Shape-changing linear molecular bottlebrushes with dually pH- and thermo-responsive diblock copolymer side chains

Kent, Ethan W.; Henn, Daniel M.; Zhao, Bin

doi:10.1039/c8py01137k

Cited by 19 publications

(41 citation statements)

References 48 publications

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“…The PEO mBBs used in this study were synthesized by a grafting-to method, where alkyne end-functionalized PEO was grafted onto an azidebearing backbone polymer using the highly efficient copper(I)catalyzed azide-alkyne cycloaddition click reaction (Supplementary Fig. 1) 21,[28][29][30][31] . Detailed synthesis and characterization of mBBs are summarized in the supporting information (SI, Supplementary Figs.…”

Section: Resultsmentioning

confidence: 99%

Breaking translational symmetry via polymer chain overcrowding in molecular bottlebrush crystallization

Liu

Henn

et al. 2020

Nat Commun

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One of the fundamental laws in crystallization is translational symmetry, which accounts for the profound shapes observed in natural mineral crystals and snowflakes. Herein, we report on the spontaneous formation of spherical hollow crystals with broken translational symmetry in crystalline molecular bottlebrush (mBB) polymers. The unique structure is named as mBB crystalsome (mBBC), highlighting its similarity to the classical molecular vesicles. Fluorescence resonance energy transfer (FRET) experiments show that the mBBC formation is driven by local chain overcrowding-induced asymmetric lamella bending, which is further confirmed by correlating crystalsome size with crystallization temperature and mBBʼs side chain grafting density. Our study unravels a new principle of spontaneous translational symmetry breaking, providing a general route towards designing versatile nanostructures.

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Section: Resultsmentioning

confidence: 99%

Breaking translational symmetry via polymer chain overcrowding in molecular bottlebrush crystallization

Liu

Henn

et al. 2020

Nat Commun

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“…MBBs are commonly synthesized by one, or a combination, of the following methods: − (i) grafting-from, in which side chains are grown from pendant initiating sites on a backbone polymer typically by a “living”/controlled polymerization method; (ii) grafting-through, in which macromonomers are polymerized to produce brushes directly; and (iii) grafting-to, in which end-functionalized side chain polymers are covalently attached to a backbone bearing complementary reactive pendant groups. While each method has its own advantages and disadvantages, grafting-to allows for thorough characterization of backbone and side chain polymers and provides a modular route for the synthesis of heterografted MBBs composed of two or more distinct side chain polymers with varying molar ratios and tunable overall grafting densities. − The grafting-to synthesis of MBBs has benefited greatly from the advent of click-chemistry; using the highly efficient copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC) reaction, molecular brushes with high and tunable grafting densities now can be routinely prepared. − …”

Section: Introductionmentioning

confidence: 99%

Stimuli-Induced Star-Globule Shape Transitions of Dually Responsive Binary Heterografted Three-Arm Star Molecular Brushes in Aqueous Solution

Kent

Zhao

2019

Macromolecules

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This article reports on the synthesis of doubly responsive binary heterografted, three-arm star molecular brushes and the study of their stimuli-induced star-to-globule shape transitions in aqueous solution. The star brushes were prepared using the highly efficient copper(I)-catalyzed azide–alkyne cycloaddition reaction to simultaneously graft an alkyne end-functionalized thermoresponsive polymer of ethoxydi(ethylene glycol) acrylate (PDEGEA), with a lower critical solution temperature (LCST) of 9 °C, and a pH-responsive polymer of 2-(N,N-diethylamino)ethyl methacrylate (PDEAEMA), with a pK a of 7.4 at room temperature, onto an azide-bearing three-arm star backbone polymer. The star architecture of the formed brushes was confirmed by atomic force microscopy. The use of two different stimuli-responsive polymers as side chains allowed for the stabilization of collapsed brushes against aggregation when one side chain polymer became insoluble in water and for the formation of two distinct globular states with different polymers in the core. At temperatures below the LCST of PDEGEA, upon increasing the pH from 5.00 to 9.40, the brushes underwent a shape transition from an extended starlike to a collapsed globular state stabilized by the hydrated PDEGEA side chains. On the other hand, at pH values slightly lower than the pK a of PDEAEMA, upon heating across the LCST of PDEGEA, the brushes also exhibited a star-to-globule shape transition, forming a globular state distinct from the one induced by pH changes.

