AbstractsChemistry

The goal of this thesis is to investigate the by Gainaru et al. [2013] newly discovered low frequency mechanical crossover observed in monohydroxy alcohols by diluting neat 2-ethyl-1-hexanol (2E1H) with squalane. The complex shear modulus is being measured using a PSG transducer, developed by Christensen and Olsen [1995] at Roskilde University, that allows measurements with frequencies ranging from 10^(-3) - 10^6 Hz. From the assumption that monohydroxy alcohols can be described as shortchain polymers, a model proposed by Bo Jakobsen based on an addition of the Maxwell and the Rouse model from Gray et al. [1977] is being investigated and compared to existing mechanical data of 2E1H. The model is fitted to data for the monohydroxy alcohol 2E1H obtained from Gainaru et al. [2013], indicating that monohydroxy alcohols may be described as short-chain polymers. The three investigated properties of the liquids are low frequency crossovers, the broadness of the alpha-peaks, and the low frequency viscosities. It is concluded that the experimental equipment at NSM Roskilde University needs to be optimized with a wider shear modulus and frequency measuring range, to be able to observe crossovers in solutions of 2E1H and squalane. The broadest alpha-peak is observed for 0.353 mole fraction squalane in 2E1H, indicating a hindering in the forming of H-bonds at relatively low concentrations of squalane. An extra contribution to the viscosity is observed for both liquids and intermediate solutions. By comparing data of solutions of 2E1H and squalane with experimental data from the Glass & Time data repository, it is suggested that a broad alpha-peak and an extra viscosity contribution are generic for monohydroxy alcohols and possibly also polymers of low molecular weight. Similar properties are observed for liquid squalane, which in addition shows a strong temperature dependence, comparable to the structurally similar polymer polybutadiene (PB20).