Berlin 2005 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 30: POSTER: Chemical physics

CPP 30.44: Poster

Tuesday, March 8, 2005, 16:30–18:30, Poster TU D

Equilibrium domain spacing and structure of PEO-PPO-PEO triblock copolymers studied by means of SAXS, DSC and OM — •Fajun Zhang and Bernd Stühn — Technische Universität Darmstadt, Institut für Festkörperphysik, D-64289 Darmstadt

Phase-separated morphology and domain structure of a series of PEO-PPO-PEO triblock copolymers (Pluronics) were studied. Phase separation was induced by crystallization of PEO block at the temperatures lower than the melting point. While in the melt state, PEO and PPO blocks are miscible, a disordered state with composition fluctuation was observed by SAXS. Upon crystallization of the PEO block, the amorphous PPO block was forced into the amorphous layer. The long-period and the thickness of crystalline phase were calculated from SAXS profiles, while the morphology and melting behavior were characterized by POM and DSC respectively. Both chain-extended and chain-folded crystalline phase could be formed depending on the relative length of PPO and PEO block, and the chain-folding structure could also be tuned by varying crystallization temperature. Equilibrium domain spacing was determined and compared to the results of mean-field theory. A detailed analysis of the SAXS profiles indicated that the phase-separated structure was not always formed by amorphous/mono-crystal alternating structure. An amorphous/bilayer-crystal structure was observed for samples with weight fraction of PEO less than 50 percent and crystallized at lower supercooling.