SincetheSecondWorldWar,polymericmaterialshavebeenthefastest-growingsegmentsoftheworldchemicalindustry.Ithasbeenestimatedthatmorethanathirdofthechemicalresearchmoneyisspentonpolymers,withacorrespondinglylargeproportionoftechnicalpersonnelworkinginthearea.A...[繼續(xù)閱讀]

    Almosthalfacenturyago,WolfgangOstwaldcoinedthephrase“thelandofneglecteddimensions”todescribetherangeofsizesbetweenmolecularandmacroscopicwithinwhichoccurmostcolloidalparticles.Theterm“neglecteddimensions”mighthavebeenappliedequallywelltotheworldofpolymerm...[繼續(xù)閱讀]

    Thelargenumberofnaturalandsyntheticpolymershasbeenclassifiedinseveralways.Thesewillbeoutlinedbelow.Theearliestdistinctionbetweentypesofpolymerswasmadelongbeforeanyconcreteknowledgeoftheirmolecularstructure.Itwasapurelyphenomenologicaldistinction,basedonth...[繼續(xù)閱讀]

    Asanappreciationforthemolecularstructureofpolymerswasgained,threemajorstructuralcategoriesemerged.TheseareillustratedschematicallyinFigure4.1.Figure4.1　SchematicdiagramofpolymerstructuresLinearIfapolymerisbuiltfromstrictlydifunctionalmonomers,theresultisa...[繼續(xù)閱讀]

    Weknowthatthegeometricarrangementoftheatomsinpolymerchainscanexertasignificantinfluenceonthepropertiesofthebulkpolymer.Toappreciatewhythisisso,thesubjectofpolymermorphology,thestructuralarrangementofthechainsinthepolymer,isintroducedhere.Althoughtheprecis...[繼續(xù)閱讀]

    Thethermodynamicsandstatisticsofpolymersolutionsisaninterestingandimportantbranchofphysicalchemistry,andisthesubjectofmanygoodbooksandlargesectionsofbooksinitself.Itisfarbeyondthescopeofthischaptertoattempttocoverthesubjectindetail.Instead,wewillconcentra...[繼續(xù)閱讀]

    TheGlassTransitionIthaslongbeenknownthatamorphouspolymerscanexhibittwodistinctlydifferenttypesofmechanicalbehavior.Some,likepolymethylmethacrylate(Lucite,Plexiglas)andpolystyrene,arehard,rigid,glassyplasticsatroomtemperature,whileothers,forexample,polybut...[繼續(xù)閱讀]

    Polymerizationreactionsmaybedividedintotwocategoriesaccordingtothemechanismbywhichthechainsgrow.Instep-growthpolymerization,alsoknownascondensationpolymerization,chainsofanylengthsxandycombinetoformlongerchains:　　　x-mer+y-mer→(x+y)-mer　　　　stepgrowth(8.1a)...[繼續(xù)閱讀]

    Oneofthemostimportanttypesofadditionpolymerizationisinitiatedbytheactionoffreeradicals,electricallyneutralspecieswithanunsharedelectron①.Inthedevelopmentstofollow,adot(·)willrepresentasingleelectron.Thesinglebond,apairofsharedelectrons,willbedenotedbyadou...[繼續(xù)閱讀]

    Theprecedingdiscussionoffree-radicaladditionpolymerizationhasconsideredonlyhomogeneousreactions.Considerablepolymerisproducedcommerciallybyacomplexheterogeneousfree-radicaladditionprocessknownasemulsionpolymerization.ThisprocesswasdevelopedintheUnitedStat...[繼續(xù)閱讀]