Polymers in Special Uses 2-55
at relatively high temperatures (w1208C). Although this temperature of operation may be suitable for
certain application, for example, vehicle traction, quite clearly it would be unsuitable for other
applications, such as consumer products.
Recently, a new polymeric electrolyte consisting of polyester-substituted polyphosphazene [71] has
been developed. This polymer, which is designated MEEP, forms complexes with a large number of
metallic salts, the complexes having a higher conductivity at room temperature than earlier polymer
electrolytes. For example, MEEP-LiF3SO3 has a conductivity of 10K4 ohmK1-cmK1, which is sufficient
for battery use, since the polymeric electrolyte can be shaped as films between the electrodes. This holds
promise of very light batteries with potentially very great energy density.
While it is possible that future polymeric batteries will be all-polymeric solid-state batteries, it is
predicted, however, that the most promising solid state batteries will combine polymeric electrolytes with
nonpolymeric electrode materials such as TiS2, V6O13, Li or LiAl, the specific capacity of which surpasses
that of polyacetylene electrodes.
As a great number of combination possibilities exist for electrode as well as electrolyte materials, the
probability of developing rechargeable batteries with considerably increased performance may be
considered to be high. For potential use in electric cars and other electrically operated vehicles, which
may become an environmental requirement in densely populated areas, such developments in polymeric
batteries are eagerly awaited.
Drastic improvement in rechargeable batteries is also of great interest militarily. One example is
submarine batteries. Compared to lead-acid batteries, the polymeric batteries enjoy potential advantages
in this area: faster charge, smaller volume, and great freedom in shaping the batteries to available space.
Though the energy density (KWh/kg) of polymeric batteries are, in current estimation, comparable to
that of the lead-acid battery, charging of the batteries, which is the most critical routine operation of a
diesel-powered submarine and requires about two hours to complete, can be reduced drastically with the
use of polymeric batteries.
Polymer electrolyte membrane fuel cell (PEMFC) technology has been receiving increased attention
due to its high energy efficiency and environmentally friendly nature [74,75]. Among the different
technologies developed, PEMFCs which operate at temperatures above 1508C have certain advantages
that result in better overall performance and simplification of the system. The polymer electrolyte
membranes (PEMs) in high-temperature PEMFCs must enable proton conduction and, at the same time,
exhibit mechanical, thermal, and oxidative stability under operating conditions. The state-of-art material
used in high-temperature PEMFCs is polybenzimidazole (PBI) which can be doped with various strong
acids. In the case of phosphoric acid, PBI exhibits high acid uptake, resulting in highly conductive
materials [76]. However, PBI has several drawbacks, such as moderate mechanical properties, reduced
oxidative stability, limited availability, and high cost.
Among the alternative polymeric structures developed recently for PEMFC application, mention may
be made of aromatic polyethers containing polar pyridine units in the main chain [77,78]. Novel poly
(aryl ether sulfone) copolymers containing 2,5-biphenylpyridine and tetramethyl biphenyl moieties have
been synthesized [78] by polycondensation of 4-fluorophenyl sulfone with 2,5-(4 0 , 4 00 -dihydroxy
biphenyl)-pyridine and tetramethyl biphenyl diol (see Figure 2.38). These polymers exhibit excellent
film-forming properties, mechanical integrity, high modulus up to 2508C, high glass transition
temperatures (O2808C) as well as high thermal stability up to 4008C. In addition to the above properties
required for PEMFC application, this polymer shows high oxidative stability and acid doping ability,
enabling proton conductivity in the range of 10K2 S.cmK1 above 1308C [78].
2.5 Polymers in Photoresist Applications
Polymers and polymeric systems that can undergo imagewise light-induced reactions are of great
technological importance [79–84]. Photoresists are polymers or polymeric systems (polymer binders
containing dispersed or dissolved photoactive compounds) which, applied as a surface coating to an
at relatively high temperatures (w1208C). Although this temperature of operation may be suitable for
certain application, for example, vehicle traction, quite clearly it would be unsuitable for other
applications, such as consumer products.
Recently, a new polymeric electrolyte consisting of polyester-substituted polyphosphazene [71] has
been developed. This polymer, which is designated MEEP, forms complexes with a large number of
metallic salts, the complexes having a higher conductivity at room temperature than earlier polymer
electrolytes. For example, MEEP-LiF3SO3 has a conductivity of 10K4 ohmK1-cmK1, which is sufficient
for battery use, since the polymeric electrolyte can be shaped as films between the electrodes. This holds
promise of very light batteries with potentially very great energy density.
While it is possible that future polymeric batteries will be all-polymeric solid-state batteries, it is
predicted, however, that the most promising solid state batteries will combine polymeric electrolytes with
nonpolymeric electrode materials such as TiS2, V6O13, Li or LiAl, the specific capacity of which surpasses
that of polyacetylene electrodes.
As a great number of combination possibilities exist for electrode as well as electrolyte materials, the
probability of developing rechargeable batteries with considerably increased performance may be
considered to be high. For potential use in electric cars and other electrically operated vehicles, which
may become an environmental requirement in densely populated areas, such developments in polymeric
batteries are eagerly awaited.
Drastic improvement in rechargeable batteries is also of great interest militarily. One example is
submarine batteries. Compared to lead-acid batteries, the polymeric batteries enjoy potential advantages
in this area: faster charge, smaller volume, and great freedom in shaping the batteries to available space.
Though the energy density (KWh/kg) of polymeric batteries are, in current estimation, comparable to
that of the lead-acid battery, charging of the batteries, which is the most critical routine operation of a
diesel-powered submarine and requires about two hours to complete, can be reduced drastically with the
use of polymeric batteries.
Polymer electrolyte membrane fuel cell (PEMFC) technology has been receiving increased attention
due to its high energy efficiency and environmentally friendly nature [74,75]. Among the different
technologies developed, PEMFCs which operate at temperatures above 1508C have certain advantages
that result in better overall performance and simplification of the system. The polymer electrolyte
membranes (PEMs) in high-temperature PEMFCs must enable proton conduction and, at the same time,
exhibit mechanical, thermal, and oxidative stability under operating conditions. The state-of-art material
used in high-temperature PEMFCs is polybenzimidazole (PBI) which can be doped with various strong
acids. In the case of phosphoric acid, PBI exhibits high acid uptake, resulting in highly conductive
materials [76]. However, PBI has several drawbacks, such as moderate mechanical properties, reduced
oxidative stability, limited availability, and high cost.
Among the alternative polymeric structures developed recently for PEMFC application, mention may
be made of aromatic polyethers containing polar pyridine units in the main chain [77,78]. Novel poly
(aryl ether sulfone) copolymers containing 2,5-biphenylpyridine and tetramethyl biphenyl moieties have
been synthesized [78] by polycondensation of 4-fluorophenyl sulfone with 2,5-(4 0 , 4 00 -dihydroxy
biphenyl)-pyridine and tetramethyl biphenyl diol (see Figure 2.38). These polymers exhibit excellent
film-forming properties, mechanical integrity, high modulus up to 2508C, high glass transition
temperatures (O2808C) as well as high thermal stability up to 4008C. In addition to the above properties
required for PEMFC application, this polymer shows high oxidative stability and acid doping ability,
enabling proton conductivity in the range of 10K2 S.cmK1 above 1308C [78].
2.5 Polymers in Photoresist Applications
Polymers and polymeric systems that can undergo imagewise light-induced reactions are of great
technological importance [79–84]. Photoresists are polymers or polymeric systems (polymer binders
containing dispersed or dissolved photoactive compounds) which, applied as a surface coating to an
