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Thermoresponsive Poly(2-Oxazoline) Molecular Brushes by Living Ionic Polymerization: Modulation of the Cloud Point by Random and Block Copolymer Pendant Chains
Thermoresponsive Poly(2-Oxazoline) Molecular Brushes by Living Ionic Polymerization: Modulation of the Cloud Point by Random and Block Copolymer Pendant Chains
Molecular brushes (MBs) of poly(2-oxazoline)s were prepared by living anionic polymerization
of 2-isopropenyl-2-oxazoline to form the backbone and living cationic ring-opening
polymerization of 2- n -propyl-2-oxazoline and 2-methyl-2-oxazoline to form random and block
copolymers. Their aqueous solutions displayed a distinct thermoresponsive
behavior as a function of the side-chain composition
and sequence. The cloud point (CP) of MBs with random
copolymer side chains is a linear function of the hydrophilic
monomer content and can be modulated in a wide range. For
MBs with block copolymer side chains, it was found that the
block sequence had a strong and surprising effect on the CP.
While MBs with a distal hydrophobic block had a CP at 70 ° C,
MBs with hydrophilic outer blocks already precipitated at 32 ° C.
