Temporally Stable Supramolecular Polymeric Salts Enabling High‐Performance 3D All‐Aromatic Polyimide Lattices

Abstract

Vat photopolymerization (VP) Additive Manufacturing (AM), in which UV light is selectively applied to cure photo‐active polymers into complex geometries with micron‐scale resolution, has a limited selection of aliphatic thermoset materials that exhibit relatively poor thermal performance. Ring‐opening dianhydrides with acrylate‐containing nucleophiles yielded diacrylate ester‐dicarboxylic acids that enabled photo‐active polyimide (PI) precursors, termed polysalts, upon neutralization with an aromatic diamine in solution. In situ FTIR spectroscopy coupled with a solution and photo‐rheological measurements revealed a previously unknown time‐dependent instability of 4,4′‐oxydianiline (ODA) polysalts due to an aza‐Michael addition. Replacement of the electron‐donating ether‐containing diamine with an electron withdrawing sulfone‐containing monomer, e.g., 4,4′‐diaminodiphenyl sulfone (DDS), prohibited the aza‐Michael addition of the aromatic amine to the activated acrylate double bond. Novel DDS polysalt photocurable solutions are similarly analyzed and validated long‐term stability, which enabled reproducible printing of polyimide organogel intermediates. Subsequent VP AM afforded 3‐dimensional (3D) structures of intricate complexity and excellent surface finish, as demonstrated with scanning electron microscopy. In addition, the novel PMDA‐HEA/DDS solution enabled the production of the first beam latticed architecture comprised of all‐aromatic polyimide. The versatility of a polysalt platform for multi‐material printing is further demonstrated by printing parts with alternating polysalt compositions.

Waterborne Polyurethane Latexes for Vat Photopolymerization

“…The resulting three-dimensional (3D) objects demonstrate isotropic properties, smooth surface finish, and microscale resolution; however, viscosity limitations typically restrict material options to lower molecular weight precursors. − Predominantly, VP employs patterned UV light to selectively cure photosensitive polymers in a layer-by-layer fashion with free-radical photoinitiated polymerization. Upon UV exposure, efficacious VP printing requires a sufficiently high plateau modulus, typically on the order of 10 4 to 10 6 Pa, to maintain geometric fidelity during the printing operation. − The combination of low viscosity limitations and high modulus requirements often provides mechanically poor 3D-printed parts due to high cross-link densities. Thus, VP compositions that employ copolymerization reduce cross-link density, but high concentrations of cross-linker are required to achieve sufficient modulus and maintain feature fidelity.…”

Soluble Fluorinated Cardo Copolyimide as an Effective Additive to Photopolymerizable Compositions Based on Di(meth)acrylates: Application for Highly Thermostable Primary Protective Coating of Silica Optical Fiber

“…There are approaches to obtain biocompatible materials by the modification of implantable polyimide films [34] and polyimide covalent organic frameworks for drug delivery applications [35]. Photosensitive compositions based on aromatic heterochain polymers and reactive solvents can be used to form mechanically durable three-dimensional objects by laser stereolithography [36][37][38][39][40][41], digital light processing (DLP) [42][43][44][45][46][47] and liquid crystal display (LCD) [48][49][50] 3D printing.…”