Two novel donor–acceptor copolymers were synthesized by Sonogashira cross-coupling of alkyl/alkoxy thiophene and dibromo-substituted squaraine moieties. The structures and properties of these polymers were characterized using FT–IR, NMR, UV–Vis, gel permeation chromatography, and cyclic voltammetry. Both copolymers are readily soluble in common organic solvents. The polymer films exhibit broad absorption in the wavelength range from 300 to 1000 nm with the maximum peaks over 750 nm. Electrochemical studies reveal that the band gaps of the polymers range from 1.05 to 1.36 eV. Compared to the alkyl thiophene, the alkoxy thiophene units can effectively lower the band gap and result in significant red-shift absorption spectrum of the resulted polymer. The strong overlap of the solar spectrum and the extremely low band gaps of the polymers suggest that they may be promising candidates for solar cells.

Two novel copolymers based on squaraine and fluorine units have been synthesized through palladium catalyzed Suzuki coupling reaction and Sonogashira coupling reaction, respectively. The structures and properties of the two copolymers were characterized by FT-IR, NMR, UV–vis absorbance (Abs), gel permeation chromatography (GPC), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC) and cyclic voltammetry (CV). The solution absorption spectrums of P1 and P2 show two distinct absorption bands, one locates at 300–500 nm and the other at 600–800 nm. The absorption spectrums of P1 and P2 in films are broadened obviously and the spectral responses are extended up to 900 nm. Thermal gravimetric analysis demonstrates that the polymers are stable. Cyclic voltammetry experiment shows that the band gaps of the copolymers are 1.65 eV and 1.67 eV, respectively, suggesting their potential for applications as solar cells materials.

Two novel π-conjugated polymers composed of alkyl carbazole/dialkoxyphenylene and squaraine units were synthesized by Sonogashira cross-coupling reactions. The structures and properties of these copolymers were characterized using FT-IR, NMR, UV–Vis, gel permeation chromatography and cyclic voltammetry (CV). Both polymers possess adequate thermal stability and exhibit good solubility in common organic solvents such as chloroform, THF, and toluene. The polymer films show intense and broad visible and near IR absorption with the long wavelength absorption maximum peaks of 796 and 851 nm for P1 and P2, respectively, which are apparently red-shifted compared with poly(phenyleneethynylene). CV studies reveal that the band gaps of these copolymers are about 1.45 eV, implying that the resulted polymers may be promising candidates for solar cells.

A novel water-soluble chitosan (CS) derivative methoxy poly(ethylene glycol)-O-chitosan-polyethylenimine (mPEG-O-CS-PEI), was synthesized. The synthesized intermediates and final product were characterized and confirmed by 1H NMR and FT-IR spectra. The particle size and zeta potential of mPEG-O-CS-PEI/DNA complexes were 65 nm and +28.5 mV at the mass ratio of 20:1, respectively. Agarose gel electrophoresis study showed strong DNA binding ability of mPEG-O-CS-PEI. The transfection of L-02 cells proved that mPEG-O-CS-PEI/plasmid was significantly less toxic than PEI 35 kDa and Lipofectin. The result of real-time quantitative PCR and GFP expression imaging showed that the transfection efficiency of mPEG-O-CS-PEI was significantly higher than PEI 35 kDa and Lipofectin in L-02 cells (P < 0.05). Therefore, mPEG-O-CS-PEI copolymer may be attractive cationic polymers for nonviral gene therapy.

Novel main-chain-conjugated poly(carbazol-alt-squaraine) and poly(dipyridyl-alt-squaraine) were successfully synthesized through direct polycondensation of 9-(2-ethylhexyl)carbazole-bridged or dipyridyl-bridged bispyrrole and squaric acid. The structures and properties of the polymers were characterized using 1H NMR, FT-IR, UV–vis and cyclic voltammetry. Both polymers exhibit excellent solubility in common organic solvents and good thermal stability. Their UV–vis absorption spectra indicated the polymers have broad and strong spectral responses from 200 nm to 900 nm, which reveals a low optical band gap around 1.38 eV, suggesting that they may be promising candidates for organic solar cells.

Two novel copolymers based on benzothiadizole-thiophene-phenylenevinylene have been synthesized through palladium catalyzed triple-bond polycondensation method. The copolymers exhibit good solubility in common organic solvents such as CHCl3, CH2Cl2 and THF. The structures and properties of the two copolymers are characterized by FT-IR, 1H-NMR, UV-Vis absorbance (Abs), gel permeation chromatography (GPC), thermal gravimetric analysis and cyclic voltammetry (CV). The copolymers of P1 and P2 show absorption spectra with maximum peak at 532 nm and 573 nm in solution, respectively. Compare to their monomers M1 and M2, the absorption peaks of P1 and P2 were red-shifted by 34 nm and 54 nm respectively. Thermal gravimetric analysis demonstrated that the polymers were stable and little weight loss was observed below 300°C. Cyclic voltammetry experiments showed that the band gaps of the copolymers were 1.81 eV and 1.62 eV, respectively, suggesting their potential for applications as organic solar cell materials.

