Synthesis of Multicomponent and Multiblock Copolymers and Their Sustained Release Behavior for Fluorescein Sodium

In order to improve the sustained release properties of carriers and explore the effect of copolymer sequence structures on sustained release, 5 groups of 12 block copolymers (12-BCPs) with different sequences were prepared using 4 monomers and the microstructure was controlled by changing the sequence of monomers. The results show that each polymer chain contains an average of 228 monomers and the proportion of 4 monomers basically conforms to 1:1:1:1. The release kinetics of fluorescein sodium (FS) as a drug model molecule was detected by UV–vis spectroscopy, and the result proves that sequence microstructures have great effect on their sustained release behaviors. The five groups of copolymers all show high initial loading (49.6–74.6 mg/g) and long sustained release time (18–30 days). The copolymer with the largest monodisperse self-assembly size (13.40 μm) in which the block sequence is 2-hydroxyethyl acrylate/styrene/4-vinylpyridine/tert-butyl acrylate has the optimal drug loading capacity (74.6 mg/g) compared with others. At the same time, it owns the most stable release state and the longest sustained release time (30 days).