Synthesis and characterization of pH-responsive diblock copolymers with cadaverine side groups

In this paper, we report the synthesis and characterization of a new pH-responsive diblock copolymer, methoxy poly(ethylene glycol)-b-poly[N1-(4-vinylbenzyl) pentane-1,5-diamine dihydrochloride] (mPEG-b-PVBPDA). The monomer with cadaverine side group (N1-(4-vinylbenzyl)pentane-1,5-diamine dihydrochloride, VBPDA) and the macroinitiator (mPEG-ACVA) were synthesized, respectively, and mPEG-b-PVBPDA was then obtained by free radical polymerization. The structure and molecular weight of mPEG-b-PVBPDA was confirmed by FTIR, 1H NMR, and GPC-MALLS measurements. At low pH, it is hydrophilic due to the protonation of the amine groups. With increasing pH, deprotonation occurs, and the hydrophobicity of PVBPDA block increases. This molecular feature leads to interesting aggregation behavior of mPEG-b-PVBPDA in aqueous solutions at different pH as revealed by DLS measurements, TEM observations, and fluorescence spectrometry. This polymer was further subjected to gene delivery evaluations, and promising DNA transfection capacity has been found.