We report on synthesis and pH-responsive properties of hydrogel capsules of spherical and cubical shapes. Three types of  poly(methacrylic acid) (PMAA)-based hydrogel capsules were produced  as hollow replicas of inorganic sacrificial templates through chemical cross-linking of hydrogen-bonded layer-by-layer (multilayer) films; one-component PMAA, one-component poly(methacrylic acid-co-(aminopropyl)methacrylamide) [PMAA-co-NH2], and two-component PMAA-co-NH2 with poly(vinyl pyrrolidone--co-(aminopropyl)methacrylamide) [PVPON].  We found than while spherical PMAA capsules increased in size due to a shift from pH=3 to pH=8, cubical capsules changed shape and became bulged at the faces. The PMAA-co-NH2 single component cubical capsules similarly changed shape, while the two-component PMAA/PVPON cubical system maintained cubical geometry while increasing in size upon pH shift. The differing pH-triggered response was hypothesized to be a result of differing hydrogel rigidity, expressed as the ratio of the contour length between cross-links as compared to persistence polymer length. PVPON/PMAA cubical capsules were found to be ten times more rigid than their one component counterparts, that can explain the expansion of two component cubical capsules  uniformly in all directions. We believe these results allow for developing new polymeric materials with predictable shape and size transformation useful in drug delivery, cell uptake, and microfluidic sensing applications.

PH-triggered responses of spherical and cubical multilayer hydrogel capsules

247th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.