Synthesis And Performance Reasearch Of Dovetail Amphiphilic Block Copolymers

Biodegradable amphiphilic block copolymers have been a hotspot in the research field of polymer chemistry worldwide for a long time. They can self-assemble into polymeric micelles or vesicles in selective solutions emerged as promising nanocarriers for controlled release of various drugs. However,these polymeric micelles could cause a burst release of drug because of the higher critical micelle concentration. To overcome this disadvantage, a reliable strategy is to design stereocomplex block copolymers which were got by interaction of two different chiral polymer chain segment. Based on above,in this paper we designed to synthesized dovetail amphiphilic block copolymers. Details are as follows:In the first part of this paper, a series of polymers were synthesized. Firstly, 5-Propargyl oxygen methyl-2,2,5-trimethyl-1,3-dioxane were synthesized from propargyl bromide and 5-hydroxy-methyl-2,2,5-trimethyl-1,3-dioxane, which was prepared from trimethylol-ethane and 2,2-dimethoxypropane in the presence of p-toluenesulfonic acid catalyst. After deprotection under acidic condition,2-Methyl-2-Methylene propargyl oxygen-1,3-propanediol were prepared. Secondly, a series of PLLA and PDLA that containing terminal alkyne were prepared by ring-opening polymerization of L-LA and D-LA with 2-Methyl-2-Methylene propargyl oxygen-1,3-propanediol as initiator. Thirdly, dovetail amphiphilic block copolymers were synthesized by click reaction of alkynyl in PLLA/PDLA and azide group in MPEG(1.9K)-N3/MPEG(5K)-N3. Finally, stereocomplexs were prepared through mixing equal molar of MPEG-PLLA and MPEG-PDLA. The structures and properties of these obtained polymers were characterized through nuclear magnetic resonance spectroscopy(1HNMR), gel permeation chromatography(GPC), differential scanning calorimetry(DSC) and fourier transform infrared spectroscopy(FT-IR).In the second part of this paper, self-assembly behavior of the obtained polymers in aqueous solution was studied. Fluorescence analysis shows that stereocomplex can lower the critical micelle concentration of the polymer. DLS and TEM show that the stereocomplex compound formed by MPEG(1.9K)-PLLA(4.5K) and MPEG(1.9K)-PDLA(4.5K) could self-assemble into vesicle whose diameter is about 200 nm, while the stereocomplex compound formed by MPEG(5K)-PLLA(4.5K) and MPEG(5K)-PDLA(4.5K) could self-assemble into spherical particle whose diameter is also about 200 nm. Moreover, these particles formed bystereocomplex compounds are more uniform than the particles that formed by single chiral amphiphilic block copolymer. The biological activity of these obtained polymers were evaluated by FITC-phalloidin staining fluorescence method. The results show that both single chiral amphiphilic block polymers and stereocomplex compounds are biocompatible.In the third part of this paper, based on single dovetail amphiphilic polymers, double dovetail amphiphilic polymers were synthsized through ring-opening polymerization of LA in the presence of double dovetail initiators which were prepared from polyethylene oxide-polypropylene oxide-polyethylene oxide(PEO-PPO-PEO) triblock copolymers. The structures and properties were also characterized through1 H NMR, GPC, and FT-IR.