Isothermal Crystallization Kinetics of Poly(ethylene oxide)/Poly(ethylene glycol)--silica Nanocomposites.

In this work, the crystallization kinetics of poly(ethylene oxide) (PEO) matrix included with poly(ethylene glycol) (PEG) grafted silica (PEG--SiO) nanoparticles and bare SiO were systematically investigated by differential scanning calorimetry (DSC) and polarized light optical microscopy (PLOM) method. PEG--SiO can significantly increase the crystallinity and crystallization temperature of PEO matrix under the non-isothermal crystallization process. Pronounced effects of PEG--SiO on the crystalline morphology and crystallization rate of PEO were further characterized by employing spherulitic morphological observation and isothermal crystallization kinetics analysis.

Substituting copolymeric poly(alkylenetetrasulfide) for elemental sulfur to diminish the shuttling effect of modified intermediate polysulfides for high-performance lithium-sulfur batteries.

Poly(alkylenetetrasulfide) can be synthesized to replace sulfur in a chitosan-derived porous carbon (CPC) based composite cathode of lithium-sulfur batteries. Introducing a -CH2- or -CH2CH2- unit in-between the S-S bond of a polysulfide (e.g.

Oil-in-Water Emulsion Templated and Crystallization-Driven Self-Assembly Formation of Poly(l-lactide)-Polyoxyethylene-Poly(l-lactide) Fibers.

A molecular solution of an amphiphilic block copolymer may act as an oil phase by dispersing into an aqueous micellar system of small-molecular surfactant, forming oil-in-water (O/W) emulsion droplets. In this paper, an as-synthesized triblock copolymer poly(l-lactide)-polyoxyethylene-poly(l-lactide) (PLLA-PEO-PLLA) was dissolved in tetrahydrofuran (THF) and then added to an aqueous micellar solution of nonaethylene glycol monododecyl ether (AEO-9), forming initially coalescent O/W emulsion droplets in the size range of 35 nm-1.3 μm.

Unusual Interfacial Freezing Phenomena in Hexacontane/Silica Composites.

The crystallization behaviors of n-hexacontane (CH)/Stöber silica (SiO) composites with various compositions were investigated by a combination of differential scanning calorimetry (DSC), solid-state C nuclear magnetic resonance (solid-state C NMR), and proton NMR relaxation experiments. By means of DSC, CH molecules in CH/silica composites were observed to be involved in the interfacial freezing not present in the free bulk CH. The orientation of CH molecules, being preferentially normal to silica surface, was confirmed by grazing incidence X-ray diffraction experiments on thin n-hexacontane film adsorbed on the silicon wafer with a native SiO layer.

In situ synthesis of bilayered gradient poly(vinyl alcohol)/hydroxyapatite composite hydrogel by directional freezing-thawing and electrophoresis method.

Bilayered poly(vinyl alcohol) (PVA)/hydroxyapatite (HA) composite hydrogels with anisotropic and gradient mechanical properties were prepared by the combination of directional freezing-thawing (DFT) and electrophoresis method. Firstly, PVA hydrogels with aligned channel structure were prepared by the DFT method. Then, HA nanoparticles were in situ synthesized within the PVA hydrogels via electrophoresis.

Mechanical properties of PNIPAM based hydrogels: A review.

Materials which adjust their properties in response to environmental factors such as temperature, pH and ionic strength are rapidly evolving and known as smart materials. Hydrogels formed by smart polymers have various applications. Among the smart polymers, thermoresponsive polymer poly(N-isopropylacrylamide)(PNIPAM) is very important because of its well defined structure and property specially its temperature response is closed to human body and can be finetuned as well.

Two-Step Freezing in Alkane Monolayers on Colloidal Silica Nanoparticles: From a Stretched-Liquid to an Interface-Frozen State.

