Melting Kinetics of Thermally Responsive Microgel Crystals

Tang, Shijun; Hu, Zhibing; Zhou, Bo; Cheng, Zhengdong; Wu, Jianzhong; Márquez, Manuel

doi:10.1021/ma0716682

Cited by 25 publications

(21 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Figure A also shows that the incorporation of small spheres results in a reduced intensity of the diffraction peak, suggesting a reduced degree of crystallinity. The relative degree of crystallinity of the binary CCs compared with that of the corresponding unary CC was calculated from the integrated area of the Bragg peak according to Hu and co‐workers . As shown in Figure B, the degree of crystallinity of the binary CCs decreases with increasing size of the small spheres.…”

Section: Methodsmentioning

confidence: 99%

“…Again the Bragg peak position of the binary systems remains at the almost same position of the unary one, suggesting the large 450 nm spheres self‐assembled into a same fcc lattice and the small 105 nm spheres fit into the interstitial voids. The relative degree of crystallinity of the systems was calculated from the integrated area of the Bragg peak . As shown in Figure B, incorporation of small spheres results in a decrease in the degree of crystallinity.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Facile Assembly of 3D Binary Colloidal Crystals from Soft Microgel Spheres

Liu

Guan

Zhang

2014

Macromol. Rapid Commun.

View full text Add to dashboard Cite

It still remains a big challenge to fabricate binary colloidal crystals (binary CCs) from hard colloidal spheres, although a lot of efforts have been made. Here, for the first time, binary CCs are assembled from soft hydrogel spheres, PNIPAM microgels, instead of hard spheres. Different from hard spheres, microgel binary CCs can be facilely fabricated by simply heating binary microgel dispersions to 37 °C and then allowing them to cool back to room temperature. The formation of highly ordered structure is indicated by the appearance of an iridescent color and a sharp Bragg diffraction peak. Compared with hard sphere binary CCs, the assembly of PNIPAM microgel binary CCs is much simpler, faster and with a higher "atom" economy. The easy formation of PNIPAM microgel binary CC is attributed to the thermosensitivity and soft nature of the PNIPAM microgel spheres. In addition, PNIPAM microgel binary CCs can respond to temperature change, and their stop band can be tuned by changing the concentration of the dispersion.

show abstract

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Facile Assembly of 3D Binary Colloidal Crystals from Soft Microgel Spheres

Liu

Guan

Zhang

2014

Macromol. Rapid Commun.

View full text Add to dashboard Cite

show abstract

“…Later 2D melting experiments employed tunable colloids so that the melting process can be better controlled and observed in one sample region . Large, micrometer‐sized NIPA spheres were synthesized for the first time by Alsayed in 2005, which opened the way for directly observing 3D melting inside bulk, face‐centered‐cubic (fcc) crystals . Attractive colloidal particles can better mimic atoms and molecules which all have attractions or else atoms would not be able to condense into crystals with free surfaces.…”

Section: Introductionmentioning

confidence: 99%

Melting of Colloidal Crystals

Wang

Zhou

Han

2016

Adv Funct Materials

View full text Add to dashboard Cite

8903wileyonlinelibrary.com ClassificationCrystal melting can be categorized into two types: homogeneous melting in which the melting is equally likely to occur anywhere in the crystal, and heterogeneous melting in which the melting is more likely to occur at the surfaces and defects than the defectfree regions. Heterogeneous melting can be divided into surface melting from a free surface (i.e., the solid-vapor interface), interfacial melting from the interface of two materials (e.g., a crystal and its substrate), grain-boundary melting and melting at weaker defects such as dislocations and vacancies. Homogeneous melting exists in defect-free crystals whose surface melting is suppressed. This type of melting is of theoretical importance but is difficult to achieve experimentally because most crystals melt from surfaces and are not defect-free, which leads to heterogeneous melting. However, homogeneous melting can be conveniently studied by simulation using defect-free crystals under periodic boundary conditions.In heterogeneous melting, particles at the surfaces or defects usually have a higher free energy than those in a perfect crystal. If the free energy is high enough, melting can take place even before the melting point is reached, which is known as premelting. If none of the surfaces and defects has a high enough free energy, then the crystal can be superheated to form a metastable crystal above the bulk melting point. The bulk melting point is the point at which the solid and liquid phases share the same chemical potential, and surfaces are negligible at the thermodynamic limit, i.e., the crystals are infinitely large. For 3D crystals, the likelihood of inducing melting in decreasing order is roughly as follows: 0D corners and 1D edges (intersection of three or two free surfaces) > 1D surface grain boundaries (intersection of a free surface and a bulk grain boundary) > free surfaces > bulk triple junctions > high-angle grain boundaries > the interface between two solids (e.g., on a flat substrate) > lowangle grain boundaries > dislocations > partial dislocations > vacancies > interstitials. [4] Melting starts from the strongest defects and spreads rapidly into the crystal, and thus usually preempts the melting from other weaker defects. Note that this order may not always hold. For example, the energy of free surfaces and grain boundaries varies with their orientations and the interfacial energy at the substrate depends on the affinity between the two solids. Consequently, most free surfaces, some grain boundaries and some solid interfaces will premelt below the bulk melting point T m , while other solid interfaces and grain boundaries and a few free surfaces will only induce melting above T m , i.e., they can be superheated.Crystal melting is affected by many factors such as defects, surfaces, dimensionality, lattice structure, and particle interaction, and thus exhibits rich phenomenology. It is usually a first-order phase transition which currently lacks a fundamental theory. Despite numerous studies ove...

show abstract

“…Therefore it is believed that PNIPAM microgels are promising candidates for the fabrication of large arrays of colloidal crystals 10. Unfortunately the ordered structure of microgel colloidal crystals is fragile 11. It remains an unresolved problem for their use in the large‐scale production of photonic crystals 10…”

Section: Methodsmentioning

confidence: 99%

Polymerized Microgel Colloidal Crystals: Photonic Hydrogels with Tunable Band Gaps and Fast Response Rates

et al. 2013

View full text Add to dashboard Cite

Alle Farben im Angebot: Die hoch geordnete Struktur eines PNIPAM‐Mikrogel‐Kolloidkristalls (MCC) wird durch Photopolymerisation von angebundenen Vinylgruppen an seiner Oberfläche stabilisiert. Es entstehen polymerisierte MCCs, die schnell und reversibel auf externe Reize, z. B. Änderungen von Temperatur und Ionenstärke des Mediums, reagieren. Dabei können die Farbe (siehe Bilder) und die Bandlücke über das gesamte sichtbare Spektrum genau eingestellt werden.

show abstract

Melting Kinetics of Thermally Responsive Microgel Crystals

Cited by 25 publications

References 33 publications

Facile Assembly of 3D Binary Colloidal Crystals from Soft Microgel Spheres

Facile Assembly of 3D Binary Colloidal Crystals from Soft Microgel Spheres

Melting of Colloidal Crystals

Polymerized Microgel Colloidal Crystals: Photonic Hydrogels with Tunable Band Gaps and Fast Response Rates

Contact Info

Product

Resources

About