Abstract: In this paper, the thermal stability of poly[(DR1M)-co-(MMA)] and poly[(DR1M)-co-(St)] have been evidently improved by copolymerizing with epoxy GMA through sealed-tube reactive method. The two regular crosslinkable PMMA and PS types of nonlinear optical(NLO) polymers with a high yield were acquired. The two types of polymers, to which side chains containing NLO chromophores(DR1) were covalently attached, were of high thermal stability for nonlinear optics. Studied with DSC and TGA, it can be concluded that the glass transition temperatures of the two polymers, 398 and 397 K, respectively, approximately increased 30—50 K compared with that before crosslinked. Besides, the decomposition temperatures(at 5% mass loss) of the polymers were 552 and 546 K, respectively. The second-order nonlinearity of the polymers was measured with the simple reflection technique at 1.3 μm wavelengths. The values of electro-optic coefficient( r₃₃) of the two types of polymers after crosslinking were 12.50, 8.60 pm/V respectively and they were both stabilized around 75% of their initial values after 100 h at room temperature. The above results confirmed that the thermal stability of copolymers was improved significantly, which is due to the opening and crosslinking of the epoxy group in the copolymers.

Key words: Second-order nonlinear optical materials, Crosslinkable materials, Thermal stability, Sealed-tube reactivity