The crystallization behavior of an archetypical soft/hard hybrid nanocomposite, that is, an n-octadecane C18/SiO2-nanoparticle composite, was investigated by a combination of differential scanning calorimetry (DSC) and variable-temperature solid-state (13)C nuclear magnetic resonance (VT solid-state (13)C NMR) as a function of silica nanoparticles loading. Two latent heat peaks prior to bulk freezing, observed for composites with high silica loading, indicate that a sizable fraction of C18 molecules involve two phase transitions unknown from the bulk C18. Combined with the NMR measurements as well as experiments on alkanes and alkanols at planar amorphous silica surfaces reported in the literature, this phase behavior can be attributed to a transition toward a 2D liquid-like monolayer and subsequently a disorder-to-order transition upon cooling.

A novel biocompatible double network hydrogel consisting of konjac glucomannan with high mechanical strength and ability to be freely shaped.

A novel physically linked double-network (DN) hydrogel based on natural polymer konjac glucomannan (KGM) and synthetic polymer polyacrylamide (PAAm) has been successfully developed. Polyvinyl alcohol (PVA) was used as a macro-crosslinker to prepare the PVA-KGM first network hydrogel by a cycle freezing and thawing method for the first time. Subsequent introduction of a secondary PAAm network resulted in super-tough DN hydrogels.

Catanionic surfactant-assisted mineralization and structural properties of single-crystal-like vaterite hexagonal bifrustums.

Crystalline vaterite is the most thermodynamically unstable polymorph of anhydrous calcium carbonate (CaCO3), and various morphologies can be controlled in the presence of organic additives. Constructing vaterite with minimal defects, determining its distinctive properties, and understanding the formation mechanism behind a biomimetic process are the main challenges in this field. In this paper, a unique single-crystal-like vaterite hexagonal bifrustum with two hexagonal and 12 trapezoidal faces has been fabricated through a catanionic surfactant-assisted mineralization approach for the first time.

Nanoparticle enlarged interfacial effect on phase transition of 1-octadecanol/silica composites.

Motivated by the interest in an interfacial effect on crystallization behaviors and material properties of polymer nanocomposites, phase behaviors of a novel model system for polymer nanocomposite, 1-octadecanol/silica nanosphere composites (C18OH/SiO2), were studied by means of thermal analysis and wide-angle X-ray diffraction. Although a huge specific surface area of silica nanoparticles enlarges the surface-volume ratio of C18OH molecules, surface freezing phenomenon is not observed by DSC in the C18OH/SiO2 composites. While pure C18OH exhibits rotator RIV phase with molecules tilted with respect to the layer normal, the silica network favors and enhances untitled RII phase by disturbing the layering arrangement.

Nano-hydroxyapatite/polyacrylamide composite hydrogels with high mechanical strengths and cell adhesion properties.

Nano-hydroxyapatite/polyacrylamide composite hydrogels were successfully fabricated by physically mixing nano-hydroxyapatite (nHAp) particles into a peroxidized micelles initiated and cross-linked (pMIC) polyacrylamide (PAAm) hydrogel. The nanocomposite hydrogels exhibited excellent mechanical properties. The fracture tensile stresses of the gels were in the range of 0.

Confined phase diagram of binary n-alkane mixtures within three-dimensional microcapsules.

The confined phase behaviors of microencapsulated normal hexadecane/octadecane mixtures (abbreviated as m-C16/C18) have been investigated by combination of differential scanning calorimetry and in situ wide-angle X-ray scattering. The binary alkane mixtures confined in three-dimensional geometrical space demonstrate two novel crystallization features. The surface freezing is significantly enhanced after C16/C18 mixtures being encapsulated, and the surface monolayer formed is proved to be an ideal solid solution composed by C16 and C18.

Phase transition behavior of a series of even n-alkane C(n)/C(n+2) mixtures confined in microcapsules: from total miscibility to phase separation determined by confinement geometry and repulsion energy.

