

200

250

300

0 50 100 150 200 250tlowast1 t

lowast2 t

lowast3

Time (h)

1 2

3

Visc

osity

(Pas

)





CC

C CC

C

C

CO

O

O

O

O

O

O O

O

O

O

O

O OO

NR3NR3

R998400

R998400

HCHC

CH2

CH2

CH2CH CH

C C

CC

O

OO

O

OO

O

O

O NR3


R

R

R

R R

R

+

(2)



N NN

R

R

R998400

R998400

CHCH R998400998400 R998400998400CH2

O

ON+

+H2C (3)










178 120∘C 3 h160∘C 3 h 135 60 12 017 330 360


30 120∘C 3 h160∘C 3 h 105 55 10 011 335 360


240 80∘C 72 h120∘C 3 h minus82 4 415 mdash 300 340


40 80∘C 72 h120∘C 3 h minus76 22 142 mdash 305 340



R

R

R R

RR

R

R

RR

R

N N

N

N

N

N

N

N

N

H

H

H

HeatN +

N N +

other compounds

CH

CH

CH

CHCH O

O

O

CCH2

CH2

CH2CH2

CH2

CH2

OH

OH

OH

Iminus

Ominus

OH (4)









4 Conclusions






References








































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0

05

1

700120017002200270032003700


Abso

rban

ce

123306

1776

1723

1846

1239

971

923


700120017002200270032003700


0

05

15

1

Abso

rban

ce

2965

1796

1732

1508

1242

1

2




0

05

1

700120017002200270032003700


Abso

rban

ce

1

2

3045

1532

1446


Exo

up

1

2

75 100 125 150 175 200

T (∘C)




1


2



50

100

150

200

250

300

0 50 100 150 200 250tlowast1 t

lowast2 t

lowast3

Time (h)

1 2

3

Visc

osity

(Pas

)





CC

C CC

C

C

CO

O

O

O

O

O

O O

O

O

O

O

O OO

NR3NR3

R998400

R998400

HCHC

CH2

CH2

CH2CH CH

C C

CC

O

OO

O

OO

O

O

O NR3


R

R

R

R R

R

+

(2)



N NN

R

R

R998400

R998400

CHCH R998400998400 R998400998400CH2

O

ON+

+H2C (3)










178 120∘C 3 h160∘C 3 h 135 60 12 017 330 360


30 120∘C 3 h160∘C 3 h 105 55 10 011 335 360


240 80∘C 72 h120∘C 3 h minus82 4 415 mdash 300 340


40 80∘C 72 h120∘C 3 h minus76 22 142 mdash 305 340



R

R

R R

RR

R

R

RR

R

N N

N

N

N

N

N

N

N

H

H

H

HeatN +

N N +

other compounds

CH

CH

CH

CHCH O

O

O

CCH2

CH2

CH2CH2

CH2

CH2

OH

OH

OH

Iminus

Ominus

OH (4)









4 Conclusions






References








































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




50

100

150

200

250

300

0 50 100 150 200 250tlowast1 t

lowast2 t

lowast3

Time (h)

1 2

3

Visc

osity

(Pas

)





CC

C CC

C

C

CO

O

O

O

O

O

O O

O

O

O

O

O OO

NR3NR3

R998400

R998400

HCHC

CH2

CH2

CH2CH CH

C C

CC

O

OO

O

OO

O

O

O NR3


R

R

R

R R

R

+

(2)



N NN

R

R

R998400

R998400

CHCH R998400998400 R998400998400CH2

O

ON+

+H2C (3)










178 120∘C 3 h160∘C 3 h 135 60 12 017 330 360


30 120∘C 3 h160∘C 3 h 105 55 10 011 335 360


240 80∘C 72 h120∘C 3 h minus82 4 415 mdash 300 340


40 80∘C 72 h120∘C 3 h minus76 22 142 mdash 305 340



R

R

R R

RR

R

R

RR

R

N N

N

N

N

N

N

N

N

H

H

H

HeatN +

N N +

other compounds

CH

CH

CH

CHCH O

O

O

CCH2

CH2

CH2CH2

CH2

CH2

OH

OH

OH

Iminus

Ominus

OH (4)









4 Conclusions






References








































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials












178 120∘C 3 h160∘C 3 h 135 60 12 017 330 360


30 120∘C 3 h160∘C 3 h 105 55 10 011 335 360


240 80∘C 72 h120∘C 3 h minus82 4 415 mdash 300 340


40 80∘C 72 h120∘C 3 h minus76 22 142 mdash 305 340



R

R

R R

RR

R

R

RR

R

N N

N

N

N

N

N

N

N

H

H

H

HeatN +

N N +

other compounds

CH

CH

CH

CHCH O

O

O

CCH2

CH2

CH2CH2

CH2

CH2

OH

OH

OH

Iminus

Ominus

OH (4)









4 Conclusions






References








































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






4 Conclusions






References








































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










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



Documents

Research Article 1-Butyl-3-methylimidazolium Salts as New ...downloads.hindawi.com/journals/ijps/2014/607341.pdfResearch Article 1-Butyl-3-methylimidazolium Salts as New Catalysts