Synthesis and characterization of organosoluble aliphatic–aromatic copolyimides based on cycloaliphatic dianhydride

https://doi.org/10.1016/S0014-3057(01)00206-3Get rights and content

Abstract

A series of aliphatic–aromatic polyimides have been synthesized. These polyimides were prepared by high-temperature polycondensation of the aliphatic diamines: 1,4-diaminobutane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,9-diaminononane, 1,10-diaminodecane, 1,12-diaminododecane and 4,4-methylenebis(2,6-dimethylaniline) with 1,2,3,4-cyclopentanetetracarboxylic dianhydride. Various ratios of diamines (aromatic:aliphatic) have been applied for preparation of copolyimides. Polycondensation proceeded at 190 °C and produced copolyimides with reduced viscosities up to 0.92 dl/g. The polyimides were soluble in a wide range of organic, common solvents and showed high-thermal stability. In most cases these polymers formed flexible films which presented excellent transparency.

Introduction

Polyimide materials have been extensively studied for many years and are widely used in many fields in industry [1]. Polyimide investigations have mainly been concentrated on wholly aromatic polyimides [2]. Such polyimides have attracted much interest because of their high-temperature resistance and good mechanical and dielectrical properties. These properties make them highly desirable for high-performance applications. However, their lack of processability in their imidized form is one of their drawbacks. Fully aromatic polyimides are mostly insoluble in conventional organic solvents and infusible materials [3]. As a consequence, potential applications are limited. Much research has focused on different chemical modifications in order to improve their processability. There are different methods available which tend to induce solubility of polyimides. One of them is employing aliphatic monomers which tend to give soluble polyimides, although thermal stability is compromised [4]. Most wholly aromatic polyimides strongly absorb in the visible region and in therefore they are usually colored. The formation of intermolecular and intramolecular charge-transfer complex (CTC) could be the reason of coloration of aromatic polyimides ranging from pale yellow to deep brown [5], [6]. They cannot be used in the areas where colorlessness and transparency are important requirements. Aerospace, electronic and optoelectronics industry need transparent polymers in the applications such as covering solar cells, orientation films in liquid crystal display devices, optical waveguides for communication and optical half-waveplates for planar lightwave circuits [5], [7], [8], [9].

In recent years considerable research has been carried out aimed at the aliphatic polyimides because of their potential applications, including the use as liquid crystal orientation layers, NLO buffer layers or low dielectric materials [10], [11], [12].

Introduction of aliphatic monomers, for example aliphatic diamines as comonomers seems reasonable to reduce the chain–chain interaction because the aliphatic diamines are more flexible and may disrupt the interactions between aromatic moiety effectively. On the one hand using aliphatic monomers causes enhancement of the transparency, decrease the dielectric constant and improvement of solubility but on the other hand the thermal stability of such polyimides may be reduced. But the use of the alicyclic monomers may be a good compromise between processability and thermal properties [13]. There are a few papers which described the use of cyclic aliphatic diamines to reduce chain–chain interactions [6], [14] or cyclic dianhydrides [10], [15], [16], [17], [18], [19].

In our work we have synthesized a series of mixed aromatic–aliphatic polyimides. Soluble and almost entirely colorless copolyimides synthesized from cyclic dianhydride: 1,2,3,4-cyclopentanetetracarboxylic dianhydride and aromatic diamine with methyl groups and a few aliphatic diamines are presented in this paper. It is expected that the utilization of aliphatic diamines enhances solubility through reduction of the formation of CTC, which should improve the transparency and decrease the dielectric constant as well. Whereas employing the alicyclic dianhydride and aromatic diamine may preserve thermal stability [13].

Section snippets

Materials

1,2,3,4-Cyclopentanetetracarboxylic dianhydride (CPDA) as received was recrystallized from acetic anhydride, 4,4-methylenebis(2,6-dimethylaniline) (MDMA) (Aldrich), 1,4-diaminobutane (Fluka), 1,6-diaminohexane (Fluka), 1,7-diaminoheptane (Fluka), 1,9-diaminononane (Fluka), 1,10-diaminodecane (Fluka), 1,12-diaminododecane (Fluka), 1,4-diazabicyclo[2,2,2]octane (Aldrich) were used as laboratory reagents without purification, m-cresol was distilled prior to polycondensation.

