Precise Control of Lower Critical Solution Temperature of
Thermosensitive Poly(2-isopropyl-2-oxazoline) via Gradient
Copolymerization with 2-Ethyl-2-oxazoline as a Hydrophilic
Comonomer
Joon-Sik Park
Kazunori Kataoka
10.1021/ma0605548.s001
https://acs.figshare.com/articles/journal_contribution/Precise_Control_of_Lower_Critical_Solution_Temperature_of_Thermosensitive_Poly_2_isopropyl_2_oxazoline_via_Gradient_Copolymerization_with_2_Ethyl_2_oxazoline_as_a_Hydrophilic_Comonomer/3058516
The lower critical solution temperature (LCST) of amphiphilic poly(2-isopropyl-2-oxazoline)
(P<i>i</i>PrOx) was precisely tuned via the copolymerization with 2-ethyl-2-oxazoline (EtOx) as a hydrophilic
comonomer. The copolymerization was cationically initiated by methyl <i>p</i>-tosylate at the optimum condition (42
°C in acetonitrile) for living polymerization, obtaining the copolymers with a narrow molecular weight distribution
(<i>M</i><sub>w</sub>/<i>M</i><sub>n</sub> ≤ 1.02). The monomer reactivity ratios of 1.78 and 0.79 respectively were derived for EtOx and <i>i</i>PrOx
from the cumulative and instantaneous compositions of the copolymers determined from the <sup>1</sup>H NMR and MALDI-TOF mass spectrometry. This set of the reactivity ratios are sufficiently different enough to form the gradient
copolymers, in which each polymer chain has a trend of a gradually decreasing EtOx and an increasing <i>i</i>PrOx
composition along the backbone from the α-terminal to ω-chain end. These gradient copolymers followed a
rather simple rule in their thermosensitive behaviors to show a linear increase in LCST with an increasing mol
% of EtOx. Consequently, a series of P(EtOx-<i>co</i>-<i>i</i>PrOx) with finely tuned LCST in aqueous medium were obtained
through the cationic copolymerization simply by varying the initial composition of both monomers, opening a
new way to engineer the thermosensitivity of polymeric materials directing to particular applications.
2006-09-19 00:00:00
iPrOx
LCST
1 H NMR
EtOx
copolymerization
monomer reactivity ratios
gradient copolymers
Critical Solution Temperature