Siloxane polyimide copolymers

The earlier sections of this review have attempted to review the synthesis and characterization of the segmented copolymer materials as well as to highlight fundamental efforts related to a number of structure-property relationships. Polyimide-siloxane copolymers are high performance materials that have been driven by applications frequently identified with aerospace. However, this section will also include surface phenomena which are critical for certain electronic applications and high performance blends utilizing imide-siloxane copolymers. 

Arnold CA, Summers JD, Bott RH, Taylor L T, Ward TC, McGrath JE (1987) Structure-property relationship of polyimide-siloxane copolymers prepared by bulk and solution imidization techniques. Polym Preprints, ACS National Meeting 28(2) 217... 

Szesztay M, Ghadir M (1993) GPC investigation of polyimide-siloxane copolymers. Angew Makromol Chem 209 111... 

Chen DH, Chen YP, Arnold CA, Hedrick JC, Graybeal JD, McGrath JE (1989) Compatible blends of segmented polyimide siloxane copolymers with engineering thermoplastics I polybenzimidazole (PBI). 34th International SAMPE Symposium 1247... 

DepalmaVA,Sharma R, Tunney SE, Brust DP Slipping layer of polyimide-siloxane copolymer for dye-donor element use in thermal dye transfer. US Patent 5252534 14 pp... 

Proton NMR Analysis All proton spectra were measured on a Varian Unity 400 MHz NMR. Samples were dissolved in deuterated chloroform. TMS was used as an internal reference standard for the polyimide oligomers. Chloroform was used as a reference for the polyimide-siloxane copolymers. 

The use of d catalyst is not necessary In the copolymerization of polyimides arxf amtnopropyl terminated polydimethylsiloxanes. Intrinsic viscosities after 2 hours reaction time are comparable for copolymerization either with or without a catalyst. Solution cast films from the reaction flask were tough, flexible and transparent. Figure 2 shows a representative NMR of a polyimide-siloxane copolymer. 

PERFECTLY ALTERNATING SEGMENTED POLYIMIDE SILOXANE COPOLYMERS... 

The polyimide siloxane copolymers are generally synthesized, as shown in Scheme 1, from a combination of a dianhydride and diamine monomer and an aminopropyl terminated polysiloxane to form the segmented polyamic acid. The polyamic acid is then cyclodehydrated by either thermal or solution imidization to give randomly segmented polyimide siloxane copolymers (4). This is indeed the classical approach of reacting one flexible oligomer with two monomers which form the "hard segment (9). 

Scheme 1. Synthesis of Randomly Segmented Polyimide Siloxane Copolymers...

Figure 2 shows a representative NMR of a polyimide siloxane copolymer with 31 wt% polysiloxane. The theoretical molecular weight of the polyimide oligomer is 4000 g/mole and the polysiloxane had a number average molecular weight of 2670 g/mole. The disappearance of the 2AP proton at 8.7 ppm indicates that the reaction went to near complete conversion. 

PEEK can be blended with polyimide/siloxane copolymers to produce materials with improved ductility. Such materials may be suitable... 

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