Per Nyholm

Melt and solution processable poly(3-alkylthiophenes) and their blends

Abstract We report on the properties of melt and solution processable poly(3-alkylthiophenes), P3AT, and on the fabrication of electrically conducting polymer blends consisting of P3AT, specifically poly(3-octylthiophene), POT, and a thermoplastic matrix polymer made using ordinary melt processing techniques. The POT used in this work was synthesized using two different chemical polymerization techniques. Films made from as-synthesized POT powder, either by solution casting or melt processing techniques were found to be easily doped by electron acceptors to conductivities of 20–30 S/cm. Blending of POT with thermoplastics such as ethylenevinylacetate copolymer, EVA, in the molten state yields polymer blends with excellent mechanical properties that might be doped to conductivities exceeding 1 S/cm.

Conducting polymer blends

Abstract We report the production and properties of electrically conducting polymer blends utilizing the melt-processability properties of high molecular weight poly(3-octylthiophene), POT. We have found that polymer blends produced by mixing appropriate amounts of POT with a variety of thermoplastic matrix polymers have excellent mechanical properties and that they can be doped to yield electrically conducting polymer blends with conductivities exceeding 1 S/cm.

Self-organized cross-linked phenolic thermosets: thermal and dynamic mechanical properties of novolac/block copolymer blends

Abstract We have recently demonstrated a concept to prepare self-organized spherical, cylindrical and lamellar nanostructures of phenolic thermosets by blending novolac and poly(2-vinylpyridine)- block -poly(isoprene), i.e. P2VP- block -PI, followed by thermal curing by hexamethyltetramine (HMTA) [Macromolecules 34 (2001) 3046]. In the present work, hydrogen bonding, dynamic mechanical properties and glass transition temperatures are investigated using Fourier transform infrared spectroscopy (FTIR), dynamic mechanical spectroscopy (DMA) and differential scanning calorimetry (DSC). Even after curing, FTIR shifts indicate hydrogen bonding between the hydroxyl groups of novolac and nitrogens of P2VP, thus promoting the self-organization. DMA shows that the storage E ′ and loss moduli E ″ do not change considerably as PI forms the spherical or cylindrical phases. A slightly larger drop takes place in the lamellar phase. In agreement with the self-organization, a separate glass transition temperature of PI is observed at ca. −62°C. Based on hydrogen bonds that tolerate the thermal curing and the possibility to tailor the self-organized morphologies, it is suggested that the properties of phenolic thermosets might be tailored in a systematic way, upon blending with proper block copolymers.

Micro- and Macrophase Separation in Phenolic Resol Resin/PEO-PPO-PEO Block Copolymer Blends: Effect of Hydrogen-Bonded PEO Length

We demonstrate microphase-separated thermosets based on blends of phenolic resol resin and poly(ethylene oxide)-block-poly(propylene oxide)-block- poly(ethylene oxide) (PEO-PPO-PEO), i.e., so-called Pluronics. Three triblock copolymers are used (PE 9200, PE 10300 and PE 9400) where the molecular weights of the PPO blocks are nearly equal and the weight fractions of the PEO blocks f PEO are 0.20, 0.30 and, 0.40, respectively. The blends are prepared in a particularly straight-forward way using aqueous solutions and thermal crosslinking. Structure formation is characterized using transmission electron microscopy and small-angle X-ray scattering. PPO turns out to be sufficiently repulsive to allow microphase separation in the bulk crosslinked phase and the tendency for macrophase separation upon curing is reduced due to the hydrogen bonding between the PEO and resol. The weight fraction of PEO-PPO-PEO in the present blends has been limited to a relatively small value, i.e., 20 wt.-%, and spherical microphase-separated structure is observed for f PEO = 0.40 with a long period of the order 120 A. Macrophase separation manifests upon curing if the weight fraction of the PEO blocks is smaller, i.e., f PEO = 0.30 or f PEO = 0.20. In addition, in order to prevent macrophase separation, the molecular weights of PEO blocks and resol resin before curing are of the same order. In that respect, the system behaves qualitatively similar to the corresponding thermoplastic homopolymer/ block copolymer blends.

