Synthesis And Self-assembly Behaviors Of Rod-coil PANI/PEG Block Copolymers

Self-assembly of macromolecules is an efficient and rapid pathway to nanometer- or micrometer-sized materials with new structure and function, and has attracted more and more attentions in recent years. Due to their unique molecular structure, rod-coil block copolymers exhibit a serious of novel self-assembling structures and properties under weak intermolecular interaction.In the present work, PANI-PEG-PANI tri-block copolymer and mPEG-PANI di-block copolymer were designed by molecular engineering, in which poly (ethylene glycol) acts as the coil block and polyaniline acts as the rod block. These rod-coil block copolymers with defined chemical structure were synthesized via chemical oxidation. Their self-assembling structure was controlled by selecting solvents. The results showed that the chemical structure of these block copolymers could be controllably synthesized by selecting the PEG with different chemical structure and molecular weight, adjusting the concentrations of aniline and oxidant during polymerization. TGA results showed that the chemical structures of these block copolymers are (PANI)98-(PEG)136-(PANI)98 and m(PEG)12-(PANI)27, respectively. Static laser light scattering results indicated that the block copolymers tend to aggregate into spherical micelle in DMF which is a selective solvent for PEG, the block copolymers with low molecular weight form more regular micelles, and the size of the formed micelle is dependant on the chemical structure and molecular weight of the block copolymer. The di-block copolymers are easier to aggregate than the tri-block copolymers, and so is the block copolymer with low molecular weight. Moreover, (PANI)98-(PEG)136-(PANI)98 copolymer with high molecular weight tends to take place the second aggregation in the selective solvent of PEG.The self-assembly behavior of (PANI)98-(PEG)136-(PANI)98 tri-block copolymer in different selective solvents, such NMP, DMF,CHCl3 and ethanol, were studied by SEM and AFM. The results showed that (PANI)98-(PEG)136-(PANI)98 tri-block copolymers form some novel aggregates such as spherical, rods, vesicles and flowers, in the above selective solvents. The multiple morphologies were influenced by the solvent concentration, solvent type, volatility of solvent, applied outfield and so on.