PDMS-b-PI-b-PDMS triblock copolymer self-supported membranes with microphase separated structures for efficient ethanol dehydration

Abstract

High concentration ethanol dehydration had attracted great attentions through membrane separation methodology in the past years, of which membrane is the key factor to decide the separation performance. In this paper, a series of novel self-supported membranes were prepared based on PDMS-b-PI-b-PDMS triblock copolymers by solution casting method. The composition and structure of the copolymers were confirmed by FTIR, GPC and 1HNMR. The self-supported dehydrated membranes showed good thermal, chemical, and mechanical stability. Their water contact angle decreased obviously from 96° to 61° with the increasing PI contents from 50% to 100% in the triblock copolymers. The clear microphase separation with continuous PI domains of PDMS-b-PI-b-PDMS based membranes were observed in the TEM image. The microphase domain size increased with the increasing of molecular weight and content of PDMS. The higher domain size resulted in lower flux and higher separation factor of these membranes. The membrane M3, which has 70 wt% of PI content in the triblock copolymer, exhibit excellent ethanol dehydration performance with flux of 3.96 kg·m−2·h−1, separation factor of 255 and maintained 120 h with barely decreasing in separation performance, for 95 wt% ethanol solution at 20 °C. When elevated the feed temperature upto 60 °C, the dehydration flux increased to 16.90 kg·m−2·h−1, and the separation factor decreased to 37. Membranes with microphase separation have great potential application in the ethanol dehydration.