Synthesis of p -and n-type Gels Doped with Ionic Charge Carriers

Abstract

In this study, we synthesized the new kinds of semiconducting polymeric gels having negative (n-type) and positive (p-type) counter ions as charge carriers. The polyacrylamide gel was doped with pyranine (8-hydroxypyrene-1,3,6-trisulfonic acid, trisodium salt), havingions as side groups and Na+ as counter ions, so-called p-type semiconducting gel. The doping process was performed during the polymerization where the pyranine binds to the polymer strands over OH group chemically via radical addition. In a similar way, N-isopropylacrylamide (NIPA) gel was doped with methacrylamidopropyltrimethyl ammonium chloride (MAPTAC), having Cl− as counter ions, so-called n-type semiconducting gel. Here MAPTAC was embedded by copolymerization within the polymer network (NIPA). These semiconducting gels can show different electrical properties by changing the concentration of the doping agents, swelling ratio etc. We have shown that the pn junction, formed by combining p-type and n-type gels together in close contact, rectifies the current similar to the conventional Si and Ge diodes.

Synthesis of polyacrylamide hydrogels as p–n‐junction with ionic charge carriers

“…Gels were synthesized via free‐radical crosslinking copolymerization by using AAm as monomer and BIS as crosslinker and APS as initiator. Pyranine was used as the positively charged molecule, having Na + ions as charge carrier, and added to pregel solution to form the p ‐type PAAm gel, as discussed in detail in reference . Similarly, TAAB molecules, having Br − as negative counter ion, was added to the pregel solution to form the n ‐type PAAm gel.…”

“…Synthesis was performed at 60°C. These gelation processes are explained in detail in the literature .…”

“…Recently we synthesized p‐ and n ‐type polyacrylamide (PAAm) gels using some doping molecules having counter ions . These ions move through the gel and carry the current under applied voltage when the gel is in swollen state .…”

Estimation of the Generation and the Weight Fraction of Dense Polymer Regions in Heterogeneous Hydrogels

“…[42] All of these ionic charges may contribute to the current when the gels are swollen to some extent. When V/V 0 > 1, some of the ions in the gel become mobile and a current flows through the gels.…”

“…The covalent binding mechanism of the pyranine to the polymer strands is described in recent literature in detail. [37][38][39][40][41][42] After the gels were prepared, they were washed over a period of 15 d in excess refreshed water. Then, the gels were dried in an oven at 40 8C.…”