Extended-chain lamellar packing of poly(3-butylthiophene) in single crystals

We developed an approach, i.e. solvent-assist crystallization (SAC), for growing high quality single crystals of head-to-tail regio-regular poly(3-butylthiophene) (P3BT). By means of atomic force microscopy, electron diffraction and X-ray diffraction, we found that P3BT macromolecules formed lamella single crystals through gradient crystallization, and in the single crystals, molecules packed normal to the lamella with extended-chain conformation with alkyl side chains in the growth front during crystallization.

Morphology of electrodeposited poly(3,4-ethylenedioxythiophene)/poly(4-styrene sulfonate) films

Poly(4-styrene sulfonate)-doped poly(3,4-ethylenedioxythiophene) (PEDOT/PSS) films with ring-, arrow-, and bubble-like microstructures have been electrochemically generated simply by a one-step cyclic voltammetry in an aqueous media. Influences of applied potentials and surfactant/dopant-PSS on morphology of the resulting film were investigated, and a gas bubble template mechanism has been proposed. The result confirmed a well-doping of PSS in the PEDOT film. Electrochemical property and conductivity of the micro-structured PEDOT/PSS film were investigated further. Similar preparation with potential applications in fabrication of microdevices and micro-sensors can be extended to other micro-structured conducting polymers.

Electro-assisted precipitation of electrolytes in poly(3,4-ethylenedioxythiophene) film

The electrolyte, NaBF4, can be enriched into the matrix of poly(3,4-ethylenedioxythiophene) (PEDOT) film during the p-doping potential cycling between 0.6 and -0.9 V. It has been demonstrated that this enrichment is originated from the mixed ion transfer between doping and dedoping, i.e. BF4- anion migrate into the PEDOT film during the oxidation process, the Ne cation insert into the film during the reduction process, and then, the electrolyte is accumulated into the film matrix after the multiple CV cycling. The quantitative analysis of energy-dispersive X-ray spectroscopy (EDX) confirmed the enrichment of NaBF4 in the PEDOT film.

Characterization and properties of biodegradable poly(hydroxyalkanoates) and 4,4-dihydroxydiphenylpropane blends: Intermolecular hydrogen bonds, miscibility and crystallization

Intermolecular hydrogen bonds, miscibility, crystallization and thermal stability of the blends of biodegradable poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(3HB-3HHx)] with 4,4-dihydroxydiphenylpropane (DOH2) were investigated by FTIR, C-13 Solid state NMR, DSC, WAXD and TGA. Intermolecular hydrogen bonds were found in both blend systems, which resulted from the carbonyl groups in the amorphous phase of both polyesters and the hydroxyl groups of DOH2. The intermolecular interaction between P(3HB-3HHx) and DOH2 is weaker than that between PHB and DOH2 owing to the steric hindrance of longer 3HHx side chains. Because of the effect of the hydrogen bonds, the chain mobility of both PHB and P(3HB-3HHx) components was limited after blending with DOH2 molecules. Single glass transition temperature depending on the composition was observed in all blends, indicating that those blends were miscible in the melt. The addition of DOH2 suppressed the crystallization of PHB and P(3HB-3HHx) components. Moreover, the crystallinity of PHB and P(3HB-3HHx) components also decreased with increasing DOH2 content in the blends.

Thermotropic liquid crystallinity, thermal decomposition behavior, and aggregated structure of poly(propylene carbonate)/ethyl cellulose blends

Maleic anhydride end capped poly(propylene carbonate) (PPC-MA) was blended with ethyl cellulose (EC) by casting from dichloromethane solutions. The thermotropic liquid crystallinity, thermal decomposition behavior, and aggregated structure were investigated by differential scanning calorimetry (DSC), thermogravimetry (TGA), and wide angle X-ray diffraction (WAXD). DSC exhibits thermotropic liquid crystallinity in the rich EC composition range. TGA shows that thermal decomposition temperatures were elevated upon interfusing EC into PPC-MA. WAXD corroborates that EC and PPC-MA/EC blend films cast from dilute dichloromethane solution possessed cholesteric liquid crystalline structure in the rich EC composition range, and that dilution of PPC-MA with EC increased the dimension of noncrystalline region, leading to a more ordered packed structure.

