| Autor: |
Kozhunova EY; Faculty of Physics, Lomonosov Moscow State University, Leninskie Gory, 1, bld. 2, 119991 Moscow, Russia.; Faculty of Chemistry, Lomonosov Moscow State University, Leninskie Gory, 1, bld. 3, 119991 Moscow, Russia., Plutalova AV; Faculty of Chemistry, Lomonosov Moscow State University, Leninskie Gory, 1, bld. 3, 119991 Moscow, Russia., Sybachin AV; Faculty of Chemistry, Lomonosov Moscow State University, Leninskie Gory, 1, bld. 3, 119991 Moscow, Russia., Chertovich AV; Faculty of Physics, Lomonosov Moscow State University, Leninskie Gory, 1, bld. 2, 119991 Moscow, Russia.; Semenov Federal Research Center for Chemical Physics, Kosygina, 4, 119991 Moscow, Russia., Chernikova EV; Faculty of Chemistry, Lomonosov Moscow State University, Leninskie Gory, 1, bld. 3, 119991 Moscow, Russia. |
| Abstrakt: |
For the first time, double stimuli-responsive properties of poly(N-isopropylacrylamide) (PNIPA) and poly(1-vinylimidazole) (PVIM) block copolymers in aqueous solutions were studied. The synthesis of PNIPA 60 - b -PVIM 90 and PNIPA 28 - b -PVIM 62 - b -PNIPA 29 was performed using reversible addition-fragmentation chain transfer (RAFT) polymerization. The polymers were characterized by size exclusion chromatography and 1 H NMR spectroscopy. The conformational behavior of the polymers was studied using dynamic light scattering (DLS) and fluorescence spectroscopy (FS). It was found that PNIPA and block copolymers conformation and ability for self-assembly in aqueous medium below and above cloud point temperature depend on the locus of hydrophobic groups derived from the RAFT agent within the chain. Additionally, the length of PVIM block, its locus in the chain and charge perform an important role in the stabilization of macromolecular micelles and aggregates below and above cloud point temperature. At 25 °C the average hydrodynamic radius (R h ) of the block copolymer particles at pH 3 is lower than at pH 9 implying the self-assembling of macromolecules in the latter case. Cloud points of PNIPA 60 - b -PVIM 90 are ~43 °C and ~37 °C at a pH of 3 and 9 and of PNIPA 28 - b -PVIM 62 - b -PNIPA 29 they are ~35 °C and 31 °C at a pH of 3 and 9. Around cloud point independently of pH, the R h value for triblock copolymer rises sharply, achieves the maximum value, then falls and reaches the constant value, while for diblock copolymer, it steadily grows after reaching cloud point. The information about polarity of microenvironment around polymer obtained by FS accords with DLS data. |
