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.     

Molecular motions in poly(vinyl acetate) revisited. A thermally stimulated current study

The dipolar relaxation mechanisms in poly(vinyl acetate) have been studied in detail using the technique of thermally stimulated currents. The papers published in the literature about this subject are very contradictory, particularly with respect to the assignment of the observed discharges to the corresponding motions at the molecular level. This work aims at clarifying these problems. We detected and characterised three different relaxation mechanisms: (1) a low temperature one (around ?140°C) which was attributed to local internal rotations in the acetate side-groups; (2) a relaxation whose maximum occurs at 42°C, which corresponds to the glass transition relaxation, and shows a compensation behaviour; (3) an upper glass transition relaxation whose maximum appears at 87°C and was attributed to a liquid-liquid transition. These assignments have been made on the basis of the analysis of the behaviour of the samples when submitted to different thermal and electrical treatments.     

Thermal analysis of complex relaxation processes in poly(desaminotyrosyl-tyrosine arylates)

The goal of this study is to better understand the thermal characteristics and molecular behavior of two poly(desaminotyrosyl-tyrosine arylates). These two polymers were chosen from a combinatorial library of polymers developed by changing the type and size of the two substitutable chain locations. The objective of this work was to describe the origin of the complex relaxation processes that have been observed by thermal analysis methods. DSC, TMA and TSC studies were conducted on poly(desaminotyrosyl-tyrosine dodecyl dodecanedioate), poly(DT 12,10), and poly(desaminotyrosyl-tyrosine ethyl succinate), poly(DT 2,2), in film and fiber form. DSC experiments on poly(DT 2,2) show only a glass transition at about 80 °C which is characteristic of an amorphous polymer. The DSC of poly(DT 12,10) shows multiple thermal events indicative of a more complex internal structure. The thermally stimulated current (TSC) analysis results for poly(DT 2,2) indicate a region of molecular mobility at about 80 °C consistent with the T_g from DSC. For poly(DT 12,10) there is a dipole relaxation process observed at about 40 °C. An additional region of mobility at 60 °C for poly(DT 12,10) fibers is observed. The comparison of conventional TSC with a modified TSC procedure suggests that this process represents a spontaneous reorganization of the internal structure of the solid. The comparison of DSC and TSC results suggests that poly(DT 12,10) has two distinct modes of organization with a transition between these modes at about 60 °C. Previously published results indicate that solid state structure formation is related to two different modes of hydrogen bonding in the internal structure of the solid.     

Preparation of diamine-POSS/Ag hybrid microspheres and its application in epoxy resin

Carbon nanowires having different functionality has been synthesized through the template assisted approach using poly(vinyl alcohol) (PVA) as precursor polymer at 400?°C, 600?°C, 700?°C and 800?°C in the absence of any catalyst. Carbon nanowires with a diameter range of about 90?C120?nm have been obtained. Scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy are been adopted to characterize the morphology, thermal properties and chemical configuration of the synthesized samples. Raman spectroscopy indicates carbonization of the samples upto 600?°C. Above that carbon-cluster formation is observed at 700?°C and 800?°C. SEM images show the formation of nanowires in alumite template by infiltration of PVA into the pores at 400?°C. The nanowires produced are very flexible at about 700?°C, above which the nanowires tended to retain their rigidity due to the formation of graphite clusters / crystallites.     

Preparation and properties of a liquid crystalline segmented block copolyester

A segmented block copolyester with a liquid crystalline (LC) “hard block” and poly(tetramethylene glycol) (PTMG) “soft block” was prepared and characterized by intrinsic viscosity [η], by gel permeation chromatography (GPC) for number average molecular weight and molecular weight distribution, by differential scanning calorimetry (DSC), and by dynamic mechanical thermal analysis (DMTA). The “soft block” had a melting transition at about ?30°C and the hard block had a glass transition at about 70°C and a nematic-to-isotropic transition at 260°C. Mechanical testing, which included tensile testing, hysteresis analysis and stress relaxation at small strains, revealed that the block copolyester was a flexible rubbery material with an elongation at break of about 1000% and showed reversible extension below 50% strain.     

