THERMAL TRANSITIONS IN POLYMER NETWORKS - FLUORESCENCE STUDY OF CROSS-LINKED POLYETHYLACRYLATE

The glass transition temperatures of poly(ethylacrylate), PEA, network s with several crosslink densities were determined by DSC and results were compared with those obtained from steady state fluorescence spect ra of PEA networks with anthracene probes and labels. The latter measu rements were performed as a function of temperature in the range 5 to 370K. PEA with phenylene labeled knots were studied in the range 240 t o 370K. The fluorescence intensity decreases upon increasing temperatu re with several transition points in which the slope changes, both for probes and labels. One of the thermal transitions, set at about 320K, was compared to a liquid-liquid transition, while the glass transitio n was assumed to occur (at the microscopic level) in a broad range of temperatures which depends on the crosslink density and the position o f the chromophore in the network. The first and the second temperature scans were not reproducible, similar to DSC thermograms, whereas the second and third were very similar.