High‐optical transparency and low‐dielectric constant of new organosoluble polyamides containing trifluoromethyl and xanthene groups

Abstract

A series of fluorinated polyamides was prepared directly by low-temperature polycondensation of a new cardo diacid chloride, 9,9-bis[4-(4-chloroformylphenoxy)phenyl]xanthene (BCPX), with various diamines containing trifluoromethyl substituents in N,N-dimethylacetamide (DMAc). Almost all polyamides showed excellent solubility in amide-type solvents such as DMAc and could also be dissolved in pyridine, m-cresol, and tetrahydrofuran. These polymers had inherent viscosities between 0.77 and 1.31 dL g À1, and their weight-average molecular weights and number-average molecular weights were in the range of 69,000-102,000 and 41,000-59,000, respectively. The resulting polymers showed glass transition temperatures between 240-258 C and 10% weight loss temperatures ranging from 484 C to 517 C and 410 C to 456 C in nitrogen and air, respectively, and char yields at 800 C in nitrogen higher than 55%. All polymers were amorphous and could be cast into transparent, light-colored, and flexible films with tensile strengths of 81-100 MPa, elongations at break of 8-12%, and tensile modulus of 1.6-2.1 GPa. These polymers had low-dielectric constants of 3.34-3.65 (100 kHz), low-moisture absorption in the range of 0.76-1.91%, and high transparency with an ultraviolet-visible absorption cut-off wavelength in the 322-340 nm range.

Spiro[fluorene-9,9′-xanthene] containing fluorinated poly(ether amide)s: Synthesis, characterization and gas transport properties

“…The spirofluorene moiety and trifluoromethyl groups brought about less efficient interchain packing; subsequently increase fractional free volume of these polyamides and the strong electronegativity of fluorine atom also results in very low polarizability of the CAF bonds. Therefore, all the PAs showed lower dielectric constant values (2.34-3.09) [10,25,34,35]. The lower dielectric constant values of PA 'S1' and PA 'S2' might be due to the presence of tert-butyl group and hexafluoroisopropylidene linkage in acidic counter, respectively, compared to the other polyamides.…”

“…The presence of bulky spirofluorene moiety, ether linkages and bulky ACF 3 groups in the polymer backbone inhibits the intermolecular interaction between the polymer chains and also disturbs the conjugation throughout the polymer chain [25,34,35]. Therefore, these PAs showed lower cut-off wavelength (k 0 ) and higher optical transparency values.…”

“…Therefore, the spiroskeletons linkage containing polyamides showed improved solubility in comparison to the many other reported polyamides. The presence of kinked units (spirofluorene), pendant trifluoromethyl groups and flexible ether linkages in the polymer repeat unit inhibits the close packing of polymer chains by reducing the hydrogen bonding and improves processability [10,25,31,34].…”

Fluorinated Polyamides

“…The PAs showed good solubility in amide-type solvents and also dissolved in tetrahydrofuran (THF). The analogous nonfluorinated PA synthesized from nonfluorinated diamine 1,4-bis(4-amino-phenoxy)benzene and fluorinated PA was synthesized from fluorinated diamine, 1,4-bis(4-amino-2-trifluoromethylphenoxy) benzenes [14]. The PA having a sulfone group showed the highest T g value in this series.…”

“…This is attributed to their decomposition temperature being below their melt temperature [1]. It is reported in the literature that the presence of bulky hexafluoroisopropylidene [-C(CF 3 ) 2 ] or trifluoromethyl (-CF 3 ) groups in the polyamide structure endows remarkable improvements in several properties compared to nonfluorinated polyamides [12][13][14][15][16][17][18][19][20][21][22][23][24][25]. The solubility of a less rigid and less linear structure like PMPI is higher due to the concomitant reduction in cohesive energy and crystallization tendency compared to PPPT.…”