Molecular motions and transitions in a poly(p-hydroxystyrene) derivative

The dielectric relaxation mechanisms in a poly(p-hydroxystyrene) derivative have been studied by Thermally Stimulated Depolarization Currents (TSDC) in the temperature range between −160 and 130°C. A broad relaxation was observed at low temperatures, from −160 up to 0°C, which obeyed to the zero entropy approximation. In contrast, the glass transition relaxation showed the usual behavior, a strong departure to the zero entropy prediction. Both relaxations have been studied in detail by the technique of thermal sampling. The thermal behavior of this poly(p-hydroxystyrene) derivative was also studied by Differential Scanning Calorimetry in the temperature range between 20 and 200°C. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1921–1926, 1999     

Thermomechanical behavior of poly(vinyl chloride) in the process of degradation

The thermomechanical behavior of poly(vinyl chloride) (PVC) was investigated during its thermal degradation by using torsional braid analysis. In thermomechanical behavior as a function of temperature, the relative rigidity G_r decreased initially with increasing temperature, then began to increase passing through a minimum at about 200°C, and finally decreased at 340°C. Increase in G_r from 200°C was caused by formation of a conjugated polyene chain accompanied by dehydrochlorination and by crosslinking reaction, and decrease in G_r at 340°C was related to scission reactions of the crosslinking network by oxidation. In the change in logarithmic decrement Δ, three peaks were observed: at 90°C, coinciding with the glass transition of the polymer; at about 200°C, due to the melting transition of crystallites, and at about 300°C, due to a loss of mechanical energy in the rheological transition of the polymer from a liquid state to a glassy state passing through a viscoelastic region. The thermomechanical properties of PVC with different molecular weights were also measured, and the effect of molecular weight G_r and Δ are discussed. In isothermal measurements of the relative rigidity in air, exponentially increasing curves were observed as a function of time. These curves were analyzed kinetically as a first-order reaction, and an activation energy of 22.7 kcal/mole was obtained.     

Synthesis and properties of PMR type poly(benzimidazopyrrolone‐imide)s

PMR type poly(benzimidazopyrrolone‐imide) or poly(pyrrolone‐imide) (PPI) matrix resin was synthesized using the diethyl ester of 4,4′‐(hexafluoroisopropylidene)diphthalic acid (6FDE), 3,3′‐diaminobenzidine, para‐phenylenediamine, and monoethyl ester of cis‐5‐norbornene‐endo‐2,3‐dicarboxylic acid (NE) in anhydrous ethyl alcohol with N‐methylpyrrolidone. The homogeneous matrix resin solution (40–50% solid) was stable for a storage period of 2 weeks and showed good adhesion with carbon fibers, which ensured production of prepregs. The chemical and thermal processes in the polycondensation of the monomeric reactant mixture were monitored by Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy, etc. Thermosetting PPI as well as short carbon fiber‐reinforced polymer composites was accomplished at optimal thermal curing conditions. The polymer materials, after postcuring, showed excellent thermal stability, with an initial decomposition temperature > 540°C. Results of MDA experiments indicate that the materials showed > 70–80% retention of the storage modulus at 400°C and glass transition temperatures as high as 440–451°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1600–1608, 2001     

Synthesis of poly(aryl ether phenylquinoxaline) via Ullmann ether condensation of chlorine-substituted A-B quinoxaline monomers

