Li Li, Guo Xuhong, Fu Lin, Prud'homme Robert K, Lincoln Stephen F
State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China.
Langmuir. 2008 Aug 5;24(15):8290-6. doi: 10.1021/la800859w. Epub 2008 Jun 21.
A systematic study of the host-guest complexation by alpha-, beta-, and gamma-cyclodextrin (CD) in either the free state or as substituents of poly(acrylic acid) (PAA) with the hydrophobic n-octadecyl groups, C18, substituted onto PAA (HMPAA) and its effect on polymer aggregation and network formation is reported. Free alpha-CD, beta-CD, and gamma-CD mask hydrophobic associations between the C18 substituent of HMPAA in aqueous solution and form host-guest complexes with a 1:1 or CD:C18 substituent stoichiometry at 0.5 wt % polymer concentration. For alpha-CD this host-guest stoichiometry changes to 2:1 or 2alpha-CD:C18 at > or =1 wt % polymer concentrations but not for beta-CD and gamma-CD. Shear-thickening occurs when gamma-CD complexes C18 HMPAA substituents. Upon addition of sodium dodecyl sulfate, SDS (SDS:CD = 1:1), the hydrophobic associations between C18 diminished by alpha-CD masking were fully restored, were only partly restored in the case of beta-CD, and not restored for gamma-CD. When alpha- and beta-CD substituted PAA (alpha-CDPAA and beta-CDPAA) were mixed with HMPAA polymer, networks formed. As for free beta-CD, the beta-CD substituents of beta-CDPAA also formed 1:1 or beta-CD:C18 stoichiometry host-guest complexes with the C18 substituents of HMPAA. The alpha-CD substituents of alpha-CDPAA also formed 1:1 or alpha-CD:C18 stoichiometry host-guest complexes with some indication of the formation of 2:1 or 2alpha-CD:C18 stoichiometry host-guest complexes at polymer concentrations > or =1 wt %. The polymer networks formed by beta-CDPAA with HMPAA are less viscous than those formed by alpha-CDPAA, for which shear-thickening occurs at polymer concentrations > or =2 wt %. It is evident that the difference in CD annular size and its match with the C18 of HMPAA control the diversity of the interactions of alpha-CD, beta-CD, gamma-CD, alpha-CDPAA, and beta-CDPAA with HMPAA.
本文报道了对α-、β-和γ-环糊精（CD）在游离态或作为聚丙烯酸（PAA）的取代基（其中疏水性正十八烷基（C18）取代在PAA上形成HMPAA）时的主客体络合作用及其对聚合物聚集和网络形成影响的系统研究。游离的α-CD、β-CD和γ-CD在水溶液中掩盖了HMPAA的C18取代基之间的疏水缔合，并在聚合物浓度为0.5 wt%时以1:1或CD:C18取代基的化学计量比形成主客体络合物。对于α-CD，在聚合物浓度≥1 wt%时，这种主客体化学计量比变为2:1或2α-CD:C18，但β-CD和γ-CD并非如此。当γ-CD与C18 HMPAA取代基形成络合物时会发生剪切增稠现象。加入十二烷基硫酸钠（SDS，SDS:CD = 1:1）后，α-CD掩盖导致的C18之间的疏水缔合完全恢复，β-CD的情况下仅部分恢复，而γ-CD则未恢复。当α-和β-环糊精取代的PAA（α-CDPAA和β-CDPAA）与HMPAA聚合物混合时，会形成网络。与游离的β-CD一样，β-CDPAA的β-CD取代基也与HMPAA的C18取代基形成1:1或β-CD:C18化学计量比的主客体络合物。α-CDPAA的α-CD取代基也形成1:1或α-CD:C18化学计量比的主客体络合物，在聚合物浓度≥1 wt%时，有迹象表明形成了2:1或2α-CD:C18化学计量比的主客体络合物。β-CDPAA与HMPAA形成的聚合物网络的粘性低于α-CDPAA形成的网络，α-CDPAA在聚合物浓度≥2 wt%时会发生剪切增稠。显然，CD环尺寸的差异及其与HMPAA的C18的匹配控制了α-CD、β-CD、γ-CD、α-CDPAA和β-CDPAA与HMPAA相互作用的多样性。
