Solubility of Polymethyl Methacrylate in Organic Solvents

RussianJournalofAppliedChemistry,Vol.78,No.10,2005,pp.1576!1580.TranslatedfromZhurnalPrikladnoiKhimii,Vol.78,No.10,2005,pp.1605!1609.

OriginalRussianTextCopyright+2005byEvchuk,Musii,Makitra,Pristanskii.

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PHYSICOCHEMICALSTUDIESOFSYSTEMSANDPROCESSES

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SolubilityofPolymethylMethacrylateinOrganicSolvents

I.Yu.Evchuk,R.I.Musii,R.G.Makitra,andR.E.Pristanskii

LitvinenkoInstituteofPhysicoorganicandCoalChemistry,NationalAcademyofSciencesofUkraine,

DepartmentofPhysicalChemistryofFuelResources,Lviv,Ukraine

ReceivedJune7,2005

Abstract-Solubilityofpolymethylmethacrylatein12organicsolventsat30370oCwasstudied.

Theresistanceofpolymerstoorganicsolventsistheoreticallyandpracticallyimportant.Atthesametime,studiesinthisareaaremainlyconcernedwithswellingofpolymersinvariousmedia.Thedissolu-tionprocessitself,despiteitswideapplicationinvar-ioustechnologies,hasbeenstudiedtoaconsiderablylesserextent.

AccordingtotheNernstdiffusiontheory,thedis-solutionoflow-molecularcompoundsinliquidsoc-cursatthephaseboundaryrapidlyandislimitedbydiffusionofcomponentstowardandawayfromthesurfaceofasolid.TheprocessratevisdeterminedbythediffusioncoefficientD,boundarylayerthick-nessl,anddifferenceofthesoluteconcentrationsinthesurfacelayer(c0)andinthebulk(c):

D(c3c).v=70l

(1)

(Disthediffusioncoefficient;h,viscosity;andr,

radiusofasolventmolecule)failed.Thisresultisnotsurprisingbecausenosatisfactorycorrelationhasbeenfounduntilrecentlybetweentheamountofad-sorbedliquidSortheswellingrateandthephysico-chemicalcharacteristicsofsolventsevenforthefirstpresumedstageofthedissolution,i.e.,forswell-ing.ThegenerallyacceptedFlory3Hagginstheory,basedontheHildebrandtmodelofregularsolutions,yieldsonlysemiquantitativerelationsandrequiresthatanempiricalcorrectioninteractioncoefficientshouldbeused[5].AttemptstorelateStotheelec-trophilicityETofsolventsbyReichardt[6],theirmolalvolumeVM[7],etc.havebeennosuccessfuleither.

Atthesametime,itwasestablishedin[8]thattheonlyrelationshipbetweenthelimitingviscositynumberofapolymerandthedegreeofitsequilibriumswellingisthattheybehaveinasimilarway[8].Itwasassumedthatdifferenttypesofinteractionsareinvolvedinswellingofpolymersanddiffusionofsolventsinthesematerials[9,10].Therefore,toobtainanadequaterelationbetweenSorDandsol-ventcharacteristics,itisnecessarytotakeintoac-count,inaccordancewiththelinearfreeenergies(LFE)principle,allmutuallyindependentchangesintheGibbsenergyofthecomponents,associatedwiththeseparameters:DG=SDgi.

Torevealthepossiblecorrelationbetweenthephys-icochemicalcharacteristicsoforganicsolventsandtherateofpolymerdissolutioninthem,westudiedthedissolutionofpolymethylmethacrylate(PMMA)sampleswithanaveragemolecularweightof139000in12organicsolvents.Thedissolutionratesat30,40,50,and70oCweredeterminedgravimetrically.

However,theprocessisconsiderablymorecom-plexinthecaseofpolymers.Here,mentionshouldbeprimarilymadeofstudiesbyUeberreiteretal.[134],whoestablishedfortheexampleofpolystyrenethatthedissolutionofapolymerisprecededbyitsswell-ing,withthesubsequentformationofcaoutchouc-likelayeronthesurface.Also,itwassuggestedthattheoverallrateoftheprocessisdeterminedbytherateofdiffusionofaliquidintothepolymer,inaccordancewithsecondFick’slaw.Itwasfoundin[4]thatthedissolutionrateofpolystyrenesteadilydecreasesintheseriesofalkylacetatesastheirmolecularweightincreases.However,attemptstorelatetheexperimen-tallydeterminedrateofpolystyrenedissolutiontotheEinstein3Stokescoefficients

D=kT/6phr

(2)

1070-4272/05/7810-1576C2005PleiadesPublishing,Inc.

