Ternary composites of linear and hyperbranched polyimides with nanoscale silica for low dielectric constant, high transparency, and high thermal stability

Abstract

A new series of ternary polyimide-silica composites was developed to obtain polymer films with low dielectric constant, high optical transparency, and good thermal stability. By using a linear polyamic acid with triethoxysilane termini and a hyperbranched polyimide with peripheral hydroxyl groups (HBPI BPADA-TAP(OH) ), the ternary composites were fabricated through in situ imidization and sol-gel reaction with tetraethoxysilane. The results show that the composite films exhibit significantly improved properties due to the strong silica cross-linkages between organic-inorganic phases. The triethoxysilane termini can effectively enhance transparency because of the homogeneous dispersion of the inorganic phase in the PI matrices and the improved dispersibility through their strong covalent and partial hydrogen bonding with inorganic silica networks. With an appropriate content of 30% HBPI BPADA-TAP(OH) and 20% SiO 2 in the linear polyimide (PI 6FDA-APB(Si) ), the dielectric constant (D k ) can reach the lowest value of 2.19 at 100 kHz. The highest transmittance of 96% at 450 nm is obtained for a ternary hybrid containing 20% SiO 2 and 10% HBPI BPADA-TAP(OH) . The incorporation of HBPI BPADA-TAP(OH) does not cause negative effects on the thermal stability. The ternary hybrid containing 20% SiO 2 and 10% HBPI BPADA-TAP(OH) also exhibits the lowest coefficient of thermal expansion (CTE) of 27.8 ppm C À1 , when compared with 29.9 ppm C À1 for the binary composite as PI 6FDA-APB(Si) with 20% SiO 2 . These properties can well match the requirements for potential applications in the microelectronics insulator fields as interlayer dielectrics of advanced electronic devices.Scheme 1 Synthetic route for PAA 6FDA-APB(Si) and a binary composite (SF-1, PI 6FDA-APB(Si) _SiO 2 -20%). This journal isScheme 2 Synthetic route for PI 6FDA-APB(Si) _HBPI BPADA-TAP(OH) _SiO 2 hybrid ternary composite.40048 | RSC Adv., 2015, 5, 40046-40054This journal is

Polyhedral oligosilsesquioxane-modified boron nitride enhances the mechanical properties of polyimide nanocomposites

“…Second, the fracture interface of the PI/Gh-BN film was observed to be densely branched, enabling the film to prevent crack propagation via energy absorption. 46 Fig. 2(g) and (h) show the fracture cross-sections of the PI/EPPOSS film.…”

Green one-pot synthesis and processing of polyimide–silica hybrid materials

“…TEOS is a standard sol-gel precursor of SiO 2 , and APTES is a standard network-modier that has been used to (i) introduce amino-functionalities in SiO 2 , 20 and (ii) as a compatibilizer between SiO 2 and PIs in the preparation of PI/SiO 2 hybrids. 21,22 Note that other approaches to covalently link PIs to SiO 2 include (i) employing epoxy-functionalized silicon alkoxides, 23 (ii) the use of PI monomers with pendant OH groups able to co-condense with TEOS, 24 (iii) employing pre-formed PMMA-functionalized SiO 2 particles, where the PMMA-functionalization allows for crosslinking with the PI via transesterication, 25 (iv) to decorate PIs with pendant silane side-groups that are able to co-condense with TEOS, 26 or to employ APTES end-capped poly(amic acid) species. 27 However, all the PI/SiO 2 hybrids and composites reported to date have been prepared employing classical, non-green routes, i.e.…”

“…by polycondensation in toxic solvents such as DMF or NMP via poly(amic acid) intermediates. [21][22][23][24][25][26][27] From our studies of HTP of PI6, we restricted the employed reaction parameters to T R ¼ 200 C, t R ¼ 24 h and the autogenous pH ¼ 4, generated by the acidity of PMA. We investigated three types of precursor mixtures: (i) HMDA/PMA/TEOS (experiments #1-3) (ii) HMDA/PMA/TEOS/APTES (experiments #4-6), and (iii) HMDA/PMA/APTES (experiments #7-9), all summarized in Table 1.…”

“…APTES has been used as a compatibilizer in several studies on PI/SiO 2 hybrids. 21,22 On one hand, the presence of Si-OEt moieties allows for hydrolysis to Si-OH, and subsequent co-condensation with Si-OH from hydrolyzed TEOS to Si-O-Si functions. On the other hand, the NH 2 functionality of the aminopropyl moiety is able to cocondense with 1,2-dicarboxylic acid moieties of PMA to form imide functions (Fig.…”

Highly dispersible ternary composites with high transparency and ultra low dielectric constants based on hyperbranched polyimide with organosilane termini and cross-linked polyimide with silica

“…19,[26][27][28][29] We have recently fabricated a novel ternary hybrid system: a hydroxyl terminated hyperbranched polyimide with linear PI/SiO 2 (ref. [30][31][32] that has excellent properties, for example, a very low dielectric constant, reduced organic particle size [30][31][32][33] and good thermal stability. Additionally, we have reported that by using a exible organosilane agent nano-sized domains of SiO 2 are formed and that this produces a highly dispersed material.…”