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Putative role of attractive and repulsive forces in the glass transition

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Abstract At a given temperature a balance between repulsive and attractive molecular forces determines liquid density. As temperature is lowered, attractive forces increase, but eventually saturate and asymptote to a… Click to show full abstract

Abstract At a given temperature a balance between repulsive and attractive molecular forces determines liquid density. As temperature is lowered, attractive forces increase, but eventually saturate and asymptote to a near fixed value. At saturation, the attractive/repulsive force balance stabilizes the liquid density, which thereafter becomes effectively temperature independent. Configurational entropy also saturates, but at a much lower temperature. Once entropy begins to saturate, it converges to zero at absolute zero. There is no second order phase transition nor is there a divergent temperature above absolute zero predicted for glass relaxation phenomena. Using a phenomenological argument, it is shown that the relaxation time for volume relaxation varies inversely with configurational entropy. Stoichiometric electron density is proposed as a metric for repulsive force strength, which was determined at T g and averaged 0.61 ± 0.03 mol/cc for 15 polymers that contain oxygen and 0.53 ± 0.02 mol/cc for 7 hydrocarbon polymers. Qualitatively, similar polymer liquids that pack to higher electron densities at a given temperature are expected to experience a glass transition earlier as temperature is lowered. For certain polymer types, the glass transition appears to be an isoelectronic state.

Keywords: temperature; transition; glass; putative role; attractive repulsive; glass transition

Journal Title: Polymer
Year Published: 2018

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