Synthesis and Cationic Polymerization of Vinyl Ethers Containing Oxynitrobenzylidenemalononitrile and Oxynitrobenzylidenecyanoacetate as the NLO-phores in the Side Chain

摘要

5-Nitro-2-(2`-vinyloxyethoxy)benzylidenemalononitrile (2a), methyl 5-nitro-2-(2`-vinyloxyethoxy)benzylidenecyanoacetate (2b), 3-nitro-4-(2`-vinyloxyethoxy)benzylidenemalononitrile (4a), methyl 3-nitro-4-(2`-vinyloxyethoxy)benzylidenecyanoacetate (4b), 2-nitro-5-(2`-vinyloxyethoxy)benzylidenemalononitrile (6a), and methyl 2-nitro-5-(2`-vinyloxyetboxy)benzylidenecyanoacetate (6b) were prepared by the condensation of 5-nitro-2-(2`-vinyloxyethoxy)benzaldehyde (1), 3-nitro-4-(2`-vinyloxyethoxy)benzaldehyde (3), and 2-nitro-5-(2`-vinyloxyethoxy)benzaldehyde (5) with malononitrile or methyl cyanoacetate, respectively. Vinyl ether monomers 2a-b, 4a-b, and 6a-b were polymerized with boron trifluoride etherate as a cationic initiator to yield poly(vinyl ethers) 7-9 having oxynitrobenzylidenemalononitrile and oxynitrobenzylidenecyanoacetate, which is effective chromophore for second-order nonlinear optical applications. Polymers 7-9 were soluble in common organic solvents such as acetone and DMSO. Tg values of the resulting polymers were in the range of 67-83 ∩. Electrooptic coefficient (r33) of the poled polymer films were in the range of 15-27 pm/V at 633 nm. Polymers 7-9 showed a thermal stability up to 300 ∩ in TGA thermograms, which is acceptable for NLO device applications.