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Date of Publication:2022-10-10

Journal:高分子学报

Issue:06

Page Number:692-699

ISSN No.:1000-3304

Abstract:Through molecular design, three different block copolymers PPENK-b-PEEKK with phthalazinone moiety were synthesized via modest polycondensation reaction from the two macromers PEEKK-OH and PPENK-F. Hydroxy terminated PEEKK-OH macromer was obtained by solution polymerization from HQ and BFBB with sulfolane as the solvent. And the molecular weight of PEEKK-OH was successfully controlled by adjusting the monomer ratio, and the polymerized conditions were optimized by orthogonal experiments. While different molecular weight PPENK-F macromer, endcapped with -F groups, was prepared from DHPZ, DFK and DFBN. Chemical structures and properties of these block copolymers were inverstigated by Fourier transforming infrared spectrum (FTIR), wide X-ray diffraction (WXRD), differantial scanning calorimetry (DSC) and thermogravimetric analyses (TGA). The FTIR spectra confirmed the formation of the block copolymers. Furthermore, WXRD measurement showed that all the block copolymers presented crystalline structure, and the crystallinity of the coplolymers decreased with increasing molecular weight of PPENK-F chain segments. All the block copolymers showed only one glass transition temperature (T-g), above that of PEEKK-OH. The T-g of the block copolymers increased with the molecular weight of PPENK-F, due to the introduction of PPENK chain segments into the block copolymers. Moreover, for the reason of of PEEKK incorporation, all these copolymers have a same melting point (T-m) of about 340 degrees C, which would facilitate their thermal processing. Besides, all the three copolymers also exhibited remarkable thermal stability in nitrogen atmosphere with the T-d5(%) weight loss temperature ranging from 491 degrees C to 510 degrees C, and T-d10(%) from 523 degrees C to 530 degrees C, respectively. The char yields of the three copolymers at 800 degrees C were higher than 63%. Finally, all the copolymers showed improved solubility in selectively tested organic solvents, such as NMP and sulfolane, due to the introduction of twisted and non-coplanar DHPZ structure. Consequently, theses materials are potential candidates for the aerospace applications.

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