Polymer synthesis

One-step catalytic

Results and discussion

In our study we have synthesized a series of semi-aromatic copolyimides from CPDA and five commercially available aliphatic diamines: 1,4-diaminobutane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,9-diaminononane, 1,10-diaminodecane, 1,12-diaminododecane and one aromatic diamine, namely MDMA using high-temperature polycondensation. The structure of these copolyimides is shown in Fig. 1.

The polymers we studied can be subdivided into four groups. These groups consist of copolyimides derived from the

Conclusion

Soluble, in most cases colorless semi-aromatic polyimides which form flexible films have been synthesized. Aliphatic moieties as comonomer reduce the rigidity of polymer chain, which enhanced the solubility and decreased coloration. Aromatic part and alicyclic compound preserve thermal stability of these polymers. The glass transition temperature of the copolyimides is in the range of 330–189 °C. Temperature of 10% weight loss in nitrogen for these polymers is in the range of 425–495 °C. Most

Acknowledgements

The authors thank Dr. H. Janeczek for DSC measurements and Mrs. A.A. Burian for X-ray diffraction measurements.

References (20)

  • Ch.-P. Yang et al.

    Polymer

    (2001)
  • Y.T. Chern

    J Polym Sci Polym Chem Ed

    (1996)
  • M. Goyal et al.

    J Polym Sci Polym Chem Ed

    (1998)
  • L. Litauszki et al.

    J Polym Sci Polym Chem Ed

    (1992)
  • Z.A.P. Falcigno et al.

    J Polym Sci Polym Chem Ed

    (1992)
  • Q. Jin et al.

    J Polym Sci Polym Chem Ed

    (1994)
  • A.L. Rusanov et al.

    High Perform Polym

    (1999)
  • Ch.-P. Yang et al.

    J Polym Sci Polym Chem Ed

    (1999)
  • Ch.-P. Yang et al.

    Macromol Chem Phys

    (2000)
  • Matsumoto T. Polycondensation 2000:70, Tokyo,...
There are more references available in the full text version of this article.

Cited by (32)

  • Colorless polyimides with excellent optical transparency and self-healing properties based on multi-exchange dynamic network

    2021, Applied Materials Today
    Citation Excerpt :

    Aromatic polyimides, however, pose a challenge because of their dark-brown color; they absorb light in the visible spectrum area at approximately 500 nm owing to the charge transfer complex (CTC) within the polyimide molecules and between chains, caused by the conjugated system of π electrons found in the main chain [6]. Therefore, to solve this problem, studies have continuously reported findings on colorless polyimides (CPI), where a monomer is introduced to lower the CTC effect, thereby resolving the color problem and, at the same time, enhancing flexibility [7–12]. The CPI film is referred to as the “dream material” in the field of electronic materials, particularly in the display market.

  • Synthesis of highly transparent poly(amide–imide)s based on trimellitic acid and dependence of thermal properties on monomer sequence

    2016, Reactive and Functional Polymers
    Citation Excerpt :

    The molded plastic has good thermal properties: glass transition (Tg) of 290 °C and 5% weight loss temperature (Td5) of 470 °C. However, these PEIs still absorb light around 400 nm, making them appear pale yellow, because of the formation of inter- and intramolecular charge transfer complexes; moreover, they have serious processing issues [5–15]. Yang and coworkers studied the preparation of colorless PAIs by decreasing the imide content, changing the monomer sequences, or introducing sulfone group for aromatic amide monomers [16–19].

  • 4-(4-Nitrophenoxy)butanol

    2011, Acta Crystallographica Section E: Structure Reports Online
  • 1,10-Bis(4-nitrophenoxy)decane

    2010, Acta Crystallographica Section E: Structure Reports Online
View all citing articles on Scopus
View full text