IMAGING OF ALIPHATIC POLYCARBONATES WITH PHOTOGENERATED BASE

A series of aliphatic polycarbonates based on the condensation copolym erization of the bischloroformate of 2,2,4,4-tetramethyl-1,3-cyclobuta nediol (TMCBD) with itself and the diols of 3-cyclohexene-1,1-dimethan ol, 1,4-cyclohexanediol (CHD), in various molar ratios, exo,exo-tricyc lo[2.2.1.0(2,6)] heptane-3,5-diol, and 4,8-bis(hydroxymethyl)tricyclo[ 5.2.10(2,6)]decane (BTD) were synthesized. Incorporation of cyclic and tricyclic repeat units produced polycarbonates with high glass transi tion temperatures (T-g's), high molecular weights, and low refractive indexes. The crystallinity of the TMCBD homopolymer was minimized in t he CHD/TMCBD copolymers with little effect on T-g but with decreased t hermal stability. Thermal analysis yields decomposition temperatures r anging from 354 degrees C for the TMCBD homopolymer to 292-298 degrees C for the CHD/TMCBD copolymers; all polymers undergo complete thermal degradation. Refractive indexes range from 1.493 for the 1:1 copolyme r of BTD and TMCBD to 1,481 for the CHD/TMCBD copolymers. Thin films c omposed of an aliphatic polycarbonate and a base-releasing cobalt(III) photoinitiator can be imaged with deep-UV light. The polycarbonates s elected for study were the 9:1 copolymer of CHD and TMCBD and the 1:1 copolymer of BTD and TMCBD. The first step of image formation is the e fficient photoredox decomposition of the photoinitiator with the relea se of multiequivalents of Lewis base. In the case of [Co(en)(3)](BPh(4 ))(3) (en is ethylenediamine, BPh(4)(-) is tetraphenylborate), photoge nerated ethylenediamine cross-links the polymer chains via formation o f bis(dicarbamate) linkages. Development with solvent dissolves the un irradiated areas to yield negative-tone images. For [CO(NH3)(6)](BPh(4 ))(3), photoreleased ammonia causes chain scission in the exposed regi ons of the film, and wet or dry development results in positive-tone i mages,