Thermotropic copolyesters. II. Synthesis and characterization of copolyesters containing the bicyclo[2.2.2]oct‐2‐ene mesogenic unit

Harruna, Issifu I.; Polk, Malcolm B.

doi:10.1002/pola.1988.080260814

Cited by 1 publication

(1 citation statement)

References 19 publications

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“…The result suggests that the CHDA unit is very stiff and linear as well as the PDA unit, corresponding to our previous conclusion that the PI chain linearity is a primary factor in promoting the spontaneous in-plane orientation during thermal cure [3]. In fact, the trans-1,4-cyclohexyl group functions as a mesogenic unit to form thermotropic liquid crystalline polyesters [22,23] and polyamides [22]. One may believe that cyclohexyl group is not so rigid, since it includes the inversion reaction through internal rotation.…”

Section: 23supporting

confidence: 80%

Semi-Aromatic Polyimides with Low Dielectric Constant and Low CTE

Hasegawa

2001

High Performance Polymers

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Semi-aromatic polyimides (PIs) possessing simultaneously a low dielectric constant (K) and low linear coefficient of thermal expansion (CTE) were molecularly-designed. Two PI systems were focused on, i.e. the s-BPDA/CHDA polyimide derived from 3,3 ,4,4 -biphenyltetracarboxylic dianhydride with trans-1,4-cyclohexanediamine and CBDA/TFMB derived from 1,2,3,4-cyclobutanetetracarboxylic dianhydride and bis(2,2trifluoromethyl)benzidine. In the s-BPDA/CHDA system, poly(amic) acid (PAA) polymerization using the common procedure was prevented by strong salt formation at the initial stage. However, heating the salt-forming reaction mixture at a selected temperature for a short period allowed the system to polymerize and resulted in a high-molecular-weight PAA (reduced viscosity η red > 2 dl g −1 ). On the other hand, in the CBDA/TFMB system, a highmolecular-weight PAA (η red > 3 dl g −1 ) was readily obtained by choosing the solid content without any salt formation. The chosen PIs almost achieved the current goal; CTE < 20 ppm K −1 , K < 3.0, and T g > 300 • C concurrently with adequate film flexibility. In particular, CBDA/TFMB accomplished a very low K (∼2.6). Although these PIs have a much lower thermo-oxidative stability than wholly aromatic PIs, the results suggested that there is no serious problem for the short-term thermal stability required for soldering processes.

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Section: 23supporting

confidence: 80%

Semi-Aromatic Polyimides with Low Dielectric Constant and Low CTE

Hasegawa

2001

High Performance Polymers

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Thermotropic copolyesters. II. Synthesis and characterization of copolyesters containing the bicyclo[2.2.2]oct‐2‐ene mesogenic unit

Cited by 1 publication

References 19 publications

Semi-Aromatic Polyimides with Low Dielectric Constant and Low CTE

Semi-Aromatic Polyimides with Low Dielectric Constant and Low CTE

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