TY  - GEN
A1  - Hechenbichler, Michelle
A1  - Laschewsky, Andre
A1  - Gradzielski, Michael
T1  - Poly(N,N-bis(2-methoxyethyl)acrylamide), a thermoresponsive non-ionic polymer combining the amide and the ethyleneglycolether motifs
T2  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - Poly(N,N-bis(2-methoxyethyl)acrylamide) (PbMOEAm) featuring two classical chemical motifs from non-ionic water-soluble polymers, namely, the amide and ethyleneglycolether moieties, was synthesized by reversible addition fragmentation transfer (RAFT) polymerization. This tertiary polyacrylamide is thermoresponsive exhibiting a lower critical solution temperature (LCST)-type phase transition. A series of homo- and block copolymers with varying molar masses but low dispersities and different end groups were prepared. Their thermoresponsive behavior in aqueous solution was analyzed via turbidimetry and dynamic light scattering (DLS). The cloud points (CP) increased with increasing molar masses, converging to 46 degrees C for 1 wt% solutions. This rise is attributed to the polymers' hydrophobic end groups incorporated via the RAFT agents. When a surfactant-like strongly hydrophobic end group was attached using a functional RAFT agent, CP was lowered to 42 degrees C, i.e., closer to human body temperature. Also, the effect of added salts, in particular, the role of the Hofmeister series, on the phase transition of PbMOEAm was investigated, exemplified for the kosmotropic fluoride, intermediate chloride, and chaotropic thiocyanate anions. A pronounced shift of the cloud point of about 10 degrees C to lower or higher temperatures was observed for 0.2 M fluoride and thiocyanate, respectively. When PbMOEAm was attached to a long hydrophilic block of poly(N,N-dimethylacrylamide) (PDMAm), the cloud points of these block copolymers were strongly shifted towards higher temperatures. While no phase transition was observed for PDMAm-b-pbMOEAm with short thermoresponsive blocks, block copolymers with about equally sized PbMOEAm and PDMAm blocks underwent the coil-to-globule transition around 60 degrees C.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1345 
KW  - polyacrylamide
KW  - water-soluble polymers
KW  - responsive systems
KW  - lower
KW  - critical solution temperature
KW  - polymer amphiphile
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-598378
SN  - 0303-402X
SN  - 1435-1536
SN  - 1866-8372
VL  - 299
IS  - 2
PB  - Springer
CY  - Berlin; Heidelberg
ER  - 
TY  - GEN
A1  - Inal, Sahika
A1  - Kölsch, Jonas D.
A1  - Chiappisi, Leonardo
A1  - Janietz, Dietmar
A1  - Gradzielski, Michael
A1  - Laschewsky, André
A1  - Neher, Dieter
T1  - Structure-related differences in the temperature-regulated fluorescence response of LCST type polymers
N2  - We demonstrate new fluorophore-labelled materials based on acrylamide and on oligo(ethylene glycol) (OEG) bearing thermoresponsive polymers for sensing purposes and investigate their thermally induced solubility transitions. It is found that the emission properties of the polarity-sensitive (solvatochromic) naphthalimide derivative attached to three different thermoresponsive polymers are highly specific to the exact chemical structure of the macromolecule. While the dye emits very weakly below the LCST when incorporated into poly(N-isopropylacrylamide) (pNIPAm) or into a polyacrylate backbone bearing only short OEG side chains, it is strongly emissive in polymethacrylates with longer OEG side chains. Heating of the aqueous solutions above their cloud point provokes an abrupt increase of the fluorescence intensity of the labelled pNIPAm, whereas the emission properties of the dye are rather unaffected as OEG-based polyacrylates and methacrylates undergo phase transition. Correlated with laser light scattering studies, these findings are ascribed to the different degrees of pre-aggregation of the chains at low temperatures and to the extent of dehydration that the phase transition evokes. It is concluded that although the temperature-triggered changes in the macroscopic absorption characteristics, related to large-scale alterations of the polymer chain conformation and aggregation, are well detectable and similar for these LCST-type polymers, the micro-environment provided to the dye within each polymer network differs substantially. Considering sensing applications, this finding is of great importance since the temperature-regulated fluorescence response of the polymer depends more on the macromolecular architecture than the type of reporter fluorophore.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 251 
KW  - anionic polymerizations
KW  - dilute aqueous-solutions
KW  - ether methacrylates
KW  - n-isopropylacrylamide
KW  - oligo(ethylene glycol) methacrylate
KW  - phase-transitions
KW  - protein interactions
KW  - solvatochromic fluorophore
KW  - thermoresponsive polymers
KW  - to-coil transition
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95379
SP  - 6603
EP  - 6612
ER  -