Sulfonic acid doped thermoreversible polyaniline gels. 2. Influence of sulfonic acid content on morphological, thermodynamical, and conductivity properties

Authors
Citation
T. Jana et Ak. Nandi, Sulfonic acid doped thermoreversible polyaniline gels. 2. Influence of sulfonic acid content on morphological, thermodynamical, and conductivity properties, LANGMUIR, 17(19), 2001, pp. 5768-5774
Citations number
28
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
LANGMUIR
ISSN journal
07437463 → ACNP
Volume
17
Issue
19
Year of publication
2001
Pages
5768 - 5774
Database
ISI
SICI code
0743-7463(20010918)17:19<5768:SADTPG>2.0.ZU;2-G
Abstract
Thermoreversible gelation behavior of polyaniline (PANI) in the presence of varying concentrations of sulfonic acids are studied. Four different sulfo nic acids are used, e.g., dinonylnaphthalene sulfonic acid (DNNSA), dinonyl naphthalene disulfonic acid (DNNDSA), (+/-)-camphor-10-sulfonic acid TSA), and n-dodecyloxo sulfonic acid (DOSA). The composition range studied here i s W-PANI = 0.05-0.80 (W-PANI is the weight fraction of PANI in the gel). It has been found from the SEM study that for all the sulfonic acids in the c omposition range W-PANI = 0.05-0.40, fibrillar network is present. The TEM study also supports the above viewpoint. The thermodynamic study of the gel s has been done by DSC-7, and for all the systems broad peaks consisting of two fused gel melting/gel formation peaks are observed. After proper decon volution of the two peaks the gel melting/gel formation temperatures are me asured. When they are plotted with W-SO3H (weight fraction of sulfonic acid ), typical phase diagrams consisting of two almost parallel curves are foun d. They are explained by considering the lamellar model where the bilayer a nd monolayer portions of the surfactant form different crystalline domains. The higher melting point curve is due to the former and the lower one is d ue to the later in each phase diagram. The lowering of gel melting/gel form ation points with increase in PANI concentration of each curve has been att ributed to the dilution effect of PANI in the gel. The corresponding enthal py values (DeltaH also show similar decrease with increasing PANI concentra tion and are explained also from the dilution effect of PANI. The conductan ce of these gels varies with weight fraction of PANI (Wp-ANI), showing a ma ximum, and it has been explained by considering that conductivity in the ge l is due to both intrachain and interchain contributions. Attempt is made t o discuss the above results by using a molecular model of the PANI-DOSA sys tem with the help of MMX program.