Solvent replacement to thermo‐responsive nanoparticles from long‐subchain hyperbranched PSt grafted with PNIPAM for encapsulation

Long‐subchain hyperbranched polystyrene (lsc‐hp PSt) with uniform subchain length was obtained through copper‐catalyzed azide‐alkyne cycloaddition click chemistry from seesaw macromonomer of PSt having one alkynyl group anchored at the chain centre and two azido group attached to both chain ends [alkynyl‐(PSt‐N₃)₂]. After precipitation fraction, different portions of lsc‐hp PSt having narrow overall molecular weight distribution were obtained for further grafting with alkynyl‐capped poly(N‐isopropylacrylamide) (alkynyl‐PNIPAM), which was obtained via single‐electron transfer living radical polymerization of NIPAM with propargyl 2‐bromoisobutyrate as the initiator and grafted onto the peripheral azido groups of lsc‐hp PSt via click chemistry. Thus, amphiphilic lsc‐hp PSt grafted with PNIPAM chains (lsc‐hp PSt‐g‐PNIPAM) was obtained and would have star‐like conformation in tetrahydrofuran (THF). By replacing THF with water, lsc‐hp PSt‐g‐PNIPAM was dissolved at molecular level in aqueous solution due to the hydrophilicity of PNIPAM and exhibited thermal induced shrinkage of PNIPAM arms. The water‐insoluble lsc‐hp PSt would collapse densely and could be served as a reservoir to absorb hydrophobic chemicals in aqueous solution. The influence of overall molecular weight of lsc‐hp PSt on the absorption of pyrene was studied. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Conjugated polymer‐functionalized graphite oxide sheets thin films for enhanced photovoltaic properties of polymer solar cells

In this study, the maleimide‐thiophene copolymer‐functionalized graphite oxide sheets (PTM21‐GOS) and carbon nanotubes (PTM21‐CNT) were developed for polymer solar cell (PSC) applications. The grafting of PTM21‐OH onto the CNT and GO sheets was confirmed using FTIR spectroscopy. PTM21‐CNT and PTM21‐GOS exhibited excellent dispersal behavior in organic solvents. Better thermal stability was observed for PTM21‐CNT and PTM21‐GOS as compared with that for PTM21‐OH. In addition, the optical band gaps of PTM21‐GOS and PTM21‐CNT were lower than that of PTM21‐OH. We incorporated PTM21‐GOS and PTM21‐CNT individually into poly(3‐hexylthiophene) (P3HT)/[6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PCBM) blends for use as photoconversion layers of PSCs. Good distributional homogeneity was observed for PTM21‐GOS or PTM21‐CNT in the P3HT/PCBM blend film. The UV–vis absorption peaks of the blend films red‐shifted slightly upon increasing the content of PTM21‐GOS or PTM21‐CNT. The band gap energies and LUMO/HOMO energy levels of the P3HT/PTM21‐GOS and P3HT/PTM21‐CNT blend films were slightly lower than those of the P3HT film. The conjugated polymer‐functionalized PTM21‐GOS and PTM21‐CNT behaved as efficient electron acceptors and as charge‐transport assisters when incorporated into the photoactive layers of the PSCs. PV performance of the PSCs was enhanced after incorporating PTM21‐GOS or PTM21‐CNT in the P3HT/PCBM blend. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

1,1′‐Methylenedipyridinium tetrachloridocuprate(II) and bis[tetrachloridoaurate(III)] hybrid salts by X‐ray powder diffraction

In order to explore the potential propensity of the 1,1′‐methylenedipyridinium dication to form organic–inorganic hybrid ionic compounds by reaction with the appropriate halide metal salt, the organic–inorganic hybrid salts 1,1′‐methylenedipyridinium tetrachloridocuprate(II), (C₁₁H₁₂N₂)[CuCl₄], (I), and 1,1′‐methylenedipyridinium bis[tetrachloridoaurate(III)], (C₁₁H₁₂N₂)[AuCl₄]₂, (II), were obtained by treatment of 1,1′‐methylenedipyridinium dichloride with CuCl₂ and Na[AuCl₄], respectively. Both hybrid salts were isolated as pure compounds, fully characterized by multinuclear NMR spectroscopy and their molecular structures confirmed by powder X‐ray diffraction studies. The crystal structures consist of discrete 1,1′‐methylenedipyridinium dications and [CuCl₄]²⁻ and [AuCl₄]⁻ anions for (I) and (II), respectively. As expected, the dications form a butterfly shape; the Cu^II centre of [CuCl₄]²⁻ has a distorted tetrahedral configuration and the Au^III centre of [AuCl₄]⁻ shows a square‐planar coordination. The ionic species of (I) and the dication of (II) each have twofold axial symmetry, while the two [AuCl₄]⁻ anions are located on a mirror‐plane site. Both crystal structures are stabilized by intermolecular C—H...Cl hydrogen bonds and also by Cl...π interactions. It is noteworthy that, while the average intermolecular centroid–centroid pyridinium ring distance in (I) is 3.643 (8) Å, giving strong evidence for noncovalent π–π ring interactions, for (II), the shortest centroid–centroid distance between pyridinium rings of 5.502 (9) Å is too long for any significant π–π ring interactions, which might be due to the bulk of the two [AuCl₄]⁻ anions.