The Synthesis And Properties Studies On The Polyimides Containing Five-membered Alicyclic Structure Derived From Natural Camphor

Polyimides are well known as functional material with outstanding thermal resistance and thermal stability,low dielectric constant and excellent mechanical strength,which are widely applied for adhesives,coating and composites in advanced aerospace and electrical applications etc.Traditional aromatic polyimide materials have excellent thermal, mechanical, electrical properties, however, due to the rigid polymer backbone structure, electron polarization and crystallinity, there is a strong polyimide inter-molecular chain interaction, resulting in close packing of polymer chains. These structural characteristcs lead to poor solubility, high refractory, difficulty in molding and high dielectric constant.In recent years,polyimides with high optical transparencies and low dielectric constants have been in demand for optoelectronic and microelectronic applications. Alicyclic polyimides are candidates for applications in optoelectronics and interlayer dielectrics due to their higher transparency and low dielectric constants when compared to aromatic polyimides.These properties result from their low molecular density,low polarity,and low probability of undergoing inter-or intramolecular charge transfer.According to the latest researches, the introduction of alicyclic structure into main chain of polyimid can diminish intra-molecular and inter-molecular charge transfer, which could reduce the dielectric constant, raise transparency and improve processing performance. Therefore, aliphatic polyimides have attracted great attention in recent years due to their potential applications including use as liquid crystal orientation layers, light-guide and high-temperature low dielectric materials.This paper discussed the developmental process of polyimides,displayed the structural characteristics of polyimides from the diamine and the dianhydride.Based on the viewpoint of molecular design and combined the research background and the abundant natural product resources in Jiangxi province. Starting from the renewable forestry chemical camphor, a new alicyclic diamine,BAMT,was prepared and structurally characterized. Thereby, a series of alicyclic polyimide films were synthesized, and their thermal, mechanical, optical, electrical properties and contact angle were studied, and the relationship of structure-performance also was theoretically investigated.The research in this thesis was mainly divided into three parts of work.Natural camphor with two-ring[2,2,1] structure was oxidized to diacid, reduced to diol, followed by substitution reaction with parachloronitrobenzene and further reduction to produce a novel alicyclic chiral diamine monomer (BAMT) containing1,2,2-trimethyl-cyclopentyl strutcure, and the structure of the diamine was confirmed by IR and NMR spectra. The new diamine monomer showed good solubility in most common solvents.Polyimide films derived from alicyclic diamine were synthesized by two-step polymerization of BAMT and DMB with ODPA and BPDA,and ODA with ODPA respectively, and the performance of five different films was investigated systematically.Compared with aromatic polyimide film, the thermal performance of polyimide film containing aliphatic ring unit was decreased. Still, it has good thermal stability, with5%weight loss temperature reaching440℃. Alicyclic polyimide films also have good mechanical property, and the flexural modulus were between the2750-3240MPa, the tensile modulus between92-133Mpa, and elongation at break between5.6-18%. In addition, the transmittance of alicyclic polyimide films at450nm can reach70%, and were almost colorless and transparent.Using natural camphor as original materials which was oxidized to diacid,followed by substitution reaction with oxalyl chloride and ammonia,and then further reduction with LiAlH4to produce a diamine monomer which is a new type of alicyclic chiral diamine monomer.