Characterization of poly(3-octylthiophene). I: Molecular characterization in dilute solution

The poly(3-alkylthiophenes) are a class of electrically conducting polymers which are of particular scientific and commercial interest due to their solubility and meltability. A series of poly(3-octylthiophene) (P3OT) fractions having molecular weights in the range M_w=30,000 to 400,000 were generated by preparative gel permeation chromatography (GPC). Although the polymer remained weakly aggregated when dissolved in pure THF, the addition of an organic salt (1 wt.% tetrabutylammonium p-toluenesulfonate) resulted in complete molecular dissolution. We were thus able to completely and consistently describe the polymer's single-chain properties using three dilute solution characterization methods: viscometry, GPC, and integrated light scattering. The molecular weight dependence of the intrinsic viscosity and the radius-of-gyration were established, and were characteristic of solutions near the theta condition, indicating poor solvent quality. Calculation of the persistence length from our data revealed that the polymer backbone is only 2 to 3 times more rigid than common flexible polymers, despite its conjugated ring structure.     

Structure characterization of sulfuric acid-doped poly(3-octylthiophene)

The structures of sulfuric acid-doped and water-undoped poly(3-octylthiophene) (P30T) were investigated by gel permeation chromatography (GPC), elemental analysis (EA), conductivity measurement, ultraviolet-visible-near-Infrared spectroscopy (UV-Vis-near-IR), Electron spin resonance (ESR), infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). For H₂SO₄-doped P3OT, the counter ion is HSO₄ ^– and the positive charge formed on the main chain distributes only on the conjugated C-C bond and does not distribute on the S atoms. The conductivity is found to increase by 5 orders as the doping level is 0.22. After the undoping with water, C-OH groups are formed on the main chains, which results in a decrease in conjugating length and in a less order chain arrangement. The undoped P3OT film can be redoped by 98% H₂SO₄; however, the doping level is less than its original value at the same doping condition.     

Thermal undoping behavior of FeCl3-doped poly(3-octylthiophene)

For neutral and FeCl₃-doped poly(3-octylthiophene) (P3OT), measurements of ⁵⁷Fe Mössbauer spectroscopy, conductivity, thermogravimetric analysis, differential scanning calorimetry and dynamic mechanical analysis are performed in order to understand the thermal undoping behavior. It is found that the counter anion for the doped P3OT is FeCl₄. At the doping level 0.33, its glass transition temperature (T_g) shifts from 11.2 °C at the neutral state to 137 °C. During the heat treatment, the aggregation of the dopant occurs between 65 to 150 °C (centered at 99 °C) and the decomposition of dopant anions occurs between 150 to 236 °C (centered at 188 °C). The aggregation of the dopant anion in the glass transition period is resulted from the increased ring distortion in the subchains, which leads to a slow decrease in conductivity. As the dopant anions decomposes, the conductivity drops sharply.     

Melt viscosity increase during rheological testing of poly(phenylene sulfide)

Poly(phenylene sulfide) (PPS) made via the melt polymerization of p-diiodobenzene and sulfur has previously been reported to increase in melt viscosity with time during rheological testing. Analysis of the oligomer from cleavage of PPS chains at the disulfide bonds via solution in 1-chloronaphthalene demonstrated that the disulfide content of the polymer decreased with rheological testing time. DSC of the polymer before and after rheological testing in combination with the T_cc and T_m of the chain fragments after the dissolution/cleavage in 1-chloronaphthalene showed that many samples exhibited primarily chain extension rather than chain branching, whereas for many others, some degree of chain branching occurred. This is currently only qualitatively understood. Chain branching as the exclusive mechanism of melt viscosity increase during rheological testing appears untenable in light of the T_m, in particular, of the chain fragments and also the polymer prior to chain cleavage. © 1993 John Wiley & Sons, Inc.     

Electrochemical synthesis of poly(3′-alkyl-terthiophenes). Characterization and applications

A new series of polymers obtained from 3′-alkyl-terthiophene monomers have been electropolymerized aimed at using them as raw materials for the development of electronic devices, e.g., solar cell and organic light-emitting diodes, among others. The polymers were characterized by infrared and UV–Vis spectroscopy and cyclic voltammetry. Cyclic voltammetry results revealed that during polymerization both terthiophene system and substituent groups are oxidized, but these processes are reversible. The products were tested in solar cells and the maximum yield obtained was 0.01%.     