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“…In particular, temperature and pH are two of the most widely used stimuli even tunable in the body environment, which enables innovative approaches to drug delivery, biological diagnostics, and tissue engineering. For example, poly(meth)acrylates including poly(2‐( N , N ‐dimethylamino) ethyl (meth)acrylate) (PDMAE[M]A) and poly[2‐( N , N ‐diethylamino) ethyl methacrylate] (PDEAEMA) have been extensively studied to develop novel carriers that were sensitive to both pH and temperature for controlled drug delivery . Such polymers were generally synthesized from monomers that are weakly basic of a tertiary amine substituted with different alkyl groups.…”

Section: Introductionmentioning

confidence: 99%

“…For example, poly(meth)acrylates including poly(2-(N, N-dimethylamino) ethyl (meth)acrylate) (PDMAE[M]A) and poly Ndiethylamino) ethyl methacrylate] (PDEAEMA) have been extensively studied to develop novel carriers that were sensitive to both pH and temperature for controlled drug delivery. [7][8][9][10][11] Such polymers were generally synthesized from monomers that are weakly basic of a tertiary amine substituted with different alkyl groups. It has been reported that both of the charge/discharge state of amine moiety and hydrophilic/hydrophobic balance of the polymer have contributed to their dual responsiveness.…”

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confidence: 99%

Dual stimuli‐responsive polypeptide prepared by thiol‐ene click reaction of poly(l‐cysteine) and N, N‐dimethylaminoethyl acrylate

et al. 2019

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Stimuli‐responsive polymers that can undergo conformational changes with external triggers have enabled themselves as smart materials for various utilizations, among which biodegradability is of particular importance to be engineered for biomedical application. In this study, a thermo and pH dual responsive polypeptide (N, N‐dimethylaminoethyl acrylate‐modified poly(l‐cysteine)) (PLC‐g‐DMAEA) was prepared by the combination of N‐carboxyanhydride ring‐open polymerization and thiol‐ene click chemistry. The biodegradable poly(l‐cysteine) (PLC) with pendant thiol groups provided an easily clickable backbone for postmodification, which was demonstrated by reacting with a well‐known monomer of N, N‐dimethylaminoethyl acrylate (DMAEA) to achieve both temperature and pH responsiveness. The irreversible thermo‐response of PLC‐g‐DMAEA could be attributed to the ordered β‐sheets formed upon heating, leading to the trapped side groups with poor water accessibility. Moreover, this copolymer precipitated at pH ranging from 7.5 to 9.7, but protonation of tertiary amine groups (pH < 7.5) and salt forming of masked thiol groups (pH > 9.7) rendered it soluble in water. Our results revealed that a ready available vinyl monomer could be easily clicked onto the biodegradable PLC and its stimuli responsiveness would be reserved. Moreover, the primary and secondary structures of PLC might influence the conformation, thus leading to the unique responsive behavior of the resulted copolymer.

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Shape-changing linear molecular bottlebrushes with dually pH- and thermo-responsive diblock copolymer side chains

Abstract: The collapse of inner pH-responsive blocks drives cylindrical-to-globular shape transition while outer thermoresponsive blocks provide additional control of solution state.

Cited by 19 publications

References 48 publications

Breaking translational symmetry via polymer chain overcrowding in molecular bottlebrush crystallization

Breaking translational symmetry via polymer chain overcrowding in molecular bottlebrush crystallization

Stimuli-Induced Star-Globule Shape Transitions of Dually Responsive Binary Heterografted Three-Arm Star Molecular Brushes in Aqueous Solution

Dual stimuli‐responsive polypeptide prepared by thiol‐ene click reaction of poly(l‐cysteine) and N, N‐dimethylaminoethyl acrylate

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