GROWTH MECHANISMS OF POLYPYRROLES

The oligomerization mechanisms of several derivatives of pyrrole have been studied by quantum-mechanical methods. Different growth processes are compared from the point of view of thermodynamic stabilities to g ain insight into the branching possibilities. For the simple polypyrro le, polymerization may proceed through either an a or a beta carbon wi th equal probabilities. When an aldehyde group is attached to the nitr ogen, beta positions are definitely favoured owing to strong steric hi ndrance. For 2-pyrrole carboxaldehyde and 3-pyrrole carboxaldehyde, th e most stable forms of the bonding are alternating ones that go throug h alpha-beta pairs.