Summary An improved, less expensive route to a high-performance poly(aryl ether phenylquinoxaline) has been developed. Thus, an isomeric mixture of self- polymerizable (A-B) quinoxaline monomers, 2-(4-hydroxyphenyl)-3-phenyl-6- chloroquinoxaline and 3-(4-hydroxyphenyl)-2-phenyl-6-chloroquinoxaline, was prepared by the condensation of 1,2-diamino-4-chlorobenzene with 4-hydroxybenzil The mixture was polymerized at 200°C in benzophenone containing potassium carbonate and a freshly prepared copper(I)chloride/quinoline catalyst mixture. The polymer obtained displayed an intrinsic viscosity of 1.53 dl/g (m-cresol at 30.0±0.1°C and a glass transition temperature of 252°C (DSC), similar to samples prepared previously from an analogous fluorine-substituted mixture. Received: 13 August 2001/Accepted: 18 September 2001     

Synthesis and properties of novel aromatic poly(ester–amide)s derived from 1,5‐bis(3‐aminobenzoyloxy)naphthalene and aromatic dicarboxylic acids

A new naphthalene‐ring‐containing bis(ester–amine), 1,5‐bis(3‐aminobenzoyloxy)naphthalene, was prepared from the condensation of 1,5‐dihydroxynaphthalene with 3‐nitrobenzoyl chloride followed by catalytic hydrogenation. A series of novel naphthalene‐containing poly(ester–amide)s was synthesized by direct phosphorylation polyamidation from this bis(ester–amine) with various aromatic dicarboxylic acids. The polymers were produced in high yields and had moderate inherent viscosities of 0.47–0.81 dL g^?1. The poly(ester–amide) derived from terephthalic acid was semicrystalline and showed less solubility. Other polymers derived from less rigid and symmetrical diacids were amorphous and readily soluble in most polar organic solvents and could be solution‐cast into transparent, flexible and tough films with good mechanical properties. The amorphous poly(ester–amide)s displayed well‐defined glass transition temperatures of between 179 and 225 °C from differential scanning calorimetry and softening temperatures of between 178 and 211 °C from thermomechanical analysis. These poly(ester–amide)s did not show significant decomposition below 400 °C in nitrogen or air. Copyright © 2004 Society of Chemical Industry     

Synthesis and characterization of novel aromatic-aliphatic poly(amide-imide-imide)s (PAII)

Novel poly(amide-imide-imide)s (PAII) were prepared by polycondensation of a new monomer synthesized from trimellitic anhydride and glutamic acid, followed by reflux condensing with thionyl chloride and several diamines. Polymers and monomers were characterized by ¹H NMR and FT-IR spectroscopy, elemental analysis and mass spectrometry. Inherent viscosities of the resulting polymers were in the range of 17–26 mL g^–1 (M_w 13 400–29 160, polydispersity (M_w/M_n) ca. 1.3–1.7), representing rather low molecular weights. The glass transition temperatures of the polymers were in the range of 210–285°C depending on the structure of diamines, and the thermal stability of the polymers was up to 400°C, comparable with that of polyimides and poly(amide imide)s. All the polymers synthesized are well soluble in aprotic polar solvents such as dimethylformamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone and dimethylacetamide. Particularly, polymers containing oxydianiline and 4,4′-diaminodiphenyl sulfone were quite soluble in m-cresol, pyridine, nitrobenzene and tetrahydrofuran.     

Redox-active and electrochromic aromatic poly(amide-imide)s with 2,4-dimethoxytriphenylamine chromophores

A dicarboxylic acid monomer with two built-in imide rings, namely 4,4′-bis(4-carboxyphthalimido)-2″,4″-dimethoxytriphenylamine, was synthesized and then directly polymerized with aromatic diamines leading to new series of aromatic poly(amide-imide)s (PAIs) containing the redox-active 2,4-dimethoxy-substituted triphenylamine (TPA) unit. These PAIs were highly soluble in many organic solvents and could be solution-cast into flexible and strong films. The polymers showed excellent thermal stability, up to 400 °C, and displayed glass transition in the range of 266–294 °C. It is noted that the PAIs have an ambipolar character (n- and p-doping processes) and are capable of repeated, stable electrochemical cycling between a neutral form and an oxidized state. For the PAIs containing the TPA unit on both the imide and amide sides, they showed two pairs of reversible oxidation couples and displayed multi-colored electrochromic behavior: pale yellow in the neutral state, yellowish-green in the semioxidized state, and cyan in the fully oxidized state.     

