Agnieszka Marcinkowska

Ionic liquid – containing ionogels by thiol–ene photopolymerization. Kinetics and solvent effect

Photopolymerization of monomers in ionic liquids (ILs) leads to the formation of conducting ionogels. In the frame of our continuing investigations in this field we report the first example of thiol–ene polymerization in ILs. The work focuses on the polymerization kinetics and reaction mechanism. The model system is based on a difunctional thiol and a divinyl ether (to exclude ene homopolymerization) with spacers built from oxyethylene units. The photo-initiated polymerization was carried out in the presence of various amounts of imidazolium-based ILs and was compared to the polymerization in non-ionic solvents. It was found that the addition of the solvents to the investigated system accelerates the reaction; however, the reaction occurs faster in non-ionic solvents than in ILs. The accelerating effect is associated with the additional stabilization of a partial charge separation in the transition state and its magnitude is closely related to the Kamlet–Taft β parameter which describes the hydrogen bond accepting ability of the solvent. In the case of ILs, the stabilizing effect is exerted by the ILs anion. However, the imidazolium cation interacts with the ether oxygen of the monomer decreasing its stabilizing influence on the transition state (which is related to the Kamlet–Taft α parameter representing the hydrogen bond accepting ability). The knowledge of the presented relationships provides a tool for designing thiol–ene systems containing ILs.

Brillouin study of photopolymerization process of two-monomer systems

The results of Brillouin scattering investigations of two-component system: 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane/polyethylene glycol methacrylate (bis-GMA/PEGMM) containing 0, 30, 50, 70, 85 and 100 mol% of PEGMM are presented. For the first time the Brillouin spectroscopy was used to monitor the progress of the polymerization process. The polymerization was initiated by ultraviolet radiation (λ=365 nm), at temperature 20°C and 40°C. Some of the physical parameters characteristic for this system such as velocity V, adiabatic compressibility β(ad) and attenuation coefficient α of the acoustic waves have been estimated from Brillouin spectra as a functions of the polymerization time. The obtained results have been discussed in terms of changes of the elastic properties of the two-component system occurring during polymerization process and their dependence on bis-GMA/PEGMM system composition.

The Influence of Deep Cryogenic Treatment on Transformation during Tempering of Quenched D2 Steel. Studies oF XRD, Structures, DSC, Dilatometry, Hardness and Impact Energy

The study analyses of influence of cryogenic treatment on the resultant structures, the development of changes during tempering and the charcteristic obtained. It was observed that cryo treatment affects the changes through: a significant reduction in retained austenite content, gradual reduction in value of martensite tetragonality and an increase in the number of carbon atoms in transformations during tempering. The consequence of the transformations taking place during cryogenic treatment is precipitation of η – carbide during low tempering instead of ε – carbide. The number of η – carbides precipitated is higher than that of ε – carbide. This affects the functional properties of steel products. Key words: cryogenic processing, supersaturation, dilatometry, DSC, ageing.

Methacrylate-based polymer blends containing oligomeric 1,2-polybutadienes

Partly miscible polymer blends with semi-IPNs structure built from polydimethacrylate networks and hydroxyl-terminated liquid polybutadienes with predominant 1,2-structure (LBH) were prepared by photopolymerization method. Photopolymerization kinetics of dimethacrylate–LBH mixtures were monitored by DSC technique under isothermal conditions. Kinetic curves and related parameters, like polymerization rate and degree of double bond conversion were determined as functions of dimethacrylate structure, LBH molecular mass, and its content in the mixture as well as polymerization temperature. The photopolymerization kinetics and activation energy for the polymerization rate were discussed taking into account the phase separation occurring during the curing reaction. The extent of phase separation (based on Tg’s measurements) depended on LBH content and dimethacrylate chemical structure. The effect of LBH content on hardness of polymer blends was also examined.

