Cyclodextrin-Based Hyperbranched Polymers: Molecule Design, Synthesis, and Characterization

The cyclodextrin (CD) molecule, a host for a variety of smaller molecular guests, and hyperbranched polymers both possess molecule cavities in their molecular architectures. If the hyperbranched polyo(beta-cyclodextrin)s are established using modified beta-CD molecules as monomers, their molecular inclusion capabilities for smaller molecular guests may be enhanced due to the combination of two different molecule cavities from both their hyperbranched topography architecture and CD molecule chain segments. Herein, three types of hyperbranched poly(beta-cyclodextrin)s, i.e., HBP-A.B-x from AB(x)-type beta-CD monomers, HBP-(B-y + AB(x)) from B-y core molecules and AB(x)-type beta-CD monomers, and water-soluble HBP-AB(2) from AB(2)-type beta-CD monomers, were synthesized via hydrosilylation reaction under the thermal or ultraviolet activated polymerization. The hyperbranched structures of resultant poly(beta-cyclodextrin)s were characterized using H-1 NMR, C-13 NMR, Si-29 NMR, H-1-Si-29 heteronuclear multiple bond correlation, and size exclusion chromatography/multiangle laser light scattering (SEC/MALLS). The molecule inclusion and recognition behaviors of the novel hyperbranched poly(beta-cyclodextrin)s as well as their macromolecular structures, degree of branching, and thermal properties were investigated in detail. UV-vis spectroscopy results show that HBP-AB(2) has molecular inclusion capabilities and also can form inclusion complexation with single or double guests, including phenolphthalein (PP) and methyl orange (MO). Compared with AB(2)-type beta-CD monomer, the molecular inclusion capability of the hyperbranched polymer was enhanced. Furthermore, HBP-AB(2) presents molecular recognition behavior when MO solution is added into their PP solution.