Kinetics of the aggregation of poly(N -phenylisocyanide), optical detection of strain using polymer sensors, and photochemistry of azobenzene analogues

Jingxian Sun, University of Rhode Island


Organoisocyanide polymers have been studied intensively since the 1960s. It has been assumed that polyisocyanides exist as a tightly wound helix and this is always present in these polymers. However, our results indicate that the N-phenyl-polyiminomethylene (N-$\varphi$-PIM) is not a purely helical polymer in solution. N-$\varphi$-PIM is fairly soluble in THF, CH$\sb2$Cl$\sb2$ and CCl$\sb4$ but aggregation and precipitation occur in solution. UV-Vis spectra were obtained to probe the kinetics of the aggregation process in solution. Our results are best interpreted by assuming that N-$\varphi$-PIM undergoes an uncoiling of the rigid rod helix in solution. Possible mechanisms of aggregation are also discussed in this study.^ Conventional metal strain gages are inexpensive but the reproducibility is not good at high strains and they are not sensitive at very low strain. Polymer sensors have the advantages of being cheap, easily manipulated and tunable by synthesis. It has been found that the optical band gap shifts with the application of strain in wide band gap semiconductors. Polymers are also wide band gap materials, so polymers should also respond optically to applied strain. A simple one-dimensional model was introduced to illustrate how polymers might respond to applied strain. The four point flexure method was employed for measuring strain optically. A polyaniline/polyelectrolyte complex was used in our study because polyaniline has a chromophore which fits our model. Our results demonstrated that polymer thin films could be used to monitor strain optically and the gage factors of polymer sensors are much bigger than that of metals. The short term reproducibility is good, however the environmental sensitivity of the polyaniline/polyelectrolyte complex remains a minor problem. ^

Subject Area

Chemistry, Analytical|Chemistry, Organic|Chemistry, Polymer

Recommended Citation

Jingxian Sun, "Kinetics of the aggregation of poly(N -phenylisocyanide), optical detection of strain using polymer sensors, and photochemistry of azobenzene analogues" (1998). Dissertations and Master's Theses (Campus Access). Paper AAI9902580.