高分子材料 论文.docx

高分子材料 论文.docx

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高分子材料论文

Abstract

Traditionalshapememorypolymers（SMPs）arethosecapableofmemorizingatemporaryshapeandrecoveringtothepermanentshapeuponheating.Althoughsuchabasicconcepthasbeenknownforhalfacentury,recentprogresseshavechallengedtheconventionalunderstandingofthepolymershapememoryeffectandsignificantlyexpandedthepracticalpotentialofSMPs.Inthisarticle,notablerecentadvancesinthefieldofSMPsarehighlighted.ParticularemphasisisplacedonhowthenewdevelopmentshavechangedtheconventionalviewofSMPs,whattheymeanforpracticalapplications,andwherethefutureopportunitiesare.

Graphicalabstract

Keywords

Shapememorypolymer;

Stimuli-responsivepolymer;

Polymeractuator

1.Introduction

Shapememorypolymers（SMPs）representatechnologicallyimportantclassofstimuli-responsivematerialsforwhichtheresponseliesintheshapechange.Morespecifically,theconventionaldefinitionofanSMPisapolymercanbedeformedandsubsequentlyfixedintoatemporaryshape,whichwouldremainstableunlessitisexposedtoanappropriateexternalstimulusthattriggersthepolymertorecovertoitsoriginal（orpermanent）shape.Accordingly,theassociatedbehaviorofSMPiscalledpolymershapememoryeffect（SME）.Althoughvariousformsofexternalstimulimaybeutilizedastherecoverytrigger,themosttypicaloneisdirectheatingthatleadstoatemperatureincrease.

ThefirstrecognitionofpolymerSME,assuggestedbyMatheretal.,canbetracedbacktoapatentin1940sinwhich“elasticmemory”wasmentioned[1].Thewell-knownheatshrinkagetubingthatappearedin1960s,ontheotherhand,representsacommercialapplicationofSMPevenbeforetheterminologybecamebeingused.ItisthoughtthatthefirstofficialuseoftheSMPtermmayhavestartedin1984,withthedevelopmentofthepolynorbornenebasedSMPbyCDFChimieCompany（France）[2].DespitethelonghistoryofSMP,however,thephenomenonofpolymerSMEhadremainedlittleknownandthescientificpaperinthisareahadbeenratherlimiteduntil1990s.Alongthistimeframe,thediscoveryofsegmentedpolyurethaneSMPbyMitsubishiHeavyIndustriesLtd.stimulatedsignificantinterestsinSMPs,presumablyduetotheversatilityofurethanechemistrythatallowseasystructuraltuningandtheindustrialsignificanceofpolyurethane.Forthesamereasons,researchonshapememorypolyurethaneshasremainedquiteactiveeventoday,despitemanydifferentSMPsthathavesincebeendiscovered.

Historically,theadvancementoftheSMPfieldhasbeencloselyassociatedwithitspracticalpotential.Assuch,thelackofexcitementandresearchactivitiesintheearlydaysofSMPscanbeattributedtothelimitedapplicationsenvisionedforsuchmaterials.In2002,Lendleinetal.demonstratedthatSMPcouldbeusedasself-tighteningsutureforminimuminvasivesurgery[3].TheSMPintheformofsuturewasfirstdeformedintoanelongatedform.TheSMPsutureinthistemporaryshapewasappliedlooselytothewound（theleftimageinFig.1）.Theshaperecoveryofthesuturewasthentriggeredbyhumanbodyheat,leadingtotheshrinkageofthesutureandthetighteningoftheknot（therightimagesinFig.1）withoutexternalintervention.Here,thepolymericnatureofthematerialcanbeconvenientlyutilizedtoincorporateadditionalfunctionalitiessuchasbiodegradability,whicheliminatestheneedforanadditionaloperationforsutureremoval.ThisprototypedemonstrationhasraisedsignificantinterestsinotherbiomedicalusesofSMP.Today,tailoringSMPforvariousbiomedicalusesrepresentsasignificantportionoftheSMPresearch[4]and[5].ThisintensefocusonbiomedicalapplicationsofSMPisinpartduetotheassociatedhighvaluethatisunmatchedbymostnon-biomedicalapplications.Anadditionaldrivingforceliespresumablyintherelativelylargefundingallocatedtobiomedicalresearchingeneral.

Fig.1.SMPbasedself-tighteningsutureforwoundclosure.Thephotosfromlefttorightshowtheshrinkageandtighteningofthesuturewithtemperatureincrease.ReproducedfromRef.[3]withpermission.

Benefitedinnosmallparttothepotentialforbiomedicaluses,theSMPfieldhasundergoneexplosivegrowthwithinthelastdecade.Alongtheway,manySMPsystemsandinnovativenon-biomedicalapplicationshaveemerged.Since2000s,anumberofexcellentreviewshavebeenpublishedthatcoverthegeneralaspectsofSMPs[6],[7],[8],[9],[10]and[11],SMPcomposites[12]and[13],biomedicalapplications[4]and[5],andnon-biomedicalapplications[14]and[15].Ontheotherhand,recentprogressesinthelastfiveyearsintheSMPfieldhavesignificantlychallengedtheconventionalviewofpolymerSME.Assuch,theintentofthecurrentpaperisnottoprovideanextensivereviewoftheSMPresearch.Instead,thefocusisonh