An addition scheme of heat capacities of linear macromolecules. Carbon backbone polymers

Abstract

It is shown that heat capacities of linear macromolecules consisting of all-carbon singlebonded backbones can be calculated from the appropriate contributions of substituted carbon atoms to a precision of about -0.2 + 2.5 % (155 data points), which is similar to the experimental precision. Heat capacity contributions of 42 groups are given over the full range of measurement and reasonable extrapolation. The quality of the addition scheme is tested on 16 series of measurements on homopolymers, copolymers and blends. The addition scheme works for all these different states of aggregation of the constituent groups. The basis of the addition scheme is discussed.The possible additivity of heat capacities of different constituents of linear macromolecules has been a topic of long standing interest in our laboratory. A first attempt to establish an addition scheme was published in 1969 [1]. Based on literature data on 30 polymers, it could be shown at that time that from 60 K to the glass transition temperature additivity seemed to exist with an accuracy of 4-5%. In the meantime, our collection of heat capacities of polymers has grown into the ATHAS Data Bank with data on about 100 polymers [2], During the collection of the data bank it became clear that even polymer melts may show additivity [3]. Of particular interest was that copolymer heat capacities could be generated from the heat capacities of the homopolymer constituents [1]. Heat capacities of multiphase polymers, such as partially crystallized polymers [4] and phase separated block copolymers [5] and blends [6] could also be analyzed by comparison with heat capacities derived from additivity of the components [7]. Even the increase in heat capacity at the glass transition was found to be additive and empirically predictable in terms of the rigid atomic groupings, "beads", in the macromolecule [8].

Heat capacity of solid-state biopolymers by thermal analysis

“…It was also developed in the ATHAS laboratory. 22 This treatment is particularly useful for the description of the heat capacity of solid copolymers above 100 K, and for liquid polymers over the whole temperature range. The empirical addition scheme was first tested on four copoly(amino acid)s by simply adding the homopolymer heat capacities in the proper molar ratios of their compositional content.…”

Heat capacity of poly(lactic acid)

“…Using the addition scheme developed for the ATHAS [26], the total heat capacity of liquid PLA can be obtained from contributions of the various structural groups as…”

An addition scheme of heat capacities of linear macromolecules

“…In the first paper [1] we could show that for macromolecules with single-bonded carbon atoms in the backbone there exists additivity in heat capacity almost within the experimental precision. For the solid state this additivity is limited in the low temperature range (below 30-50 K) due to non-additive heat capacity contributions based on intermolecular forces.…”