M. Still

Bio: M. Still is an academic researcher from Åbo Akademi University. The author has contributed to research in topics: Isomerization & Maleic acid. The author has an hindex of 2, co-authored 2 publications receiving 43 citations.

Synthesis, characterization and crosslinking of functional star-shaped poly(ε-caprolactone)

Abstract: Star-shaped low molecular weight poly(e-caprolactone)s (PCLs) were synthesized and functionalized with crosslinkable terminal groups for subsequent crosslinking. The e-caprolactone (CL) prepolymers were polymerized by ring-opening in the presence of polyglycerine (PGL) as an initiator (1, 3 and 5 mol%) and Sn(II)2-ethylhexanoate as a catalyst. Characterization of the prepolymer by 13C/1H nuclear magnetic resonance (NMR) spectroscopy, size exclusion chromatography (SEC), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) revealed a six-armed star-shaped structure for the prepolymer with the molecular weight controlled by the ratio of PGL and CL. Functionalization of the hydroxyl-terminated prepolymer was carried out with maleic or itaconic anhydride. In both cases, the characterization of the functionalized prepolymer showed that the hydroxyl groups were completely substituted. The functionalized PCLs were successfully crosslinked through the reaction of double bonds. The crosslinking was induced either thermally with organic peroxide or photochemically with a photosensitive initiator. Characterization of the crosslinked PCLs by Soxhlet extraction, DSC and FTIR showed that the itaconic double bond was much more reactive in thermal crosslinking than the maleic double bond. Thus, the crosslinked prepolymers that were functionalized with itaconic double bonds achieved a gel content of about 90%. A gel content of 100% was achieved with several compositions where crosslinking agents were employed. © 2002 Society of Chemical Industry

Kinetic model for the increase of reaction order during polyesterification

Abstract: A simple two-parameter model was proposed for the kinetics of polyesterification reactions. The kinetic model is based on the true reaction mechanism, i.e. on the shift of the ionic equilibria in the carboxylic acid (RCOOH) protolysis during the reaction, and on the bimolecular nucleophilic substitution of the protolysed acid with the alcohol (R′OH). The model describes the increase of the reaction order with respect to the carboxylic acid from 1 to 2 as the esterification proceeds. The rate equation r = kc COOH n c OH was used, where n is a function of the carboxylic acid concentration. The kinetic model was tested with the classical data of Flory obtained for diethylene glycol–adipic acid and the lauryl alcohol–adipic acid reactions. The model provided an excellent description of the data over the entire range of conversions of the carboxylic acids and it can be extended to new polyesterification systems.

Kinetic model for the homogeneously catalyzed polyesterification of dicarboxylic acids with diols

Abstract: A generally applicable stoichiometric and kinetic model was developed for the polyesterification of unsaturated dicarboxylic acid with diols in the presence of a homogeneous acid catalyst. The model also incorporates, besides the esterification, the cis-trans isomerization and the double-bond saturation reactions. Rate equations based on plausible mechanistic reaction steps were derived, and the parameters of the rate equations were determined with nonlinear regression analysis using the polyesterification of maleic acid with propylene glycol at 150-190 °C as a demonstration system. Comparisons of the model predictions with the experimental data showed that the approach is useful in predicting the polyesterification kinetics and the product distribution.

Synthesis and Kinetic Modeling of Biomass-Derived Renewable Polyesters

Abstract: The biomass‐derived polyesters poly(1,3‐propylene 2,5‐furandicarboxylate) (PPF), poly(1,3‐propylene succinate) (PPS) and poly(1,3‐propylene 2,5‐furandicarboxylate‐co‐1,3‐propylene succinate) (PPFPS) have been synthesized via a two‐step process involving polycondensation and azeotropic distillation. The kinetic parameters were obtained by fitting the experimental data from a batch polymerization reactor to three different kinetic models for polyesterification reactions. The activation energies of the all monomer systems were obtained by Arrhenius plots. Given the increasing availability of biomass‐derived monomers their use in renewable polyesters as substitutes for fossil fuel derived chemicals becomes a distinct possibility. The kinetic modeling of the uncatalyzed polyesterification reactions will enable further integrative process simulation of the studied bioderived polymers and provide a reference for future practical study or industrial applications of catalyzed polyesterification reactions and other bioderived monomer systems. © 2016 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2876–2887