Controlled preparation of poly(ethylene glycol) and poly(L-lactide) block copolymers in the presence of a monomer activator

다국어 초록 (Multilingual Abstract)

<P>Polymerization of L-lactide (LA) was performed in the presence of trifluoromethanesulfonic acid (CF<SUB>3</SUB>SO<SUB>3</SUB>H) via an activated monomer mechanism to synthesize various block copolymers composed of polyethyleneglycol (PEG) and poly(L-lactide) (PLLA). The PLLAs obtained had molecular weights close to theoretical values calculated from LA/PEG molar ratios and exhibited monomodal GPC curves. A <SUP>1</SUP>H NMR spectroscopic study showed that the LA carbonyl carbon signal exhibited a change in chemical shift to lower field, caused by electron delocalization of the carbonyl carbon by CF<SUB>3</SUB>SO<SUB>3</SUB>H. We successfully prepared PEG and PLLA block copolymers using this activated monomer mechanism. We concluded that synthesis proceeded by LA ring-opening polymerization caused by PEG in the presence of CF<SUB>3</SUB>SO<SUB>3</SUB>H to yield PEG and PLLA block copolymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5917–5922, 2009</P>
<B>Graphic Abstract</B>
<P>Polymerization of L-lactide by PEG as an initiator was performed in the presence of CF<SUB>3</SUB>SO<SUB>3</SUB>H as monomer activator. The hydroxyl end group of PEG attacked the carbonyl carbon of protonated LA rather than the PLLA carbonyl carbon, even though CF<SUB>3</SUB>SO<SUB>3</SUB>H can interact with the carbonyl carbon of both LA and PLLA. PEG and PLLA block copolymers successfully prepared by using activated monomer mechanism in the presence of CF<SUB>3</SUB>SO<SUB>3</SUB>H.
<img src='wiley_img/0887624X-2009-47-21-POLA23638-gra001.gif' alt='wiley_img/0887624X-2009-47-21-POLA23638-gra001'>
</P>