Aqueous worm gels can be reconstituted from freeze-dried diblock copolymer powder

Kocik, Marzena K.; Mykhaylyk, Oleksandr O.; Armes, Steven P.

doi:10.1039/c4sm00415a

Cited by 40 publications

(61 citation statements)

References 59 publications

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“…[75] Free-standing gels could be reconstituted after freeze-drying by re-dissolving in water at 3-5 °C prior to heating to room temperature. [76] The (de)gelation temperature of p(GMA x -b-HPMA y ), below room temperature in the above cases, could be increased to 31 °C by the incorporation of 30 mol-% of hydrophilic di(ethylene glycol) methyl ether methacrylate (DEGMA) co-monomers into the core-forming block. Upon cooling from above 31 °C to 5 °C, the worm particles reversibly disintegrated into weakly interacting copolymer chains with an average aggregation number of ≈4.…”

Section: Temperature Responsiveness In Aqueous Dispersionmentioning

confidence: 98%

“…In this and subsequent studies, the p(GMA x ‐ b ‐HPMA y ) system and its thermoresponsiveness were investigated in detail including through electron microscopy, dynamic light scattering, variable temperature 1 H NMR measurements, SAXS, rheology, and fluorescence correlation spectroscopy . Free‐standing gels could be reconstituted after freeze‐drying by re‐dissolving in water at 3–5 °C prior to heating to room temperature . The (de)gelation temperature of p(GMA x ‐ b ‐HPMA y ), below room temperature in the above cases, could be increased to 31 °C by the incorporation of 30 mol‐% of hydrophilic di(ethylene glycol) methyl ether methacrylate (DEGMA) co‐monomers into the core‐forming block.…”

Section: Temperature‐responsive Dispersion Pisa Nano‐objectsmentioning

confidence: 99%

See 1 more Smart Citation

Stimulus‐Responsive Nanoparticles and Associated (Reversible) Polymorphism via Polymerization Induced Self‐assembly (PISA)

Pei

Lowe

Roth

2016

Macromol. Rapid Commun.

118

131

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"smart" materials rely on very distinct material responses on a macroscopic and/or microscopic level. This can be achieved by crafting stimulus-responsive polymers into nanostructured materials, including smart nanoparticles, which are receiving increasing attention specifically in the biomedical field. [2,3] Amphiphilic block copolymers are well-known to undergo self-directed assembly in selective solvents providing access to a range of soft matter nanoparticles [4][5][6][7] with applications in coatings, [8] electronics, [9] drug delivery, [10] and cancer therapy, [11,12] among others. Traditionally, the preparation of such nanoparticles has been accomplished by initial synthesis and molecular dissolution of well-defined parent copolymers which are subsequently "processed", often via time-consuming step-wise dialysis, to give the targeted nano-object. Another drawback of this well-established approach is the generally low concentration of the final copolymer nanoparticles (≤1.0 wt% is common) which limits industrial application and study of such nanoparticles in areas where high Polymerization-induced self-assembly (PISA) is an extremely versatile method for the in situ preparation of soft-matter nanoparticles of defined size and morphologies at high concentrations, suitable for large-scale production. Recently, certain PISA-prepared nanoparticles have been shown to exhibit reversible polymorphism ("shape-shifting"), typically between micellar, worm-like, and vesicular phases (order-order transitions), in response to external stimuli including temperature, pH, electrolytes, and chemical modification. This review summarises the literature to date and describes molecular requirements for the design of stimulus-responsive nano-objects. Reversible pH-responsive behavior is rationalised in terms of increased solvation of reversibly ionized groups. Temperature-triggered order-order transitions, conversely, do not rely on inherently thermo-responsive polymers, but are explained based on interfacial LCST or UCST behavior that affects the volume fractions of the core and stabilizer blocks. Irreversible morphology transitions, on the other hand, can result from chemical post-modification of reactive PISA-made particles. Emerging applications and future research directions of this "smart" nanoparticle behavior are reviewed.

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Section: Temperature Responsiveness In Aqueous Dispersionmentioning

confidence: 98%

Section: Temperature‐responsive Dispersion Pisa Nano‐objectsmentioning

confidence: 99%

Stimulus‐Responsive Nanoparticles and Associated (Reversible) Polymorphism via Polymerization Induced Self‐assembly (PISA)

Pei

Lowe

Roth

2016

Macromol. Rapid Commun.

118

131

View full text Add to dashboard Cite

show abstract

“…Similar patterns, albeit at even lower temperatures, have been recently reported for an aqueous dispersion of a PGMA57-PHPMA140 diblock copolymer. 39 This is reasonable, since incorporation of the relatively hydrophilic DEGMA comonomer should favor molecular dissolution.…”