SOLUBILITYOFPOLYMETHYLMETHACRYLATEINORGANICSOLVENTS1577

Table1.DegreeQofPMMAdissolutioninorganicsolventsat30oC

????????????????????????????????????????????????????????????????????????????????????3Q,wt%,atindicatedtime,minSolvent????????????????????????????????????????????????????????????????????3103203303403503603903120????????????????????????????????????????????????????????????????????????????????????Benzene310.4318.9325.2329.2334.7338.6349.9368.5Toluene35.2311.8315.5318.7321.4323.1329.7340.0o-Xylene33.134.936.137.338.739.2311.3315.5m-Xylene311.8313.5314.6316.7317.8319.5326.2327.3Trichloromethane30.331.131.231.431.832.033.434.0Trichloroethylene335.8365.7388.4396.0333333331,4-Dioxane35.3310.6314.4317.2319.7321.6327.2337.9Cyclohexanone313.6324.6331.7345.2353.1365.0373.2377.3Acetophenone38.0314.0318.1321.0323.1325.8331.9345.6

3Ethylacetate319.7336.6348.1356.7364.3371.9389.53

Pentylacetate32.233.234.534.835.436.137.238.5Dimethylformamide36.7318.7326.1333.4338.7345.8361.8384.7????????????????á???????á???????á????????á????????á????????á????????á????????á??????Table2.DissolutionofPMMAsamplesinorganicsolventsatdifferenttemperatures

????????????????????????????????????????????????????????????????????????????????????3Q,wt%,atindicatedtime,min?????????????????????????????????????????????????????????????????????????Solvent310320330340360

?????????????????????????????????????????????????????????????????????????340oC350oC370oC340oC350oC370oC340oC350oC370oC340oC350oC370oC340oC350oC370oC????????????????????????????????????????????????????????????????????????????????????Benzene324.4333.3347.8338.1357.3390.3360.0377.633373.0390.733388.93333

Toluene314.1329.8351.0323.9349.1396.8339.7365.333350.4375.533361.5397.033o-Xylene35.0313.5324.636.8322.3350.4313.6326.2358.7319.1331.4380.0323.6347.633m-Xylene33.9310.3312.238.0325.2341.9310.1339.8366.0315.4354.0385.0322.2373.333Trichloro-39.532.835.7311.539.7311.4312.6312.3329.5314.2325.8342.0316.7333.9363.0methane3333333333333331,4-Dioxane311.5318.7331.9318.3339.6374.0331.1355.1393.8344.0372.8397.8360.0396.833Cyclohexanone35.7323.0316.9310.1354.5336.2313.0359.1356.4319.7371.4367.0330.6385.1397.2Acetophenone313.3321.3345.9314.0328.5334.3343.7353.9396.9353.4365.933369.6394.633Ethylacetate318.8337.0336.9339.8362.6387.6357.0380.833376.43333398.33333Pentylacetate34.638.537.739.5326.9327.3312.5341.9342.7317.6354.2366.8326.9374.1382.3Dimethylform-312.5319.6335.1325.2328.1366.8335.8348.5396.6356.0367.933375.03333amide333333333333333???????????á????á????á????á????á????á????á????á????á????á????á????á????á????á???á???Theexperimentalresultsobtainedarelistedin

Tables1,2.Thedataonthedissolutionrateof

PMMAat30oCareanalyzedinmostdetail(Table1).

Ascanbeseen,thereisnodirectcorrelationbetween

thedissolutionrateandthestructureorproperties

ofasolvent,includingitspolarity.Thebestsolvents

forPMMAarepartlysubstitutedhydrocarbons,tri-

chloromethaneandtrichloroethylene,inwhichpoly-

mersamplesdissolvevirtuallycompletelyin30min.

Atthesametime,theynearlydonotdissolveatallin

trichloromethane.Goodsolventsarepolarethyl

RUSSIANJOURNALOFAPPLIEDCHEMISTRYVol.78acetateandcyclohexanone.However,theirabilitytodissolvePMMAconsiderablydecreases,asthemo-lecularweightofestersincreases,inagreementwiththedataof[4],andanevenmorepolardimethylform-amide(DMF)dissolvesPMMAevenmoreslowly.Moreover,astrongdifferenceinthedissolvingpowerisevenobservedbetweenaromatichydrocarbons.Atthesametime,thecurvesdescribingtherelativerateofthelossofmassbysamplesinthecourseoftime,Q=(w03wJ)/w0,wherew0istheinitialmassofthesampleandwJ,itsmassataninstantoftimet,areNo.102005

1578EVCHUKet

al.

alwaysnearlylinear,irrespectiveofthetypeofasol-ventandtemperature(Fig.1).

Similarlytotherateofchemicalreactions,thedis-solutionrateincreases,ontheaverage,twofoldasthetemperatureisraisedby10oC(Table2).AtypicalexampleofhowthedissolutionproceedsinthecourseoftimeatdifferenttemperaturesisshownfordioxaneinFig.2.

AttemptstodescribetheprocessintermsoftheEin-stein3Stokesdependencewereunsuccessful.Figure3showstherelationshipbetweenthedegreeofPMMAdissolution(lossofmassinpercentat30oCin20min)andtheparameter1/hofthisequation.Itcanbeseenthatthesequantitiesexhibittoacertainextentoppo-sitetypesofbehavior:thedegreeofPMMAdissolu-tiondecreasesasthesolventviscositybecomeshigher,ratherthanalinearrelationship.Especiallystrongdeviationsareobservedforincompletelysubstitutedhydrocarbons,trichloroethyleneandchloroform.Similarresultswereobtainedforothertimeinter-vals(30,40,and60min),withthedeviationsofex-perimentalpointsfromastraightlineincreasingwiththeextentoftheprocess.Thisisnotsurprising,be-causetheviscosityoftheliquidphasegraduallyin-creasesasitissaturatedwiththedissolvedpolymer.Thedeviationsofthepointsalsomarkedlyincreasewiththetemperatureoftheexperiment,whichcanbeattributedtodissimilarchangesinviscositywithtemperaturefordifferentsolvents.