Synthesis and self-assembly of reactive h-shaped block copolymers

The H-shaped block copolymers (PTMSPMA)(2)PEG(PTMSPMA)(2) with two compositions, (EG)(91)-b( (TMSPMA)(92) and (EG)(455)-b-(TMSPMA)(176) have been successively synthesized by atom transfer radical polymerization (ATRP) of tri(methoxylsilyl)propyl metbacrylate(TMSPMA)at room temperature in methanol, and the initiation system applied in this system was composed of the 2, 2'-(alpha-bromoisobutyryloxymethyl) propionyl terminated poly( ethylene glycol) (Br(2)PEGBr(2)) with M-n = 4000 or 2 x 10(4), CuBr and 2, 2'-bipyridine. The four functional macroinitiator, Br-2 PEGBr(2) was prepared by reaction of two hydroxyl groups terminated PEG with 2, 2'(alpha-bromoisobutyryloxymethyl)proplonyl chloride. The NMR spectroscopy and GPC measurements were used to characterize the structure and molecular weight and molecular weight distribution of the resultant copolymers. When the H-shaped block copolymers Sam 1 and Sam 2 were self-assembled in DMF and water solvents, and successively condensation reaction of trimethoxysilyl groups in PTMSPMA was carried out, stable large-compound vesicles with 10 nm diameter of pores were formed for Sam I, but self-assembling of the Sam 2 in the selective solvents produced big vesicles aggregates. These two different morphologies of aggregates are attributed to their relative chain length of water soluble PEG. The vesicles formed from Saml with short PEG chains had big surface energy I which will lead them to self-assemble further, forming large-compound vesicles.