An Emulsion Polymerization Process for Soluble and Electrically Conductive Polyaniline
- PDF / 584,246 Bytes
- 12 Pages / 414.72 x 648 pts Page_size
- 71 Downloads / 321 Views
soluble, conducting emeraldine salt directly without the need for a post-doping process step. The reaction is unique since the emulsion flocculates during the course of reaction to form a two phase system, the polyaniline remaining as a soluble component in the organic phase. Ammonium sulfate, a by-product of the reaction, remains in the aqueous phase which is readily removed from the organic layer. EXPERIMENTAL SECTION PreparationofPolyaniline DinonylnaphthaleneSulfonic Acid Salt 0.1 mole DNNSA (50% w/w solution in 2-butoxyethanol from King Industries) was mixed with 0.06 moles aniline (Aldrich) and 200 ml water to form a milky white emulsion. The emulsion was chilled to 5°C, mechanically stirred and blanketed with nitrogen. Ammonium peroxydisulfate (0.074 moles in 40 ml water) was added dropwise to the mixture over a period of approximately one hour. During this period the emulsion changed color from white to amber. The reaction was allowed to proceed for 17 hours, during which time the emulsion separated into a green 2butoxyethanol phase and a colorless aqueous phase. The progress of the synthesis was monitored by pH, OCP (open circuit potential, mV) and temperature. The organic phase was washed three times with 100 ml portions of water, leaving a dark green, highly concentrated polyaniline phase in 2-butoxyethanol. This concentrate was readily soluble in xylene from which thin films were cast. Addition of acetone to a portion of the above concentrate resulted in the precipitation of the polyaniline salt as a green powder. After thorough washing of the powder with acetone and drying, elemental analysis indicated the expected stochiometric ratio of sulfonic acid to aniline of 1:2. Using the same process polyaniline DNNSA salts were prepared using acid/aniline molar ratios of 1:1, 1:2, and 1:5 while the peroxydisulfate/aniline mole ratio was kept constant at 1.23. Attempts at synthesizing the polyaniline DNNSA salt employing either kerosene or xylene as the organic solvent yielded no product. UV/VIS/NIR measurements were made on a Cary 5E spectrophotometer. ConductivityMeasurements A 6 mil wet coating of PANI-DNNSA concentrate (ca. 50% solids in xylene) was applied across a pattern of four gold contacts using a 0.006" draw down blade, 3.8 mm wide. The gold stripes sputtered onto a PET film were 6 mm wide by 50 mm long by 0.5 microns thick and spaced 6mm apart. After drying overnight at 80'C/27" Hg vacuum, the sample was stored in a descicator over P20 5 . Resistance measurements between two adjacent gold contacts was taken using a Keithly Model 2001 Multimeter in the two point resistant mode. The contact resistance was judged to be minor, since the resistance through the coating between adjacent gold bars was additive. Molecular Weight Determinations Molecular weight distribution averages determined by size-exclusion chromatography (SEC). Chromatograms were obtained with two SEC systems: a model 150-CV SEC/viscometry (SEC/VISC) system (Waters Chromatography Inc.) and a multi-component SEC system (Waters Chromatog
Data Loading...
