Tri- and penta-block copolymers of styrene and methyl methacrylate with unique nanostructures in solution

S. Kumar, C.N. Murthy
The M. S. University of Baroda, IN

Keywords: micellar, block copolymers, ATRP

Summary:

The versatility of ATRP to synthesize copolymer blocks has been attempted in this work by the way of synthesis of different tri- and pentablock copolymers of styrene, n-butyl methacrylate and methyl methacrylate. The synthesis of poly (n-BMA-b-styrene-b-n-BMA) and poly(MMA-b-n-BMA-b-Styrene-b-n-BMA-b-MMA) linear tri- and pentablock copolymers were carried out by using copper halide as the transition-metal catalyst and PMDETA as the complexing ligand and were synthesized in three steps. The thermal analysis of these blocks copolymers showed distinct glass transition temperatures (Tg’s) of PnBMA at 35 °C and 96 °C for PS in case of triblock copolymer. Different polymerization conditions such as different reaction mediums and halogen exchange were utilized to achieve the desired well-defined homo and block copolymers. In a typical BAB type of block copolymer, using a solvent that preferentially dissolves the middle block leads to spherical micelles in solution that consists of a core of less soluble B block surrounded by the more soluble A block. The phase morphology depends on the length of the blocks. In this case the block copolymers showed core-shell type flower-like micellar structures when toluene was used as a selective solvent for one of the blocks. This morphology was confirmed from the transmission electronmicroscopy.