Poly(phenylquinoxaline-imide-amide)s containing perfluoroisopropylidene units

Poly(phenylquinoxaline-imide-amide)s have been synthesized by solution polycondensation of aromatic diamines containing preformed phenylquinoxaline units with diacid dichlorides incorporating preformed imide rings and perfluoroisopropylidene units. These polymers show high thermal stability; they decompose above 400°C and have glass transition temperatures in the 225–290°C range. Comparison of these compounds with related heterocyclic polymers leads to the conclusion that the decomposition of the former ones begins with the destruction of amide groups. Films prepared from polymer solutions showed good electrical insulating properties, comparable to those of a standard film (Film H). The highest quality of these poly(phenylquinoxaline-imide-amide)s is their remarkable solubility in polar aprotic solvents, which is very important for practical applications.     

Synthesis and characterization of poly(vinyl 2,4,6‐trinitrophenylacetal) as a new energetic binder

Poly(vinyl alcohol) was modified by an aldehyde acetal reaction with 2,4,6‐trinitrophenylacetaldehyde to give a new energetic polymer poly(vinyl 2,4,6‐trinitrophenylacetal) (PVTNP). The structure of PVTNP was characterized by elemental analysis, ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectra. The glass‐transition temperature of PVTNP was evaluated by differential scanning calorimetry (DSC), and the thermal stability of PVTNP was tested by differential thermal analysis (DTA) and thermogravimetric analysis (TGA). DSC traces showed that the PVTNP polymer had one single glass‐transition temperature at 105.3°C. DTA and TGA curves showed that the thermooxidative degradation of PVTNP in air was a three‐step reaction, and the percentage of degraded PVTNP reached nearly 100% at 650°C. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and properties of nonlinear optical polymers based on poly(ether imides) for electrooptical devices

Summary : Nonlinear optical poly(ether imides) with an adequate thermal stability has been synthesized by direct coupling of hydroxy poly(ether imides) and NLO chromophores with a quantitative yield. The resultant amorphous NLO poly(ether imides) exhibited good solubility in common organic solvents, providing optical-quality thin films by spin coating. The glass transition temperatures of the polymers are at around 180 °C. The electrooptic coefficients (r₃₃, @1.3μm) of PEI-DR1 was 12.3 pm/V with an electrical poling field of 100 V/μm and it decayed about 10 % over 10 months at 90 °C under atmospheric conditions. Received: 23 February 1999/Revised version: 26 March 1999/Accepted: 29 March 1999     

Preparation and characterization of hydrophilic temperature‐dependent polyurethane containing the grafted poly(N‐isopropylacrylamide)

The polyurethane (PU) structure is modified with dimethylolpropionic acid (DMPA) and poly(N‐isopropylacrylamide; poly[IPA]) to prepare hydrophilic temperature‐dependent PU that is investigated with reference to the degree of crosslinking, thermal properties of soft segment, tensile and shape memory performance, hydrophilic conversion of surface, and temperature‐dependent water swelling and water vapor permeability (WVP). The thermal properties of soft segment (melting, crystallization, and glass transition) are significantly affected by poly(IPA). Breaking tensile stress also increases with increasing IPA monomer content due to crosslinking effect but breaking tensile strain does not significantly decrease with increasing IPA monomer content. Shape recovery capability at 10°C steeply inclines to over 90% from 46.9% for unmodified PU by the grafting of poly(IPA), whereas shape retention at ?25°C does not decrease below 90% with the increase in IPA content. Poly(IPA)‐grafted PU can display temperature‐dependent control of water swelling and WVP due to transformation of the grafted poly(IPA) depending on the surrounding temperature. POLYM. ENG. SCI., 59:1719–1728 2019. © 2019 Society of Plastics Engineers     

