TY  - JOUR
AU  - González-Gaitano, Gustavo
AU  - Müller, Céline
AU  - Radulescu, Aurel
AU  - Dreiss, Cécile A.
TI  - Modulating the Self-Assembly of Amphiphilic X-Shaped Block Copolymers with Cyclodextrins: Structure and Mechanisms
JO  - Langmuir
VL  - 31
IS  - 14
SN  - 1520-5827
CY  - Washington, DC
PB  - ACS Publ.
M1  - FZJ-2015-02836
SP  - 4096 - 4105
PY  - 2015
AB  - Inclusion complexes between cyclodextrins and polymers—so-called pseudopolyrotaxanes (PPR)—are at the origin of fascinating supramolecular structures, which are finding increasing uses in biomedical and technological fields. Here we explore the impact of both native and a range of modified cyclodextrins (CD) on the self-assembly of X-shaped poly(ethylene oxide)–poly(propylene oxide) block copolymers, so-called Tetronics or poloxamines, by focusing on Tetronic 904 (T904, Mw 6700). The effects are markedly dependent on the type and arrangement of the substituents on the macrocycle. While native CDs drive the formation of a solid PPR, most substituted CDs induce micellar breakup, with dimethylated β-CD (DIMEB) having the strongest impact and randomly substituted CDs a much weaker disruptive effect. Using native α-CD as a “molecular trap”, we perform competitive binding experiments—where two types of CDs thread together onto the polymer chains—to establish that DIMEB indeed has the highest propensity to form an inclusion complex with the polymer, while hydroxypropylated CDs do not thread. 1D 1H NMR and ROESY experiments confirm the formation of a soluble PPR with DIMEB in which the CD binds preferentially to the PO units, thus providing the drive for the observed demicellization. A combination of dynamic light scattering (DLS) and small-angle neutron scattering (SANS) is used to extract detailed structural parameters on the micelles. A binding model is proposed, which exploits the chemical shifts of selected protons from the CD in conjunction with the Hill equation, to prove that the formation of the PPR is a negatively cooperative process, in which threaded DIMEBs hamper the entrance of subsequent macrocycles.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000353177200007
C6  - pmid:25785814
DO  - DOI:10.1021/acs.langmuir.5b00334
UR  - https://juser.fz-juelich.de/record/189818
ER  -