The acid-base complexation of poly((4-carboxyphenyl)acetylene) with an optically active amine [(R)-(+)-1-(1-naphthyl)ethylamine] not only induces strong circular dichroism (CD) but also changes the molecular weight dependence of the intrinsic viscosity in dimethyl sulfoxide. From the intrinsic viscosity data, we have determined the chain stiffness parameter (the persistence length) and have estimated from this parameter the average standard deviation of the internal rotation angle around the single or double bond of the polyacetylene chain to be 21 and 15°before and after the complexation, respectively. The reduction of the torsional fluctuation may arise from the steric hindrance among the amines complexed with the carboxy pendants which makes the internal-rotation energy well steeper for the polyacetylene backbone. The reduction is however not as remarkable as the change in CD due to the complexation. We conclude that the remarkable CD behavior arises from a drastic change in population of the right-and left-handed helices of the polymer, and the helical conformation of the complex is still imperfect.

Vanadium dioxide (VO 2 ) material, known for changing physical properties due to metal-insulator transition (MIT) near room temperature, has been reported to undergo a phase change depending on the strain. This fact can be a significant problem for nanoscale devices in VO 2 , where the strain field covers a large area fraction, spatially non-uniform, and the amount of strain can vary during the MIT process. Direct measurement of the strain field distribution during MIT is expected to establish a methodology for material phase identification. We have demonstrated the effectiveness of geometric phase analysis (GPA), high-resolution transmission electron microscopy techniques, and transmission electron diffraction (TED). The GPA images show that the nanoregions of interest are under tensile strain conditions of less than 0.4% as well as a compressive strain of about 0.7% (Rutile phase VO 2 [100] direction), indicating that the origin of the newly emerged TED spots in MIT contains a triclinic phase. This study provides a substantial understanding of the strain-temperature phase diagram and strain engineering strategies for effective phase management of nanoscale VO 2 .