POSS functionalized with mixed fluoroalkyl and methacryloxy substituents as modifiers for UV-curable coatings

UV-curable acrylate-based coatings were modified by copolymerization of base resins with polyhedral oligomeric silsesquioxanes (POSS) containing four methacryloxy and four fluoroalkyl substituents in one molecule (4M4F-POSS), giving hybrid organic–inorganic coatings. Such modifiers are covalently linked to the matrix (by methacryloxy groups) preventing them from exuding onto the surface, and fluoroalkyl substituents (along with the POSS cages) improve scratch resistance and hydrophobicity. Two types of POSS derivatives differing with the length of the fluoroalkyl chain were tested. These compounds were applied in two types of formulations: wood-derived and aluminum substrates. Modification of the coatings led to a substantial increase in the hydrophobicity and enhanced scratch resistance after incorporation of only 1.5 wt% of the modifier. Water contact angle increased by up to 14–160% of the initial value, whereas the scratch hardness for the first surface stripping improved by about 30–170% in the presence of 5 wt% of POSS. The latter can be associated with the increase in the surface sliding properties caused by the presence of fluoroalkyl substituents of the modifier. Better results were obtained for POSS containing shorter fluoroalkyl substituents.

Elastic properties of some selected two-monomer systems as studied by Brillouin spectroscopy.

We present results obtained by Brillouin scattering method for four two-component systems comprising of a high viscosity monomer and a low viscosity monomer. The monomers used were crosslinking (divinyl) or linear (monovinyl) ones. The investigated systems were: divinyl/divinyl-bis-GMA/TEGDM; divinyl/monovinyl-bis-GMA/PEGMM; monovinyl/divinyl-bis-MGMA/TEGDM and monovinyl/monovinyl-bis-MGMA/PEGMM; they were formulated at various molar ratios. The measurements have been performed in temperature range 293-353 K. The following physical parameters characterizing the investigated systems were estimated: hypersonic velocity V, attenuation coefficient α and adiabatic compressibility β, all as a function of temperature and monomer molar ratio. The obtained results have been discussed in terms of the influence of the system composition and viscosity on their elastic properties. Speed of changes of the adiabatic compressibility β as derivative have been also discussed in terms of both, the temperature as well as the component of molar ratio.

Brillouin spectroscopy studies of two-component polymerizable liquid system: 2,2-Bis[4-(2-hydroxymethacryloxypropoxy)phenyl]propane/benzyl methacrylate

Brillouin spectroscopy was used to investigate viscoelastic properties of a two-component system consisting of a high viscosity liquid (HVL) and a low viscosity liquid (LVL), both able to polymerize. The model liquids were: 2,2-bis[4-(2-hydroxymethacryloxypropoxy)phenyl]propane (abbreviated as bis-GMA, HVL) and benzyl methacrylate (BzMA, LVL). The viscosity of the system was regulated by changing the monomer ratio. Hypersonic velocity and attenuation coefficient were investigated in a temperature range covering viscoelastic relaxation process. The dependence of the longitudinal viscosity on the system composition was determined. Additionally, the Brillouin studies were accompanied by some supplementary experimental methods, like low frequency shear viscosity measurements and observations of phase transitions by differential scanning calorimetry (DSC). The investigated monomer mixtures were then polymerized in a light-induced process and the polymerization kinetic curves were measured to find the possible correlation between the viscoelastic properties of the monomer mixture (as observed by Brillouin spectroscopy) and the polymerization course.

The Influence of Deep Cryogenic Treatment after Supersaturation of Al 4.7% Cu Alloy on Transformation during Ageing. Studies of Dilatometry, DSC, Hardness and XRD

Studies of dilatometry, DSC, hardness and XRD have shown that a low temperature cryogenic treatment immediately after supersaturation affects changes of structure and properties taking place during ageing after supersaturation. The third peak visible on DSC diagrams for samples conventially treated disappears on DSC diagrams for deep cryogenically treated samples, and the intensity of the two first peaks on DSC diagrams of deep cryogenically treated samples is a few times lower than on diagrams for conventionally treated samples. The dissolution process for precipitation of Al2Cu in conventionally treated samples progresses faster. Hardness of samples aged after a deep cryogenic treatment within the range of 175-220 oC for more than 60 minutes was higher than of those conventionally treated; at higher ageing temperatures (275-350 °C) the differences in hardness were smaller.