Synthesis and characterization of electroactive and biodegradable ABA block copolymer of polylactide and aniline pentamer

A triblock copolymer PLA-b-AP-b-PLA (PAP) of polylactide (PLA) and aniline pentamer (AP) with the unique properties of being both electroactive and biodegradable is synthesized by coupling an electroactive carboxyl-capped AP with two biodegradable bihydroxyl-capped PLAs via a condensation reaction. Three different molecule weight PAP copolymers are prepared. The PAP copolymers exhibit excellent electroactivity similar to the AP and polyaniline, which may stimulate cell proliferation and differentiation. The electrical conductivity of the PAP2 copolymer film (similar to 5 x 10(-6) S/cm) is in the semiconducting region. Transmission electron microscopic results suggest that there is microphase separation of the two block segments in the copolymer, which might contribute to the observed conductivity. The biodegradation and biocompatibility experiments in vitro prove the copolymer is biodegradable and biocompatible. Moreover, these new block copolymer shows good solubility in common organic solvents, leading to the system with excellent processibility. These biodegradable PAP copolymers with electroactive function thus possess the properties that would be potentially used as scaffold materials for neuronal or cardiovascular tissue engineering.

Dissolution, characterization and photo functionalization of carbon nanotubes

A simple method to disperse carbon nanotubes (CNTs) has been achieved, which gives two photofunctionalized CNTs, hydrazine nanotubes (h-CNTs) and 1,3,4-oxadiazole nanotubes (o-CNTs). Results from FTIR, H-1 NMR spectroscopy and TEM observations showed that the functionalization was successful. The modified nanombes can dissolve in most of the nonpolar organic solvents and no precipitate was observed in the solution of the nanombes even after 2 months. The functionalized nanotubes showed photo-electronic properties, which is due to the attachment of the function groups to them as proved by steady-state fluorescence spectroscopy. Both h-CNTs and o-CNTs showed good thermal stability below 300 C and might be used as functional materials.

Effects of molecular weight, solvent and substrate on the dewetting morphology of polystyrene films

Surface morphology of polystyrene (PS) films on different substrates by spin-coating before and after annealing was observed using atomic force microscopy (AFM). The effects of polymer molecular weight, substrates, solvents, and annealing conditions on the morphology of the films were investigated. Before annealing, the grain height decreases, and simultaneously the grain diameter increases with molecular weight (M-w) within the measured molecular weight. After annealing. the situation is opposite, i.e., the grain height increases while the grain diameter decreases with M-w. Furthermore, after annealing the smaller surface roughness (Ra) was obtained. It was also found that film surface roughness (Ra) depends on the vapor pressure and dipole moment of different used solvents as well as the substrates. The experimental results show that when the used solvents have similar dipole moment but different vapor pressure, the Ra of PS film decreased with the decreasing vapor pressure of solvents whether on silicon or on mica. And when the used solvents have close vapor pressure but different dipole moment, the Ra decreased with the increasing of solvent dipole moments on both substrates.

Electrochemical and bioelectrochemistry properties of room-temperature ionic liquids and carbon composite materials

Room-temperature ionic liquids (RTILs) are liquids at room temperature and represent a new class of nonaqueous but polar solvents with high ionic conductivity. The conductivity property of carbon nanotubes/RTILs and carbon microbeads/RTILs composite materials has been studied using ac impedance technology. Enzyme coated by RTILs-modified gold and glassy carbon electrodes allow efficient electron transfer between the electrode and the protein and also catalyze the reduction Of O-2 and H2O2,

Synthesis and chirooptical properties of optically active poly(ester imide)s based on axially asymmetric 1,1 '-binaphthyls

A series of optically active poly(ester imide)s (PEsI's) has been synthesized by the polycondensation reactions of new axially asymmetric dianhydrides, that is, (R)-2,2'-bis(3,4-dicarboxybenzoyloxy)-1,1'-binaphthyl dianhydride and (S)-2,2'-bis(3,4-dicarboxybenzoyloxy)-1,1'-binaphthyl dianhydride, and various diamines with aromatic, semiaromatic, and aliphatic structures. The polymers have inherent viscosities of 0.45-0.70 dL/g, very good solubility in common organic solvents, glass-transition temperatures of 124-290 degreesC, and good thermal stability. Wide-angle X-ray crystallography of these polymers shows no crystal diffraction. In comparison with model compounds, an enhanced optical rotatory power has been observed for the repeat unit of optically active PEsI's based on aromatic diamines, and it has been attributed to a collaborative asymmetric perturbation of chiral 1,1'-binaphthyls along the rigid backbones.

