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Calorimetric study of tetrahydro‐1,3‐oxazin‐2‐one and poly(oxy‐1,3‐propanediyliminocarbonyl), and the polymerization/depolymerization equilibrium
Author(s) -
Lebedev Boris V.,
Smirnova Natal'ya N.,
Kiparisova Elena G.
Publication year - 1997
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.1997.021980104
Subject(s) - depolymerization , polymerization , isothermal process , monomer , heat capacity , chemistry , polymer , atmospheric temperature range , thermodynamics , standard enthalpy of formation , polymer chemistry , analytical chemistry (journal) , organic chemistry , physics
In adiabatic vacuum and dynamic calorimeters the temperature dependence of the heat capacity C p 0 of tetrahydro‐1,3‐oxazin‐2‐one (THO) and poly(oxy‐1,3‐propanediyliminocarbonyl) (PTHO) was studied between 5 and 500 K. The melting temperature of the monomer and the polymer, the enthalpies of melting of THO and the glass transition temperature of PTHO were determined. In a calorimeter with a static bomb and an isothermal shield the energies of combustion Δ U comb of the monomer and the polymer were measured. From the experimental data the thermodynamic functions C p 0 , H 0 ( T ) – H 0 ( O ), S 0 ( T ), G 0 ( T ) – H 0 ( 0 ) were calculated in the range of 0 to 450 K, and enthalpies of combustion Δ H comb 0 and thermochemical parameters of formation Δ H f 0 , Δ S f 0 , Δ G f 0 of the compounds studied were estimated at T = 298.15 K and standard pressure. The results obtained were used to estimated the thermodynamic characteristics of the equilibrium of THO polymerization in bulk (Δ H pol 0 , Δ S pol 0 , Δ G pol 0 ), with opening of the six‐membered ring and formation of the linear polymer PTHO, in the range 0 to 450 K. It was found that the Δ G pol 0 values are always negative and change from −18 kJ · mol −1 at 0 K to −14 kJ · mol −1 at 450 K. Thus, the process equilibrium is everywhere shifted towards the formation of the polymer. The upper (ceiling) limiting temperature of THO polymerization in bulk at standard pressure is T ceil = 750 K, that is, considerably higher than the temperature of the onset of the thermal polymer decomposition (450 K).