TY  - JOUR
A1  - Machatschek, Rainhard Gabriel
A1  - Heuchel, Matthias
A1  - Lendlein, Andreas
T1  - Hydrolytic stability of polyetherimide investigated in ultrathin films
JF  - Journal of materials research : JMR / Materials Research Society
N2  - Increasing the surface hydrophilicity of polyetherimide (PEI) through partial hydrolysis of the imide groups while maintaining the length of the main-chain was explored for adjusting its function in biomedical and membrane applications. The outcome of the polymer analogous reaction, i.e., the degree of ring opening and chain cleavage, is difficult to address in bulk and microstructured systems, as these changes only occur at the interface. Here, the reaction was studied at the air-water interface using the Langmuir technique, assisted by atomic force microscopy and vibrational spectroscopy. Slow PEI hydrolysis sets in at pH > 12. At pH = 14, the ring opening is nearly instantaneous. Reduction of the layer viscosity with time at pH = 14 suggested moderate chain cleavage. No hydrolysis was observed at pH = 1. Hydrolyzed PEI films had a much more cohesive structure, suggesting that the nanoporous morphology of PEI can be tuned via hydrolysis.
KW  - 2D materials
KW  - Membrane
KW  - Polymer
KW  - Water
KW  - Nanostructure
Y1  - 2021
U6  - https://doi.org/10.1557/s43578-021-00267-6
SN  - 0884-2914
SN  - 2044-5326
VL  - 36
IS  - 14
SP  - 2987
EP  - 2994
PB  - Springer
CY  - Berlin
ER  - 
TY  - JOUR
A1  - Machatschek, Rainhard Gabriel
A1  - Heuchel, Matthias
A1  - Lendlein, Andreas
T1  - Thin-layer studies on surface functionalization of polyetherimide
BT  - hydrolysis versus amidation
JF  - Journal of materials research : JMR / Materials Research Society
N2  - Among the high-performance and engineering polymers, polyimides and the closely related polyetherimide (PEI) stand out by their capability to react with nucleophiles under relatively mild conditions. By targeting the phthalimide groups in the chain backbone, post-functionalization offers a pathway to adjust surface properties such as hydrophilicity, solvent resistance, and porosity. Here, we use ultrathin PEI films on a Langmuir trough as a model system to investigate the surface functionalization with ethylene diamine and tetrakis(4-aminophenyl)porphyrin as multivalent nucleophiles. By means of AFM, Raman spectroscopy, and interfacial rheology, we show that hydrolysis enhances the chemical and mechanical stability of ultrathin films and allows for the formation of EDC/NHS-activated esters. Direct amidation of PEI was achieved in the presence of a Lewis acid catalyst, resulting in free amine groups rather than cross-linking. When comparing amidation with hydrolysis, we find a greater influence of the latter on material properties.
KW  - Membrane
KW  - Nanostructure
KW  - Polymer
KW  - Raman spectroscopy
KW  - Scanning probe microscopy (SPM)
KW  - Surface reaction
KW  - Thin film
Y1  - 2021
U6  - https://doi.org/10.1557/s43578-021-00339-7
SN  - 0884-2914
SN  - 2044-5326
VL  - 37
IS  - 1
SP  - 67
EP  - 76
PB  - Springer
CY  - Berlin
ER  -