Continuous transition of colloidal crystals through stable random orders.

Randomly stacked 2D hexagonal close-packed (RHCP) layer structures are frequently observed in colloids and other material systems but are considered metastable. We report a stable RHCP phase domain of poly(butadiene--ethylene oxide) (PB-PEO) diblock copolymer micellar colloids in water. The stable RHCP colloidal crystals emerge in the middle of a continuously transiting phase domain of close-packed PB-PEO colloids from a face-centered cubic (FCC) polytype to a HCP polytype.

Tuneable phase behaviour and glass transition polymerization-induced phase separation in crosslinked step-growth polymers.

Once limited to chain-growth polymerizations, fine control over polymerization-induced phase separation (PIPS) has recently been demonstrated in rubber-toughened thermoset materials formed through step-growth polymerizations. The domain length scales of these thermoset materials can be elegantly tuned by utilizing a binary mixture of curing agents (CAs) that individually yield disparate morphologies. Importantly, varying the composition of the binary mixture affects characteristics of the materials such as glass transition temperature and tensile behavior.

Network structure and enzymatic degradation of chitosan hydrogels determined by crosslinking methods.

Polysaccharides can be modified by reactive functional groups to enable chemical crosslinking. We studied how different methods of crosslinking methacrylate-functionalized chitosan affected the network structures and various properties relevant for utilization of the chemically crosslinked hydrogels in biomedical applications, including tissue engineering and delivery of therapeutic agents. Four chitosan hydrogels were made by either the free radical polymerization with varying initiation kinetics and an addition of chain transfer agents or the based-catalyzed Michael-type addition reaction.