Published online by Cambridge University Press: 15 February 2011
Adding photoreactive substituents onto a biphenyldianhydride (BPDA) and p-phenylene diamine (PPD) poly(amic acid) precursor influences the onset of imidization and the development of anisotropy and crystalline morphology during processing and the resulting morphology and properties of the fully cured films. Amine salts shift the imidization to lower temperatures while the covalently bonded esters shift the imidization to slightly higher temperatures. Anisotropy of the photosensitive polyimides develops at higher cure temperatures compared to the poly(amic acid). The photoreactive substituents do not affect the crystal structure, but do influence the crystallite orientation and morphology. Out-of-plane coefficients of thermal expansion (CTEs), calculated from the volume expansivities of these systems, are an order of magnitude larger than the in-plane CTEs.
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