Photochromic copolymers containing 3-indolylfulgides/indolylfulgimides: synthesis and photochemical properties in toluene and as films.
Photochromic indolylfulgimides covalently attached to polymers have beneficial properties for optical switching. A 3-indolylfulgide and two 3-indolylfulgimides with one or two polymerizable styrene groups attached on the nitrogen atom(s) were synthesized. Copolymerization with methyl methacrylate (MMA) provided linear copolymers (one styrene group) or a cross-linked copolymer (two styrene groups). The properties of the monomers and copolymers in toluene or as thin films were characterized. The new copolymers were photochromic (reversibleZ-to-Cisomerization), absorbed visible light, and revealed good thermal and photochemical stability. At room temperature, all copolymer films showed no loss of absorbance after 5 weeks. At 80 °C in either toluene or as films, theZ-forms copolymers were less stable than theC-form copolymers, which showed little or no degradation after 400 h. The degradation rate due to repeated ring-closing - ring opening cycles was less than 3% per 100 cycles. The cross-linked copolymer showed photochemical stability comparable to monomeric fulgides in toluene, <1% per 100 cycles. In general, the properties of the linear and cross-linked copolymers were similar to the corresponding monomers in toluene. In films, the conformations of theZ-form were restricted due to the matrix indicating that the preparation of films from theC-form is advantageous.
Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States.
Nadezhda I
NI
Islamova
Xi
X
Chen
Changjun
C
Fan
Richard S
RS
Andino
Watson J
WJ
Lees
3-indolylfulgimide; cross-linked copolymer; photochromism; thin films