A series of new polyamides 3a-d containing aryl-azo, ether and sulfone groups in the main chain were synthesized from bis[4-（4-aminophenoxy）phenyl sulfone] 1 and several azo aromatic diacyl chlorides 2a-d by the low temperature solution polycondensation technique. FTIR spectroscopy, nuclear magnetic resonance （NMR） and elemental analyses confirmed the structure of these polymers. Owing to the aryl and amide groups in the main chain, these polymers exhibit photochromic properties as well as excellent thermal stabilities. The transition temperatures （Tg） are between 242 and 265℃, and the char yields at 800 ℃ in nitrogen atmosphere were above 39%. Based on incorporation of flexible ether linkages and polar sulfone groups, the polyamides show desirable solubility in organic solvents such as DMAc, N,N-dimethylformamide （DMF）, N-methyl-2-pyrroidinone （NMP） and dimethylsulfoxide （DMSO）. And it is exemplified that polyamide containing 2 and 2＇ substitutes performed better solubility.
The novel sandwich composites were prepared by sandwiching a polyvinylidene fluoride/Tb- Dy-Fe alloy composite （PVDF/Terfenol-D） between polyvinylidene fluoride/lead zirconate titanate composites （PVDF/PZT）. The maximum magnetoelectric effect voltage coefficient, （dE/dn）33max, of the sandwich composites is higher than that of three-phase composites at their own optimal loading level of Terfenol-D. This is attributed to less interface relaxations of strain and better polarization of the sandwich composites. When the volume fraction of Terfenol-D is higher than 0.10, no coupling interaction for three-phase composites could be observed, but （dE/dn）33max of sandwiched composites still reached 20 mV/（cm.Oe）. At high magnetic field intensity, the magnetoelectric effect voltage coefficient, （dE/dn）33, of sandwich composites is higher than that of three-phase composites; at low magnetic field intensity, （dE/dn）33 of sandwich composites is lower than that of three-phase composites. At their resonance frequency, the （dE/dn）33max of the sandwich composites and the three phase composites are 150 mV/（cm.Oe） and 42 mV/（cmoOe）, respectively. This significant increase of （dE/ dn）33max at resonance frequency confirms the improvement of maximum magnetoelectric effect coefficient via sandwich-structured composites.
