Strong reverse saturable absorption effect of a nonaggregated phthalocyanine-grafted MA–VA polymer

Abstract

A non-aggregated phthalocyanine grafted polymer (MA–VA-PcInCl) was developed as a novel optical-limiting material. Amino-substituted phthalocyanines (TA-PcInCl) with a high optical-limiting effect are grafted onto a copolymer matrix of maleic anhydride (MA) and vinyl acetate (VA) to obtain a novel grafted polymer (MA–VA-PcInCl) with an optimal circular or ladder configuration, which effectively prevents aggregation of the phthalocyanine conjugated units. The grafted polymer with no phthalocyanine aggregation shows an excellent nonlinear absorption effect. The molar extinction coefficient of the triplet state minus the ground state absorption (Δε_T = 3.92 × 10⁵ M⁻¹ cm⁻¹) and the nonlinear absorption coefficient (β₁ = 2.5 × 10⁻¹⁰ m W⁻¹, 89%; β₂ = 1.75 × 10⁻⁹ m W⁻¹, 71%) of MA–VA-PcInCl are much larger (nearly 4 times and 6 times) than those of the ungrafted phthalocyanine monomer, TA-PcInCl. The polymer model of the nonaggregate phthalocyanine structure provides a new concept for the design of optical-limiting materials with superior nonlinear absorption effects.