External field induced crystallization of poly(3-dodecylthiophene)

In order to investigate the effect of external field on the crystallization behavior of poly(3-dodecylthiopliene) (P3DDT), the samples were recrystallized with different electrostatic field intensity, different pressure and different solidification direction in temperature gradient field. Measurements of differential scanning calorimetry and X-ray diffraction were operated to characterize these samples for analysis. The results suggest that after recrystallization, whether the external field is added or not, a more compact packing of molecular chains in P3DDT could be obtained without the change of the crystal structure model. Moreover, the addition of electrostatic field has greater effects on the crystallization of rigid main chains than on that of flexible side chains, Merely great pressure field can effect the rearrangements of molecular chains greatly. As for the temperature gradient field induced crystallization, different oriented solidification direction will lead to different effects on the compact degree and perfect degree of molecular chains packing,

Study on the transesterification of poly(beta-hydroxybutyrate) and poly(epsilon-caprolactone)

The transesterification of poly(beta-hydroxybutyrate) (PHB) and poly(epsilon-caprolactone) (PCL) was carried out by using stannous octoate as catalyzer in liquid phase. The effects of reaction conditions on the transesterification, including reaction temperature, reaction time and catalyzer content, were investigated. The sequence distribution, crystallization behavior and thermal stability of PHB-co-PCL copolyesters were studied by C-13-NMR, FTIR, DSC, WAXD and TGA. The results showed that the transesterification of PHB with PCL was confirmed to produce a block copolymer, and enhancing reaction temperature and increasing reaction time were advantageous to the transesterification. With the increase in PCL content in the block copolymer, the crystallization behavior of PHB-co-PCL copolyesters changed evidently. On the other hand, the introduction of PCL segment into PHB chains did not change its crystalline structure; moreover, thermal stability of PHB-co-PCL copolyesters was a little improved in air, comparing with that of pure PHB.

Characterization and properties of the neutral and doped blends of poly(3-dodecylthiophene) with low-density polyethylene

In this paper, the structures and properties of the neutral and doped blends of poly(3-dodecylthiophene) (P3DDT) with low-density polyethylene (LDPE) were investigated. Wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), Fourier transform infrared spectra (FTIR), and scanning electron microscopy (SEM) were used to characterize the structures and morphologies of the blends, and conductivity was also measured. It was found that separate crystallizations occur between P3DDT and LDPE. When the amount of P3DDT is small in the blend, it has the effect of a nucleation reagent and has some influence on the crystal structure. After doping, the interaction force between the molecular chains increases, and leads to a more compact packing and a more uniform dispersion in morphology. Through blending, the thermal stability of pure component could be greatly improved, especially when the P3DDT content is 5 wt %. The conductivity measurements indicate that the conductivity increases with the increase of the P3DDT composition and doping time.

Isothermal crystallization kinetics and melting behavior of poly (beta-hydroxybutyrate) and maleated poly (beta-hydroxybutyrate)

The overall isothermal crystallization kinetics and melting behavior of poly(beta-hydroxybutyrate) (PHB) and maleated PHB with different graft degree were studied by using differential scanning calorimetry (DSC). The Avrami analysis indicates that the introduction of maleic anhydride results in the decrease in the overall crystallization rate of PHB, but does not affect its nucleation mechanism and geometry of crystal growth. The activation energy of the overall crystallization process increases with the increase in graft degree. The phenomenon of multiple melting endotherms is observed, which results from melting and recrystallization during the DSC heating run.

