Making a soft gel strong against mechanical influences

Making a soft gel strong against mechanical influences Source: Ivan Uralsky/Fotolia

Hydrogels are recognised as soft materials due to their high water content and tissue-like physical and mechanical properties, and have wide applications in many fields. They can be prepared by a variety of methods including crosslinking by physical, ionic and covalent interactions. A problem for some applications of hydrogels is their weak mechanical properties. Now Xuping Qin and his colleagues from Shandong University in China prepared multilayer hydrogels by frontal photopolymerisation of acrylamide and 2-acrylamido-2-methylpropane sulfonic acid using hydrophilic reactive microgels (HRM) as crosslinkers instead of conventional crosslinkers. The hydrophilic microgels (HM) were prepared by inverse emulsion photopolymerisation and then were chemical modified by N-methylolacrylamide (NMA) to obtain HRM with C=C double bond. The HM and HRM was characterised by dynamic light scattering measurements, SEM, TEM and FTIR, respectively. It was found that the resulting multilayer hydrogels showed high fracture strength and high tensile elongation along parallel direction. However their fracture strength and tensile elongation along perpendicular direction was very weak and could be separated by hands very easily. Therefore, this might be a new approach to yield soft and wet multilayer hydrogels with high mechanical strength. This article was published in European Polymer Journal, Volume 47, Issue 10, October 2011, pages 1903-1911.