Novel azo-containing polymethacrylates bearing spiroacetal-norbornene moiety and methylene spacers: synthesis and characterization

An eight-step synthetic strategy was followed to prepare a series of novel azobenzene-containing methacrylate monomers bearing spiroacetal-norbornene moiety and methylene spacers. Thus, the adduct 2, obtained from cyclopentad iene and acrolein, was converted to 1,3-diol 3. The diol was acetalized wit h nitrobenzaldehyde 4 under microwave irradiation to obtain nitro compound 5 that was then reduced to amino compound 6. Diazonium salt of 6 was couple d with phenol to produce phenolic compound 7 which was then reacted with n- dibromoalkanes (n = 2, 4,6,8, 10) to yield bromo compounds 9a-e. Nucleophil ic substitution reaction of the bromo compounds with lithium methacrylate p roduced the methacrylic monomers 12a-e. The monomers were finally homopolym erized via free radical solution method by using AIBN as an initiator (solv ent THF, 60 degreesC, 38 h). All the intermediate compounds as well as mono mers and polymers were characterized by means of spectroscopic (FTIR, H-1- and C-13-NMR) and thermal (DSC and TGA) techniques. Average molecular weigh ts and molecular weight distributions of the polymers were measured by GPC. The polymers were completely soluble in common organic solvents. The azopo lymers showed reversible trans-cis photo-isomerization of -N=N- bond as ind icated by using UV/VIS spectrophotometry. (C) 2001 Elsevier Science Ltd. Al l rights reserved.