Supramolecular ABA Triblock Copolymers via a Polycondensation Approach:  Synthesis, Characterization, and Micelle Formation

Abstract

The combinatorial optimization of the reaction conditions of 1,16-bis(2,2‘:6‘,2‘ ‘-terpyridin-4‘-yloxy)hexadecane 1 with RuCl3 under reductive conditions to form supramolecular polymers with a bis-tpy-Ru(II) type connectivity, utilizing gel permeation chromatography as well as UV/vis spectroscopy as screening tools, led to an improved understanding of important polymerization parameters. Moreover, the obtained knowledge could be applied to the designed synthesis of an A-b-B-b-A type supramolecular triblock copolymer utilizing a α-terpyridine-ω-methyl-poly(ethylene glycol) polymer as a chain stopper during the polycondensation-like reaction. The resulting triblock copolymer revealed a composition of approximately 33 repeat units of 1, outlining the value of the applied optimized conditions for its synthesis. Furthermore, it was observed that the synthesized triblock copolymer was able to form micelles in water. Finally, these micelles were investigated by dynamic light scattering, atomic force microscopy, as well as transmission electron microscopy.

Acyclic Diene Metathesis with a Monomer from Renewable Resources: Control of Molecular Weight and One‐Step Preparation of Block Copolymers

“…Therefore, it is possible to prepare ABA triblock copolymer architectures with control over the molecular weight of the B block by ADMET polymerizations in a single step. Similar chemistry is of course well known for classic step growth polymerizations as well as for more unusual step growth polymerizations [29] but was up to now not systematically explored for ADMET polymerization. In the future, this technique might therefore be applied as a straightforward approach towards novel ABA (and also other) block-copolymer architectures.…”

Supramolecular Self-Assembled Ni(II), Fe(II), and Co(II) ABA Triblock Copolymers

“…Several synthetic procedures have been investigated. The DMA procedure (method B) with nickel(II) chloride, as described for the tpy 2 Ru(II) connectivity, 25 was less successful in the tpy 2 Ni(II) case and was leading to low molecular weight block copolymers (as observed by SEC). Changing nickel(II) chloride to nickel(II) acetate but keeping the same solvent did not improve the polymerization results.…”

“…For the purified A-b-B-b-A triblock copolymer based on tpy 2 Fe(II) 9 (prepared by the DMA approach) the 1 H NMR ( Figure 5) revealed similar degrees of polymerization as in the case of the ruthenium polymers described elsewhere. 25 Assuming that both ends of 1,16-bis(2,2′:6′,2′′-terpyridin-4′-yloxy)hexadecane 5 were functionalized with PEG in order to obtain the A-b-Bb-A triblock copolymer structure, the ratio of signal intensities belonging to the PEG as well as 1,16-bis(2,2′:6′,2′′-terpyridin-4′-yloxy)hexadecane revealed a degree of polymerization of the central B block of ∼40 units (compared to 33 units for the corresponding ruthenium-containing polymer). 25 Therefore, the number-average molecular weight of polymer 9 can be calculated to be 35 kDa if the PF 6 -counterions are omitted and 46.5 kDa if they are taken into account.…”

“…25 Assuming that both ends of 1,16-bis(2,2′:6′,2′′-terpyridin-4′-yloxy)hexadecane 5 were functionalized with PEG in order to obtain the A-b-Bb-A triblock copolymer structure, the ratio of signal intensities belonging to the PEG as well as 1,16-bis(2,2′:6′,2′′-terpyridin-4′-yloxy)hexadecane revealed a degree of polymerization of the central B block of ∼40 units (compared to 33 units for the corresponding ruthenium-containing polymer). 25 Therefore, the number-average molecular weight of polymer 9 can be calculated to be 35 kDa if the PF 6 -counterions are omitted and 46.5 kDa if they are taken into account. Furthermore, almost full complexation was observed in the polymer as revealed by a downfield shift of the methylene protons next to the terpyridine units (from 4.29 ppm (uncomplexed) to 4.72 ppm (complexed)) in the 1 H NMR spectrum.…”

“…18,19 The success in controlling the formation of a certain supramolecular metal-containing structure lies in the careful choice of metal ion, ligand, and framework motifs. [20][21][22][23][24] Recently, we showed that the polymerization of a bisterpyridine monomer with RuCl 3 and a mono-terpyridine functionalized polymer can lead to supramolecular triblock copolymers in a one-step procedure, 25 thereby expanding the range of accessible supramolecular polymer architectures.…”