Synthesis and evaluation of a series of regular polyampholytes

Abstract

A series of three true polyampholytes with unequivocally alternating acidic and basic groups attached directly to the skeletal backbone of the polymer chain have been prepared. This was accomplished by copolymerizing 3,6‐diallyl‐2‐piperidone with the α,ω‐dithiols containing 2‐, 4‐, and 6‐methylene groups. The polymerization was carried out in an emulsion system initiated by 2,2′‐azobisisobutyronitrile (AIBN), yielding soluble piperidone‐containing polymers with molecular weights in the 20,000–30,000 range. The piperidone rings in the polymers were hydrolyzed by dilute sulfuric acid to yield the desired polyampholytes. Fibers were prepared by wet‐spinning formic acid solutions of the polyampholyte into saturated salt solution or by melt‐spinning. These fibers were quite elastic. We were unsuccessful in demonstrating that mechanical energy could be attained by the effect of pH on the fibers. Similarly, no pH effect could be elicited in Instron tests. The stress‐relaxation curve showed a marked positive force–temperature effect characteristic of rubberlike materials with few crosslinks. In a check of transition temperatures, it was noted that on repeated runs the second‐order transition temperature rose markedly, suggesting an irreversible change. Viscometric studies clearly demonstrated polyelectrolyte behavior. X‐ray diffraction studies of the polyampholytes showed that maximum crystallinity and orientation occurred in the polymer containing as part of the repeating unit the 1,4‐butane dithiol moiety.