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A new sort of nanofluid phase-change material (PCM) is developed by suspending a small amount of nanoparticles in melting paraffin. Cu, Al, and C/Cu nanoparticles were selected to add to the melting paraffin to enhance the heat-transfer rate of paraffin. Cu nanoparticles have the best performance for heat transfer. Five dispersants were chosen to make Cu nanoparticles stably suspended in melting paraffin. The nanofluids with Cu nanoparticles show good stability in melting paraffin under the action of Hitenol BC-10, even suspending for 12 h in a constant temperature trough. The Fourier transform infrared (FTIR) spentrum shows that it is a physical interaction among Cu, paraffin, and Hitenol BC-10. The differential scanning calorimetric (DSC) results reveal that the latent heats of Cu/paraffin shift to lower values compared to those of pure paraffin; however, the melting and freezing temperatures are kept almost the same as pure paraffin. The latent heats and phase-change temperatures change very little after 100 thermal cycles. Furthermore, the heating and cooling rates of PCMs were significantly improved upon the addition of Cu nanoparticles. For composites with 1 wt % Cu nanoparticle, the heating and cooling times can be reduced by 30.3 and 28.2%, respectively.

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Instead of the traditional isocyanate curing system as the binder of solid propellant, a triazole curing system has been developed by the reaction of azide group and alkynyl group due to a predominant advantage of avoiding to the interference of humidity. In this work, the propargyl-terminated polybutadiene (PTPB) was blended with glycidyl azide polymers (GAPs) to produce new composites under the catalysis of cuprous chloride at ambient temperature. The triazole-crosslinked network structure was regulated by changing the molar ratio of azide group in GAP versus alkynyl group in PTPB, and hence various crosslinked densities together with the composition changes of GAP versus PTPB cooperatively determined the mechanical properties of the resultant composites. Furthermore, the formed triazole-crosslinked network derived from the azide group in GAP and alkynyl group in PTPB resulted in the slight increase of glass transition temperatures and a-transition temperatures, and improved the miscibility between GAP and PTPB.

Supramolecular crystals were prepared via self-assembly of a series of inclusion complexes of β-cyclodextrin (β-CD) with poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-b-PPO-b-PEO) block copolymer. In this study, two PEO-b-PPO-b-PEO copolymers were used with different molecular weights for the PEO blocks. On the basis of two-dimensional (2D) wide-angle X-ray diffraction (WAXD) and selected area electron diffraction (SAED) experiments, the supramolecular crystal structure was determined to be a monoclinic lattice with a = 1.910 nm, b = 2.426 nm, c = 1.568 nm, and β = 111°f or both inclusion complex systems. Each crystal unit cell contained four inclusion complexes. The space group was identified to be C 2 symmetry based on the relationship among diffraction spot intensity and systematic extinctions. With the help of computer simulations of the supramolecular structure, the packing of inclusion complexes in the crystal lattice could be achieved. The simulated 2D WAXD fiber patterns and SAED patterns agreed well with the experimental results. Observations of the morphology in transmission electron microscopy combined with the [001] zone SAED patterns indicated that the supramolecular crystals are lozenge-shaped, bound by four (110) planes. Furthermore, the tethered PEO blocks were found to crystallize, and the c-axis of the PEO crystals was nearly parallel to the lamellar surface normal of the supramolecular crystals. The existence of PEO crystals resulted in additional proof that β-CDs are only selectively threaded onto the PPO blocks when forming the inclusion complexes. These PEO crystals acted as locks to prevent the dethreading of the β-CDs from the complexes and physically stabilized the supramolecular structure.

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In situ photopolymerized hydrogel dressings create minimally invasive methods that offer advantages over the use of preformed dressings such as conformability in any wound bed, convenience of application, and improved patient compliance and comfort. Here, we report an in situ-formed hydrogel membrane through ultraviolet cross-linking of a photocross-linkable azidobenzoic hydroxypropyl chitosan aqueous solution. The hydrogel membrane is stable, flexible, and transparent, with a bulk network structure of smoothness, integrity, and density. Fluid uptake ability, water vapor transmission rate, water retention, and bioadhesion of the thus resulted hydrogel membranes (0.1 mm thick) were determined to range from 97.0-96.3%, 2,934-2,561 g/m(2)/day, 36.69-22.94% (after 6 days), and 4.8-12.3 N/cm(2), respectively. These data indicate that the hydrogel membrane can maintain a long period of moist environment over the wound bed for enhancing reepithelialization. Specifically, these properties of the hydrogel membrane were controllable to some extent, by adjusting the substitution degree of the photoreactive azide groups. The hydrogel membrane also exhibited barrier function, as it was impermeable to bacteria but permeable to oxygen. In vitro experiments using two major skin cell types (dermal fibroblast and epidermal keratinocyte) revealed the hydrogel membrane have neither cytotoxicity nor an effect on cell proliferation. Taken together, the in situ photocross-linked azidobenzoic hydroxypropyl chitosan hydrogel membrane has a great potential in the management of wound healing and skin burn.

Surface acetylation of cellulose nanocrystals (CNCs) imposes an important effect on CNC-related mechanical enhancement of hydrophobic polyester-based composites, of which interfacial properties still need optimization. In the present work, the surface acetylation of CNCs was adjusted as a gradient of above ca. 10%. Then, we found that the surface energy of acetylated CNCs (ACNs) decreased and thus their hydrophobicity increased as the surface acetylation degree increased. Hence, the ACNs with varied degrees of acetyl substitution (DS surface-acetyl ) values were attempted to reinforce a kind of hydrophobic polyester, poly(3-hydroxybutyrate- co -4-hydroxybutyrate) (PHB). The results indicated that a smaller discrepancy in the surface energy between the CNC surface and the PHB matrix was obtained, as the surface acetylation degree increased, and then, the affinity and interaction between the two components increased, which improved the homogeneous distribution of ACNs in the PHB matrix. Besides, in comparison to the nanocomposites filled with 15 wt % unmodified CNCs, the tensile strength of those with ACNs of 62.9% DS surface-acetyl was 43.3% higher. This study was the first attempt to adjust the surface substitution degrees with a gradient profile for the surface modification of CNCs and prove that acetylation gradient control is an effective and facile strategy to optimize the mechanical properties.