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Nano α-glycine crystals, γ-glycine crystals, and amorphous solid dispersion (ASD) of glycine were prepared through solvent-free ball milling of commercial α-glycine. The solid-state polymorph conversion of glycine from α to γ was completely realized by ball milling with 0.2 wt.% NaCl for 1 h or by ball milling with 0.02 wt.% NaCl for 1 h with subsequent storage for one week. The ASD of glycine was prepared by ball milling α-glycine with an equal amount of CaCl2 for 1 h. We studied the effect of inorganic salt types and their concentrations on the extent of polymorph conversion and amorphization of glycine in our experiments. This solvent-free ball milling method could be used for the synthesis of polymorphs and amorphous phase of drugs and other organic materials.

Polymorph control of 5-fluorouracil (5-FU) was achieved by ball milling. Form II was synthesized through one-step neat grinding of raw 5-FU (RFU), and Form III (a new polymorph) was obtained by neat grinding RFU twice. Forms II and III of 5-FU were prepared separately through ball milling with different amounts of ethanol as an additive at the same period without influencing each other.

Guanosine (GR) dihydrate and inosine (IR) dihydrate have similar crystal structure, water molecules are almost at the same locations in them. GR dihydrate has the reversible dehydration/hydration property and is a good candidate for materials harvesting water from atmosphere. IR dihydrate is not stable and can be easily transformed to anhydrous IR α form. In this work, doping of IR in GR dihydrate in all the range was realized for the first time by using a solution method. The successful preparation of doped dihydrate of IR and GR by the solution method was attributed to the similar molecular conformations of IR and GR in solution. The doped dihydrates could maintain the reversible dehydration/hydration property similar to pure GR dihydrate even the ratio of IR was up to 71.1 ± 1.2 mol% under a mild drying treatment with freeze-dry. A pure amorphous GR was prepared by ball milling, and it showed a similar dehydration/hydration property to GR dihydrate with a lower dehydration temperature (about 84 °C). The implementation of doping IR in GR dihydrate would shed light on the design and fabrication of functional doped organic crystals. And study on the structural insights and the dehydration/hydration processes of the doped dihydrates and the pure amorphous GR would shed light on the design and fabrication of novel hydrogen-bonded organic frameworks (HOFs) materials for water harvesting.

Printable hydrogels desired in bioengineering have extremely high demands on biocompatibility and mechanic strength, which can hardly be achieved in conventional hydrogels made with biopolymers. Here, we show that on employment of the strategy of coordination-triggered hierarchical self-assembly of naturally occurring small-molecule folic acid, supramolecular hydrogels with robust mechanical elastic modulus comparable to synthetic double-network polymer gels can be made at concentrations below 1%. A sequence of hierarchical steps are involved in the formation of this extraordinary hydrogel: petrin rings on folate form tetramers through hydrogen bonding, tetramers stack into nanofibers by π-π stacking, and zinc ions cross-link the nanofibers into larger-scale fibrils and further cross-link the fibril network to gel water. These supramolecular qualities endow the hydrogel with shear-thinning and instant healing ability, which makes the robust gel injectable and printable into various three-dimensional structures. Owing to the excellent biocompatibility, the gel can support cells three-dimensionally and can be used as an ideal carrier for imaging agent (Gd

Polyvinyl alcohol (PVA) hydrogels have been proposed for use as promising biomaterials in biomedical and tissue engineering, and graphene oxide (GO) has been recognized as a unique two-dimensional building block for various graphene-based supramolecular architectures. In this article, we systematically studied the influence of three kinds of PVA with different molecular weights on the interaction between PVA and GO. Moreover, the effects of PVA on the gelation of GO were also investigated. The native PVA hydrogel, as well as PVA–GO hybrid hydrogels, have been thoroughly characterized by the phase behavior study and various techniques including field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA) and rheological measurements. It can be seen that with the increase of the molecular weight of PVA, the addition of GO can effectively promote the gelation of PVA which can be reflected by a decrease of the critical gel concentration (CGC) for PVA–GO hydrogels. Dye adsorption experiments indicate that the toxic dye, i.e., methylene blue (MB), was efficiently entrapped in the PVA–GO xerogels. It is also demonstrated that the gelation of PVA and GO composites can be promoted by different supramolecular interactions, including hydrogen bonding and electrostatic interaction. This work indicates that the PVA–GO composite is a good candidate for preparing “super” and “smart” hydrogels and will enable further studies on the supramolecular chemistry of PVA, graphene and its derivatives.