Organo-soluble polyimides: synthesis and polymerization of 2,2′-disubstituted-4,4′,5,5′-biphenyltetracarboxylic dianhydrides
1996; Elsevier BV; Volume: 37; Issue: 22 Linguagem: Inglês
10.1016/0032-3861(96)00365-5
ISSN1873-2291
AutoresFrank W. Harris, Sheng‐Hsien Lin, Fuming Li, Stephen Z. D. Cheng,
Tópico(s)Silicone and Siloxane Chemistry
ResumoThe objective of this research was to investigate the effects of introducing pendant groups in the 2- and 2′-positions of 4,4′,5,5′-biphenyltetracarboxylic dianhydrides on the properties of polyimides produced from the dianhydrides. Thus, the work was begun with the syntheses of 2,2′-dibromo-4,4′,5,5′-biphenyltetracarboxylic tetracarboxylic dianhydride (DBBPDA) and 2,2′-diphenyl-4,4′,5,5′-biphenyltetracarboxylic dianhydride (DPBPDA). The two new dianhydrides were polymerized with several substituted 4,4′-diaminobiphenyls including 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl (PFMB) in refluxing m-cresol containing isoquinoline to afford two new series of soluble polyimides. The polyimides had intrinsic viscosities that ranged from 1.80 to 5.58 dl g−1 (N-methyl-2-pyrrolidinone or m-rmcresol at 30°C). Their glass transition temperatures (Tgs) ranged from 322 to 351°C (thermal mechanical analysis). Several of the polymers obtained from the new dianhydrides were soluble in acetone and tetrahydrofuran. The polymers formed water-white, tough films that were transparent above 350 nm. The films displayed negative birefringence, i.e. their in-plane refractive indices (n∥) were higher than their out-of-plane refractive indices (n⊥). For example, the DBBPDA/PFMB polymer, which was soluble in acetone and had a Tg of 330°C, formed films with n∥ = 1.637 and n⊥ = 1.564. The films had coefficients of thermal expansion that ranged from 1.05 × 10−5 to 2.12 × 10−5°C−1. The films may be useful as retardation layers in liquid crystal displays.
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