Synthesis and characterization of poly(keto-amines). 3. poly(keto-amines) containing phenolic groups

Self polycondensations of 5-amino-2-hydroxyphenacyl chloride (5A2HP), 3-amino-4-hydroxyphenacyl chloride (3A4HP), and 4-amino-2-hydroxyphenacyl chloride (4A2HP) are carried out in nitrobenzene using pyridine as an acid acceptor. The poly(keto-amines) thus formed are characterized by elemental analysis, IR spectral studies, estimation of M?_n by non-aqueous conductometric titration and/or by VPO method, by measurement of solution viscosity in formic acid, and by TGA in air. All three poly(keto-amines) are reduced to poly(amines) by Wolf-Kishner reduction. The poly(amines) thus formed are characterized and compared. Polymeric metal chelates of poly(keto-amines) derived from 5A2HP and 3A4HP with various metal ions are prepared and characterized.     

Spectroelectrochemical behaviour of poly (3-octylthiophene): application to electrochromic windows with polyaniline and iridium oxide

The spectroelectrochemical behaviour of cast poly(3-octylthiophene) (POT) films (0.2 and 0.5 m) on indium-tin-oxide (ITO) glass electrodes has been investigated in organic media. These thin films exhibit interesting electrochromic properties and their application in electrochromic devices has been examined in liquid (CH₃CN + LiClO₄ 0.3 M) and viscous electrolyte (PEO + CH₃CH + LiClO₄). Polyaniline (PANI) film appears to be a convenient complementary counter electrode since its transmission maximum corresponds to its oxidized state and that of POT film to its reduced state. Thin films of iridium oxide (IrO₂) are also possible counter electrodes, even in acetonitrile, the electrochemical behaviour being mostly capacitive with a low transmission change. However, the best contrast is obtained with the POT/PANI system.     

Thermal analysis of poly(phenylene sulfide). II: Non-isothermal crystallization

The non-isothermal crystallization of Fortron poly(phenylene sulfide), PPS, was examined to better understand its behavior during injection molding. The nonisothermal Avrami formalism was applied to this system, but this method was found to be questionable because of the sometimes severe curvature that appears in the plots of the transformed data. A method of ranking crystallization rates at low cooling rates by plotting the peak in the crystallization exotherm versus the cube root of cooling rate has been considered and shown to have limitations at the higher cooling rates of interest. The growth rate expression developed by J. D. Hoffman for polymer crystallization of chain folded lamella in three dimensions has been used to simulate crystallization exotherms. It was found that this could only fit the data at low cooling rates. At high cooling rates it was necessary to use a growth rate expression developed by Calvert and Ulhmann for polymer crystallization without chain folding. When this is used to describe a two dimensional growth geometry, close agreement in the positions of high cooling rate exotherms could be obtained. The implication is that a change in crystallization mechanism is possible as the conditions go from low to high cooling rates.     

Effect of thermal annealing on surface morphology and physical properties of poly(3-octylthiophene) films

An unusual morphology observed in poly(3-octylthiophene) (P3OT) films, solution grown at room temperature, which is previously shown by highly regioregular-poly(3-alkylthiophenes) (rr-P3ATs), is reported. Upon thermal annealing a rare well-arranged corrugated-rod-type (CRT) morphology, comes up gradually. It is observed by soft-heat treatment of pristine P3OT films, which is not reported for any members of polythiophenes family. This novel CRT morphology, observed by scanning electron microscopy (SEM), is supported by photoluminescence (PL) quenching, red shift of λ_max (π-π* absorption) in UV-vis spectra, and increase in conductivity. These improvements in physical properties are perhaps due to the increase in the planarity and 3D-π-π stacking of polymer chains by gradual soft-thermal annealing. It is worthwhile to mention here that the P3OT synthesized for the present investigation, with changed polymerization parameters, is comparable with its rr-P3ATs counterparts. The improvement in the quality of P3OT may induce self-assembling nature in former which results due to increased π-π interactions.     

Functional gold nanorod particles on conducting polymer poly(3-octylthiophene) as non-enzymatic glucose sensor

The immobilization of surface-functionalized self-assembled monolayer (SAM) gold nanoparticles onto poly(3-octylthiophene) (POT) was achieved by the cooperation of hydrophobic forces. SAMs were prepared by 11-mercaptoundecanoicacid (MUA), 4-mercaptophenyl boronic acid (MPB), and 1-decanethiol (DT) hydrophobic substrates. Nanoparticles-SAM-POT system was characterized by cyclic voltammetry, SEM, EDAX and contact angle measurements. SAMs (MUA) is closely packed providing effective blocking of the underlying platinum electrode and preventing a ferrocyanide molecule from penetrating. However, potential scanning was applied at SAMs (MUA) modified electrode on which electron penetrating holes or defects were occured. Since SAMs (MPB) is poorly packed according to SAMs (MUA), ferrocyanide molecules could penetrate to SAMs (MPB) modified electrode surface. POT-Au-SAM (MPB) electrode was used for glucose determination as potentiometric non-enzymatic glucose sensor. The analytical performance was evaluated and linear calibration graphs were obtained in the concentration range of 5-30 mM glucose including the level of human blood glucose.     

