An amphiphilic hyperbranched polymer containing large amounts of pH sensitive bonds was synthesized by our group. The hydrophobic chains are hyperbranched polyacetals (HBPAs) and the hydrophilic chains are polyethylene glycols. Polyethylene glycols are attached to the hyperbranched polyacetals by the hydrazone bonds. The amphiphilic hyperbranched polymer could be assembled into micelles easily by the dialysis method. The micelles containing large amounts of pH sensitive bonds were quite fragile in pH 5.0 buffer solution but very stable in pH 7.4 buffer solution. DOX-loaded micelles were also prepared by the dialysis method. The sizes of the blanked micelle and DOX-loaded micelle were 30 nm and 35 nm, respectively.The increase of the diameter confirmed that DOX was successfully loaded into the micelle. Drug loading content and drug loading efficiencies were 2.34% and 23.4%, respectively, which was detected by the UV-VIS at the wavelength of 482 nm. The drug release behavior demonstrated that DOX was released faster in pH 5.0 buffer solution than in pH 7.4 buffer solution.

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The formation process of poly( N -isopropylacrylamide) (PNIPAM)-based ionic microgels was investigated in this work. Different from the traditional formation process of covalent bond cross-linked PNIPAM-based microgels, a disassembling and reassembling process for PNIPAM-based ionic microgels was observed. During the formation process, loose microgels were first formed in a short time, and then, these loose microgels disassembled into smaller nanogel pieces. Meanwhile, the nanogel pieces reassembled into microgels by electrostatic interaction. After reassembling, large amounts of nanogels could be seen clearly in the interior of PNIPAM-based ionic microgels. The thermo-sensitivity and composition of the final prepared microgels were characterized by dynamic light scattering, infrared spectroscopy, and X-ray photoelectron spectroscopy.