Synthesis and Third-order NLO Properties of polymethacrylates containing Pendent Azobenzene Groups

Abstract

Six azobenzene monomers containing methacrylate groups were prepared and characterized. The monomers varied by having alkyl spacers of varying lengths and either nitro or methoxy substituents in conjugation with the azo groups. The monomers were polymerized via atom transfer radical polymerization (ATRP) to give polymethyacrylates with pendent azobenzene groups. The pendent azobenzene groups were separated from the polymer backbone by alkyl spacing groups of varying lengths. The side-chain nonlinear optical (NLO) polymers with variable and controllable molecular weight and low polydispersity (1.2—1.4) were obtained. The kinetics of ATRP for each azo monomer was also studied. The third-order NLO property of azo monomers and their polymers were measured using the degenerated four wave mixing technique. Each of the polymers exhibited relatively high χ (3 ) value and rapid response times. The effects of the substituent and spacer length on the ATRP of the methacrylate monomers and the effect of molecular weight on the third-order NLO property of polymers were investigated.