CO(2)-responsive polyacrylamide microspheres with interpenetrating networks.

HYPOTHESIS: CO2-responsive microspheres fabricated via co-polymerization protocol are attractive due to their promising applications. However, the inevitable particles-agglomeration restrained their further utilizations. Towards this challenge, interpenetrating network (IPN) protocol would be a potential choice to construct the "intelligent" microspheres, which presents superiority in comparison with co-polymerization mode.

EXPERIMENTS: A series of CO2-responsive microspheres with polyacrylamide (PAM)/poly(dimethyl aminopropyl methacrylamide) (PDMAPMA) IPN-structure were fabricated via inverse seed suspension polymerization by adjusting DMAPMA loading and crosslinking-degree of seeds. The resultant particles and responsiveness were examined using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), optical microscopy (OM) and laser particle size analyzer (LS), respectively.

FINDINGS: The interior-structure and fracture-morphology of IPN-particles could be intuitively observed by SEM, showing homogeneous and compact structure without phase separation, offering the direct proof for the formation of IPN-microstructures; the particle morphology altered from IPN to IPN-membrane when gradually increasing DMAPMA concentration. Upon alternating treatment with CO2 and N2, these particles experience reversible volume expansion and collapse. Besides, the non-agglomerated responsive particles with varying composition can be prepared by changing the crosslinking-degree of seeds, from which maximum responsiveness, relative swelling volume (RSV), could reach 11.6 when PDMAPMA loading is at 87%.