Comparison of conventional and super-glassy polymers

In the field of gas separation, polymeric membranes are favorable materials. Polymers are inexpensive compared to ceramics and metals, offer a good processability, and possess the ability to operate at large scale. The most important fact about polymeric membranes is their good selectivity. Nevertheless, most of the polymeric membranes show a strong tendency to physical aging and plasticization, which lead to changes in their performance with time. Up to know, it is not fully understood how these drawbacks are connected to the internal molecular mobility. In this study, a commonly used non-porous polyimide for gas separation applications, Matrimid, was compared to a microporous, high performance polymer, PIM-1. PIMs are Polymers with Intrinsic Microporosity and were firstly introduced by Budd and McKoewn in the early 2000s. PIM-1 was the first synthesized PIM and, even if many more PIMs followed , PIM-1 shows the most promising gas transport properties. The molecular mobility of the solution casted Matrimid and PIM-1 was investigated by Broadband Dielectric Spectroscopy (BDS). For both polymers, one relaxation process, denoted as beta*, and a conductivity contribution were found. Due to a very high activation energy for this beta*–relaxation (86 kJ/mol for PIM-1 and 99 kJ/mol for Matrimid) and the high temperature range where the peak appeared, it was concluded that the beta*–relaxation has to be of cooperative nature. A sandwich like structure, formed by pi−pi–stacking, was assumed. The conductivity, observed for both polymers quite well below their glass transition temperatures, was attributed to the pi−pi–stacked structure as well. One approach to reduce and/or overcome plasticization and physical aging is the incorporation of nanofiller. In this study, PhenethylPOSS was embedded in PIM-1 and Matrimid due to an expected interaction of the phenyl substituents of POSS with the pi–systems of the polymers and thus probably stabilizing the polymer matrix. Therefore, concentrations of 0 to 20 wt% (0 to 40 wt%) were mixed in Matrimid (PIM-1). A miscibility on a molecular level was observed up to 4 wt% for Matrimid, whereas up to 10 wt% for PIM-1. For higher POSS contents, a phase separation was found, while the size and distribution within the polymers strongly differed from one another. Enhanced permeability for PIM-1 and Matrimid was achieved with embedding 1 wt% of POSS. Furthermore, the phase separated Matrimid composites yielded a reduced plasticization effect for CO2.

Author dc:creator

• Konnertz, Nora Magdalena

Advisors dc:contributor.advisor

• Schönhals, Andreas
• Böhning, Martin

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Identifier URI

http://dx.doi.org/10.14279/depositonce-5924

OAI identifier oai:identifier

oai:depositonce.tu-berlin.de:11303/6374