摘要
A novel biphenyl side-chained diamine with alkyloxy spacer and alkyloxy tail,4＇-butoxy-4-（3,5-diaminobenzoyloxy）hexyloxybiphenyl（C6BBC4）,was synthesized and characterized by FTIR and 1 H NMR.A series of polyimide（PI） films with different side chain contents was synthesized from biphenyltetracarboxylicdianhydride（BPDA）,4,4＇-oxydianiline（ODA） and C6BBC4,and their thermal properties,optical transparency and liquid crystal alignment property,and so on,were investigated by thermogravimetric analysis（TGA）,differential scanning calorimetry（DSC）,crystal rotation method,polarizing microscopy and UV-Vis spectra.With the content of side chained diamine increasing from 0 to 100%,the η inh of poly（amide acid）（PAA） decreased rapidly from 3.0 to 0.51,the glass transition temperature（T g） of polyimides（PIs） decreased from 274 ℃ to 203 ℃ and the Vis-light transmittance of alignment films substantially increased.As for the alignment properties,the pretilt angle of PI alignment films without rubbing could reach 90° when the content of C6BBC4 was 60% or more.At the same time,the alignment stability could meet the industrial requirements.It was considered that the alkoxy spacer,the biphenyl unit and the alkoxy tail may all play important roles in achieving a large pretilt angle even up to 90°,and the introduction of only the alkoxy spacer or alkoxy tail can also improve the pretilt angle,but not by much.
A novel biphenyl side-chained diamine with alkyloxy spacer and alkyloxy tail,4＇-butoxy-4-（3,5-diaminobenzoyloxy）hexyloxybiphenyl（C6BBC4）,was synthesized and characterized by FTIR and 1 H NMR.A series of polyimide（PI） films with different side chain contents was synthesized from biphenyltetracarboxylicdianhydride（BPDA）,4,4＇-oxydianiline（ODA） and C6BBC4,and their thermal properties,optical transparency and liquid crystal alignment property,and so on,were investigated by thermogravimetric analysis（TGA）,differential scanning calorimetry（DSC）,crystal rotation method,polarizing microscopy and UV-Vis spectra.With the content of side chained diamine increasing from 0 to 100%,the η inh of poly（amide acid）（PAA） decreased rapidly from 3.0 to 0.51,the glass transition temperature（T g） of polyimides（PIs） decreased from 274 ℃ to 203 ℃ and the Vis-light transmittance of alignment films substantially increased.As for the alignment properties,the pretilt angle of PI alignment films without rubbing could reach 90° when the content of C6BBC4 was 60% or more.At the same time,the alignment stability could meet the industrial requirements.It was considered that the alkoxy spacer,the biphenyl unit and the alkoxy tail may all play important roles in achieving a large pretilt angle even up to 90°,and the introduction of only the alkoxy spacer or alkoxy tail can also improve the pretilt angle,but not by much.
基金
Supported by the National Natural Science Foundation of China(Nos.50773044,50973073)
