Synthesis of new amphiphilic diblock copolymers and their self-assembly in aqueous solution
Synthesis of new amphiphilic diblock copolymers and their self-assembly in aqueous solution
复制标题
DOI：
10.1021/ma0506785
复制
发表时间：
2005-09-06
期刊：
影响因子：
5.5
通讯作者：
Laschewsky, A
中科院分区：
文献类型：
--
作者：
Garnier, S;Laschewsky, A
以低玻璃化转变温度的聚丙烯酸丁酯为疏水嵌段，由6个不同的亲水嵌段（1个阴离子、1个阳离子和4个非离子型亲水嵌段）通过可逆加成断裂链转移（RAFT）聚合制备了两亲二嵌段共聚物。非离子型亲水性嵌段除了包括经典的聚（二甲基丙烯酰胺）、热敏聚（n -丙烯酰吡啶）和由聚（丙烯酸乙二醇酯）大单体制成的梳型聚合物，以及一种新的强亲水性亚砜聚合物。聚合物的多分散性指数很低，得到的摩尔质量与理论期望质量之间有很好的相关性，这支持了聚合反应的“活性”特性。差示扫描量热法发现了嵌段共聚物的两个不同的玻璃化转变温度，表明块状嵌段的不混溶性。采用核磁共振波谱技术和动态光散射技术研究了两亲性二嵌段共聚物在水介质和有机介质中的自组装性能，研究了两亲性二嵌段共聚物的极性、两嵌段长度比和总摩尔质量对其自组装性能的影响。在水中发现了直径为25至100 mn的胶束状聚集体，在有机溶剂中也发现了反胶束。疏水块的长度似乎是决定水中聚集体大小的主要因素。经稀释和温度循环后，聚集体非常稳定。对于大的疏水块，在水中分散后，除了最初的小胶束外，还观察到大的结构。由于大聚集体缓慢消失，胶束化过程在热力学上似乎更有利。如果两种由不同嵌段共聚物组成的胶束聚集在一起，就会形成“混合”胶束。聚合物的隐式交换证明了以聚丙烯酸丁酯为疏水嵌段的胶束体系的动力学特性。
Amphiphilic diblock copolymers composed of poly(butyl acrylate) as the hydrophobic block with a low glass transition temperature and of six different hydrophilic blocks (one anionic, one cationic, and four nonionic hydrophilic blocks) are prepared via reversible addition fragmentation chain transfer (RAFT) polymerization. The nonionic hydrophilic blocks comprise in addition to the classical poly(dimethylacrylamide), the thermally sensitive poly(N-acryloylpyrrolidine), and a comb-type polymer made of a poly(ethylene glycol acrylate) macromonomer, as well as a new strongly hydrophilic sulfoxide polymer. The "living" character of the polymerizations is supported by very low polydispersity indexes and a good correlation between the molar masses obtained and the theoretically expected ones. Two distinct glass transition temperatures were found by differential scanning calorimetry for the block copolymers, suggesting the immiscibility of the blocks in bulk. The self-assembling properties of the amphiphilic diblock copolymers in aqueous and organic media were studied by nuclear magnetic resonance spectroscopy and dynamic light scattering, as a function of the polarity of the hydrophilic blocks, the ratio of the lengths of the two blocks, and the overall molar mass of the diblock copolymers. Micellelike aggregates with diameters from 25 to 100 mn in water are found, as well as inverse micelles in organic solvents. The length of the hydrophobic block seems to be the main factor governing the size of the aggregates in water. The aggregates are very stable upon dilution and temperature cycles. For large hydrophobic blocks, big structures are observed in addition to small micelles initially after the dispersion in water. As the big aggregates disappear slowly, the micellization process seems thermodynamically favored. If two populations of micelles made from different block copolymers are brought together, "mixed" micelles are formed. The implicit exchange of polymers proves the dynamic character of the micellar systems based on poly(butyl acrylate) as hydrophobic block.