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@ARTICLE{Zinn:278745,
author = {Zinn, Thomas and Willner, Lutz and Pipich, Vitaliy and
Richter, Dieter and Lund, Reidar},
title = {{E}ffect of {C}ore {C}rystallization and {C}onformational
{E}ntropy on the {M}olecular {E}xchange {K}inetics of
{P}olymeric {M}icelles},
journal = {ACS Macro Letters},
volume = {4},
number = {6},
issn = {2161-1653},
address = {Washington, DC},
publisher = {ACS},
reportid = {FZJ-2015-07012},
pages = {651 - 655},
year = {2015},
abstract = {Here we systematically study the equilibrium molecular
exchange kinetics of a series of amphiphilic
n-alkyl-poly(ethylene oxide) (Cn-PEO) micelles containing
partly crystallized cores. Using differential scanning
calorimetry (DSC), we determined the melting transition and
extracted the enthalpy of fusion, ΔHfus, of the n-alkyl
chains inside the micellar core. Molecular exchange kinetics
was measured below the melting point using a time-resolved
small-angle neutron scattering technique (TR-SANS) based on
mixing deuterated and proteated but otherwise identical
micelles. Comparing both kinetic and thermodynamic data, we
find that crystallinity within the micellar cores leads to
significant enthalpic and the entropic contributions to the
activation barrier for molecular exchange. While the former
leads to an enhanced stability, the positive entropic gain
favors the process. Interestingly, the entropic term
contains an excess term beyond what is expected from the
measured entropy of fusion. Based on calculations using the
Rotational Isomeric State (RIS) model, we suggest that the
excess entropy is due to the gain in conformational entropy
upon releasing the chain from the confined state in the
core. The study thus provides deep insight into the
fundamental processes of micellar kinetics and which might
be relevant also to other semicrystalline soft matter and
biological systems including lipid membranes.},
cin = {Neutronenstreuung ; JCNS-1 / JCNS (München) ; Jülich
Centre for Neutron Science JCNS (München) ; JCNS-FRM-II /
ICS-1},
ddc = {540},
cid = {I:(DE-Juel1)JCNS-1-20110106 /
I:(DE-Juel1)JCNS-FRM-II-20110218 /
I:(DE-Juel1)ICS-1-20110106},
pnm = {6215 - Soft Matter, Health and Life Sciences (POF3-621) /
6G4 - Jülich Centre for Neutron Research (JCNS) (POF3-623)},
pid = {G:(DE-HGF)POF3-6215 / G:(DE-HGF)POF3-6G4},
experiment = {EXP:(DE-MLZ)KWS1-20140101 / EXP:(DE-MLZ)KWS2-20140101},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000356757800011},
doi = {10.1021/acsmacrolett.5b00197},
url = {https://juser.fz-juelich.de/record/278745},
}