In this paper, we report the synthesis and self-assembly of double-hydrophilic hyperbranched graft copolymers of HPG-g-PDMAEMA, which consist of a hyperbranched polyglycerol (HPG) core and several grafted poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) arms. HPG was synthesized by cationic polymerization. Then HPG-Br macroinitiator was obtained by esterification of HPG with 2-bromoisobutyryl bromide, which was subsequently used in the preparation of HPG-g-PDMAEMA graft copolymers through atom transfer radical polymerization (ATRP) of DMAEMA monomers. The molecular structures were studied by 1H NMR and GPC. The pyrene-based fluorescent probe method, 1H NMR and DLS were used to study the self-assembly behavior of HPG-g-PDMAEMA. The drug loading and pH-responsive release properties of HPG-g-PDMAEMA were also investigated by using coumarin 102 as a model drug. The results show that the HPG-g-PDMAEMA micelles can continuously release and re-encapsulate coumarin 102 as the pH continuously changes from 11.5 to 2.5; however, this process is not totally reversible.
Poly(allylamine hydrochloride) (PAH), which is frequently used in fabricating polyelectrolyte multilayer films, was studied by single molecule force spectroscopy (SMFS). Plenty of force-extension curves with a long plateau were obtained in water, indicating that train-like structure was predominant when PAH was adsorbed on the substrate. It was found that the peak-type force-extension curves of PAH in water were not able to be fitted by the modified freely-jointed chain model. Additionally, there was a flat region in the derivative of force-extension curves. Thus, it was inferred that PAH chain in water was in a special conformation and underwent a "conformational transition" under the stretching of an external force. This phenomenon did not appear in the SMFS experiment in 1 mol/L urea solution, which indi-cated that urea was able to break the special conformation.
YU Ying WANG Fang SHI WeiQing WANG LiYan WANG WenBin SHEN JiaCong
A series of sulfonated polybenzimidazoles(sPBI-SF)were prepared from 2,2-bis(4-carboxyphenyl)hexafluoro- propane(BIS-B-AF),3,3′-disulfonyl-4,4′-dicarboxyldiphenylsulfone(DSDCDPS)and 3,3′-diaminobenzidine(DAB)at various stoichiometric ratio by solution copolycondensation in poly(phosphoric acid).The chemical structure of the resulting sPBI-SF was confirmed by FTIR and ~1H-NMR.The sPBI-SFs with high molecular-weights(M_n=39400-65500)were soluble in DMF,DMSO or DMAc.Therefore,they could form some transparent a...
