A functional diamine

3

5-diamino-N-(2-octyl-1

3-dioxoisoindolin-5-yl)benzamide (D8) containing imide unit and an assistant diamine monomer 4

4'-dimethyldiphenylmethane (DMMDA) were molecularly designed and synthesized successfully.Polyimides (PIs) containing asymmetric units in the main chain and imide pendant groups were prepared with the copolymerization of DMMDA

D8 and commercial aromatic dianhydride 4

4-oxydiphthalic (ODPA) by chemical imidization.Five PIs were obtained by controlling the mole ratio of diamines and dianhydride.The structures and properties of the resulting co-condensation type PIs were characterized by nuclear magnetic resonance (NMR)

Fourier transform infrared spectroscopy (FTIR)

gel permeation chromatography (GPC)

differential scanning calorimetry (DSC) and ultraviolet analysis (UV-Vis) etc. The PIs obtained were favorably soluble in aprotic polar solvents

such as N-methylpyrrolidone (NMP) and N

N-dimethyl form amide (DMF)

and even in common organic solvents such as tetrahydrofunan (THF) and trichloromethane (TCM).The molecular weights of the soluble copolyimides obtained were high and influenced by the mole ratio of the functional diamine monomers.The molecular weights of PIs decreased with the increment of D8.Creasable PI films could be attained by casting from PI solutions.The liquid crystals (LCs) alignment ability of PI films was investigated and the pretilt angles were measured by the crystal rotation method using a pretilt angle tester.It was observed that the pretilt angle increased with the increasing content of functional diamine D8.When the content of D8 was greater than 20%

the PIs obtained high pertilt angles above 89even after five-times rubbing and showed outstanding rubbing-resistant ability.Moreover

the transmittances of the PIs were more than 80%

and their glass transition temperatures were above 260 ℃.This kind of PIs containing imide side chains could be promising materials in vertical-alignment-mode LC displays.