Conformation of polydiacetylene macromolecules in solution: Field induced birefringence and rotational diffusion constant

Abstract

Application of an external electric field induces birefringence in a solution of polydiacetylene (poly-4BCMU) in toluene due to orientation of the macromolecules. The field induced orientation in the red phase indicates an anisotropic polarizibility tensor characteristic of a rod-like conformation. The birefringence due to the polymer in its coil conformation (yellow phase) is extremely weak. The transient response of the anisotropic light scattering was studied in the red phase after switching the electric field on or off. We find a free rotational relaxation time of ∼0.1 s, consistent with the rotational diffusion constant expected for rod-like polydiacetylene macromolecules. These results rule out the large aggregate interpretation proposed to explain the color change transition. The field induced birefringence data independently demonstrate the existence of the rod-coil conformational transition for polydiacetylene 4BCMU macromolecules in solution.

Artificial Molecular Machines

“…The rate of macrocyclic pirouetting in some hydrogen-bonding rotaxanes can be controlled by changing the strength of an electric field, which alters the strength of the hydrogen bonds. 820 − 824 In some cases, direct manipulation of macrocycle/axle interactions can either restrict rotation or increase its frequency by weakening intracomplex interactions. The formation of weaker hydrogen bonds with maleamide units as compared to fumaramide units has been discussed in previous sections.…”

Optical and Electrochemical Transducers Based on Functionalized Conjugated Polymers

“…This intriguing effect has been extensively studied and has led to the development of various thermochromic polythiophene [4,5,[12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29], polysilane [30][31][32][33][34][35][36][37][38][39][40][41], and polydiacetylene [42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57] derivatives (Figure 2.1). As an example of thermochromism reported for some neutral conjugated polymers, Figure 2.2 shows the temperature-dependent UV-vis spectrum of sodium poly[2-(4-methyl-3-thienyloxy)ethanesulfonate] in...…”

Electrochromic carbon nanotube polydiacetylene and zinc oxide hybrids

“…The study was based on the fact that light intensity detected due to field induced orientation is proportional to (Δn) 2 , where Δn is the birefringence. Even though the ratio of Δn(rod)/ Δn(coil) was found to be greater than 300 by Lim et al [22], the result could not be considered as concrete proof for rod-like chain structure of the PDAs. This is because the study could not confirm whether the change in birefringence was induced by orientation of rod-like molecules or large aggregates in which the individual chains are more or less aligned [23].…”