A Low Temperature Polycondensation for the Preparation of Highly Fluorinated Poly(arylene ether sulfone)s Containing Crosslinkable Pentafluorostyrene Moieties

• Published in: Macromolecular chemistry and physics 2005-12, Vol.206 (23), p.2396-2407
• Main Authors: Ding, Jianfu, Qi, Yinghua, Day, Michael, Jiang, Jia, Callender, Claire L.
• Format: Article
• Language: English
• Subjects: Applied sciences; crosslinkable; Exact sciences and technology; fluorinated; low temperature; Organic polymers; Physicochemistry of polymers; poly(arylene ether sulfone)s; polycondensation; Polymers with particular properties; Preparation, kinetics, thermodynamics, mechanism and catalysts; waveguide
• ISSN: 1022-1352; 1521-3935
• DOI: 10.1002/macp.200500327

The polycondensation of pentafluorophenyl sulfone (PPSO) with hexafluorobisphenol A (6F‐BPA), or a model compound, 4‐phenoxylphenol (POPOH), has been studied in order to find optimized reaction conditions for the preparation of fluorinated poly(arylene ether sulfone)s (FPAESs). It was found that PPSO had a very high reactivity in N,N‐dimethylacetamide (DMAc), allowing the reaction to occur at temperatures as low as 22 °C, even in the absence of any catalyst. This reaction was promoted by the addition of a trace amount of potassium fluoride (KF). Increasing the amount of KF to 1.05 equiv enhanced the conversion and allowed the reaction to be completed in a short time. Under this reaction condition, KF acted as a catalyst to activate the phenol group and also acted as a base to absorb the HF, which was a by‐product of the polycondensation, to produce high molecular weight polymer. The use of calcium hydride (CaH2) instead of KF as a base in this reaction produced a similar effect with a slightly lower reaction rate. Both base systems were also applicable to the reaction of pentafluorostyrene (FSt) with 6F‐BPA. However, a much higher reaction temperature (125 °C) was required due to the low reactivity of FSt. Reacting FSt with an excess of 6F‐BPA produced a mixture of mono‐ and di‐substituted products of FSt with a controllable ratio, which could further react with PPSO to produce a polymer containing crosslinkable FSt moieties both as end‐capping groups and inserting units. This structure allowed the molecular weight of the polymer and the content of FSt to be adjusted independently. Crosslinked films of this polymer demonstrated an excellent processability and performance in waveguide applications, having refractive indices of 1.5061 (TE) and 1.5038 (TM), and a straight waveguide loss of 0.7 dB · cm−1. Reaction scheme for the preparation of fluorinated poly(arylene ether sulfone)s.