Thermoresponsive Dendronized Poly(phenylacetylene)s Showing Tunable Helicity

Wang, Fang; Zhou, Changyong; Liu, Kun; Yan, Jiatao; Wen, Li; Masuda, Toshio; Zhang, Afang

doi:10.1021/acs.macromol.9b01881

Cited by 32 publications

(36 citation statements)

References 61 publications

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“…Chiroptical properties of PG1 in aqueous solutions containing different salts were studied with CD spectroscopy during the thermally induced aggregation to examine the possible effects of thermoresponsiveness on their helical conformations. CD spectra and plots of the first peak intensities against temperature are shown in Figure 4b−d. As reported previously, 39 in the absence of salts, the CD intensity of PG1 at 375 nm remained nearly unchanged in the temperature range well below its T cp (34 °C) (Figure 4b). However, the CD intensity at 375 nm sharply decreased with increasing temperature close to T cp .…”

Section: Resultssupporting

confidence: 87%

“…Scheme 1 illustrates the synthesis of dendronized phenylacetylene homopolymer and random copolymers. Monomer G1 was synthesized according to our previous report, 39 and the polymerizations were carried out in tetrahydrofuran (THF) solution at 25 °C with [Rh(nbd)Cl] 2 as the catalyst. Tetraethylammonium (TEA) was used as a base to greatly accelerate the reaction and enhance the polymer S7), and the ratios of G1 to EB moieties were found to be 14:1 and 64:1.…”

Section: Resultsmentioning

confidence: 99%

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Remarkable Effects of Anions on the Chirality of Thermoresponsive Helical Dendronized Poly(phenylacetylene)s

et al. 2021

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Tunable chirality of helical polymers through external achiral stimuli is highly valuable for fabrication of intelligent chiral materials. Recently, we reported that through dendronization of phenylacetylene (PA) with threefold dendritic oligo(ethylene glycols) (OEG) via alanine linkage, the corresponding polymers feature water solubility, thermoresponsiveness with cloud points (T cps) around 31.5 °C, and helical structures. In the present study, effects of various anions on the chiral structures and properties of dendronized PA homopolymer (PG1) and copolymers (PG1 m EB n ) from dendronized macromonomer (G1) and the hydrophobic comonomer 4-ethynylbenzaldehyde (EB) were examined. The T cp of PG1 largely increased in the presence of so-called salt-in anions such as PF6 – (47.0 °C) and SCN– (37.7 °C), whereas it slightly decreased with salt-out anions like SO4 2– (29.2 °C) and Cl– (30.8 °C). These results can be correlated with Hofmeister series (HS), and essentially explained in terms of the competitive interactions of the three components, i.e., OEG moiety, water molecule, and the anions. PG1 assumed a right-handed helical conformation at room temperature in the absence and presence of salt-in anions including PF6 – and underwent helix inversion above T cp according to circular dichroism (CD) spectroscopy. On the other hand, in the presence of salt-out anions like SO4 2–, the CD spectral pattern changed above T cp with a red shift, suggesting formation of a different type of helix. Phase transition processes were further clarified by IR spectroscopy. Copolymers PG1 m EB n with different OEG coverages were utilized to confirm the crowding effects of dendritic pendants. When carrying a lower coverage of OEG dendrons, chirality of the copolymer PG1 14 EB 1 became much dependent on anions. We assume that the crowded OEG moieties along the poly(phenylacetylene) (PPA) backbone provide a molecular envelope, which plays a key role for the differential interactions between polymers and anions below and above the T cps.

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Section: Resultssupporting

confidence: 87%

Section: Resultsmentioning

confidence: 99%

Remarkable Effects of Anions on the Chirality of Thermoresponsive Helical Dendronized Poly(phenylacetylene)s

et al. 2021

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“…Subsequently, a series of PPAs carrying G1 dendrons were further synthesized with different linkages between the backbone and dendron pendants, including benzamide (PPA‐AC), inverted acylamide (PPA‐AM), diamide (PPA‐dAM), and benzoate (PPA‐ES) (Figure 9b). [ 49 ] The periphery of the OEG dendrons was also tuned with either an ethoxy (PPA‐ACe) or a methoxy group (PPA‐ACm) to afford the dendronized PPAs with different hydrophilicity. PPAs with hydrogen bonding interactions between neighboring repeating units, as in the case of PPA‐AC, PPA‐AM, and PPA‐dAM, adopted helical conformations with preferred excess of one handedness in different solvents.…”

Section: Thermoresponsive Dendronized Polymers Acting As Molecular Enmentioning

confidence: 99%

Confined Microenvironments from Thermoresponsive Dendronized Polymers

Liu

et al. 2020

Macromol. Rapid Commun.

