A Study on Dielectric or Adsorption Properties of Network Polymers Containing Cyclotriphosphazene Rings

Abstract

Cyclotriphospazenes are cyclic compounds having alternate nitrogen and phosphorus atoms. With a diverse combination of two substituent groups attached to the phosphorous atoms, they can have a broad range of chemical and physical properties. In this study, reactive cyclotriphosphazene derivatives were synthesized and used for the preparation of functional materials. Firstly, flame retardant and low dielectric epoxy resins based on cyclotriphosphazene were studied. Cyclotriphosphazenes having epoxy groups and 2-biphenol (B-PE), 4-phenylphenol (P-PE), and 2-naphtol (N-PE) as co-substituents were synthesized. Highly cross-linked polymers were obtained by thermal polymerization with an active ester type hardener and dimethylaminopyridine. The resulting epoxy polymers showed good thermal stability. The temperatures of 5% weight loss, measured by TGA, were above 300℃. The polymers having B-PE, P-PE, and N-PE as co-substituents showed low dielectric constants of about 2.192, 2.388, and 2.175 and low dielectric losses of about 6.08 * 10-3, 6.13 * 10-3, and 4.97 * 10-3 at 10 GHz, respectively. The flame-retardant property of the B-PE polymer was excellent, showing a very high LOI value of 31. Secondly, porous cyclophosphazene-based polymers were prepared by Friedel-Crafts alkylation reaction of a biphenol substituted cyclophosphazene and dichloroxylene or bis(chloromethyl)biphenyl. Dichloroxylene and bis(chloromethyl)biphenyl acted as linkers and the microporosities of the polymers were tuned by adjusting their molar ratios to the cyclotriphosphazene monomer. All PCPs showed large Brunauer-Emmett-Teller surface areas, hierarchical pore size distributions, and good CO2 uptake properties.