THERMODYNAMIC CHARACTERIZATION OF INTERPENETRATING POLYMER NETWORKS

Citation
Vp. Privalko et al., THERMODYNAMIC CHARACTERIZATION OF INTERPENETRATING POLYMER NETWORKS, Polymer engineering and science, 36(8), 1996, pp. 1052-1057
Citations number
33
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Polymer Sciences","Engineering, Chemical
ISSN journal
0032-3888
Volume
36
Issue
8
Year of publication
1996
Pages
1052 - 1057
Database
ISI
SICI code
0032-3888(1996)36:8<1052:TCOIPN>2.0.ZU;2-G
Abstract
Crosslinked poly(methyl methacrylate) (PMMA-c), poly(carbonate-urethan e) (PCU-c), poly(vinyl pyridine) (PVP-c), and full, simultaneous inter penetrating polymer networks (IPNs) based on the above polymers were c haracterized by precise heat capacity (C-p) measurements in the temper ature interval 4.2-450 K. The raw values of C-p scaled with temperatur e (T) as C-p similar to T-d with d = 2 and 5/3, as expected for a frac ton-like vibration regime, in the temperature intervals 8-10 and 10-30 K, respectively. A single glass transition temperature (T-g) and two T-g's were observed for apparently homogeneous and microphase-separate d IPNs, respectively. Judged by the positive sign of the excess Gibbs free energy, the apparently single-phase state of homogeneous IPNs is thermodynamically unstable; however, its kinetic stability is ensured by permanent topological constraints (network junctions) prohibiting t he incipient phase separation.