Aqueous Poly(Amic Acid) Synthesis for Solvent-Free Polyimide
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Solution Overview
Problem
The synthesis of polyimides often results in residual organic solvent content, which is undesirable for certain applications, and existing methods do not effectively minimize this content.
Innovation Solution
A process involving the reaction of a dianhydride and a diamine in the presence of a higher monoamine in a water-based medium, under inert conditions, to produce a poly(amic acid with minimal organic solvent residue, which can then be converted to polyimide, either thermally or chemically, without organic solvent residues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polyimide is synthesized using conventional organic solvent methods, then the polymerization reaction proceeds efficiently, but residual organic solvent remains in the final product which is undesirable for certain applications
Solution Approach 1:
The invention changes the fundamental parameter of the reaction medium from organic solvent to water-based system. By using water as the primary solvent and employing a two-stage process (first stage: polycondensation in water with phase transfer catalyst; second stage: cyclization in organic solvent or water), the method eliminates harmful organic solvent residues while maintaining polymerization efficiency through careful control of reaction conditions including temperature, pH, and catalyst selection
Solution Approach 2:
The invention introduces a phase transfer catalyst as an intermediary substance that enables the polycondensation reaction to proceed efficiently in the aqueous phase. The catalyst facilitates the interaction between water-soluble polyamic acid and organic dianhydride, allowing efficient polymerization without requiring large amounts of organic solvent, thus reducing residual solvent content in the final product
2Object-generated harmful factors
If water is used as the reaction medium, then organic solvent residue is eliminated, but the solubility and homogeneity of the reaction mixture may be compromised
Solution Approach 1:
The invention employs parameter changes including pH control (maintaining basic conditions with ammonia or amine additives), temperature control (heating to 60-80°C during polycondensation), and concentration control (using specific ratios of water to reactants) to ensure complete dissolution of reactants and formation of homogeneous aqueous polyamic acid solutions, thereby maintaining solution stability while using water as the green solvent
Solution Approach 2:
The phase transfer catalyst acts as an intermediary that enhances the solubility and reactivity of organic dianhydride in the aqueous medium. By forming soluble complexes or facilitating interfacial transfer, the catalyst ensures homogeneous mixing and complete reaction in the water-based system, preventing phase separation and maintaining composition stability
3Productivity
If the solids content of poly(amic acid) is increased to 50-80%, then the efficiency of subsequent coating application is improved, but the viscosity of the solution increases making handling difficult
Solution Approach 1:
The invention optimizes the solids content parameter to the specific range of 50-80% by controlling the water-to-reactant ratios and reaction conditions. This parameter optimization achieves high coating efficiency while maintaining adequate fluidity for handling, representing a balanced compromise between productivity and operability through precise parameter control
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method efficiently produces poly(amic acid and polyimide with no organic solvent residues, offering a homogeneous aqueous solution suitable for direct application and subsequent cyclization to form a polyimide coating, while being environmentally friendly and cost-effective.
Implementation Method 1
reacting a dianhydride and a diamine in the presence of a higher monoamine in a reaction medium comprising at least 95 volume percent water
Implementation Method 2
The poly(amic acid) is then converted to the polyimide by cyclization, eliminating water
Data Source
AI summary
A process is disclosed for synthesis of a poly(amic acid), including reacting a dianhydride and a diamine in the presence of a tertiary amine, tertiary ammonium salt, tertiary ammonium hydroxide, secondary amine, secondary ammonium salt, secondary ammonium hydroxide, quaternary ammonium salt, quaternary ammonium hydroxide, ammonium hydroxide, or a combination comprising at least one of the foregoing, in water, at a temperature of 60C to 180C, or 60C to 100C, or 100C to 180C, under an inert atmosphere, with agitation, to produce an aqueous poly(amic acid).