Synthesis And Rheological Study Of Self-assembly Polymer Networks Based On γ-CD

In recent years, cyclodextrins get more and more attention because they can construct macromolecular network with various hydrophobic guests. The structure of crosslinking network is easily controlled. These networks not only provide ideal experimental models for polymer associating theory, but also can be widely used in drug delivery system or be used as polymer viscosity adjustment.In this article, a systematic study on macromolecule networks based on gamma cyclodextrin (y-CD) was presented, Firstly, y-CD or alkyl chains grafted onto poly (acrylic acid) (y-CD-PAA or Cn-PAA) was synthesized, and then polymer networks based on the inclusion association between y-CD and alkyl chains were build. Lastly, rheological method was used to study the factors which can affect the structure of the polymer networks.There were three steps for synthesis of the y-CD-PAA. Firstly monomer y-CD was mono-sulfonated. We used column to remove the by-product and got the pure sulfonated y-CD (y-CD-6-OTs). Secondly, the aminated y-CD (y-CD-6-EDA) was obtained by reaction of y-CD-6-OTs with ethylenediamine. At last, y-CD-6-EDA was grafted onto the poly (acrylic acid). The synthesis procedure of Cn-PAA (n=12,16, or 18) was same as y-CD-PAA.Due to the successful synthesis of y-CD-PAA, C18-PAA, C16-PAA and C12-PAA, the host-guest inclusion association by y-CD in either the monomer state or as substituent of poly (acrylic acid) (PAA) and the hydrophobic n-octadecyl groups, C18, n-dodecyl groups, C12, and other suitable guests grafted onto PAA was investigated. Polymer networks were formed by mixing y-CD-PAA with Cn-PAA. Rheology methods was performed to prove the existence of the polymer networks and study the effect factors of the network structures, such as molar ratio of y-CD/Cn, polymer concentration, length of alkyl chains, and temperature. It is obvious that a maximum viscosity appeared at a molar ratio of 1:2 of y-CD/C18 groups, which implies that two alkyl chains can enter into oneγ-CD cavity at the same time. Because of the difference between hydrophobic association interaction of alkyl chains and inclusive association interaction between y-CD and hydrophobic guests, viscosity of two systems are different at the same polymer concentration. Viscosity increased upon increasing the alkyl length from 12 to 18 at the same polymer concentration and decreased upon heating because the molecules thermal motion was aggregate.The effect of native y-CD and SDS on both systems of Cn-PAA and y-CD-PAA/Cn-PAA were studied by adding them into the complex system or pure C18-PAA system. It is concluded that nativeγ-CD can destroy the crosslinking structure due to the competition between nativeγ-CD and substituentγ-CD, so the viscosity of the complex system decreased to a lowest value. Nativeγ-CD was added into the pure C18-PAA solution too. When adding a fewγ-CD, viscosity of the system decreased. But as amount ofγ-CD increasing, the viscosity rose again. Add some SDS into the C18-PAA system with nativeγ-CD, viscosity can increase, when adding more SDS, viscosity decreased. So we can control the formation of the polymer networks and regulate the viscosity of the C18-PAA system by adding nativeγ-CD and SDS into C18-PAA solution at same time.Innovation of this article is that graftingγ-CD onto the poly (acrylic acid) chains and prepared a new cyclodextrin polymer. A new polymer network based on the inclusion association betweenγ-CD and hydrophobic guests was constructed. This laid a theoretical foundation for cyclodextrins used in medical industry.