The phase behaviors of binary consecutive even normal alkane (n-alkane) mixtures (n-C(n)H(2n+2)/n-C(n+2)H(2n+6), with mass ratios of 90/10 and 10/90) with different average carbon numbers n¯ both in the bulk state (abbreviated as C(n)/C(n+2)) and in nearly monodisperse microcapsules (abbreviated as m-C(n)/C(n+2)), have been investigated by the combination of differential scanning calorimetry and temperature-dependent X-ray diffraction. The phase behavior of n-alkane mixtures gradually shifts from complete phase separation, partial miscibility to total miscibility in both bulk and microcapsules with the increase of average carbon numbers n¯. There are critical points for average carbon numbers of C(n)/C(n+2), where the corresponding mixtures exhibit coexistence of a triclinic phase (formed by alkane with a longer chain) and an orthorhombic ordered phase (formed by the two components of mixtures).

Crystallization features of normal alkanes in confined geometry.

How polymers crystallize can greatly affect their thermal and mechanical properties, which influence the practical applications of these materials. Polymeric materials, such as block copolymers, graft polymers, and polymer blends, have complex molecular structures. Due to the multiple hierarchical structures and different size domains in polymer systems, confined hard environments for polymer crystallization exist widely in these materials.

Confined crystallization of n-hexadecane located inside microcapsules or outside submicrometer silica nanospheres: a comparison study.

Crystallization and phase transition behaviors of n-hexadecane (n-C16H34, abbreviated as C16) confined in microcapsules and n-alkane/SiO2 nanosphere composites have been investigated by the combination of differential scanning calorimetry (DSC) and temperature-dependent X-ray diffraction (XRD). As evident from the DSC measurement, the surface freezing phenomenon of C16 is enhanced in both the microcapsules and SiO2 nanosphere composites because the surface-to-volume ratio is dramatically enlarged in both kinds of confinement. It is revealed from the XRD results that the novel solid-solid phase transition is observed only in the microencapsulated C16, which crystallizes into a stable triclinic phase via a mestastable rotator phase (RI).

A tough hydrogel-hydroxyapatite bone-like composite fabricated in situ by the electrophoresis approach.

Mechanically strong hydrogel-HAp composites have been successfully fabricated through in situ formation of hydroxyapatite (HAp) in a tough polyacrylamide (PAAm) hydrogel with a modified electrophoretic mineralization method. The pre-swelling of the PAAm hydrogels in CaCl buffer solutions makes the electrophoresis method able to produce large area (10 × 8 cm) hydrogel-HAp composites. At the same time the CaCl solution with different concentrations could control the HAp contents.

Binary n-alkane mixtures from total miscibility to phase separation in microcapsules: enrichment of shorter component in surface freezing and enhanced stability of rotator phases.

The crystallization behaviors of binary normal alkane (n-alkane) mixtures with a series of carbon number difference (denoted as Δn), both in the bulk state and in nearly monodisperse microcapsules, have been investigated by the combination of differential scanning calorimetry (DSC) and temperature-dependent X-ray diffraction (XRD). As revealed by the DSC data, the surface freezing temperature (denoted as T(s)) of spatially confined binary n-alkane mixtures with large Δn is lower than the calculated value due to the enrichment of shorter component in the surface freezing phase. More alkane molecules with shorter carbon chain are located on the interface between the inner shell of microcapsules and the bulk mixture, thus leading to the decrease of the average chain length of the surface freezing phase and corresponding lower T(s).

Integrative and intermediate self-assembly of multi-walled hybrid nanotubes for catanionic biomimetics.

Hollow cylindrical multi-walled hybrid nanotubes go through dynamic growth and subsequent disappearance during the biomimetic fabrication of hexagonal calcite platelets, simulating the in vivo purpose-driven self-assembly of tubular plasma-membrane calcium-ion channels for biomaterials to adapt, respond and repair.

Confined crystallization of binary n-alkane mixtures: stabilization of a new rotator phase by enhanced surface freezing and weakened intermolecular interactions.

