TY  - JOUR
A1  - Chandran, Sivasurender
A1  - Dold, Stefanie
A1  - Buvignier, Amaury
A1  - Krannig, Kai-Steffen
A1  - Schlaad, Helmut
A1  - Reiter, Günter
A1  - Reiter, Renate
T1  - Tuning Morphologies of Langmuir Polymer Films Through Controlled Relaxations of Non-Equilibrium States
JF  - Langmuir
N2  - Langmuir polymers films (LPFs) frequently form non-equilibrium states which are manifested in a decay of the surface pressure with time when the system is allowed to relax. Monitoring and manipulating the temporal evolution of these relaxations experimentally helps to shed light on the associated molecular reorganization processes. We present a systematic study based on different compression protocols and show how these reorganization processes impact the morphology of LPFs of poly(gamma-benzyl-L-glutamate) (PBLG); visualized by means of atomic force microscopy. Upon continuous compression, a fibrillar morphology was formed with a surface decorated by squeezed-out islands. By contrast, stepwise compression promoted the formation of a fibrillar network with a bimodal distribution of fibril diameters, caused by merging of fibrils. Finally, isobaric compression induced in-plane compaction of the monolayer. We correlate these morphological observations with the kinetics of the corresponding relaxations, described best by a sum of two exponential functions with different time scales representing two molecular processes. We discuss the observed kinetics and the resulting morphologies in the context of nucleation and growth, characteristic for first-order phase transitions. Our results demonstrate that the preparation conditions of LPFs have tremendous impact on ordering of the molecules and hence various macroscopic properties of such films.
Y1  - 2015
U6  - https://doi.org/10.1021/acs.langmuir.5b01212
SN  - 0743-7463
VL  - 31
IS  - 23
SP  - 6426
EP  - 6435
PB  - American Chemical Society
CY  - Washington
ER  -