Shape and stimuli-responsiveness in addition to size and surface chemistry of micro-engineered delivery carriers play an important role in functional responses of polymeric particulates. We report on the effect of rhombic dodecahedron shape on mechanical properties of poly(methacrylic acid) (PMAA) multilayer hydrogel capsules at various pH values. The (PMAA)n hydrogel capsules where the subscript denotes the number of PMAA layers in the capsule wall were obtained from chemical cross-linking of PMAA layers within the hydrogen-bonded (PMAA/polyN-vinylpyrrolidone)n (PVPON) multilayer capsules with ethylenediamine. We explore the effect of the PMAA hydrogel capsule wall thickness and hydrogel cross-link density on the ability of these rhombic dodecahedron capsules to retain their non-spherical shape in the pH range from 3 to 7.5 after dissolution of a sacrificial metal-organic-framework core. Also, we investigate mechanical stability of rhombic dodecahedron and spherical (PMAA)n capsules against deformation in solution under various osmotic pressures induced by increased concentrations of polystyrene sulfonate chains in exterior solution. We have found that increasing the number of faces of the (PMAA)10 multilayer hydrogel capsules from 0 (spherical) to 12 (dodecahedron) can improve their mechanical stability against pressure-induced deformations up to 6.7-fold. Also, the dodecahedron capsule shape results in capsule ‘reinforcement’ against deformation upon capsule swelling by 1.3-fold when the solution pH is increased from 5 to 7. We believe this study on shape- and pH-regulated mechanical stability of rhombic dodecahedral multilayer hydrogel capsules can give new insights for developing advanced hydrogel materials with the controllable shape.

Shape stability and mechanical properties of rhombic dodecahedron multilayer hydrogel capsules at various pH

253rd National Meeting (2017)

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