Methoxy poly(ethylene glycol)–polyethylenimine–chitosan (mPEG–PEI–CS) was synthesized via chitosan conjugated with polyethylenimine and methoxy poly(ethylene glycol). The intermediates and final copolymer were characterized and confirmed by 1H NMR and FT-IR spectra. mPEG–PEI–CS was water soluble and its intrinsic viscosity was 0.446 dL/g. The contents of mPEG and PEI conjugated in the copolymer were 51.3% (w/w) and 28.9% (w/w), and the degree of substitution of PEI by mPEG was 176%. Gel electrophoresis confirmed that DNA was retained completely by the copolymer nanoparticles. The average diameter and zeta potential of mPEG–PEI–CS/DNA were 155 nm and 17.5 mV. The transfection of human embryonic kidney 293 (HEK293) cells proved that mPEG–PEI–CS/VRfat-1 plasmid had little toxicity on the growth and gene expression of cells, and the ratio of ω-3/ω-6 fatty acids was obviously increased after 72 h transfection compared to CS/VRfat-1 (P < 0.05). These indicated that mPEG–PEI–CS was a promising effective gene delivery and package molecule.

Chitosan and its derivatives are attractive non-viral vectors. To produce target-cell specificity and improve the solubility of chitosan, a novel chitosan derivative, modified with galactose and methoxy poly(ethylene glycol) (mPEG) was synthesized, and structure changes of chitosan and its derivatives were characterized. Compared to chitosan, the solution viscosity of the novel chitosan derivative drastically decreased. And, the degree of substitution (DS) of chitosan by galactose and mPEG were calculated as 0.09 and 0.30. The average diameter and zeta potential of mPEGylated galactosylated chitosan (GaC) nanoparticle containing VRMFat plasmid were 178 nm and +2.93 mV, suggesting suitable properties for gene delivery system. The gel electrophoresis confirmed that the plasmid DNA was remained completely by the mPEGylated GaC nanoparticle. And, the cytotoxic effect of mPEGylated GaC nanoparticles on human embryonic kidney (HEK 293) cells was negligible in comparison with that of control chitosans. Therefore, it is expected that the mPEGylated GaC will have the potential as a targeting gene delivery system for a further application.

A series of novel copolymers with fluorene and 2-pyran-4-ylidene-malononitrile (PM) moieties were synthesized successfully through Suzuki coupling reactions. The structures and properties of these polymers were characterized using FT-IR, NMR, UV-vis, elemental analysis and cyclic voltametry. All of the copolymers exhibit excellent solubility in common organic solvents. The electrochemical and photophysical properties were investigated, and the results show that the spectral response of these copolymers are extended up to 560 nm, 640 nm, 625 nm and 625 nm for P1, P2, P3 and P4, respectively. The PL spectra of the copolymer and TiO2 bulk-heterojunction films exhibit strong photoinduced electronic interactions. Cyclic voltanmetry studies reveal that the band gaps of these copolymers range from 1.7 to 2.0 eV, implying that they may be promising candidates for solar cells.

A novel series of soluble conjugated polyfluorene copolymers comprised of porphyrin and thiophene moieties were synthesized by palladium-catalyzed Suzuki coupling reactions with various feed ratios. Chemical structures of the copolymers were characterized by 1H NMR and IR. All of the polyfluorene copolymers demonstrated good thermal stability, relatively high glass transition temperatures, and strong absorption over 600 nm and nearly cover 400∼700 nm visible region. It was revealed by cyclic voltammetry that the bandgaps of copolymers were between 1.96 and 2.03 eV. And the polymer:TiO2 bulk-heterojunction films were made from mixtures of polymer and titanium isopropoxide (Ti(OC3H7)4) via hydrolysis in air. The photoluminescence (PL) at 380∼800 nm of the blend film of PT-TPP20:TiO2 bulk-heterojunction in the 20% Ti(OC3H7)4 blend film was decreased compared to that of a pristine copolymer film. PL was significantly quenched in the 50% Ti(OC3H7)4 blend film, indicative of rapid and efficient separation of photoinduced electron-hole pairs with electrons on the TiO2 and holes on the polymer.

A new squaraine dye Bis(4-N,N-dicarboxymethyl-2-hydroxyphenyl)squaraine (SQ) which could be used as organic photovoltaic materials, was synthesized, and its molecular structure was fully characterized by elemental analysis, IR, 1H NMR and MS. SQ exhibits strong absorption band over 600–700 nm. Addition of TiO2 colloids to the ethanol solution of SQ resulted in the increase of optical density, quenching of fluorescence and shortened fluorescence lifetime. The apparent association constant between the sensitizer and semiconductor as measured from the fluorescence quenching data, was 2427 M−1. Fluorescence lifetime measurements gave the rate constant for the electron injection process from the excited singlet of SQ to the conduction band of TiO2 nanoparticles as 2.55 × 10 8 s−1. In addition, SQ doped SiO2 gel glass slices were prepared and characterized by absorption and emission spectra.