Synthesis and self-assembly of a novel amphiphilic diblock copolymer consisting of isotactic polystyrene and 1,4--polybutadiene--poly(ethylene oxide).

Herein, a novel amphiphilic diblock copolymer consisting of isotactic polystyrene (PS) and 1,4--polybutadiene--poly(ethylene oxide) (1,4--PBD--PEO), PS--(1,4--PBD--PEO), was synthesized by the combination of living coordination copolymerization and graft copolymerization. PS--1,4--PBD was firstly synthesized sequential monomer addition in the presence of 1,4-dithiabutandiyl-2,2'-bis(6-cumenyl-4-methylphenoxy) titanium dichloride (complex 1) activated by triisobutyl aluminum modified methylaluminoxane (MMAO). Moreover, hydroboration of double bonds in the 1,4--PBD blocks were performed with 9-borabicyclo[3.3.1]nonane (9-BBN) and subsequent oxidation by NaOH/HO to form hydroxyls. Consequently, PEO was grafted into the hydroxylated 1,4--PBD block in terms of ring-opening polymerization of ethylene oxide with potassium/naphthalide as initiatior. We also described solvent-evaporation-induced self-assembly of PS--1,4--PBD in -dodecane and PS--1,4--PBD-g-PEO in aqueous solution, which were selective solvent for 1,4--PBD and for 1,4--PBD--PEO blocks, respectively. In these cases, tetrahydrofuran (THF) was used as good and volatile solvent. These resultant PS-containing diblock copolymers could self-assemble into spherical nano-micelles with an PS core as amorphous agglomeration or a very low degree of crystallinity resulting from slow crystallization rate and nanoconfinement. In addition, after isothermal crystallization of PS in the micellar cores self-assembled in -dodecane at 120 °C for 3 hours, the micellar morphology changed from sphere-like to platelet-like. It was believed that isothermal crystallization of PS induced the deformation of the micelles.