Kinetics of melt polymerization of maleic acid phthalic acids with propylene glycol

Abstract The kinetics of melt polymerization of maleic anhydride and phthalic anhydride with propylene glycol was studied in a laboratory-scale batch reactor operating at 160–220°C and at atmospheric pressure. Phthalic and maleic anhydrides are suitable model molecules for the polyesterification studies, since in the polymerization of phthalic anhydride only the esterification reaction takes place, but in the polymerization of maleic anhydride the double bonds isomerize and become partially saturated by the alcohol. A kinetic model was developed which included the polyesterification, isomerization and double bond saturation during the polymerization. The kinetic model was based on the principle of equal reactivities of the functional groups. The rate equations were coupled to the reactor mass balances, in which the change of the reaction mass due to water evaporation was included. The rate parameters for esterification, isomerization and double bond saturation were estimated from the experimental data by using nonlinear regression analysis. The kinetic model described well the polymerization data of maleic and phthalic anhydrides.

Synthesis and characterization of conducting polymer blends of poly(3-alkylthiophenes)

Abstract Poly(3-alkylthiophenes) (alkyl > butyl) are soluble in several common organic solvents and, furthermore, are melt-processable at temperatures below 200°C. They can be blended with thermoplastics and elastomers in the molten state using a Brabender, blow molding or extrusion molding, or they can be hot-pressed on a substrate. After doping these blends can reach conductivities as high as high as 1 S/cm. We have studied the chemical and physical properties of poly(3-octylthiophenes) (POT), including how the polymerization route affects the molar mass, how the POT content in the blends or doping time affect the conductivity and how stretching affects the conductivity of POT and its blends.

Kinetic model for main and side reactions in the polyesterification of dicarboxylic acids with diols

A rate model based on a reaction mechanism was proposed for the melt polyesterification of dicarboxylic acids with diols for the case that no catalyst is added. The model includes the esterification, the cis-trans isomerization and the double bond saturation reactions. All three reactions are acid catalyzed. The overall reaction order of the main reaction increases with conversion due to a shift of the ionic equilibria in the liquid phase. This increase of the reaction order was described with a semi-empirical function. Experiments were carried out for the esterification of maleic acid with propylene glycol at 160–220°C in a laboratory scale batch reactor. The derived rate model successfully described the isomerization of maleic acid to fumaric acid, the saturation of the double bonds, and the polyesterification of maleic and fumaric acids. The model included two parameters for each of the three types of reactions taking place simultaneously.

Polyesterification kinetics of complex mixtures in semibatch reactors

Abstract A systematic stoichiometric and kinetic model was developed for the acid-catalysed polyesterification of unsaturated dicarboxylic acids and mixtures of dicarboxylic acids. The model was based on a rigorous treatment of the functional groups and their reactions: esterification, cis–trans isomerization and double-bond saturation through Ordelt reaction. The model was applied on the polyesterification of maleic and phthalic acids with ethylene glycol, propylene glycol, diethylene glycol and dipropylene glycol in a semi-batch reactor at 160–195°C. Kinetic and thermodynamic parameters included in the model were estimated with non-linear regression. It was found that important simplifications can be introduced: the rate constants of the different esterification and isomerization reactions can be set equal, whereas it was necessary to treat the different double-bond saturation reactions with individual rate constants. A comparison of model predictions with experimental data revealed that the proposed kinetic treatment is relevant for polyesterification of complex mixtures.

Determination of impurity effects of solubility and processability of poly(3-octyl thiophene)

Abstract Impurities in poly(3-octyl thiophene) negatively affect the solubility and mouldability of the polymer. To ensure good melt processability and solubility the polymer has to very pure. The structure of the polymer and the stability of the undoped polymer was also studied.

Dynamic modelling of simultaneous reaction and distillation in a semibatch reactor system

A dynamic model for a system containing a semi-batchwise operating reaction vessel connected to a distillation unit was developed. The approach consisted of kinetic equations for the reactions as well as a dynamic model for the distillation unit. As an example reaction, the catalyzed polyesterification of maleic acid with propylene glycol was used. The kinetic and the mass transfer parameters at 170°C were estimated from experimental data. The fit of the model to the data indicated that the approach is suitable for the description of semibatch liquid phase reaction-separation systems.