Preparation of porous thin films of a partially aliphatic polyimide

Abstract

A thermally labile polymer, poly(propylene glycol), was modified to obtain PPG having an amino end group. PPG was incorporated into a partially aliphatic polyimide based on an alicyclic dianhydride, and this afforded triblock copolymers containing various amounts of PPG blocks. The thermal properties of the copolymers were investigated by thermogravimetric analysis and differential scanning calorimetry. The thermal decomposition of the PPG block in the copolymers was carried out at 240°C under various pressures to obtain porous polyimide films. The pores remained during the thermolysis under a reduced pressure of 710 mmHg, whereas they collapsed under (near) atmospheric pressure. The pore size increased as the amount of the PPG block in the copolymers increased. The dielectric constants of the porous polyimides varied from 2.60 to 2.42 with the original copolymer composition.

Thermo-stabilized, porous polyimide microspheres prepared from nanosized SiO2 templating via in situ polymerization

“…Additionally, another alternative approach has been employed to fabricate meso-and macro-porous polymer materials using block copolymers that have two or more chemically immiscible blocks covalently linked together (e.g. the IBM Almaden Research Center, 1990s [13][14][15]; Chung et al [16] (2006); Olson et al, [17] (2008); Wu et al, [4] (2012)). In these studies, the morphological structure of porous PI was determined by the initial morphology of the microphase separated structures of the copolyimides [17].…”

Nanoporous thin films of fully alicyclic polyimides

“…It was thought that low-molecular-weight copolymer fractions, rich in PPG, were lost due to fractionation during the polymer isolation procedure. 22 On the other hand, the isothermal TGA experiments helped establish that heating the samples at 230 o C for 200 min in air is sufficient for complete removal of PPG block from the copolyimides. It was also confirmed by 1 H NMR spectroscopy that the peaks due to the protons in the PPG block completely disappeared after heating at 230 o C for 200 min (Figure 3(b)).…”

“…This is attributable to the increase in domain size of phase-separated PPG block in the polyimide matrix with increasing PPG content. 22,27,28 There was difficulty in measuring dielectric constants of the porous films: impedance measurements and refractive index measurements were performed, but reliable data could not be obtained.…”

“…20,21 In our previous paper we reported the generation of nanopores in thin films of a partially alicyclic polyimide. 22 In the present study, the nanopore generation could successfully be accomplished in thin films of fully alicyclic polyimides derived from an alicyclic dianhydride and diamines.…”

“…13 reported procedure. 22 Characterization. 1 H NMR spectra were taken on a Bruker 400-MHz spectrometer in DMSO-d 6 .…”