- NSF-PAR ID:
- 10298766
- Date Published:
- Journal Name:
- Soft Matter
- Volume:
- 17
- Issue:
- 27
- ISSN:
- 1744-683X
- Page Range / eLocation ID:
- 6566 to 6579
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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null (Ed.)This article reports on the conformational behavior of binary heterografted three-arm star molecular bottlebrushes composed of poly(ethylene oxide) (PEO) and either poly(2-( N , N -dimethylamino)ethyl methacrylate) (PDMAEMA, the brushes denoted as SMB-1) or poly(2-( N , N -diethylamino)ethyl methacrylate) (PDEAEMA, the brushes denoted as SMB-2) side chains in aqueous solutions in response to pH changes and addition of salts containing chaotropic anions (CAs). PEO was introduced into the brushes as a stabilizer when the tertiary amine-containing side chains collapsed. While a small size decrease of SMB-1 was observed with increasing pH from acidic to basic, SMB-2 exhibited a large and abrupt size transition caused by the pH-induced solubility change of PDEAEMA. Atomic force microscopy imaging revealed a star-to-globule shape transition of SMB-2 upon increasing pH across the p K a ; in contrast, SMB-1 stayed in the starlike state at both low and high pH values. Intriguingly, both SMB-1 and -2 displayed star-to-globule shape transitions in acidic solutions upon addition of salts containing sufficiently strong CAs such as ClO 4 − , with SMB-2 showing a greater sensitivity to moderate CAs than SMB-1. Moreover, superchaotropic anions ( e.g. , Fe(CN) 6 3− and S 2 O 8 2− ) were significantly more efficient in inducing shape changing than common CAs. The CA-induced shape transitions resulted from the ion pairing of CAs and protonated tertiary amine groups and the high propensity of CAs to associate with hydrophobic moieties in the brushes, which decreased the solubility of the tertiary amine-containing side chains and caused the brushes to collapse. The findings reported here may enable potential applications of molecular bottlebrushes in, e.g. , encapsulation and release of ionic substances.more » « less
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We infer the swelling/de-swelling behavior of weakly ionizable poly(acrylic acid) (PAA) brushes of 2–39 kDa molar mass in the presence of KCl concentrations from 0.1–1000 mM, pH = 3, 7, and 9, and grafting densities σ = 0.12–2.15 chains per nm 2 using a Quartz Crystal Microbalance with Dissipation (QCM-D), confirming and extending the work of Wu et al. to multiple chain lengths. At pH 7 and 9 (above the p K a ∼ 5), the brush initially swells at low KCl ionic strength (<10 mM) in the “osmotic brush” regime, and de-swells at higher salt concentrations, in the “salted brush” regime, and is relatively unaffected at pH 3, below the p K a , as expected. At pH 7, at low and moderate grafting densities, our results in the high-salt “salted brush” regime ( C s > 10 mM salt) agree with the predicted scaling H ∼ Nσ +1/3 C s −1/3 of brush height H , while in the low-salt “osmotic brush” regime ( C s < 10 mM salt), we find H ∼ Nσ +1/3 C s +0.28–0.38 , whose dependence on C s agrees with scaling theory for this regime, but the dependence on σ strongly disagrees with it. The predicted linearity in the degree of polymerization N is confirmed. The new results partially confirm scaling theory and clarify where improved theories and additional data are needed.more » « less
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Water vapor (H2O) is one of the brightest molecular emitters after carbon monoxide (CO) in galaxies with high infrared (IR) luminosity, allowing us to investigate the warm and dense phase of the interstellar medium (ISM) where star formation occurs. However, due to the complexity of its radiative spectrum, H2O is not frequently exploited as an ISM tracer in distant galaxies. Therefore, H2O studies of the warm and dense gas at high-
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Rare earth elements (REEs) are a vital part of many technologies with particular importance to the renewable energy sector and there is a pressing need for environmentally friendly and sustainable processes to recover and recycle them from waste streams. Functionalized polymer scaffolds are a promising means to recover REEs due to the ability to engineer both transport properties of the porous material and specificity for target ions. In this work, REE adsorbing polymer scaffolds were synthesized by first introducing poly(glycidyl methacrylate) (GMA) brushes onto porous polyvinylidene fluoride (PVDF) surface through activator generated electron transfer atom transfer radical polymerization (AGET ATRP). Azide moieties were then introduced through a ring opening reaction of GMA. Subsequently, REE-binding peptides were conjugated to the polymer surface through copper catalyzed azide alkyne cycloaddition (CuAAC) click chemistry. The presence of GMA, azide, and peptide was confirmed through Fourier transform infrared spectroscopy. Polymer scaffolds functionalized with the REE-binding peptide bound cerium, while polymer scaffolds functionalized with a scrambled control peptide bound significantly less cerium. Importantly, this study shows that the REE binding peptide retains its functionality when bound to a polymer surface. The conjugation strategy employed in this work can be used to introduce peptides onto other polymeric surfaces and tailor surface specificity for a wide variety of ions and small molecules.more » « less
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Abstract By combining the unique characteristics of molecular bottlebrushes (MBBs) and the properties of stimuli‐responsive polymers, we show that MBBs with randomly grafted poly(
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