title: Poly(vinylamine) microgel-dextran composite hydrogels: characterisation; properties and pH-triggered degradation.
abstract: The present study involves an investigation of the formation, characterisation and triggered-degradation of mixed dispersions involving cationic poly(vinylamine-co-bis(ethyl vinylamine) ether) (PVAM-BEVAME) microgel (MG) particles and partially oxidised dextran (Dexox). In this approach to colloidal hydrogel composite formation, imine bonds were formed by reaction between aldehyde groups of Dexox and the primary amine groups on the MG particles. The composite hydrogels contained MG particles that were externally cross-linked by Dexox to form an elastically effective network with high storage modulus (G') values and low tanδ (=G″/G', where G″ is the loss modulus) values. The G' values for the MG-Dexox gels increased exponentially with increasing mass ratio (MR) of Dexox to MG. Interestingly, the yield strains determined from rheology also increased with MR and yield strains of up to 130% were measured. Au nanoparticles of comparable size to the Dexox chains adsorbed to the surface of the MG particles, which suggests that the pore size of the MG particles may have been smaller than that of the Dexox coils. The MG-Dexox gels were also subjected to acidic conditions to demonstrate pH-triggered gel network breakdown via imine bond cleavage. We show that new PVAM MG/aldehyde mixtures studied here for the first time form ductile and versatile colloidal gels and our new method provides a route to increasing ductility of hydrogels containing MG particles.
authors.affiliation: Biomaterials Research Group, Manchester Materials Science Centre, School of Materials, The University of Manchester, Grosvenor Street, Manchester M1 7HS, UK. Electronic address: judith.mccann@postgrad.manchester.ac.uk.
authors.forename: Judith
authors.initials: J
authors.lastname: McCann
authors.affiliation: Biomaterials Research Group, Manchester Materials Science Centre, School of Materials, The University of Manchester, Grosvenor Street, Manchester M1 7HS, UK. Electronic address: jonathan.behrendt@manchester.ac.uk.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Behrendt
authors.affiliation: Biomaterials Research Group, Manchester Materials Science Centre, School of Materials, The University of Manchester, Grosvenor Street, Manchester M1 7HS, UK. Electronic address: junfeng.yan@manchester.ac.uk.
authors.forename: Junfeng
authors.initials: J
authors.lastname: Yan
authors.affiliation: University of Bolton, Institute for Materials Research and Innovation, Deane Road, Bolton, Greater Manchester BL3 5AB, UK. Electronic address: s.halacheva@bolton.ac.uk.
authors.forename: Silvia
authors.initials: S
authors.lastname: Halacheva
authors.affiliation: Biomaterials Research Group, Manchester Materials Science Centre, School of Materials, The University of Manchester, Grosvenor Street, Manchester M1 7HS, UK. Electronic address: brian.saunders@manchester.ac.uk.
authors.forename: Brian R
authors.initials: BR
authors.lastname: Saunders
mesh_terms: D003911:Dextrans / Q000737:chemistry*; D020100:Hydrogels / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D011145:Polyvinyls / Q000737:chemistry*; D012212:Rheology
chemical_list: D003911:Dextrans; D020100:Hydrogels; D011145:Polyvinyls; C008996:poly(vinylamine)
keywords: Dextran; Gel; Imine; Microgel; Mixed dispersion; N-vinylformamide; Polyvinylamine