Blends of Poly(ether imide) and Styrene Sulfonic Acid Based Polymer: Thermal,Mechanical and Ionic Conduction Behavior

Dense membranes based on poly(ether imide) (PEI) and poly(styrene sulfonic acid-co-maleic acid) (PSSAMA) was obtained by extrusion and compression molding. Blends with different PSSAMA content (1, 3, 5, and 10 wt%) were prepared. Their morphology was investigated by scanning electron microscopy (SEM) and their thermal properties by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic-mechanical analysis (DMA). Two glass transition temperatures (T_g) (100 and 216°C) appeared when high contents of PSSAMA were added to PEI, indicating that the polymers form an immiscible system. TGA curves showed that the first weight loss occurred above 400°C for all blends, indicating a good thermal stability. Water uptake measurements have shown that the membranes presented low swelling when compared with Nafion®. The proton conductivity of the membrane with 10 wt% of PSSAMA obtained bv impedance measurements was 0.006 × 10^?2 S·cm^?1.     

Poly(amide‐ester)s derived from dicarboxylic acid and aminoalcohol

A series of alternating aliphatic poly(amide‐ester)s, derived from dicarboxylic acid and aminoalcohols, were obtained by polycondensation in melt. All poly(amide‐ester)s were characterized by FTIR and ¹H/¹³C‐NMR spectroscopies. The synthesized polymers showed an inherent viscosity ranging from 0.4 to 1.0 dL g^?1. Thermal analysis showed melting points within the range 100–115°C and glass transition within the range 30–60°C. Decomposition temperatures were more than 200°C higher than the corresponding melting temperatures. The polymers can thus be processed from the melt. The processed polymers were partially crystalline with good thermal stability. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 362–368, 2005     

Thermally stimulated creep of polyethylene,polypropylene, copolymers,and blends

The technique of Thermo Stimulated Creep (TSC) has been applied to the study of anelastic properties of polyethylene, polypropylene, their copolymers and blends. In the temperature range ?200 to 100°C, complex TSC peaks were observed in all samples, namely around 0°C, about the same temperature as for the homopolypolymer polypropylene. By applying “fractional stresses”, with a convenient choice or the loading program, these peaks have been experimentally resolved. Two components can be distinguished: 1. The “low temperature” component is characterized by mechanical retardation times following a compensation law. It has been attributed to microbrownian motions of polypropylene sequences liberated at the glass transition of the “true” amorphous regions. 2. The “high temperature” component which is influenced by thermal treatment has been assigned to microbrownian motions of polypropylene sequences liberated at the glass transition of the “constrained” amorphous regions. In block polymers, an additional TSC peak is observed around ?50°C: it has been associated with the glass transition of ethylene-propylene-rubber (EPR) interphase. The coupling of this interphase with polyethylene and polypropylene phases is insured by diffusion of some ethylene and propylene sequences in-EPR. At about ?140°C, a TSC peak associated with the low temperature component of the glass transition of polyethylene can be distinguished in all the materials studied.     

Influence of the thermal history on dielectric properties of poly(vinyl chloride)

In this paper, we report dielectric permittivity and loss of poly (vinyl chloride) samples that have received three different thermal treatments: (a) as received, (b) quenched from 110°C to 20°C and (c) slow cooled at 5°C/h. There are several observations: first, the secondary (β) loss peak-is not representative of a simple mechanism of transition, in agreement with results of other authors (10), second, in the glass transition zone, there are clearly two peaks (α₁ and α₂)—α₁, is a typical peak of an amorphous glass transition; the second, α₂, has possibly a crystalline origin—and, third (and the most interesting fact), there is an increase of the loss tangent in the intermediate zone between α and β peaks showing a new relaxational peak with high activation energy (70 Kcal/mole), in agreement with dynamic mechanical results (6).