Nanohybrid Hydrogels Research Articles

Preparation and characterization of PMAA/MWCNTs nanohybrid hydrogels with improved mechanical properties

A novel nanohybrid hydrogel was in situ prepared by means of a free radical crosslinking polymerization route of methacrylic acid in the presence of multi-walled carbon nanotubes (MWCNTs). The structural and morphological characterizations revealed that poly(methacrylic acid) networks (PMAA) closely covered the MWCNTs, and a MWCNT-well-dispersed nanohybrid hydrogel was formed. The addition of MWCNTs strikingly improved pH response and mechanical properties, depending on the component ratios and particle sizes of MWCNTs as well as crosslinker concentrations. The swelling rate was obviously faster than that of the pure PMAA hydrogel. The hydrophilic nature of polyelectrolytes, the capillarity effect, cation-pi or charge-transfer interaction and hydrogen bonds, as well as a subtle balance among these interactions were adopted to interpret the above swelling behavior. Load transfer to the MWCNTs in the networks played important part in compression mechanical improvements. MTT assays were adopted to evaluate the cytocompatibility of the developed biomaterials. This smart hydrogel is expected to be used as potential candidate for specific biological applications.

Preparation and characterisation of polyacrylamide/MWCNTs nanohybrid hydrogels with microporous structures

Nanohybrid hydrogels with micro or mesoporores were designed and synthesised in the case of polyacrylamide and multiwalled carbon nanotube (MWCNT) or hydroxyl functionalised MWCNT (MWCNT-OH). Investigations indicated that the addition of carbon nanotubes can induce an improved swelling with the temperature increased from 25 to 42°C. The nanohybrid hydrogel samples displayed relatively sensitive response to an acidic environment of pH ≤3, although the equilibrium swelling ratios declined as the MWCNT proportions and pH values were elevated. Mechanical analysis affirmed that the hydrogels exhibited high compression strength and low retention rate of elastic deformation. Fourier transform infrared, SEM and TEM findings implied that MWCNT or MWCNT-OH chains may be wrapped or inserted in the polyacrylamide networks by a non-covalent interaction like intermolecular hydrogen bonding. Hence, a supramolecular assembly was created, which was adopted to shed light on the compression mechanical properties and swelling behaviour.

Preparation and Theophylline Delivery Applications of Novel PMAA/MWCNT-COOH Nanohybrid Hydrogels

A series of nanohybrid hydrogels was designed and developed based on a hydrogen bond self-assembly of poly(methacrylic acid) (PMAA) networks and carboxyl-functionalized multi-walled carbon nanotubes (MWCNT-COOH). The nanohybrid hydrogels show low micropore densities and large mesh sizes with an increase in MWCNT-COOH content. Particularly, the hydrogels containing 10 wt% MWCNT-COOH was observed to collapse at pore walls because of large holes, which is believed to be responsible for high swelling. The ability of the MWCNT-COOH to self-associate with PMAA or water molecules via hydrogen-bonding interactions and an additional electrostatic repulsion govern both pH response of the network and drug release. Increasing pH values causes equilibrium swelling ratios and accumulative release to be elevated. On the other hand, modified mechanical behavior can be obtained under a low content of the MWCNT-COOH in that the high MWCNT-COOH filling effects the formation of PMAA gel networks. Swelling and controlled release profiles of theophylline could be modulated by changing pH values, introducing the MWCNT-COOH and adjusting the proportions of the MWCNT-COOH component.