TY  - JOUR
A1  - Navarro, Salvador
A1  - Shkilnyy, Andriy
A1  - Tiersch, Brigitte
A1  - Taubert, Andreas
A1  - Menzel, Henning
T1  - Preparation, characterization, and thermal gelation of amphiphilic alkyl-poly(ethyleneimine)
N2  - Amphiphilic alkyl-poly(ethyleneimine)s (alkyl-PEI) with different degrees of polymerization have been produced by alkaline hydrolysis of alkyl-poly(2-methyl-2-oxazoline). Potentiometric titration of the alkyl-PEI shows the influence of the alkyl chain and the degree of polymerization on the titration curves and hence on the polymer conformation. Karl Fischer titration has been used to determine the water content in the polymers. Subsequent X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC) measurements prove the existence of different hydration states of the PEI even under dry storage conditions. Upon cooling from hot aqueous Solutions, hydrogels form. The gelation concentration decreases with increasing degree of polymerization of the PEI segment. Scanning electron microscopy (SEM and cryo-SEM) of the hydrogels reveal an alkyl-PEI fibrous network composed of fan-like units. DSC shows that the percentages of bound and free water in the hydrogels depend on the concentration of polar amino groups.
Y1  - 2009
UR  - http://pubs.acs.org/journal/langd5
U6  - https://doi.org/10.1021/La9013569
SN  - 0743-7463
ER  - 
TY  - JOUR
A1  - Gharagozloo-Hubmann, Kati
A1  - Kulikovska, Olga
A1  - Boerger, Volker
A1  - Menzel, Henning
A1  - Stumpe, Joachim
T1  - Surface relief gratings in azobenzene-containing polymers with linear and star-branched architectures : a comparison
N2  - The influence of molecular architecture on light-induced SRG formation was investigated. Polymers with different degree of branching were synthesized by ATRP and functionalized with azobenzene chromophores. The polymers differ only in their architecture - linear, 4-, 6-, or 12-arms stars. The photo-induced dichroism as well as the efficiency of SRG formation was similar for all polymers of this series. New consideration for the origin of the driving force was used to explain this behavior. The comparable SRG inscription rate in differently branched polymers can be rationalized by assuming that azobenzene acts as an internal molecular motor and can cause a non-turbulent motion on a scale smaller than that on which normal entanglement restriction forces act.
Y1  - 2009
UR  - http://www3.interscience.wiley.com/journal/10003495/home
U6  - https://doi.org/10.1002/macp.200900218
SN  - 1022-1352
ER  -