Search

Thermo-responsive diblock copolymer, poly(N-isopropylacrylamide)-block-poly(N-vinylisobutyramide) was synthesized via switchable reversible addition–fragmentation chain transfer (RAFT) polymerization and its thermal transition behavior was studied. Poly(N-vinylisobutyramide) (PNVIBA), a structural isomer of poly(N-isopropylacrylamide) (PNIPAM) shows a thermo-response character but with a higher lower critical solution temperature (LCST) than PNIPAM. The chain extension of the PNVIBA block from the PNIPAM block proceeded in a controlled manner with a switchable chain transfer reagent, methyl 2-[methyl(4-pyridinyl)carbamothioylthio]propionate. In an aqueous solution, the diblock copolymer shows a thermo-responsive behavior but with a single LCST close to the LCST of PNVIBA, indicating that the interaction between the PNIPAM segment and the PNVIBA segment leads to cooperative aggregation during the self-assembly induced phase separation of the diblock copolymer in solution. Above the LCST of the PNIPAM block, the polymer chains begin to collapse, forming small aggregates, but further aggregation stumbled due to the PNVIBA segment of the diblock copolymer. However, as the temperature approached the LCST of the PNVIBA block, larger aggregates composed of clusters of small aggregates formed, resulting in an opaque solution. [ABSTRACT FROM AUTHOR]

A new polyacetylene-based polyelectrolyte with the ferrocene-containing pyridinium substituents was synthesized by the quaternization polymerization of 2-ethynylpyridine using (6-bromo-1-oxohexyl)ferrocene. The analysis results on the chemical structure of the resulting polymer revealed that it contains the conjugated polymer backbone system with the bulky N-(6-ferrocenyl-6-oxohexyl)pyridinium bromide substituents. The absorption spectrum exhibited the maximum peak of 519 nm which comes from the π → π∗ transition of the conjugated polyene group. The overall redox current shape showed irreversible results and the related values were very stable in the range of −1.5 V to 1.5 V under up to 50 cycles. The oxidation peak value was 0.5 V and 1.25 V and the reduction peak value was −1.3 V. [ABSTRACT FROM AUTHOR]

A new polyacetylene based polyelectrolyte, poly(N-3,4-dimethoxybenzoyl-2-ethynylpyridinium chloride), was synthesized by the direct polymerization of 2-ethynylpyridine and 3,4-dimethoxybenzoyl chloride. The polymerization successfully proceeded without any additional catalyst or initiator to give a high yield of the product. The chemical structure of poly(N-3,4-dimethoxybenzoyl-2-ethynylpyridinium chloride) was confirmed using 1H and 13C nuclear magnetic resonance spectroscopy, as well as Fourier transform infrared spectroscopy. Further, optical properties, electrochemical properties, and thermal stabilities were investigated by cyclic voltammetry, UV-Vis absorption spectra, photoluminescence spectra, thermogravimetric analysis. Comparing UV-Visible absorption and photoluminescence spectrum, the polymer showed the band gap of 2.18 eV and photon energy of 2.58 eV. [ABSTRACT FROM AUTHOR]

The thermally induced phase separation behavior of poly(ethersulfone) (PES) in organic solvents is applied in sensing the hydrogenation state of benzene. A non-solvent of PES, benzene and its reduction products lower the clouding point temperature (T cp) of a polymer solution. The T cp decreases as the number of π electrons decreases, and a linear correlation between the temperature and concentration is obtained. In addition, the T cp of the mixed system can be predicted according to the proportion of components, and the calculated results are found to be in good agreement with the experimental results. [Display omitted] • Synthesis of thermos-responsive PES by chain-growth condensation polymerization. • Influence of benzene and its reduction products on the phase transition temperature of the PES/chloroform solution. • Prediction of the effect of binary and ternary mixture of benzene and its reduction product. • Application of thermo-responsive system to determine hydrogenation state of benzene. [ABSTRACT FROM AUTHOR]