Synthesis And Properties Of Polyacrylamide Series Microspheres

Polyacrylamide series microspheres, which are sort of microspheres whose skeleton are acrylamide homopolymer or acrylamide copolymer, have attracted much attention due to their inherent low toxicity, biodegradability and good biocompatibility in the medical and biological fields. However, it is difficult and expensive to synthesize polyacrylamide series microspheres directly through conventional suspension polymerization. Thus, a novel route to synthesize polyacrylamide series microspheres from acrylonitrile (AN) was developed. In the first step, crosslinked porous polyacrylonitrile (PAN) spheres were prepared by copolymerization of AN and DVB. Then PAN spheres were hydrolyzed to form polyacrylamide (PAM) spheres. In the final step, the porous PVAm spheres were obtained via Hofmann degradation of PAM spheres.PAN spheres were prepared by copolymerization of AN and DVB. Then PAN spheres were hydrolyzed to form PAM spheres. FTIR, NMR and XPS analysis proved the successful synthesis of PAM spheres. The characterization of SEM indicated that these PAM microspheres have rough surfaces and porous interior structure. The equilibrium water content and swelling ratio increased with the increase of DVB and porogen content and to a maxinum value (42.35%and 73.46%), then decreased. Compare to the conventional route, these PAM spheres have better equilibrium water content and swelling ratio. The surface area of PAM spheres increased with the DVB content, and got a max value (6.13m2/g) at 5% DVB content.PVAm spheres were obtained via Hofmann degradation of PAM spheres. FTIR and NMR proved the successful synthesis of PVAm spheres. The characterization of SEM indicated that the Hofmann degradation did not destroy the porous interior structure of the spheres. The amino content increased with the increase of DVB and n(NaClO)/n(NaOH) and to a maxinum value (15.8mmol/g), then decreased. The equilibrium water content and swelling ratio of PAM spheres changed in accordance with the amino content, and the max value was 96.48%and 520.00%. PAA spheres were prepared by the conversion of PAN spheres. Then acyl chlorination of PAA spheres with thionyl chloride in order to attach the linear poly (ethylene glycol) (PEG) to the surface of the PAA spheres. FTIR and XPS analysis proved the successful synthesis of PEG-g-PAA spheres. The hydroxyl content of the spheres were dependent on the crosslinking degree and n(PEG/PAA), and got to a maxinum value(74.12% and 89.75%)at the experimental condition of 3% DVB content and n(PEG/PAA)=4. The swelling ratio was influenced only by the DVB content, indicated that the graft reaction did not destroy the porous structure of the spheres.