cloning polymer single crystals through self-seeding

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1、ARTICLESPUBLISHEDONLINE:15MARCH2009

2、DOI:10.1038/NMAT2405Cloningpolymersinglecrystalsthroughself-seedingJianjunXu1,2*3,4,WenbingHu41,2andGünterReiter3(,YuMa*,MatthiasRehahnIngeneral,whenacrystalismolten,allmoleculesforgetabouttheirmutualcorrelationsandlong-rangeorderislost.Thus,areg

3、rowncrystaldoesnotinheritanyfeaturesfromaninitiallypresentcrystal.Suchistrueformaterialsexhibitingawell-definedmeltingpoint.However,polymercrystalliteshaveawiderangeofmeltingtemperatures,enablingparadoxicalphenomenasuchasthecoexistenceofmeltingandcrystallization.Here,wereportaself-s

4、eedingtechniquethatenablesthegenerationofarraysoforientation-correlatedpolymercrystalsofuniformsizeandshape(‘clones’)withtheirorientationinheritedfromaninitialsinglecrystal.Moreover,thenumberdensityandlocationsoftheseclonedcrystalscantosomeextentbepredeterminedthroughthethermalhist

5、oryofthestartingcrystal.Weattributethisuniquebehaviourofpolymerstothecoexistenceofvariablefoldlengthsinmetastablecrystallinelamellae,typicalfororderingofcomplexchain-likemolecules.wingtothestatisticalnatureofnucleiformation,thereobservedmorphologies.Thesecrystalswereheatedtoatemper

6、aturearenoorientationcorrelationsbetweenneighbouringTSSwheremorphologicalfeaturescharacterizingthecrystallineOcrystals.Itisnormallynotpossibletopredictwhenandstatedisappearedunderanopticalmicroscope.Subsequently,thewherecrystalswillstarttogrow.Inaddition,inmacromolecularsampleswere

7、broughttoalowertemperatureTRC.InFig.1,weshowsystemsnucleationoftenrepresentsasevereprobleminpolymertypicalresultsofsuchaself-seedingprocedureforsinglecrystalsprocessing,requiringheterogeneousnucleation(forexample,(Fig.1a)ofadiblockcopolymer,poly(2-vinylpyridine-block-nucleatingagen

8、ts13)tostartthecrystallization.Asanalternative,apolyethyleneoxide)(PVP-b-PEO),inwhichPVPisamorphous22self-seedingapproach1,47enablestheproblemsofnucleationtobeandPEOiscrystalline.Wecanclearlyobservethegenerationofavoided.Itconsistsoftwosteps.First,analreadycrystallinesamplemanysm

9、allcrystals(Fig.1be),whic