1、DendrimersTree-like molecule ?34“Dendrimers” in naturePleomele angustifolia (龙血树) “Dendrimers” in nature34Topological structures of polymersHow to synthesize dendrimers?1. Divergent2. ConvergentBy cascade reactions:Topological considerationsExamples of important synthesis of dendrimersSome are comme
2、rcializedPoly(propylene imine): PPI by divergentVgtle et alDivergentrouteAstramolTMby DSMPhysical property of PPIPPI in THFFirst full paper went to PJ34Typical examples: PAMAM by divergent0-40 CAmine dropped to esterYield 95%0-40 C1 dropped to amineAmine 50 fold in excess98%Tomalia et alDivergentrou
3、tePAMAMStarburst表面官能化：Functionalized PAMAMPAMAM is nanosized moleculePAMAM propertiesLaboratory synthesistedious !Typical examples of synthesis: convergentFrechet et alConvergentrouteConvergent synthesisDendriticaliphatic etherCharacterization of dendrimersBy MALDI-TOF MS:Characterization of dendrim
4、ersBy AFM:Dilute solution on micaSpin coating on micaCharacterization of dendrimersPAMAM for G5 to G10:characterization of dendrimersDiameters are alwayslarger than height indicatethat dendrimers are domelike in shape on mica Surface.Shape of dendrimersThe shape of dendrimers depends on generation.T
5、he structure of dendrimersHigh precisePerfectionWell-definedde Gennes dense packingComparison between linear and dendrimerLinear:1. Random coil;2. (semi)crystaline; High Tg;3. Lower solubility;4. ViscosityMW5. Non-Newtonian fluid (entanglement)6. Reptation mobility; (segmental)7. Anisotropic electri
6、c conductivity;8. Polydisperse.Dendrimer:1. Predictable shape change as a function of MW and core2. Amorphous; low Tg;3. Increased solubility;4. ViscosityMW;5. Newtonian fluid;6. Mobility as a whole;7. Isotropic electric conductivity;8. Monodisperse.Application of dendrimersHost-guest chemistry: Do
7、cavity exists in dendrimers ?The presence of voids, or the conformation of dendrimers, depends on types of end-groups, the solvents and pH, or secondary interactions such as H-bondingdendritic boxMeijer, EW. et al J. Am. Chem. Soc.1999, 121, 10346.Meijer, EW. et al Science 1994, 266, 1226.Not always
8、 ! Back-folding may happen !Host-Guest chemistryHost-guest chemistry:Unimolecular micellesApplication of dendrimersAs catalyst:Dendritic Nikel catalystbehaves as homogenouscatalyst with very close activity to mono-nuclearcatalyst in ATRA or Kharash reaction(see follows).Application of dendrimersAnte
9、nna effectwas found in aresearch to decrease the self-quenchingof lanthanide ionfluorescence bysite-isolation abilityof dendrimers.Application of dendrimersLight harvesting antenna:How is nature doing?(bacteria)Light harvestingcomplexs-1Reactive centerFurther readings34Host-guest chemistry:Further readings34Host-guest chemistry:
