Yuejun Zhu

Synthesis and characterization of modified xanthan gum using poly(maleic anhydride/1-octadecene)

In this study, modified xanthan gum was prepared by esterification of xanthan gum (XG) with poly(maleic anhydride/1-octadecene) (PMAO) in order to improve the shearing and thermal degradation performance. The structure and molecular weight (Mw) of the modified xanthan gums (named as PX) and XG were characterized by FT-IR, 1H NMR, and static light scattering. The radius of gyration (Rg) and hydrodynamic radius (Rh) of these polymers in aqueous solution were obtained by light scattering measurement. From thermal gravimetric analysis (TGA) measurements, PX and XG have similar thermal stability. According to rheological determinations, PX exhibits a more outstanding property of resistance to shear force and displays highly enhanced viscoelastic behaviors. Also, it is found that PX solution has better performance on salt tolerance and temperature resistance due to the cross-linkage between XG and PMAO. In addition, the mechanical shear degradation and thermal degradation data show that PX solution keeps higher viscosity than XG.

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.

Synthesis and Properties of pH-Responsive Polymers with Cadaverine Side Groups

A water-soluble monomer N1-(4-vinylbenzyl)-pentane-1,5-diamine dihydrochloride (VBPDA) with cadaverine (1,5-pentanediamine) group was synthesized. pH-responsive polymer with cadaverine group was obtained by free radical polymerization of VBPDA using 4,4-azobis(4-cyanovaleric acid) (ACVA) as the initiator. The structure and molecular weight of the polymer were characterized by FTIR, 1H-NMR and GPC-MALLS. Aggregation behavior of the polymer in aqueous solution was investigated by dynamic light scattering (DLS), UV-Vis and fluorescence measurements. The experimental results show that the fluorescence intensity of the aggregates decreases and the size of the aggregates increases with increasing pH due to the continuous dehydration of the cadaverine side groups.