TY  - JOUR
A1  - Yan, Wan
A1  - Fang, Liang
A1  - Weigel, Thomas
A1  - Behl, Marc
A1  - Kratz, Karl
A1  - Lendlein, Andreas
T1  - The influence of thermal treatment on the morphology in differently prepared films of a oligodepsipeptide based multiblock copolymer
JF  - Polymers for advanced technologies
N2  - Degradable multiblock copolymers prepared from equal weight amounts of poly(epsilon-caprolactone)-diol (PCL-diol) and poly[oligo(3S-iso-butylmorpholine-2,5-dione)]-diol (PIBMD-diol), named PCL-PIBMD, provide a phase-segregated morphology. It exhibits a low melting temperature from PCL domains (T-m,T-PCL) of 382 degrees C and a high T-m,T-PIBMD of 170 +/- 2 degrees C with a glass transition temperature (T-g,T-PIBMD) at 42 +/- 2 degrees C from PIBMD domains. In this study, we explored the influence of applying different thermal treatments on the resulting morphologies of solution-cast and spin-coated PCL-PIBMD thin films, which showed different initial surface morphologies. Differential scanning calorimetry results and atomic force microscopy images after different thermal treatments indicated that PCL and PIBMD domains showed similar crystallization behaviors in 270 +/- 30 mu m thick solution-cast films as well as in 30 +/- 2 and 8 +/- 1nm thick spin-coated PCL-PIBMD films. Existing PIBMD crystalline domains highly restricted the generation of PCL crystalline domains during cooling when the sample was annealed at 180 degrees C. By annealing the sample above 120 degrees C, the PIBMD domains crystallized sufficiently and covered the free surface, which restricted the crystallization of PCL domains during cooling. The PCL domains can crystallize by hindering the crystallization of PIBMD domains via the fast vitrification of PIBMD domains when the sample was cooled/quenched in liquid nitrogen after annealing at 180 degrees C. These findings contribute to a better fundamental understanding of the crystallization mechanism of multi-block copolymers containing two crystallizable domains whereby the T-g of the higher melting domain type is in the same temperature range as the T-m of the lower melting domain type. Copyright (c) 2016 John Wiley & Sons, Ltd.
KW  - multiblock copolymer
KW  - oligodepsipeptides
KW  - phase morphology
KW  - thermal treatments
KW  - crystallization behavior
Y1  - 2017
U6  - https://doi.org/10.1002/pat.3953
SN  - 1042-7147
SN  - 1099-1581
VL  - 28
SP  - 1339
EP  - 1345
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Farhan, Muhammad
A1  - Rudolph, Tobias
A1  - Nöchel, Ulrich
A1  - Yan, Wan
A1  - Kratz, Karl
A1  - Lendlein, Andreas
T1  - Noncontinuously Responding Polymeric Actuators
JF  - ACS applied materials & interfaces
N2  - Reversible movements of current polymeric actuators stem from the continuous response to signals from a controlling unit, and subsequently cannot be interrupted without stopping or eliminating the input trigger. Here, we present actuators based on cross-linked blends of two crystallizable polymers capable of pausing their movements in a defined manner upon continuous cyclic heating and cooling. This noncontinuous actuation can be adjusted by varying the applied heating and cooling rates. The feasibility of these devices for technological applications was shown in a 140 cycle experiment of free-standing noncontinuous shape shifts, as well as by various demonstrators.
KW  - soft robotics
KW  - polymer actuators
KW  - thermo-sensitivity
KW  - shape shifting materials
KW  - crystallization behavior
Y1  - 2017
U6  - https://doi.org/10.1021/acsami.7b11316
SN  - 1944-8244
VL  - 9
SP  - 33559
EP  - 33564
PB  - American Chemical Society
CY  - Washington
ER  -