Berlin 2001 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 18: Poster: Polymer Blends, Heterogeneous Systems, Colloids and Nanoparticles, Interfaces, Polyelectrolytes

CPP 18.22: Poster

Mittwoch, 4. April 2001, 12:30–15:00, AT1

Freezing and melting of polymers and oligomers in nanopores — •Andrä le Coutre, Jörg Baller, and Jan Kristian Krüger — Universitaet des Saarlandes, Fachrichtung 7.2 Experimentalphysik, Bau 38, 2.OG, Postfach 151150, D-66041 Saarbruecken

By means of temperature modulated DSC (TMDSC) and light scattering (Brillouin- and Raman-scattering) we investigated the freezing and melting behavior of linear molecules (polyethyleneoxide (PEO) and n-alkanes) within nanoporous SiO2-glass with 2.5 to 20 nm pore diameter. As expected, the melting transition shifts to lower temperatures. In both cases the specific heat anomaly of the melt transition is largely broadened, but detailed investigations show that sequential processes are involved. Though the PEO molecules are larger than the n-alkanes, even in small pores PEO shows a strong crystallization kinetic with considerable latent heat which is not found in the alkanes. Additionally, in the smallest pores (2.5 nm) the onset of the specific heat anomaly coincides with the glass transition temperature of bulk-PEO. Since the kink like specific heat behavior is similar to the glass transition of canonical bulk glass formers (e.g. salol) within small pores, this cp-onset is interpreted to be caused by remaining amorphous PEO which is hindered to crystallize by the topological restrictions of the pores showing an unconventional glass transition.