Colorless and Soluble Strictly Alternating Copolyimides Containing Aliphatic Spiro Units from 2,8-Dioxaspiro[4.5]decane-1,3,7,9-tetrone

Strictly alternating copolyimides containing aliphatic spiro units were prepared via diimide (with five-membered rings)−dianhydrides (with six-membered rings) derived from 2,8-dioxaspiro[4.5]decane-1,3,7,9-tetrone (TCDA) and diamines. The polymerization was conducted by the conventional two-step procedure using the diimide−dianhydrides and diamines. The resulting poly(imide−imide)s have alternating diamine components and also a head-to-head (tail-to-tail) structure in the imide ring sequence. The poly(imide−imide) films exhibited excellent colorlessness (cutoff wavelength) and transparency (UV−visible transmittance). Most of the poly(imide−imide)s were soluble in typical polar aprotic solvents such as N,N-dimethylacetamide (DMAc) and also in m-cresol, except for the wholly aliphatic ones. These poly(imide−imide)s had decomposition temperatures between 379 and 419 °C in a nitrogen atmosphere, and the glass transition temperatures were shown to be in the wide range of 197−315 °C depending on the combination of the two kinds of diamines.