TY  - JOUR
A1  - Demirel, A. Levent
A1  - Guner, Pinar Tatar
A1  - Verbraeken, Bart
A1  - Schlaad, Helmut
A1  - Schubert, Ulrich S.
A1  - Hoogenboom, Richard
T1  - Revisiting the Crystallization of Poly(2-alkyl-2-oxazoline)s
JF  - Journal of polymer science : B, Polymer physics
N2  - Poly(2-alkyl-2-oxazoline)s (PAOx) exhibit different crystallization behavior depending on the length of the alkyl side chain. PAOx having methyl, ethyl, or propyl side chains do not show any bulk crystallization. Crystallization in the heating cycle, that is, cold crystallization, is observed for PAOx with butyl and pentyl side chains. For PAOx with longer alkyl side chains crystallization occurs in the cooling cycle. The different crystallization behavior is attributed to the different polymer chain mobility in line with the glass transition temperature (T-g) dependency on alkyl side chain length. The decrease in chain mobility with decreasing alkyl side chain length hinders the relaxation of the polymer backbone to the thermodynamic equilibrium crystalline structure. Double melting behavior is observed for PButOx and PiPropOx which is explained by the melt-recrystallization mechanism. Isothermal crystallization experiments of PButOx between 60 and 90 degrees C and PiPropOx between 90 and 150 degrees C show that PAOx can crystallize in bulk when enough time is given. The decrease of Tg and the corresponding increase in chain mobility at T > T-g with increasing alkyl side chain length can be attributed to an increasing distance between the polymer backbones and thus decreasing average strength of amide dipole interactions. (C) 2015 Wiley Periodicals, Inc.
KW  - chain mobility
KW  - crystallization
KW  - differential scanning calorimetry (DSC)
KW  - effect of alkyl side chains
KW  - glass transition temperature
KW  - melt
KW  - melt-recrystallization
KW  - polymer crystallization
Y1  - 2016
U6  - https://doi.org/10.1002/polb.23967
SN  - 0887-6266
SN  - 1099-0488
VL  - 54
SP  - 721
EP  - 729
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Noack, Sebastian
A1  - Schanzenbach, Dirk
A1  - Koetz, Joachim
A1  - Schlaad, Helmut
T1  - Polylactide-based amphiphilic block copolymers
BT  - Crystallization-Induced Self-Assembly and Stereocomplexation
JF  - Macromolecular rapid communications
N2  - The aqueous self-assembly behavior of a series of poly(ethylene glycol)-poly(l-/d-lactide) block copolymers and corresponding stereocomplexes is examined by differential scanning calorimetry, dynamic light scattering, and transmission electron microscopy. Block copolymers assemble into spherical micelles and worm-like aggregates at room temperature, whereby the fraction of the latter seemingly increases with decreasing lactide weight fraction or hydrophobicity. The formation of the worm-like aggregates arises from the crystallization of the polylactide by which the spherical micelles become colloidally unstable and fuse epitaxically with other micelles. The self-assembly behavior of the stereocomplex aggregates is found to be different from that of the block copolymers, resulting in rather irregular-shaped clusters of spherical micelles and pearl-necklace-like structures.
KW  - crystallization
KW  - polylactide
KW  - self-assembly
KW  - stereocomplexation
Y1  - 2018
U6  - https://doi.org/10.1002/marc.201800639
SN  - 1022-1336
SN  - 1521-3927
VL  - 40
IS  - 1
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Thielke, Michael W.
A1  - Secker, Christian
A1  - Schlaad, Helmut
A1  - Theato, Patrick
T1  - Electrospinning of Crystallizable Polypeptoid Fibers
JF  - Macromolecular rapid communications
N2  - A unique fabrication process of low molar mass, crystalline polypeptoid fibers is described. Thermoresponsive fiber mats are prepared by electrospinning a homogeneous blend of semicrystalline poly(N-(n-propyl) glycine) (PPGly; 4.1 kDa) with high molar mass poly(ethylene oxide) (PEO). Annealing of these fibers at approximate to 100 degrees C selectively removes the PEO and produces stable crystalline fiber mats of pure PPGly, which are insoluble in aqueous solution but can be redissolved in methanol or ethanol. The formation of water-stable polypeptoid fiber mats is an important step toward their utilization in biomedical applications such as tissue engineering or wound dressing.
KW  - biomaterials
KW  - crystallization
KW  - electrospinning
KW  - polypeptoids
KW  - thermoresponsive
Y1  - 2016
U6  - https://doi.org/10.1002/marc.201500502
SN  - 1022-1336
SN  - 1521-3927
VL  - 37
SP  - 100
EP  - 104
PB  - Wiley-VCH
CY  - Weinheim
ER  -