Synthesis and characterization of aromatic poly(ether-imide)s based on bis(4-(3,4-dicarboxyphenoxy)phenyl)-R,R-silane anhydrides (R = Me, Ph) – spontaneous formation of surface micropores from THF solutions

Abstract

Two new aromatic dianhydride monomers containing R,R-diphenylsilane (R = Me or Ph), an ether group and an isobenzofuran-1,3-dione moiety in their structure were prepared and spectroscopically characterized. They were reacted with two silylated aromatic diamines, previously reported, in order to prepare four different aromatic poly(ether-imide)s (PEIs). High yields were obtained for the synthesis of these polymers with an inherent viscosity range between 0.10 and 0.27 dL g⁻¹, corresponding to a viscosimetric average molecular weight (M_v) from 1740 to 9520. PEIs were soluble in a variety of polar aprotic solvents. The thermal decomposition temperatures measured varied between 473 and 526 °C and the glass transition temperature values obtained varied from 164 to 184 °C. All poly(ether-imide)s were transparent in the UV-visible region. Additionally, films of these polymers were prepared by deposition of a solution through a spin coating technique; this process induces a spontaneous micropore formation on the film surface by means of quasi-instantaneous solvent evaporation. The solid samples were morphologically characterized by Field Emission Scanning Electron Microscopy (FE-SEM) and Atomic Force Microscopy (AFM). Thus, shape, distribution and dimensions (diameter and height) of the pores were studied. These parameters varied in agreement with the specific polymer characteristics: molecular weight, solubility and the nature of the R groups inserted into the molecule (phenyl group presence produces larger and deeper pores), among others.