Poly(3-dodecylthiophenes) polymerized with different amounts of catalyst

The effect of the amount of the catalyst FeCl3, used during the direct oxidation polymerization, on the structure and properties of the obtained poly(3-dodecylthiophene) (P3DDT) was investigated in this paper. Such measurements as gel permeation chromatography (GPC), nuclear magnetic resonance (NMR) spectroscopy, thermal analysis, X-ray diffraction, infrared spectroscopy (FTIR) and ultraviolet-visible (W-vis) spectroscopy were applied. It is found that a suitable addition of FeCl3 can contribute to generate a P3DDT with greater percentage of head-to-tail head-to-tail (HT-HT) linkages, which are generally favored. The reduction of the other linkage defects helps to lengthen conjugation length, thus leading to more orderly chain packing. (C) 2000 Elsevier Science S.A. All rights reserved.

Nonisothermal crystallization of poly(3-dodecylthiophene) and poly(3-octadecylthiophene)

Poly(3-dodecylthiophene) (P3DDT) and poly(3-octadecylthiophene) (P3ODT) are chosen to investigate the nonisothermal crystallization behavior by using differential scanning calorimetry (DSC). When Jeziorny method is applied, the deviation from the line appears at the later stage of crystallization for both P3DDT and P3ODT. The Ozawa equation fails to describe the nonisothermal crystallization of P3DDT, but succeeds for P3ODT. However, a new method proposed by our laboratory has been proven to be convenient and applicable for both of the two polymers. The values of the crystallization activation energy of P3DDT and P3ODT are estimated as 184.79 and 246.93 kJ/mol, respectively, in light of the Kissinger method. (C) 2000 Published by Elsevier Science S.A. All rights reserved.

The crystallization of poly (3-dodecylthiophene) in an oriented solidification environment

The crystallization behaviors of poly (3-dodecylthiophene) (P3DDT) under two different oriented solidification conditions, i.e.. two different relative relations (90 degrees and 180 degrees) between the directions of gravity and solidification, were investigated. X-ray diffraction results reveal that although similar layered structures are formed, under the condition of the relative relation 180 degrees. temperature gradient has greater effects on the perfect degree of the layered structures of P3DDT. It also can be concluded that after recrystallization, the layered structures of P3DDT can be improved at relative relation 90 degrees, but the orderly degree of the arrangements of alkyl side chains are not improved yet, even is reduced for both of the oriented solidification conditions.

Mechanical properties of poly(beta-hydroxybutyrate)/poly(ethylene oxide) blends

Tensile properties of poly (P-hydroxybutyrate)/poly (ethylene oxide) (PHB/PEO) blends were reported in this paper. It was found that the blends of PHB with different molecular-weight PEO exhibited different mechanical properties. The mechanical properties of the blends of PHB and PEO3 (M-w=0.3x10(6)) were very poor. However, the blends of PHB and PEO5 (M-w=5x10(6)) showed compatible in mechanical properties. Excellent synergism was observed not only in tensile stress and tensile elongation but also in modulus. Moreover, the ductility of the blends could be improved further under proper heat-treatment.

The FeCl3-doped poly(3-alkyithiophenes) in solid state

The FeCl3-doped three poly(3-alkylthiophenes) (P3ATs) in solid state, i.e. poly( 3-octylthiophenl) (P3OT), poly(3-dodecylthiophene) (P3ODT) and poly( 3-octadecylthiophene) (P3ODT), were investigated in this paper. In X-ray diffraction results, there are obvious variations of the interlayer and interlayer spacings in the layered structures of P3ATs. In addition, it is found that some orientations of the side-chain groups occur after the doping process. The infrared spectra have also shown the microstructural changes arising from the readjustments of the polymer chains due to the intervention of the dopant. The presence of dopant leads to the formation of bipolarons and polarons at the same time. The conductivity measurements reveal that the conductivity decreases with the increase of the length of sidechain group. We have also observed the relaxation behaviors in the conductivities of the doped polymers. (C) 2001 Elsevier Science B.V. All rights reserved.