Synthesis and properties of polyquinolines and polyanthrazolines containing pyrrole units in the main chain

A series of eight new polyquinolines and polyanthrazolines with pyrrole isomeric units in main chain were synthesized and characterized. The new polymers showed high glass transition temperatures (T-g = 242-339 degreesC) and excellent thermal stability (T-5% = 398-536 degreesC in air, TGA). Compared to the series of polyanthrazolines, the series of polyquinolines exhibited higher thermal stability, better solubility in common organic solvents, and lower maximum absorption wavelengths (lambda(max)(a)). Polyanthrazolines with 2,5-pyrrole linkage showed an unusually high lambda(max)(a) (565 nm) and small band gap (2.02 eV). All polymers in solution had low photoluminescence quantum yields between 10(-2%) and 10(-5%) and excited-state lifetimes of 0.28-1.29 ns. The effects of molecular structure, especially pyrrole linkage structures, on the electronic structure, thermodynamics, and some of the optical properties of the polymers were explored. A model of hydrogen bonds in the main chain of the polymers was suggested to explain the difference in the properties of the isomer polymers. In addition, a polyquinoline (PBM) was chosen to examine the proton conductivity; the result indicated that the PBM/H3PO4 complex exhibited a high conductivity of 1.5 x 10(-3) S cm(-1) at 157 degreesC.

Solvent-induced microphase separation in diblock copolymer thin films with reversibly switchable morphology

We have studied the surface morphology of symmetric poly(styrene)-block-poly(methyl methacrylate) diblock copolymer thin films after solvent vapor treatment selective for poly(methyl methacrylate). Highly ordered nanoscale depressions or striped morphologies are obtained by varying the solvent annealing time. The resulting nanostructured films turn out to be sensitive to the surrounding medium, that is, their morphologies and surface properties can be reversibly switchable upon exposure to different block-selective solvents.

Patterned self-adaptive polymer brushes by "grafting to" approach and microcontact printing

Patterned self-adaptive PS/P2VP mixed polymer brushes were prepared by "grafting to" approach combining with microcontact printing (muCP). The properties of the patterned surface were investigated by lateral force microscopy (LFM), XPS and water condensation figures. In the domains with grafted P2VP, the PS/P2VP mixed brushes demonstrated reversible switching behavior upon exposure to selective solvents for different components. The chemical composition of the top layer as well as the surface wettability can be well tuned due to the perpendicular phase segregation in the mixed brushes. While in the domains without grafted P2VP, the grafted PS did not have the capability of switching. The development and erasing of the pattern is reversible under different solvent treatment.

Copolymerization of dichlorodiphenylsulfone with bis(chlorophthalimide) catalyzed by NiBr2/PPh3/Zn

A new high-performance material, poly(sulfone-imide) was prepared by Ni(0)-catalyzed coupling of aromatic dichlorides containing imide structure and 4,4'-dichlorodiphenylsulfone. The copolymers were produced with high yield and moderate to high inherent viscosities of 0.52-1.13 dL/g. Wide-angle X-ray diffractograms revealed that the polymers were amorphous. Most of the polymers exhibited good solubility and could be readily dissolved in various solvents such as N-methyl-2-pyrrolidinone(NMP) and N,N-dimethylacetamide (DMAc). These polysulfone-imides had glass-transition temperatures between 317 and 345 degreesC and 10% weight loss temperatures in the range of 450476 degreesC in nitrogen atmosphere. The tough polymer films, obtained by casting from cresol solution, had a tensile strength range of 21 158 MPa and a tensile modulus range of 2.1-3.3 GPa.

Cyclic oligomers of phenolphthalein polyarylene ether sulfone (ketone): Preparation through cyclo-depolymerisation of corresponding polymers

Cyclic oligomers of phenolphthalein polyarylene ether sulfone(ketone) were prepared through cyclo-depolymerisation of corresponding polymers using CsF as the catalyst in dipolar aprotic solvent DMAc and DMF, and a family of macrocycles containing from dimer up to at least heptamer were confirmed. by GPC, HPLC and MALDI-TOF-MS. The yields of cyclics get as high as 86.3% and 87.9% respectively.

Novel soluble N-phenyl-carbazole-containing PPVs for light-emitting devices: Synthesis, electrochemical, optical, and electroluminescent properties

Novel PPV derivatives (PCA8-PV and PCA8-MEHPV) containing N-phenyl-carbazole units on the back-bone were successfully synthesized by the Wittig polycondensation of 3,6-bisformyl-N-(4-octyloxy-phenyl)carbazole with the corresponding tributyl phosphonium salts in good yields. The newly formed and dominant trans vinylene double bonds were confirmed by FT-IR and NMR spectroscopy. The polymers (with (M) over bar (w) of 6289 for PCA8-PV and 7387 for PCA8-MEHPV) were soluble in common organic solvents and displayed high thermal stability (T(g)s are 110.7 degreesC for PCA8-PV and 92.2 degreesC for PCA8-MEHPV, respectively) because of the incorporation of the N-phenyl-carbazole units. Cyclic voltammetry investigations (onsets: 0.8 V for PCA8-PV and 0.7 V for PCA8-MEHPV) suggested that the polymers possess enhanced hole injection/transport properties, which can be also attributed to the N-phenyl-carbazole units on the backbone. Both the single-layer and the double-layer light-emitting diodes (LEDs) that used the polymers as the active layer emitted a greenish-blue or bluish-green light (the maximum emissions located 494 nm for PCA8-PV and 507 nm for PCA8-MEHPV, respectively).

