Journal Article

FZJ-2022-01411

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Controlled LCST Behavior and Structure Formation of Alternating Amphiphilic Copolymers in Water

Kostyurina, E. (Corresponding author)FZJ* ; De Mel, J. U. ; Vasilyeva, A. ; Kruteva, M.FZJ* ; Frielinghaus, H.FZJ* ; Dulle, M.FZJ* ; Barnsley, L. ; Förster, S.FZJ* ; Schneider, G. J. ; Biehl, R.FZJ* ; Allgaier, J. (Corresponding author)FZJ*

2022
Soc. Washington, DC

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Please use a persistent id in citations: http://hdl.handle.net/2128/30939  doi:10.1021/acs.macromol.1c02324

Abstract: Amphiphilic polymers show a rich self-assembly behavior in aqueous solutions. In experimental investigations statistical copolymer or block copolymer architectures are usually investigated, because of their ease of synthesis or their structural analogy to surfactants. A copolymer structure that links the two architectures are alternating copolymers, which are easily accessible by polycondensation reactions. Using alternating hydrophilic and hydrophobic building blocks with varying length allows a systematic variation between statistical and multi-block architectures. We synthesized alternating amphiphilic copolymers as polyesters using hydrophobic dicarboxylic acids (C4 – C20) and hydrophilic polyethylene glycol (PEG) units (EG3 – EG1000). Copolymers with long EG units were made accessible with the help of a newly developed esterification process. The solution properties of the amphiphilic copolymers feature a lower critical solution temperature (LCST) behavior in water, which can be systematically varied over a wide range from 3 – 83°C by adjusting the lengths of the Cn- and EGm–units. We find that the transition temperature depends linearly on the hydrophobic unit length Cm and logarithmically on the hydrophilic length EGn. In the one-phase region the PEG copolymer coils are more compact compared to the respective PEG homopolymers due to hydrophobic interactions between the hydrophobic units leading to loop formation. For shorter PEG-units the copolymers form micellar structures consisting only of a few copolymer chains. The micellar cores consist of hydrophobic regions containing only a few dicarboxylic acid units, embedded in a PEG-rich and water-poor matrix. The cores are surrounded by a rather diluted corona of PEG chains. Further decreasing the PEG unit length leads to the formation of highly swollen gels consisting of networks of interconnected micelles. These can self-assemble to form highly ordered liquid crystalline cubic phases. The study demonstrates how the structure of alternating amphiphilic copolymers can be systematically varied to adjust thermal solution properties such as the LCST over a wide range, as well as the self-assembly properties varying between single chain, micelle, gels and highly ordered lyotropic liquid crystals.

Keyword(s): Polymers, Soft Nano Particles and Proteins (1st) ; Soft Condensed Matter (2nd)

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Contributing Institute(s):

1. JCNS-FRM-II (JCNS-FRM-II)
2. Heinz Maier-Leibnitz Zentrum (MLZ)
3. Neutronenstreuung (JCNS-1)
4. JCNS-4 (JCNS-4)

Research Program(s):

1. 6G4 - Jülich Centre for Neutron Research (JCNS) (FZJ) (POF4-6G4) (POF4-6G4)
2. 632 - Materials – Quantum, Complex and Functional Materials (POF4-632) (POF4-632)

Experiment(s):

1. KWS-1: Small angle scattering diffractometer (NL3b)

Appears in the scientific report 2022

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Database coverage:
; ; Chemical Reactions ; Clarivate Analytics Master Journal List ; Current Contents - Physical, Chemical and Earth Sciences ; Ebsco Academic Search ; Essential Science Indicators ; IF >= 5 ; JCR ; Nationallizenz ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

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