Two isomeric diamine monomers, 2-(3-aminophenyl)benzo[d]oxazol-5-amine (2a) and 2-(3-aminophenyl)benzo[d]oxazol-6-amine (2b), were designed and synthesized. The corresponding novel series of poly(benzoxazole imide)s (PBOPIs) were prepared with commercial tetracarboxylic dianhydrides via thermal imidization. These series of PBOPIs showed great T(g)s ranging from 285 to 363 degrees C, excellent thermal stability when performed at 5% weight loss temperatures (T(d5%)s) of 510-564 degrees C in N-2 and good mechanical properties (tensile strengths of 103-126 MPa, tensile moduli of 2.9-3.7 GPa and elongations at break of 3.0-6.5%). Furthermore, controlled molecular weight (M-w) polymers PI-3a-PA and PI-3b-PA derived from 4,4 ‘-oxydiphthalic anhydride (ODPA) with 2a and 2b demonstrated good melt processability with minimum complex viscosities of 2258 and 3444 Pa center dot s at 420 degrees C and low melt viscosity ratios of 1.29 and 1.93 at 400 degrees C, respectively. The PI-b series showed higher T-g & T-d5% and lower transparency compared with the PI-a series due to the isomeric effect.
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Reference:
Benzoxazole – Wikipedia,
,Benzoxazole | C7H5NO – PubChem