Higher aliphatic aldehyde polymers. VI. Poly(n‐nonaldehyde)

Abstract

AbstractCrystalline poly(n‐nonaldehyde) (PNA) was prepared by anionic polymerization of n‐nonaldehyde (NA) in methylcyclohexane (MCH) with lithium tertiary butoxide (LTB) as the initiator. Normal low‐temperature conditions did not give polymer reprodusibly; however, when the polymerization was carried out with a gradual temperature decrease to −60°C holding at this temperature followed by completion at −78°C, a moderate yield of PNA was obtained. The polymer was acetate capped and characterized. Infrared and PMR spectroscopy, as well as degradation of the polymer in the presence of 2,4‐dinitrophenylhydrazine to the hydrazone, conclusively proved the chemical structure of the polymer. VPO measurements and measurement of the inherent viscosity showed the polymer to be of moderate molecular weight. PNA is highly crystalline and shows two transition regions, one corresponding to the melting of the main chain at temperatures above 120°C and one region between 50 and 80°C, which is related to the crystallization of the aliphatic side chains. PNA, although inherently brittle, can be extruded through an orifice at a temperature near the side‐chain melting temperature to give an extrudate whose x‐ray patterns show the characteristics of a fiber diagram. It is suggested that the crystal structure of the PNA is similar to that of poly(n‐heptaldehyde) but with a larger a spacing, which is expected from a longer aliphatic side chain.