Dr. Bernhard Wunderlich:
UT Department of Chemistry
More than twenty years ago, Bernhard Wunderlich's groundbreaking thermal analyses proved to the world that polymers crystallize at temperatures 10 to 15 degrees below their melting temperature. And so, it follows that polymer crystals melt irreversibly - that is, the entropy (energy divided by temperature) spent to melt a crystalline material can't be completely retrieved upon recrystallization.
Unlike glassy polymers with their broad range of softening temperatures and unordered structure, polymer crystals helped along by a seed (nucleating) molecule grow at specific temperatures. Once begun, the process zips through the melted polymer until entanglement and the strain of forming long molecules halts further growth. The result is partial crystallinity.
A pioneer of the relatively new fast Temperature Modulated Differential Scanning Calorimetry (TMDSC) technique, Wunderlich studies heat loss and gain during polymer softening. His experimental studies help to clarify where imperfections occur during polymer crystallization, providing clues about how flaws in the structure might be avoided.
More recently, Wunderlich's group took a leap to nano-level measurements, testing a new microcalorimeter mounted on the head of an Atomic Force Microscope. Microcalorimetry in combination with TMDSC holds the promise of direct measurement of the crystalline growth process.
In 1996, a double issue of the Journal of Thermal Analysis was dedicated to Wunderlich's pioneering efforts. That same year he received the TA Instruments Award from the International Conference for Thermal Analysis and Calorimetry.
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