Synthesis And Properties Of Polymer Containing 1, 3, 4-oxadiazole And Azobenzene (Naphtholene)

In this paper, three new congugated polymers containing azobenzenenaphtholene (azobenzene) and 1,3,4-oxadiazole unit (LPOXD)(pl,p2,p3) were synthesized by a two step polycondensation reaction 5-(4-alkoxy benzenenaphtholazo) isophthaloyl dihydrazide(6a),5-(4-alkoxy benzeneazo) isophthaloyl dihydrazide(6b) and two chlorides.The structures of monomers and LPOXD were confirmed by IR,UV-vis and 1H NMR. The molecular weights and molecular weight distributions of the LPOXD were determined by gel permeation chromatography (GPC). The Mw are 12624 g/mol (p1),7830 g/mol (p2),8486 g/mol (p3), respectively. PDI are 1.657 (p1),1.623 (p2),1.686 (p3), respectively. The intrinsic viscosities are 0.0674 dL·g-1 (p1),0.0222 dL·g-1 (p2),0.0497 dL·g-1 (p3), respectively.The thermal stability of LPOXD (p1, p2, p3) are characterized by TG, the 5% weight loss of LPOXD (p1, p2, p3) are 321℃,324℃,344℃, respectively. The introduction of long chain of alkoxy azobenzenenaphthol significantly improves LPOXD's (p1, p2, p3)solubility in common organic solvents such as chloroform and tetrahydrofuran etc. The trans-cis photoisomerization of monomer (6a) and LPOXD (p1, p2, p3) take place under the radiation of 365nm UV light. The efficiency of trans-cis photoisomerization (R), the content of cis-isomer (Y) and the rate constant of photoisomerization (kp) of monomer (6a) and LPOXD (p1, p2, p3) are calculated, Rare are 38.3%(6a),9.2%(p1),54.4%(p2-azobenzene),8.7%(p2-azobenzenenaphtholene), 70.18%(p3), respectively; Y are 40.6%(6a),9.4%(pi),56.5%(p2-azobenzene),8.9% (p2-azobenzenenaphtholene),73.69%(p3),respectively; kp are 0.507min-1(6a),0.232min-1(p1), 0.651min-1(p2-azobenzene),0.246min-1(p2-azobenzenenaphtholene),0.782 min-1 (p3). Thei R,Y and kp of monomer are greater than p1, which is attributed to the increased steric hindrance in polymer. In polymer, the R,Y and kp of azobenzene are greater than that of the azobenzenenaphtholene, which azobenzenenaphtholene is due to steric hindrance causing light-induced trans-cis isomerization limited. The emission peak of LPOXD are located at about 467nm (p1),402 nm (p2),390 nm (p3). The results indicated that the polymers emitted indigo blue fluorescence. LPOXD with azobenzenenaphtholene(azobenzene) and oxadiazole unit shows good solubility, good thermal, trans-cis photoisomerzation property and fluorescence property, which can be used in the filed of optioelectronic functional polymer materials...