Polymerization of n‐Butyl Acrylate Photoinitiated by 1‐(Bromoacetyl)pyrene and its Arsonium Salt

Abstract

A comparative study on the photoinitiating efficiency of pyrene (Py), 1‐Acetylpyrene (AP), 1‐(Bromoacetyl)pyrene (BP) and 1‐Acetylpyrene triphenyl arsonium bromide (APAS) for polymerization of n‐butylacrylate (BA) was done. An experimental investigation of the kinetics of free radical solution polymerization at 25±0.2°C using all four photoinitiators showed that pyrene was completely ineffective in initiating the polymerization of BA under all conditions employed, whereas AP was able to initiate polymerization. Incorporation of bromo group into AP markedly accelerated the rate of UV induced polymerization. Further modification of bromo derivative (BP) to its arsonium salt (APAS) produced a less effective initiator. The kinetics and mechanism of polymerization using BP and APAS as initiators have been investigated in detail. The polymerization with BP followed non‐ideal kinetics (R_p∝[BP]^0.8 [BA]^0.98) with respect to initiator concentration, whereas ideal kinetics (R_p∝[APAS]^0.49 [BA]^1.07) was observed when APAS was used as an initiator. This unusual kinetic behavior for the BP‐BA system can be interpreted in light of degradative transfer and the emergence of occlusion. The kinetic data proved that BP was a more effective and faster initiator than APAS.

Keywords:

• photopolymerization
• 1‐(bromoacetyl)pyrene
• non‐ideal kinetics
• ESR

Acknowledgements

Financial support for this research project from the University Grants Commission, New Delhi, India is gratefully acknowledged and Ms. Swati Daswal is thankful to the Council of Scientific and Industrial Research, New Delhi, India for financial assistance.