The present work reports the confined crystallization behaviours of binary even-even normal alkane (n-alkane) mixtures of n-octadecane (n-C(18)H(38)) and n-eicosane (n-C(20)H(42)), which are microencapsulated in monodisperse microcapsules, using the combination of differential scanning calorimetry (DSC) and temperature-dependent X-ray diffraction (XRD). A new metastable rotator phase (RII) absent in the bulk state, has been detected for the n-alkane mixture in confined geometry under all the investigated compositions. Such a crossover is attributed to the lower interfacial energy due to the same in-planar hexagonal structure of the surface monolayer and RII, as well as the weakened intermolecular interaction in alkane mixtures.

Crystallization behavior of binary even-even n-alkane mixtures in microcapsules: effect of composition and confined geometry on solid-solid phase separation.

The crystallization behaviors of binary even-even normal alkane (n-alkane) mixtures (n-C(18)H(38)/n-C(20)H(42), abbreviated as C(18)/C(20)) with different compositions, both in the bulk state and in nearly monodisperse microcapsules, have been investigated by the combination of differential scanning calorimetry and temperature-dependent X-ray diffraction. The solid-solid phase separation, usually observed during the cooling process of bulk samples, is greatly suppressed and even eliminated after being microencapsulated, with the orthorhombic-ordered phase dominating in the low-temperature crystal. Such a crystallization transition is attributed to the special interaction between the two even n-alkanes and the confined environment in microcapsules.

Phase change materials of n-alkane-containing microcapsules: observation of coexistence of ordered and rotator phases.

In the present investigation, the crystallization and phase transition behaviours of normal alkane (n-docosane) in microcapsules with a mean diameter of 3.6 μm were studied by the combination of differential scanning calorimetry (DSC), temperature-dependent X-ray diffraction (XRD) and variable-temperature solid-state nuclear magnetic resonance (VT solid-state (13)C NMR). The DSC and VT solid-state (13)C NMR results reveal that a surface freezing monolayer is formed prior to the bulk crystallization of the microencapsulated n-docosane.

Biomimetic fabrication of pseudohexagonal aragonite tablets through a temperature-varying approach.

Pseudohexagonal and single-crystal-like aragonite tablets, found in nacre, could be uniformly fabricated through a temperature-varying approach for the first time, indicating the triplet twinning nature and implying a potential significance in biomineralization.

Solid-solid phase transition of n-alkanes in multiple nanoscale confinement.

The crystallization behavior of n-C(19)H(40)/SiO(2) nanosphere composites was investigated by a combination of differential scanning calorimetry (DSC) and temperature-dependent X-ray diffraction (XRD). Three kinds of confined alkanes with different solid-solid phase transition supercoolings and a surface (or interface) freezing monolayer of n-C(19)H(40) at the bulk liquid/SiO(2) interface were found in the composites at high SiO(2) loading. The surface freezing monolayer induces the chain packing of bulk alkanes by forming a 2D close-packed arrangement without long-range positional ordering in 3D space.

Transcriptive synthesis of Mg(OH)2 hollow nanospheres and the non-equilibrium shell fusion assisted by catanionic vesicles.

The oriented attachment of inorganic nanocrystals controlled by adsorbed surfactants can lead to the formation of hollow nanoarchitectures with various well-defined morphologies. In this paper, Mg(OH)(2) hollow nanospheres and the "encapsulated" catanionic vesicles could be simultaneously constructed by using the cationic surfactant of cetyltrimethylammonium hydroxide (CTAOH) and the anionic surfactant of magnesium dodecyl sulfate (Mg(DS)(2)) as reactants at pH 11.0.

Effect of geometrical confinement on the nucleation and crystallization behavior of n-alkane mixtures.

The condensed structure of normal alkane (n-alkane) mixtures in confined geometry is an interesting topic concerning the difference in crystallization behavior of odd and even alkanes. In the present work, the crystallization of mixtures of normal octadecane (n-C18H38) and normal nonadecane (n-C19H40) in microcapsules with narrow size distribution was investigated using the combination of differential scanning calorimetry (DSC) and X-ray diffraction (XRD). A surface freezing monolayer for microencapsulated n-C18H38, n-C19H40, and their mixture was detected by DSC, which for the mixture is a mixed homogeneous crystalline phase with continuous change in the composition.