TY  - JOUR
A1  - Eckert, Alexander
A1  - Abbasi, Mozhdeh
A1  - Mang, Thomas
A1  - Saalwächter, Kay
A1  - Walther, Andreas
T1  - Structure, Mechanical Properties, and Dynamics of Polyethylenoxide/Nanoclay Nacre-Mimetic Nanocomposites
JF  - Macromolecules
N2  - Nacre-mimetic nanocomposites based on high fractions of synthetic high-aspect-ratio nanoclays in combination with polymers are continuously pushing boundaries for advanced material properties, such as high barrier against oxygen, extraordinary mechanical behavior, fire shielding, and glass-like transparency. Additionally, they provide interesting model systems to study polymers under nanoconfinement due to the well-defined layered nanocomposite arrangement. Although the general behavior in terms of forming such layered nanocomposite materials using evaporative self-assembly and controlling the nanoclay gallery spacing by the nanoclay/polymer ratio is understood, some combinations of polymer matrices and nanoclay reinforcement do not comply with the established models. Here, we demonstrate a thorough characterization and analysis of such an unusual polymer/nanoclay pair that falls outside of the general behavior. Poly(ethylene oxide) (PEO) and sodium fluorohectorite form nacre-mimetic, lamellar nanocomposites that are completely transparent and show high mechanical stiffness and high gas barrier, but there is only limited expansion of the nanoclay gallery spacing when adding increasing amounts of polymer. This behavior is maintained for molecular weights of PEO varied over four orders of magnitude and can be traced back to depletion forces. By careful investigation via X-ray diffraction and proton low-resolution solid-state NMR, we are able to quantify the amount of mobile and immobilized polymer species in between the nanoclay galleries and around proposed tactoid stacks embedded in a PEO matrix. We further elucidate the unusual confined polymer dynamics, indicating a relevant role of specific surface interactions.
Y1  - 2020
U6  - http://dx.doi.org/10.1021/acs.macromol.9b01931
SN  - 1520-5835
VL  - 53
IS  - 5
SP  - 1716
EP  - 1725
PB  - ACS Publications
CY  - Washington, DC
ER  - 
TY  - JOUR
A1  - Hafidi, Youssef
A1  - El Hatka, Hicham
A1  - Schmitz, Dominik
A1  - Krauss, Manuel
A1  - Pettrak, Jürgen
A1  - Biel, Markus
A1  - Ittobane, Najim
T1  - Sustainable soil additives for water and micronutrient supply: swelling and chelating properties of polyaspartic acid hydrogels utilizing newly developed crosslinkers
JF  - Gels
N2  - Drought and water shortage are serious problems in many arid and semi-arid regions. This problem is getting worse and even continues in temperate climatic regions due to climate change. To address this problem, the use of biodegradable hydrogels is increasingly important for the application as water-retaining additives in soil. Furthermore, efficient (micro-)nutrient supply can be provided by the use of tailored hydrogels. Biodegradable polyaspartic acid (PASP) hydrogels with different available (1,6-hexamethylene diamine (HMD) and L-lysine (LYS)) and newly developed crosslinkers based on diesters of glycine (GLY) and (di-)ethylene glycol (DEG and EG, respectively) were synthesized and characterized using Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) and regarding their swelling properties (kinetic, absorbency under load (AUL)) as well as biodegradability of PASP hydrogel. Copper (II) and zinc (II), respectively, were loaded as micronutrients in two different approaches: in situ with crosslinking and subsequent loading of prepared hydrogels. The results showed successful syntheses of di-glycine-ester-based crosslinkers. Hydrogels with good water-absorbing properties were formed. Moreover, the developed crosslinking agents in combination with the specific reaction conditions resulted in higher water absorbency with increased crosslinker content used in synthesis (10% vs. 20%). The prepared hydrogels are candidates for water-storing soil additives due to the biodegradability of PASP, which is shown in an exemple. The incorporation of Cu(II) and Zn(II) ions can provide these micronutrients for plant growth.
KW  - micronutrients
KW  - swelling properties
KW  - biodegradable polymers
KW  - hydrogels
KW  - superabsorbent polymers
KW  - glycine
KW  - polyaspartic acid
Y1  - 2024
U6  - http://dx.doi.org/10.3390/gels10030170
SN  - 2310-2861
VL  - 10
IS  - 3
SP  - Artikel 170
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Delaittre, Guillaume
T1  - Telechelic Poly(2-Oxazoline)s
JF  - European Polymer Journal
Y1  - 2019
U6  - http://dx.doi.org/10.1016/j.eurpolymj.2019.109281
SN  - 0014-3057
IS  - In Press, Journal Pre-proof, 109281
PB  - Elsevier
CY  - Amsterdam
ER  -