Study On Synthesis Of Double Hydrophilic Block Copolymers By ATRP And Their Aggregation Properties In Aqueous Solution

Double hydrophilic block copolymers are a new type of amphiphilic block copolymers with increasing attention being paid to by scientists in material science, pharmacy, biochemistry and polymer science. In this paper, brief research background of this work is introduced, in which the history and recent progress in double hydrophilic block copolymer are reviewed from a worldwide angle of view. Then the controlled/living radical polymerization technique (ATRP) which was studied widely in recent years was used to synthesize a series of double hydrophilic block copolymers with polyethylene glycol and their properties had been investigated. The details and key conclusions are summarized as follows:(1) The macroinitiator mPEG-Br was firstly prepared by poly(ethylene glycol mono-methy1ether)(mPEG) and2-bromoisobutyryl bromide. Then the double hydrophilic block copolymer mPEG-b-P4VP was synthesized by ATRP using macroinitiator mPEG-Br. The structure, molecular weight and molecular weight distribution of the copolymers were characterized by1H-NMR, FT-IR and gel permeation chromatography combined with laser light scattenng (GPC-MALLS) technique. The mPEG-b-P4VP can be induced to form temperature and pH-responsive complex micelles by the fluorescent indicator disodium2-naphthol-3,6-disulfonate (DNDSNa) in acid aqueous solution. The morphologies of the resultant complex micelles were observed by transmission electron microscopy (TEM). Temperature and pH-responsive behaviors of the complex micelles were studied by dynamic light scattering (DLS) and fluorescence emission spectra. The results showed the formation and dissociation of the complex micelles can be controlled by adjusting the temperature or pH. The complex micelles dissociated when the temperature is above75℃or the pH surpass6.5.(2) The double hydrophilic block copolymer mPEG-b-P4VP was synthesized by ATRP using macroinitiator mPEG-Br. Then the quaternized mPEG-b-P4VP was prepared through quaternization using n-bromobutane. In deionized water, a new type of polypseudorotaxanes was obtained by self-assembly of quaternized mPEG-b-P4VP and CB[6]. The structures of the copolymers were confirmed by1H-NMR and FT-IR. The molecular weight of the copolymers were confirmed by gel permeation chromatography combined with laser light scattering (GPC-MALLS). The properties of block copolymer and pseudopolyrotaxanes were researched by thermogravimetry analysis (TGA), UV-vis, and dynamic light scattering (DLS). The results show that the pseudopolyrotaxanes has higher thermal stability than the parent copolymer which is attributed to the bulkiness and the rigidity of the CB[6] threaded. The effects of salts (NaCl, NaBr, and Na1) to pseudopolyrotaxanes were studied by the transmittance with UV-vis, and the results show that the Nal is the satisfied precipitant to the pseudopolyrotaxanes.(3) A series of double hydrophilic block copolymers mPEG-b-PDMAEMA with different block ratios were synthesized by ATRP using macroinitiator mPEG-Br. Then the zwitterionic double-hydrophilic block copolymer mPEG-b-PDMAPS were obtained by reacting with propanesultone (CPS). The structures of the copolymers were confirmed by1H-NMR and FT-IR. The molecular weight of the copolymers were confirmed by gel permeation chromatography combined with laser light scattering (GPC-MALLS). The solution properties of the copolymers were investigated by DLS and TEM. The results showed that the concentration, ionic strength, ionic species and temperature have evident effects to the behaviors of the aggregation.