Naslov
Investigation of Upper Liquid-liquid Transition in Unsaturated Polxesters by Near Infrared Spectroscopy

Autori
Pucić, Irina ; Ranogajec, Franjo

Izvornik
Macromolecular Chemistry and Physics (1022-1352) 202 (2001), 9; 1844-1854

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
upper liquid-liquid transitions; unsaturated polyesters; hydrogen bonding; local order; near-infrared spectroscopy

Sažetak
Near infrared spectroscopy was used to investigate less familiar transition in amorphous polymer melts - upper liquid-liquid transition. This transition is related to lower liquid-liquid transition, both are caused by stepwise decrease of local order based on secondary valent interactions that remain above glass transition temperature and has been recently detected in number of polymers. If hydrogen bonding is possible in a polymer, as it is the case in the unsaturated polyesters under consideration, it may enhance the short-range order. The NIR spectroscopy was chosen as a method of investigation because it is sensitive to structural changes, distinction between hydrogen bonded and non bonded hydroxyl groups is easier and thicker samples can be used than in MID region what is very important when concentration of measured species is low. The spectra of poly(1, 3-propyleneglycol-maleate) with styrene and poly(1, 6-hexanediol-maleate) were recorded at selected temperatures. Significant intensity changes of hydroxyl and carbonyl absorptions at 1430 nm and between 1900 nm and 2100 nm accompanied by wavelength shifts occurred at upper liquid-liquid transition temperature while carbon-hydrogen absorptions showed only minor changes. That confirmed our assumption that the upper liquid-liquid transition was caused by changes in hydrogen bonding.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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