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Confined microenvironments in biomacromolecules arising from molecular crowding account for their well‐defined biofunctions and bioactivities. To mimick this, synthetic polymers to form confined structures or microenvironments are of key scientific value, which have received significant attention recently. To create synthetic confined microenvironments, molecular crowding effects and topological cooperative effects have been applied successfully, and the key is balance between self‐association of structural units and self‐repulsion from crowding‐induced steric hindrance. In this article, formation of confined microenvironments from stimuli‐responsive dendronized polymers carrying densely dendritic oligoethylene glycols (OEGs) moieties in their pendants is presented. These wormlike thick macromolecules exhibit characteristic thermoresponsive properties, which can provide constrained microenvironments to encapsulate effectively guest molecules including dyes, proteins, or nucleic acids to prevent their protonation or biodegradation. This efficient shielding effect can also mediate chemical reactions in aqueous phase, and even enhance chirality transferring efficiency. All of these can be switched off simply through the thermally‐induced dehydration and collapse of OEG dendrons due to the amphiphilicity of OEG chains. Furthermore, the switchable encapsulation and release of guests can be greatly enhanced when these dendronized polymers are used as major constituents for fabricating bulk hydrogels or nanogels, which provide a higher‐level confinement.

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“…Therefore, it is no surprise to see that [DAPip][OH] 30 showed the conductivity of 4.23 × 10 −2 S cm −1 at 30 °C while increase to 7.99 × 10 −2 S cm −1 at 80 °C. [DAPip][OH] x showed conductivity above 1×10 −2 S cm −1 , although the conductivity is lower than that of reported AEMs with higher IEC values, which exhibited their potential applications for AEMFCs . For comparison, the Br − conductivity of [DAPip][OH] x membranes in Br − form was also measured in the same way, and as shown in Figure S2, it is much lower than that in OH − form because the infinite diffusion coefficient of OH − anions is higher than that of Br − anions …”

Section: Resultsmentioning

confidence: 95%

Cross‐Linked Spirocyclic Quaternary Ammonium‐Based Anion Exchange Membrane with Tunable Properties for Fuel Cell Applications

Chu

Zhang

et al. 2019

ChemistrySelect

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The alkaline stability of anion exchange membranes (AEMs) is crucial to the performance of alkaline anion exchange membrane fuel cells (AEMFCs). Here, we have prepared and characterization of a series of new spirocyclic quaternary ammonium‐based AEMs with good alkaline stability. The AEMs was obtained by UV‐initiated polymerization of N, N‐diallylpiperidinium bromide ([DAPip][Br]), styrene and acrylonitrile. The water uptake, swelling ratio, IEC and conductivity of the AEMs increase with increasing the [DAPip][Br] content. The transparent and mechanically robust AEMs show high conductivities (7.99×10−2 S cm−1 at 80 °C) and good alkaline stability in 1 M KOH solution at 80 °C. The single cell with [DAPip][OH]20 showed a maximum power density of 93.9 mW cm−2. The spirocyclic quaternary ammonium‐based AEMs with an aliphatic backbone will open up new prospects for the preparation of AEMs with excellent alkaline stability and high conductivity.

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Thermoresponsive Dendronized Poly(phenylacetylene)s Showing Tunable Helicity

Cited by 32 publications

References 61 publications

Remarkable Effects of Anions on the Chirality of Thermoresponsive Helical Dendronized Poly(phenylacetylene)s

Remarkable Effects of Anions on the Chirality of Thermoresponsive Helical Dendronized Poly(phenylacetylene)s

Confined Microenvironments from Thermoresponsive Dendronized Polymers

Cross‐Linked Spirocyclic Quaternary Ammonium‐Based Anion Exchange Membrane with Tunable Properties for Fuel Cell Applications

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