Section: Saxs Studiesmentioning

confidence: 99%

Tuning the critical gelation temperature of thermo-responsive diblock copolymer worm gels

et al. 2014

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Abstract. Amphiphilic diblock copolymer nano-objects can be readily prepared using reversible addition-fragmentation chain transfer (RAFT) polymerization. For example, poly(glycerol monomethacrylate) (PGMA) chain transfer agents (CTA) can be chain-extended using 2-hydroxypropyl methacrylate (HPMA) via RAFT aqueous dispersion polymerization to form welldefined spheres, worms or vesicles at up to 25% solids. The worm morphology is of particular interest, since multiple inter-worm contacts lead to the formation of soft free-standing gels, which undergo reversible degelation on cooling to sub-ambient temperatures. However, the critical gelation temperature (CGT) for such thermo-responsive gels is < 20C, which is relatively low for certain biomedical applications. In this work, a series of new amphiphilic diblock copolymers are prepared in which the core-forming block comprises a statistical mixture of HPMA and di(ethylene glycol) methyl ether methacrylate (DEGMA), which is a more hydrophilic monomer than HPMA.Statistical copolymerizations proceeded to high conversion and low polydispersities were achieved in all cases (Mw/Mn < 1.20). The resulting PGMA-P(HPMA-stat-DEGMA) diblock copolymers undergo polymerization-induced self-assembly at 10% w/w solids to form free-standing worm gels. SAXS studies indicate that reversible (de)gelation occurs below the CGT as a result of a worm-to-sphere transition, with further cooling to 5 °C affording weakly interacting copolymer chains with a mean aggregation number of approximately four. This corresponds to almost molecular dissolution of the copolymer spheres. The CGT can be readily tuned by varying the mean degree of polymerization and the DEGMA content of the core-forming statistical block. For example, a CGT of 31°C was obtained for PGMA59-P(HPMA91-stat-DEGMA39). This is sufficiently close to physiological temperature (37°C) to suggest that these new copolymer gels may offer biomedical applications as readily-sterilizable scaffolds for mammalian cells, since facile cell harvesting can be achieved after a single thermal cycle.

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“…This is consistent with smallangle X-ray scattering (SAXS) studies recently reported for closely related PGMA 57 -block -PHPMA 140 in methanol. [ 37 ] Thus, the steady increase in diffusion coeffi cient that is observed in Figure 3 below the worm-to-sphere transition is consistent with the partial dissociation of the spheres to form near-molecularly dissolved copolymer chains at suffi ciently low temperatures. [ 37 ] However, the temperature at which this order-disorder transition occurs is not reached in the current study, with the smallest radius observed being 8 ± 4 nm at 5 °C.…”

Section: Resultsmentioning

confidence: 51%

“…Experiments investigating the thermoresponsive behavior of these rhodamine-labeled PGMA-PHPMA diblock copolymer nanoparticles were performed at pH 3.9; the copolymer was freeze-dried after its synthesis and then reconstituted using ice-cold water at this initial pH. [ 37 ] All FCS data were acquired using an inverted LSM510 Meta confocal microscope equipped with a ConFocor2 FCS module. The setup was calibrated using free RhB dye in order to allow optimization of the pinhole dimensions, placement, and fi lters.…”

Section: Methodsmentioning

confidence: 99%

Characterization of Diblock Copolymer Order-Order Transitions in Semidilute Aqueous Solution Using Fluorescence Correlation Spectroscopy

Clarkson

Lovett

Madsen

et al. 2015

Macromol. Rapid Commun.

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gels at relatively high concentrations. [ 1,2 ] Judicious choice of the copolymer allows the design of hydrogels that are responsive to temperature [ 3,4 ] or pH. [5][6][7][8] However, it is relatively unusual for such a copolymer to respond to both temperature and pH.In principle, biocompatible block copolymer gels can be used as a long-term cell storage medium. [ 9 ] One promising candidate for such applications is a diblock copolymer comprising poly(glycerol monomethacrylate) (PGMA) and poly(2-hydroxypropyl methacrylate) (PHPMA), which are conveniently prepared via polymerization-induced self-assembly [9][10][11][12][13] using reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion polymerization. [14][15][16] This versatile approach has enabled spherical, worm-like or vesicular copolymer morphologies to be generated in concentrated solution. [ 11,[17][18][19][20][21][22][23][24][25][26] Such a nonionic PGMA-PHPMA diblock copolymer exhibits a thermoreversibleThe temperature and pH-dependent diffusion of poly(glycerol monomethacrylate)-blockpoly(2-hydroxypropyl methacrylate) nanoparticles prepared via polymerization-induced self-assembly in water is characterized using fl uorescence correlation spectroscopy (FCS). Lowering the solution temperature or raising the solution pH induces a worm-to-sphere transition and hence an increase in diffusion coeffi cient by a factor of between four and eight. FCS enables morphological transitions to be monitored at relatively high copolymer concentrations (10% w/w) compared to those required for dynamic light scattering (0.1% w/w). This is important because such transitions are reversible at the former concentration, whereas they are irreversible at the latter. Furthermore, the FCS data suggest that the thermal transition takes place over a very narrow temperature range (less than 2 °C). These results demon strate the application of FCS to characterize orderorder transitions, as opposed to order-disorder transitions.

show abstract

Aqueous worm gels can be reconstituted from freeze-dried diblock copolymer powder

Cited by 40 publications

References 59 publications

Stimulus‐Responsive Nanoparticles and Associated (Reversible) Polymorphism via Polymerization Induced Self‐assembly (PISA)

Stimulus‐Responsive Nanoparticles and Associated (Reversible) Polymorphism via Polymerization Induced Self‐assembly (PISA)

Tuning the critical gelation temperature of thermo-responsive diblock copolymer worm gels

Characterization of Diblock Copolymer Order-Order Transitions in Semidilute Aqueous Solution Using Fluorescence Correlation Spectroscopy

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