Synthesis of novel polyimides from dianhydrides with flexible side chains - Polyimides and Other High Temperature Polymers - page 69

Synthesis of novel polyimides from dianhydrides with
flexible side chains
YONG SEOK KIM, ∗ KYUNG HOON LEE and JIN CHUL JUNG
Center for Advanced Functional Polymers/Polymer Research Institute, Department of Materials
Science & Engineering, Pohang University of Science & Technology, San 31, Hyoja-dong, Pohang,
790-784, Korea
Abstract—Polyimides have been of great interest in engineering and microectronics for a number of
applications because of their unique properties. In this study, we prepared a series of polyimides from
pyromellitic dianhydrides having two 4-( n- alkyloxy)phenyloxy groups at their 3 and 6 positions.
Also, another series of polyimides containing alicyclic units and alkyloxy side chains were prepared
from 9,10-dialkyloxy-1,2,3,4,5,6,7,8-octahydro-2,3,6,7-anthracenetetracarboxylic 2,3,6,7-dianhyd-
rides. Their physical properties such as thermal stability, phase transition and solution properties were
investigated. WAXS studies revealed that substituted rigid-rod polyimides had typical well-developed
layered structures, while non-rigid-rod polyimides had loosely packed layered structures.
In particular, uniform alignment layers, possessing high pretilt angles, have been obtained by
mechanical rubbing of the polyimide film from C n -PMDA, and their LC aligning property, such as
pretilt angle and thermal stability of the LC director, were investigated with respect to the chemical
architecture of polyimides. It is very interesting behavior that the pretilt angles in C n -OPIs have
been observed to possess both positive ( θ p ) and negative (- θ p ) angles depending on the side chain
length.
Keywords : Polyimides; modification; side chain; thermal properties; pretilt angle.
1. INTRODUCTION
Wholly aromatic polyimides are a very important class of high performance
polymers used in various applications requiring high thermal, mechanical and
electrical characteristics [1]. Most of the aromatic polyimides, however, suffer
from lack of processibility due to their infusible and insoluble nature, and must
first be prepared as a soluble precursor, e.g., poly(amic acid) and then processed
into the final form by thermal or chemical imidization methods. To overcome this
drawback, a large number of structural modifications have been attempted such as