Fibrillar morphologies of hydrogels obtained from a lamellar medium

Abstract

Hydrogels are suitable for multiple applications and their properties are strongly dependent on their morphology. Sponge-like morphologies are obtained in conventional hydrogels when the polymerization is performed in isotropic media. Fibrillar morphologies imparting new properties to hydrogels are expected when the reacting medium is anisotropic. Here, we synthesize such fibrillar hydrogels by polymerization in a lamellar medium formed by 1,4-bis(2-ethylhexyl)sodium sulfosuccinate (AOT) and water. At high surfactant content this objective is achieved, and the thickness of the obtained fibrils (0.1-1 µm) can be correlated with the physical properties of the lamellar system. At intermediate AOT concentrations, the morphology is hierarchical, with primary closed pores containing a secondary fibrillar structure that fills the pores. For low AOT concentrations, the crosslinking process is unhindered, and the hydrogels are mechanically consistent with a sponge-like morphology having large (10-10 2 µm) void pores. The time evolution of the mesophase as polymerization advances is followed by small angle X-ray scattering.

In Situ X-ray Polymerization: From Swollen Lamellae to Polymer–Surfactant Complexes

“…Additionally, a non-homogeneous distribution of the initiator in the different domains (hydrophobic or hydrophilic) could occur, leading to a modification of the expected characteristics of the polymer. It has been previously reported that X-rays act as an initiator in the polymerization of acrylamides, acrylates, or ethylene glycol . Besides, the high photon flux of synchrotron radiation provides a method to follow the polymerization process in situ, by the change in the scattering curves, from the initial mixture to the postpolymerized state .…”

Microstructures and mechanical properties of thermoplastic composites based on polyarylate/nylon6 islands‐in‐sea fibers

“…In those aspects, polyarylate (PAR)/nylon6 islands‐in‐sea fibers are considered as suitable materials for manufacturing thermoplastic composites, because PAR island part acts as reinforcing microfibers and nylon6 sea part serves as a tough semicrystalline matrix in final thermoplastic composites. PAR with a rigid chain structure is known to be one of high‐performance engineering polymers exhibiting a liquid crystalline phase under melt state and its fibers have nanofibrillar structure, which is developed during melt‐spinning and following heat‐treatment process . Furthermore, PAR fibers do not retain moisture in humid or aqueous atmosphere and thus maintain stable physical properties when used as reinforcement materials.…”