Optically transparency and light color of novel highly organosoluble alicyclic polyimides with 4-tert-butylcyclohexyl group

Novel optically transparent and highly organosoluble alicyclic polyimides derived from bulky alicyclic diamine containing trifluoromethyl group on either side, 1,1-bis[4-(2-trifluoromethyl-4-aminophenoxy)phenyl]-4-tert-butylcyclohexane (BTFAPBC), were prepared. All polymers showed excellent solubility in various organic solvents like N-methyl-2-pyrrolidinone (NMP), N,N-dimethyl acetamide (DMAc), N,N-dimethyl formamide (DMF), pyridine, cyclohexanone, and gamma-butyrolactone. The cut-off wavelength and 80% transmission wavelength for polyimides ranged from 362 to 407 nm and 436 to 492 nm, respectively. Polyimides with alicyclic tert-butylcyclohexyl cardo and trifluoromethyl substituents exhibited low dielectric constants ranging from 3.38 to 4.07 (at 1 KHz). Inherent viscosities of the polyimides were found to be in the range of 0.52-1.00 dL . g(-1). Polyimides showed glass transition temperatures in the range of 231-262 degrees C, and possessed a coefficient of thermal expansion (CTE) of 66-79 ppm . degrees C-1. Thermogravimetric analyses of the polyimides revealed high thermal stability and decomposition temperature more than 450 degrees C in nitrogen atmosphere. The 10% weight loss temperature was found to be in the range of 453-544 and 413-502 degrees C in nitrogen and air atmospheres, respectively. The polyimide films had a tensile strength ranging from 84 to 100 MPa. The elongation at break varied from 6 to 12% and the tensile modulus varied from 1.1 to 2.1 GPa.