Melt compounding and characterization of poly(lactide) stereocomplex/natural rubber composites

Poly(lactide) (PLA) is an interesting biodegradable polymer but has limited application because of its brittleness and low thermal stability. We found that both drawbacks of PLA were solved by forming stereocomplexes augmented with natural rubber (NR). Equal amounts of poly(l ‐lactide) (PLLA) and poly(d‐ lactide) (PDLA) stereoisomers were blended to form a stereocomplex (St‐PLA). Varying amounts of NR (5–30% by weight) were added simultaneously to equal amounts of the stereo isomers by melt blending. FTIR and XRD spectra demonstrated that, despite the added NR, the stereocomplex structures were still generated and complete. Stereocomplex crystallinity decreased with increasing NR content, verified by DSC and XRD, as well as polarizing optical micrographs which showed fewer spherulites at higher NR content. Measured glass transition temperatures (T_g) of St‐PLA/NR blends were significantly lower than for neat St‐PLA, exhibiting shifts to as low as 46°C at 30%wt NR content, because of rubber dispersed in St‐PLA segments expanding the free volume and enhancing chain mobility. Thermal stability of the blends, estimated by TGA, showed desired results, for example, at the 50% weight loss point, the temperature of all St‐PLA/NR blends moved to higher temperatures than neat St‐PLA. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers     

Melt viscoelasticity of biodegradable poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymers

The rheological properties of a series of microbially synthesized poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)s (PHB-HHxs), with varying comonomer (HHx) content, were systematically investigated. Shear viscosities show dependence on the rate of deformation, temperature, molecular weight, and copolymer compositions. The zero-shear viscosity η₀ follows the classical power-law relationship with the weight average molecular weight M_w. The characteristic relaxation time λ, which indicates the onset of shear thinning, ranges from 0.02 to 0.2 s for different PHB-HHxs and is roughly linearly related to η₀. The temperature dependence of rheological properties follows an Arrhenius form. Activation energies for flow E_a are obtained from the slope of the natural logarithm of the shift factor α_T plotted against the inverse of temperature curve, and the values for PHB-HHxs are found to be in the range of 27-36 kJ/mol E_a decreases with HHx content in the copolymer, a trend that can be related to the difference in chemical structure between HHx and HB, according to the method of Vankrevelen and Hoftyzer. A Generalized Maxwell model models the viscoelastic behavior of the PHB-HHx melt well. The value of the plateau modulus obtained suggests a highly entangled configuration. The molecular weight between entanglements M_e decreases from 11,600 to 9400 as HHx content increases from 3.8 to 10.0 mol%. Our results suggest that the presence of propyl groups in HHx increases the steric hindrance of the PHB-HHx chains, thus resulting in increased segmental friction and entanglement density. As a result, viscoelastic parameters for PHB-HHx copolymers, such as η₀ and , are readily tunable by varying the HHx content, making them attractive as “green” substitutes for non-degradable thermoplastics.     

Compatibility study of waste poly(ethylene terephthalate) with poly(vinyl chloride). II

In this study, exploration of possibilities for use of recycled poly(ethylene terephthalate) (PET) in powder form as a filler in the PVC matrix was made. Powdered PET surfaces were modified by plasma to enhance the degree of interaction and, hence, the compatibilities. For modification, a series of different chlorine-containing monomers at two plasma operational conditions selected were used, in addition to the direct use of an oligomer of vinyl chloride. A series of mechanical, thermal, and surface energy analyses made with the composite samples prepared showed that it is possible to improve the properties by employing proper surface modification, which, in some cases, can even lead to synergestic results. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:765–774, 1998     

Melt spinning and characterization of hollow fibers from poly(4-methyl-1-pentene)

In this article, the melt spinning behavior of poly(4-methyl-1-pentene) (PMP) hollow fibers (HF) is examined. The melt spinning trials are carried out on a pilot scale melt spinning plant with different settings while a 10-hole 2c-shaped spinneret is used. It is found that the winding speed mainly affects the outer fiber diameter. The influence of different melt spinning parameters is investigated, in particular temperatures, take-up velocities, and the use of quench air. For this purpose, the shape and crystalline structure of the fibers are analyzed using a light microscope, a scanning electron microscope, and wide-angle X-ray scattering. The shape of the fibers is mainly influenced by the temperature settings in the melt spinning process. As a reasonable lower limit, a melt spinning temperature of 280°C is identified. Concerning the crystallinity, a saturation going along with a slight reduction of the polymer chain orientation is observed at elevated take-up velocities.     

