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I made some breakthrough contributions to material physics. For example, kinetics of capillary break-up in polymer liquid systems (high viscosity), first ever schematic diagram of all phases and mesophases, rigid amorphous phase, condis crystals (I invented the concept and named it). My work resulted in well over 2000 citations, which allowed my colleagues from the field to recognize me as one of the world's top thermal analysts.


My research is focused on the characterization of morphology, phase structure and transitions, chemical transformation of various materials exposed to temperature change. The temperature range within which I perform experiments is broad: -170 ᵒC (liquid nitrogen) to 1450 ᵒC (the mouth of volcano). This capability exists today in my research lab at the University of Houston-Downtown, where I pass my experience on to students in the College of Sciences and Engineering.

first schematic of phases and mesophases



Perhaps my biggest contribution to science is the development of the schematic diagram organizing all possible phase and mesophase types, as distinguished by their glass and disordering transitions. The glass transitions link mobile and solid condensed phases of the same structure. The schematic also lists the connections to the possible transition entropies on disordering. With the development of this schematic, I came to realization that for some compounds there is a specific mechanism of disordering between crystal and mesophase which is achieved by change of molecular conformation. I gave this mesophase a name: Condis Crystal.

condis crystal mesophase


Blending of two polymers of different physical properties as the method of obtaining a new material was the topic of my PhD thesis. Together with enforced mechanical blending, a spontaneous process, based on surface and interfacial tensions between the two liquid components was suggested. This spontaneous process was the main objective of my PhD thesis. Through my systematic study, I characterized the kinetics of spontaneous break-up of long liquid threads of one polymer immersed in the molten matrix of another polymer. The result for Polystyrene-Polyamide system is shown in the picture. Kinetics of this process was determined as well. This example was first ever demonstration of capillary break-up described in the literature for molten polymers which are very high viscosity liquids.


Capillary break-up of molten polystyrene thread in the molten matrix observed at 250 ᵒC.



In the classical two-phase model of semicrystalline polymers, the contribution of the amorphous phase to the overall phase structure can be determined by the heat capacity change,  ΔCp,  during the glass transition. Experimental law developed by Wunderlich says that 11 J/Kmol of ΔCp is produced by every mobile part of the molecule during that transition.  This law agrees with experimental data for low crystallinity samples. With increasing crystallinity however, the amorphous content is smaller than expected (calculated). The difference can be extracted from the Cp curve by extending it towards the melting peak, ie. towards increasing mobility of molecules. This operation divides the heat capacity of the material into three parts: crystal, amorphous (flexible), and amorphous (rigid). Through my experiments I was able to propose a three-phase model for semi-crystalline polymers:

Cr  +  Am (flex)  +  Am (rigid) =  1


Prof. Wunderlich's research group at RPI in 1980s

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