High molecular weight poly(phthalazinone)s with high glass
transition temperatures were
prepared by a novel N−C coupling reaction. New
bis(phthalazinone) monomers (5a−f), such
as 7,7‘-oxobis[4-phenylphthalazin-1(2H)-one] (5c),
were synthesized from the corresponding bis(phthalic
anhydride)s (3a−f) in two steps. Other types of
bis(phthalazinone) monomers (8, 9) were
synthesized from
phthalic anhydride and diphenyl sulfide or diphenyl ether. AB-type
phthalazinone monomers (11a, 12−14) were also synthesized from phthalic anhydride.
Poly(phthalazinone)s, having inherent viscosities
of
0.3−0.4 dL/g, were prepared by the reaction of the
bis(phthalazinone) monomers with an activated aryl
halide such as bis(4-fluorophenyl) sulfone (22) in a
dipolar aprotic solvent in the presence of potassium
carbonate. AB-type phthalazinone monomers do not form high
molecular weight polymers because of
premature precipitation during the polymerization reaction. One of
the AB-type phthalazinone monomers,
4-[4-((4-fluorophenyl)sulfonyl)phenyl]phthalazin-1(2H)-one,
was successfully copolymerized with 4,4‘-biphenol and bis(4-fluorophenyl) sulfone to form high molecular
weight polymers. The copolymers showed
higher glass transition temperatures (T
gs) as
the phthalazinone ratio increased. All phthalazinone
homopolymers except the Bisphenol A phthalazinone polymers show
T
gs around 300 °C by differential
scanning calorimetry. The decomposition temperatures for 5%
weight losses in air and in nitrogen
measured by thermogravimetric analysis are in the range of 480−530
°C. Polymers from the Bisphenol
A phthalazinone monomer are soluble in chlorinated solvents such as
chloroform. Other polymers are
soluble in dipolar aprotic solvents such as
N-methyl-2-pyrrolidinone. The soluble polymers can be
cast
into flexible films from solution.
A novel heterocyclic diamine monomer,
2-(4-aminophenyl)-6-amino-4(3H)-quinazolinone
was
synthesized from readily available compounds in three steps in high
yield. A series of novel polyimides
containing the quinazolinone moiety were synthesized either by a
one-step solution polymerization reaction
or by a two-step procedure that included a ring-opening polyadddition
to give poly(amic acid)s, followed
by cyclodehydration to polyimides. In the one-step method in
m-cresol or p-chlorophenol with
isoquinoline
catalyst, polyimides with inherent viscosities of 0.44−0.63 dL/g were
obtained. Polyimides 4f and 4g
from dianhydrides which have a flexible linkage,
hexafluoroisopropylidene dianhydride (2f) and
BPA
dianhydride (2g), were soluble in hot m-cresol
and could be cast into tough films from m-cresol
solution.
In the two-step method, poly(amic acid)s with inherent
viscosity between 0.63 and 1.40 dL/g were obtained
in DMAc at room temperature. The poly(amic acid)s were
converted to the corresponding polyimide films
by thermal cyclodehydration. The T
g values
of the polyimides ranged from 298 to 350 °C. Polyimide
4a
from pyromellitic dianhydride (2a) did not show a clear
transition in the DSC. Polyimides 4b from
biphenyltetracarboxylic dianhydride (2b) and 4g
were semicrystalline and showed clear endothermic
peaks for T
m at 465 and 356 °C, respectively.
Degradation temperatures for 5% weight loss all
occurred
above 540 °C in nitrogen and above 537 °C in air. Young's
moduli of thin films ranged from 2.34 to 4.89
GPa at room temperature and they maintained the high moduli to high
temperatures. The monomer
was successufuly copolymerized with 4,4‘-oxydianiline and
2g. With increasing incorporation of
quinazolinone units, the copolymers had higher
T
g values, were more thermally stable, and had
higher
moduli.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.