Effects of chain flexibility on polymer conformation in dilute solution studied by lattice Monte Carlo simulation

Effects of chain flexibility on the conformation of homopolymers in good solvents have been investigated by Monte Carlo simulation. Bond angle constraint coupled with persistence length of polymer chains has been introduced in the modified eight-site bond fluctuation simulation model. The study about the effects of chain flexibility on polymer sizes reveals that the orientation of polymer chains under confinement is driven by the loss of conformation entropy. The conformation of polymer chains undergoing a gradual change from spherical iso-diametric ellipsoid to rodlike iso-diametric ellipsoid with the decrease of polymer chain flexibility in a wide region has been clearly illustrated from several aspects. Furthermore, a comparison of the freely jointed chain (FJC) model and the wormlike chain (WLC) model has also been made to describe the polymer sizes in terms of chain flexibility and quasi-quantitative boundary toward the suitability of the models.

Sequential deprotonation of meso-(p-hydroxyphenyl)porphyrins in DMF: From hyperporphyrins to sodium porphyrin complexes

Sequential deprotonations of meso-(p-hydroxyphenyl)porphyrins (p-OHTPPH2) in DMF + H2O (V/V = 1:1) mixture have been verified to result in the appearance of hyperporphyrin spectra. However, when the deprotonations of these p-OHTPPH2 are carried out in DMF, the spectral changes differ considerably from those in the mixture mentioned above. At low [OH-], the optical spectra in the visible region are still considered to have characteristics of hyperporphyrin spectra. Further deprotonation at much higher basicity makes the optical spectra form three-banded spectra similar to those in the acidic solution. To clarify the molecular origins of these changes, UV-vis, resonance Raman (RR), proton nuclear magnetic resonance (H-1 NMR) experiments are carried out. Our data give evidence that p-OHTPPH2 in DMF can be further deprotonated of pyrrolic-H by higher concentrated NaOH, due to an aprotic medium like DMF effectively weakening the basicity of the porphyrin relative to that of the NaOH, and coordinates with two sodium ions (except the sodium ions that interact with the peripherial phenoxide anions) to form the sodium complexes of p-OHTPPH2 (Na2P, to lay a strong emphasis on the sodium ions that coordinate with the central nitrogen atom), which can be regarded as the porphyrin anions being perturbed by the sodium cations due to their highly ionic character.

Investigation of sol-gel transition in Pluronic F127/D2O solutions using a combination of small-angle neutron scattering and Monte Carlo simulation

Physical gelation in the concentrated Pluronic F127/D2O solution has been studied by a combination of small-angle neutron scattering (SANS) and Monte Carlo simulation. A 15% F127/D2O solution exhibits a sol-gel transition at low temperature and a gel-sol transition at the higher temperature, as evidenced by SANS and Monte Carlo simulation studies. Our SANS and simulation results also suggest that the sol-gel transition is dominated by the formation of a percolated polymer network, while the gel-sol transition is determined by the loss of bound solvent. Furthermore, different diffusion behaviors of different bound solvents and free solvent are observed. We expect that this approach can be further extended to study phase behaviors of other systems with similar sol-gel phase diagrams.

Synthesis and characterization of hyperbranched poly(ester-amide)s from commercially available dicarboxylic acids and multihydroxyl primary amines

A new method for syntheses of hyperbranched poly(ester-amide)s from commercially available A(2) and CBx type monomers has been developed on the basis of a series of model reactions. The aliphatic and semiaromatic hyperbranched poly(ester-amide)s with multihydroxyl end groups are prepared by in situ thermal polycondensation of intermediates obtained from dicarboxylic acids (A(2)) and multihydroxyl primary amines (CBx) in N,N-dimethylformamide. Analyses of FTIR, H-1 NMR, and C-13 NMR spectra revealed the structures of the polymers obtained. The MALDI-TOF MS of the polymers indicated that cyclization side reactions occurred during polymerization. The hyperbranched poly(ester-amide) s contain configurational isomers observed by C-13 and DEPT C-13 NMR spectroscopy. The DBs of the polymers were determined to be 0.38-0.62 by H-1 NMR or quantitive C-13 NMR and DEPT 135 spectra. These polymers exhibit moderate molecular weights, with broad distributions determined by size exclusion chromatography ( SEC), and possess excellent solubility in a variety of solvents such as N, N- dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran, and ethanol, and display glass-transition temperatures (T(g)s) between -2.3 and 53.2 degrees C, determined by DSC measurements.