Poly(vinylamine) microgel–dextran composite hydrogels: Characterisation; properties and pH-triggered degradation

• Published in: Journal of colloid and interface science 2015-07, Vol.449, p.21-30
• Main Authors: McCann, Judith, Behrendt, Jonathan M., Yan, Junfeng, Halacheva, Silvia, Saunders, Brian R.
• Format: Article
• Language: English
• Subjects: Dextran; Dextrans - chemistry; Gel; Hydrogels - chemistry; Hydrogen-Ion Concentration; Imine; Microgel; Mixed dispersion; N-vinylformamide; Oxidation-Reduction; Polyvinylamine; Polyvinyls - chemistry; Rheology
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2014.09.041

[Display omitted] •Mixed dispersions of poly(vinylamine) particles cross-linked with dextran.•Formed via amine carbonyl condensation between amine and oxidised dextran groups.•Using long dextran chains produced gels with high stiffness and ductility.•Examined the degradation of the network under low pH conditions.•Shown that these MG particles are porous with a TEM study of Au NP penetration. 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.