1 research outputs found
A Vinyl Ether-Functional Polycarbonate as a Template for Multiple Postpolymerization Modifications
A highly reactive
vinyl ether-functionalized aliphatic polycarbonate
and its block copolymer were developed as templates for multiple postpolymerization
conjugation chemistries. The vinyl ether-functional six-membered cyclic
carbonate monomer was synthesized by a well-established two-step procedure
starting from 2,2-bisÂ(hydroxymethyl)Âpropionic acid. An organobase-catalyzed
ring-opening polymerization of the synthesized monomer afforded polycarbonates
with pendant vinyl ether functionalities (PMVEC). The vinyl ether
moieties on the resulting polymers were readily conjugated with hydroxyl-
or thiol-containing compounds via three different postpolymerization
modification chemistries: acetalization, thio-acetalization, and
thiol–ene reaction. Acetal-functionalized polycarbonates were
studied in depth to exploit their acid-labile acetal functionalities.
Acetalization of the amphiphilic diblock copolymer of polyÂ(ethylene
glycol) methyl ether (mPEG) and PMVEC, mPEG<sub>113</sub>-<i>b</i>-PMVEC<sub>13</sub>, with the model hydroxyl compound 4-methylbenzyl
alcohol resulted in a maximum of 42% acetal and 58% hydroxyl side
chain groups. Nonetheless, the amphiphilicity of the block polymer
allowed for its self-assembly in water to afford nanostructures, as
characterized via dynamic light scattering and transmission electron
microscopy. The kinetics of acetal cleavage within the block polymer
micelles were examined in acidic buffered solutions (pH 4 and 5).
In addition, mPEG-<i>b</i>-PMVEC and its hydrolyzed polymer
mPEG-<i>b</i>-PMHEC (i.e., after full cleavage of acetals)
exhibited minimal cytotoxicity to RAW 264.7 mouse macrophages, indicating
that this polymer system represents a biologically nonhazardous material
with pH-responsive activity