Toward Tertiary Amine Modulated Acid Triggered Hydrolysis of Copolymers Containing Pendent Ortho Ester Groups
We describe an efficient approach to modulate the hydrolysis of the ortho ester containing polymers by incorporating different amount of tertiary amino (TA) groups. The block copolymers (NE0 NE3) contain a hydrophilic poly(ethylene glycol) (PEG) segment and hydrophobic chains constituted by random methacrylate copolymers with pendent acid labile cyclic ortho ester and TA groups and were synthesized by a two step approach. First, atom transfer radical copolymerization of 2 hydroxyethyl methacrylate and 2 (diethylamino)ethyl methacrylate using mPEG45 Br as a macroinitiator afforded the block copolymer precursors. Then, reaction of the precursors with 2 ethylidene 4 methyl 1,3 dioxolane transformed the pendent hydroxyl groups into cyclic ortho ester groups. The hydrophobic chains are similar in degree of polymerization, but the percent molar content of TA increases from 0% for NE0 to ~15% for NE3. In phosphate buffer at pH 8.4, all the four amphiphilic block copolymers can self assemble into stable nanoparti.