Polyyne-Type Materials - Polyynes: Synthesis, Properties, and Applications - page 200

Another notable feature is that the carbonized material derived from
PpPB was highly porous with specific surface area (S BET ) of about
1000m 2 /g [25]. The porous carbon was obtained by the only heating pro-
cess under an argon atmosphere, although usual manufacturing of porous
carbons inevitably includes an activation process of precarbons or carbo-
nized materials. Porosity of the carbonaceous material derived from PpPB is
mainly due to micropore (diameter <2 nm) formation. The rigid character
of the polymer backbones and the intermediate C-network seems to cause
an a˚ ngstro ¨ m-level separation between entangled graphitic microcrystallites
in the contracting carbonization process. It has been also reported that
different type of porous carbon can be obtained from carbynoid materials
derived from poly(tetrafluoroethylene) PTFE [26].
In conclusion of this section, because of instability and inhomogeneity it
is difficult to answer how we directly utilize the carbynoid materials in
applications. Recently, Yasuda et al. have demonstrated the possibility that
carbynoid materials derived from PTFE are useful as precursory materials
for nano-carbons [27]. In this sense, the above-mentioned nano-structured
porous carbon formation from PTFE [26] belongs to the same category.
In the present case of poly(phenylene-alt-oligoethynylene)s having regular
alternating phenylene and linear carbons structure, they have strongly
linked rigid chains and the reactive C C moiety, thus it is thought that

the polymers are potential precursors for nano-structured graphitic carbons;
namely, size-controlled nano-porous carbons, nano-sized graphite, and
nano-functionalized graphite. Because the above-described carbonization
reaction is carried out within thermodynamically favored conditions of
graphitic carbon materials, it is mentioned last: types of carbon other than
graphite could possibly be synthesized from the polymers under unusual
carbonization conditions such as under high pressure or low pressure.
Attempts to synthesize carbon from polymers with a regular structure
might be a promising method of finding or developing new types of carbon
materials.

10.3.2 P OLY ( ARYLENEETHYNYLENE ) S

Poly( p-phenylene-alt-oligoethynylene)s without substituents were insoluble
and infusible materials that are difficult to characterize. Introduction of
appropriate substituents at the phenylene moiety or substitution of the
phenylene to arylene has greatly improved the solubility of some conducting
polymers such as polyacetylene and poly(phenylenevinylene) PPV. Such
modifications brought about a new interest in the semiconducting properties
of conducting polymers. Similarly, PPE has been modified and character-
ized, as it is recognized to be as important a semiconducting polymer as PPV.
A review by Bunz in 2000 summarized recent researches on the syntheses,
properties, structures, and applications of various poly(aryleneethynylene)s,
PAEs [28].