2016 Materials science lecture series: advanced materials - 1 april 2016
Apr 01, 2016
Agoralaan Gebouw D
Lokaal Aula H4
de heer Rajesh RAMANETI
Speaker: Dr. Christian H. Hornung.
Topic: The use of continuous flow processing for the manufacture of RAFT polymers.
Chaired by: Prof. Dr. Thomas Junkers, IMO-IMOMEC, Hasselt University
1 April 2016, 11:00 -12:00
Aula H4, Building D, Hasselt University, Campus Diepenbeek.
The Reversible Addition - Fragmentation chain Transfer (RAFT) method is a convenient and versatile approach to control free radical polymerisations; it is compatible with a wide range of monomers and standard reaction conditions. RAFT allows the synthesis of polymers with narrow molecular weight distributions and well- defined end groups, as well as complex architectures, such as blocks, stars and others. Our group has demonstrated novel continuous flow processes for the synthesis and subsequent on - processing of RAFT polymers, using a series of different tubular reactor systems with tube diameters between 1 and 6 mm and reaction volumes between 10 mL and 1 L. A variety of different monomers,such as (meth)acrylates,(meth)acrylamides, vinylmonomers and others were polymerized to high conversions typically between 80 and 100% at temperatures between 60 and 110°C and in comparatively short reaction times of 2h or less. The continuous flow approach provides a facile alternative scale-up route to conventional batch procedures,and with our current continuous reactor technology it is possible to produce thermally initiated RAFT polymers in quantities of a few mg to several kg per day.
Recently we extended our research efforts and synthesised RAFT polymers via photo -initiation in a tubular continuous flow photo -r e actor , either with or without the use of photo-initiator. In the latter case, the RAFT agent acted as an iniferter, and was initiating, controlling and terminating the reaction . Alternatively, using high photo-initiator and RAFT agent loadings, we demonstrated very fast polymerisation with close to full conversion after only 5 min at 30°C. Irrespective of the mode of initiation, any RAFT polymer can be polymerised further in a second stage to form block co-polymers, because of the living character of the RAFT approach. We have demonstrated this using a two-stage continuous flow reactor for the synthesis of di-blocks. With the help of sequential processing, it is also possible to remove or modify the end group of the polymer continuously, in a consecutive continuous stage directly after polymerisation. Due to their excellent control over process parameters such as temperature and pressure, tubular reactors present a very practical and compact design for the industrial manufacture of RAFT polymers in quantities of up to several tons per day.