Synthesis and characterization of new organosoluble poly(ether imide)s derived from various novel bis(ether anhydride)s - Polyimides and Other High Temperature Polymers - page 46

ture of polyimides [3-11]. Poly(ether imide)s were developed as a result of re-
search interests in aromatic nucleophilic displacement chemistry combined with a
perceived marketplace for high performance polymers which could be readily fab-
ricated by standard plastics extrusion and injection molding processes. An impor-
tant example is Ultem 1000® developed and commercialized by General Electric
Co. [12], which exhibits reasonable thermal stability and good mechanical proper-
ties together with good moldability.
The incorporation of 2,2'-disubstituted biphenylene in a para-linked polymer
chain reduced the interactions between polymer chains . The phenyl rings are
forced by the 2,2'-disubstitution into a noncoplanar conformation, decreasing the
intermolecular forces between the polymer chains. The crystallization tendency is
markedly lowered and the solubilities are significantly enhanced [13-18]. On the
other hand, another effective approach to obtain organosoluble polyimides is the
incorporation of substituted methylene linkages, such as isopropylidene [19-22],
hexafluoroisopropylidene [23-27] and diphenylmethylene [28] units which pro-
vide kinks between the rigid phenyl rings in the backbone and lead to enhanced
solubility of the polymer. The incorporation of these flexible linkages such as iso-
propylidene into the polymer backbone is expected to reduce the crystallinity, and
enhance the solubility and melt-moldability of the poly(ether imide)s [19-22].
The improved solubility of the polymers is ascribed to the presence of the kink
units in the polymer backbone that lower the chain rigidity. It was observed that
the polymers with diphenylmethylene unit showed better thermal stability than
those containing isopropylidene and hexafluoroisopropylidene [28]. Therefore,
the incorporation of noncoplanar 2,2'-dimethyl-4,4'-biphenylene and kink di-
phenylmethylene in the poly(ether imide) backbone was expected to provide or-
ganosoluble poly(ether imide)s with good thermal stability. The introduction of
cardo (Latin meaning loop) groups into the backbone of polymers is another ap-
proach for improving solubility and, thereby, processability. Cardo polymers ex-
hibit a valuable set of properties: the combination of an increased thermal stability
with an increased solubility in organic solvents because of the specific contribu-
tion of the cardo groups [29-32]. In our previous works, we have found several
means for the introduction of cardo groups such as cyclododecylidene [33], ada-
mantane [34], norbornyl [35] and tricyclo[5.2.1.0 2.6 ]decane [36] groups in the
polymer backbone. In these attempts, the solubility of polyimide was enhanced
while high glass transition temperature and thermal stability were maintained
[33-36]. In continuation of these studies, we were interested in the potential use-
fulness of a tert-butylcyclohexylidene group as a bulky pendent group in the
polymer backbone. The cardo group such as tert-butylcyclohexylidene could be
considered as a bulkier pendent group as compared with other pendent groups
mentioned above (such as cyclododecylidene, adamantane, norbornyl and tricy-
clo[5.2.1.0 2.6 ]decane groups [33-36]. The bulkier groups will possibly contribute
to an enhanced solubility of the polymers [37].
Our group has reported the preparation of new diols such as 2,2'-dimethyl-4,4'-
dihydroxybiphenyl (1A), bis(4-hydroxyphenyl)diphenylmethane (1B), 1,1-bis(4-