Highly ethynylated polymers: synthesis and applications for humidity sensors

The response of two novel ethynylated polymers, poly[1,4-diethynyl-2,5-bis(butyloxy)benzene] (PEBB) and poly[1,4-diethynyl-2,5bis(octyloxy)benzene (PEOB) to relative humidity (% RH) and alcohols has been investigated. The polymers have been deposited as thin-film membranes on resistive-type devices. PEBB shows a good sensitivity to RH (%) variations in the full range (0-90%), while PEOB is less affected by moisture. Both polymers give a relevant current intensity variation (5 magnitude orders) when exposed to methanol vapours and no response to alcohols with longer alkylic chain was observed. These results suggest that the selectivity of polyynes to hydroxilated molecules can be modulated by the chemical structure, that is in this case by the length of the alkoxy substituents of the benzene moiety in the polymer chain.