AbstractInvestigations of glass transition phenomena were carried out on vinylidene chloride—acrylonitrile copolymers, purified commercial samples of known composition. With a view to analyzing this effect, the following physical parameters were investigated: specific volumeVs,25,Tg, and volume expansion coefficients αL, αg, and Δα. The experimental results were analyzed on the basis of semiempirical and theoretical equations describing transitions to the glassy state. It was found thatTgdependence on weight fractionC2of acrylonitrile may be described by Wood's equation, withk= 5.88. Applying Gibb's and Kanig's theories as well as relations given by Hirai and Small, the energies associated with intermolecular interactions (A*AB,E0,Eh, CED), and intramolecular interactions (stiffness energy ε) were calculated for copolymers of different composition. The copolymerTgwas found, above all, to depend on the stiffness energy ε, which increases with increasing acrylonitrile content in the co
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