A smart material from oligomers and polymers.

摘要

A smart material, which changed its optical absorption spectrum irreversibly when stretched, was designed, synthesized, and characterized. This smart material was a segmented polyurethane elastomer containing a copolyamide in the soft segments. Copolyamides, which were synthesized from two diamines {dollar}(p,pspprime{dollar}-diaminoazobenzene and 1,6-hexanediamine) and two dichlorides (succinyl chloride and glutaryl dichloride), contained three modules: attachments, azobenzene chromophores, and conformational latches. Almost all of the azobenzene groups in a copolyamide were latched in the cis-form by irradiating the glycerine solution of this copolyamide with UV light {dollar}(lambdasb{lcub}rm max{rcub}{dollar} = 365 nm) at 160{dollar}spcirc{dollar}C for 2 hours and cooling it to room temperature. A copolyamide oligomer with a smart function was chemically inserted into polyurethane elastomers to provide a mechanism by which mechanical deformation can induce transformations from the cis- to the trans-azobenzenes. The cis-azobenzenes were created by irradiating the polyurethane copolymer film with UV light {dollar}(lambdasb{lcub}rm max{rcub}{dollar} = 365 nm) at 100{dollar}spcirc{dollar}C for 1 hour and latched by cooling to room temperature during UV irradiation. After three successive 100% stretching and relaxation cycles, the change in its UV-Vis absorption spectrum was small. However, three successive 200% stretching and relaxation cycles induced a significant increase of the trans peak at {dollar}lambda{dollar} = 380 nm. Three successive 300% stretching and relaxation cycles changed almost all the photoproduced cis-form to the trans-form. Non-linear mechanochromism was demonstrated with the polyurethane copolymer film.; Because of the commercial interest in carbon fiber reinforced composites and in carbon black reinforced rubbers, the surfaces of carbon fiber and carbon blacks were examined with a scanning tunneling microscope (STM). With the possible exception of graphitized carbon black, these surfaces were too irregular to observe a single adsorbed molecule. Octadecyl amine molecules physically adsorbed to the surface of highly oriented pyrolytic graphite (HOPG) were observed by the STM. The surface of HOPG chemically treated with RuO{dollar}sb2{dollar}/NaIO{dollar}sb4{dollar} and thionyl chloride was used to observe the attachment of polymers to a surface similar in composition of carbon fiber and carbon blacks. Copolyamide materials adsorbed to a step edge of chemically modified HOPG were observed by the STM and the atomic force microscope (AFM).