The cracking behavior of spherulites in melt-crystallized poly (l-lactic acid) and poly [(R)-3-hydroxybutyric acid] was investigated in an isothermal crystallization process. Layered spherulites with dual Tc were prepared under gradient cooling conditions. As Tc decreased the crack density reduced obviously, while width and depth of the cracks increased. A comparison of the effects of crystallization temperature (Tc) and spherulite size on cracking behavior in spherulites was present for the first time. Cracks were found to be more sensitive to Tc than spherulite size. Cracks were healed with a thermal treatment and the process was fully reversible. The crack positions were closely depended on the crystalline lamellae alignment set up at Tc.

Herein, we present a novel way for the production of self-healing hydrogels with stretch beyond 4200% than their initial length and relatively high tensile strength (0.1-0.25 MPa). Furthermore, the hydrogel was insensitive to notch. Even for the samples containing V-notches, a stretch of 2300% was demonstrated. The hydrogels were developed by in situ crosslinking of the self-assembled colloidal poly(acrylic acid) (PAA)/functionalized polyhedral oligomeric silsesquioxane (POSS) micelles. This was achieved by the addition of functionalized polyhedral oligomeric silsesquioxane with tertiary amines and hydroxyls (POSS-AH) into the PAA reaction solution. The POSS-AH led to micellar growth, then the dualcrosslinked network was constructed. One type of crosslink was formed by hydrogen-bonding and ionic interactions between PAA chains and POSS-AH, the other type of crosslink was formed by covalent bonds between PAA and bis(N,N'-methylenebis-acrylamide).

We report here the self-assembly of reversible pH intelligent aggregate from natural polysaccharide hyaluronic acid and functionalized polyhedral oligomeric silsesquioxane with tertiary amines and hydroxyls (POSS-AH). Various forms such as micelles, sacs and membranes were self-assembled through different procedures in this organic/inorganic hybrid system. The complex can be manipulated simply by changing pH to produce hydrogen-bond and ionic interaction. Furthermore the aggregates can form at a wide pH range by adjusting the proportion of the two constituents. These pH-responsive composites will offer potential opportunities in many fields, including cell immune barriers, drug and gene delivery systems and chemical sensors.Highlights► Hyaluronic acid and POSS nanaoparticals can form reversible pH-induced aggregates. ► Micelles, sacs and membranes have been observed in this hybrid system. ► Sac after defect can be resealed by triggering additional self-assembly. ► The self-sealing macroscopic structure offer opportunities in many areas.