Molecular weight characterization of poly(acrylamide-co-sodium acrylate). I. Viscometry

Mark–Houwink constants for polyacrylamide and poly(acrylamide-co-sodium acrylate) in 0.2M Na₂SO₄ were measured using eight fractionated samples of polyacrylamide and 26 hydrolyzed polyacrylamide samples. The dependence of K and a on the copolymer compositions was found for the range of acrylate content 6 ～ 40 mol %. A relationship between intrinsic viscosity and acrylate content in the form of square root law was found. Molecular weights of copolymer samples with various compositions were estimated using viscometry with Mark–Houwink equations established in this work. The molecular weights of narrow MWD copolymer samples could be measured with an error of ±5%, whereas those of broad MWD copolymer samples with an error of ±8%.     

Physico-chemical characterization of poly(vinyl chloride). I. Solution properties

Poly(vinyl chloride) was fractionated and its solution properties were studied. Calibration of the gel permeation chromatograph was carried out using poly(vinyl chloride) and polystyrene. Empirical correlations were established for the calibration plots.     

Polymer blends containing poly(vinylidene fluoride). Part II: Poly(vinyl esters)

Blends of poly(vinylidene fluoride) PVF₂, with poly(vinyl acetate), PVAc; with poly(vinyl propionate), PVPr; and with poly(vinyl butyrate), PVBu, were prepared by solution blending. Solutions containing PVF₂ with either PVPr or PVBu exhibited phase separation, and it was concluded that neither of these polymers are miscible with PVF₂. Phase separation did not occur with solutions containing PVF₂ and PVAc. Dried samples of this blend system were subjected to differential thermal analysis, dynamical mechanical testing, and visual observations of their melts. From these results, it was concluded that PVF₂ and PVAc are miscible. The detailed results and the structural implications of these observations are discussed.     

Melt grafting of n‐butyl methacrylate onto poly(vinyl chloride): Synthesis and characterization*

The graft copolymerization of n‐butyl methacrylate monomer onto compounded poly(vinyl chloride) was carried out by melt‐mixing process in a Brabender plasticorder (BPCR) using a free‐radical initiator. The reaction conditions such as initiator and monomer concentration, shear rate (rpm), residence time, and temperature were optimized in the mixing head of BPCR attached to a torque rheometer. The graft copolymers were Soxhlet extracted with cyclohexane and were characterized by intrinsic viscosity, FTIR, and ¹³C‐NMR spectroscopy. A maximum of 14% grafting was obtained. The graft copolymer showed significant improvement in processibility and both thermal and mechanical properties. Scale‐up studies of the optimized recipe were carried out in a single‐screw extruder for commercial trials/evaluation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2442–2449, 2004     

Melt blending of polylactide and poly(methyl methacrylate): Thermal and mechanical properties and phase morphology characterization

Blends of polylactide with poly(methyl methacrylate), PLA/PMMA, were prepared by a semi‐industrial twin screw extruder and afterwards were injection molded. Blends were studied using different techniques as Fourier Transform Infrared Spectroscopy (FTIR), Dynamic Mechanical Analysis (DMA), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), and mechanical properties by means of tensile and impact tests, were also studied. This work helped better understanding of apparently contradictory results reported in the literature for PLA/PMMA blends prepared by melt compounding. DSC first heating scan and DMA results showed partially miscible blends, whereas the second DSC heating scan showed miscible blends. For miscible blends, T_g values were predicted using Gordon‐Taylor equation. On the other hand, Small and Van Krevelen approaches were used to estimate the solubility parameters of neat PLA and neat PMMA, and Flory‐Huggins interaction parameter was calculated from solubility parameters. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42677.     

Processing–property interactions in poly(vinylidene fluoride). II. Morphology and property characterization of extruded films

The effects of flow history, processing temperature, and exit draw ratio have been studied for a poly(vinylidene fluoride) resin. Quantification of the stress fields and flow kinematics were described in Part I while, in this publication, attention has been addressed to the evaluation of film properties. Hot-stage and differential scanning colorimetry (DSC) analyses were used to characterize the thermal behavior; polarized light optical microscopy and electron microscopy were used to characterize the morphology; Fourier transform infrared (FTIR) and wide-angle x-ray scattering (WAXS) were used to evaluate crystal structure; and mechanical testing was used to evaluate tensile properties. Extensional melt stresses on the order of 1.4 × 10⁶ dyne/cm² were necessary to induce row-nucleated crystallization in undrawn samples, and in all cases, preorientation of the melt by extensional flow enhanced the efficiency of the α → β transformation with drawing. The various transformations on drawing were as follows: unoriented α to oriented superheatable α phase for draw ratio (DR) < 5; transformation from α to β phase for 5 < DR ≤ 25; transformation to more highly oriented α and β phases, DR > 25.